Bad Astronomy Blog

The Sun's Motion Reflected in the Universe

Thu, 10/27/2016 - 06:00

Even after all this time — 13.8 billion years, give or take — hydrogen still dominates the Universe. It’s the simplest element, and the most abundant. It fuels the stars, which convert it into heavier elements like helium, iron, calcium, and more. It’s strewn between the stars and even between the galaxies themselves.

To know hydrogen is to know the Universe.

This is no exaggeration. Hydrogen in deep space hums in the radio region of the electromagnetic spectrum, and that can be detected by radio telescopes. This is incredibly useful: For example, we discovered our own Milky Way galaxy was a spiral by tracing the hydrogen gas, which outlines the majestic, sweeping arms (for more, go watch my Crash Course Astronomy episode on the Milky Way).

The image at the top of this article is a new map of the entire sky made by tracing the radio emission of hydrogen. Two huge telescopes — a 100 meter Effelsberg telescope in Germany and the 64-meter Parkes telescope in Australia — covered both hemispheres in great detail. In this map the spherical shape of the sky is, in sense, unpeeled and shown as an ellipse, which is a convenient way to show the whole sky in a 2D way.

When done this way, the Milky Way stretches directly across the middle of the map. The galaxy is flat, and we’re in it, so we see it as a line across the sky. In this “galactic coordinates” map, the center of the galaxy is in the map center. You can see the hydrogen gas of our two companion satellite galaxies to the lower right, and the tiny smears to the lower left of the Andromeda and Triangulum galaxies, two nearby spiral galaxies not too dissimilar to our own.

Now I need to show you something, because this is utterly, utterly cool.

Hydrogen emits light at a very specific wavelength: 21.106114 centimeters. This far longer than the wavelength of the kind of light we see; a half million times longer! That’s why we need special telescopes to see it.

Effelsberg and Parkes are both very sensitive telescopes, and they can also detect minute changes in the wavelength of the light. If a hydrogen atom is moving toward us, the wavelength shortens a bit, and if it moves away it lengthens. This is related to the famous Doppler effect (see Crash Course Astronomy: Light for all about that).

The map above uses colors to represent that. The colors aren’t real; they just represent the velocity of the gas. Hydrogen colored blue is headed toward us; green is where it’s moving away. When I first saw this map, I saw the broad green line on the right and the blue one on the left, and realized that what it shows is the Sun’s motion as it orbits the center of the galaxy. We’re moving at about 200 km/sec around the galaxy, so we’re approaching gas on one side of the galaxy, and moving away from the gas on the other side. Neat!

But then I saw the gas closer to the center. The colors are reversed! On the right side of the map, the gas is blue until a third of the way out then switches to green outside of that. What the what?

Then I laughed when I figured it out. We’re not the only object in the galaxy in motion! All that galactic gas is orbiting the galactic center as well. Stuff near the center is orbiting faster than we are, and stuff farther out slower. The blue gas on the right is inside our orbit, moving faster than we are, so it’s catching up to us, approaching us. But the gas colored green is outside us, moving more slowly, so we’re leaving it behind.

I know this can be hard to picture in your head, but the beauty of it is that once you do, this map sings. You can instantly see what’s what: the motion of the gas, where it’s more dense than other locations, how it’s distributed. It also shows our location in the galaxy! All those changing velocities depend on the Sun’s velocity, the velocity of the gas, but also the direction of the Sun’s motion and its position in the Milky Way’s disk. That’s a stunning amount of information.

Maps like this allow astronomers to puzzle out the structure of our galaxy, and the dynamics of the gas inside and out, and even what other galaxies are doing as well.

I really wasn’t overstating the case: To know hydrogen is to know the Universe. Sometimes it’s the simplest stuff that leads to the most profound understanding.

Categories: Astronomy Headlines

How Just Three Stars Light Up a Stellar Nursery

Wed, 10/26/2016 - 06:00

Today I’m going to toss a little bit of math your way. If you’re an arithmophobe, never fear: It’s mostly just me throwing around some gee-whiz numbers, and I’ll help you swallow this medicine with the sweet, sweet eye candy above.

That image is from Robert Gendler, Roberto Colombari, and Martin Pugh, and it shows the young star cluster called NGC 6193 embedded in a vast cloud of gas and dust called NGC 6188. Both are very roughly 4,000 light-years away in the constellation of Ara. The image combines data from the huge 8.2 meter Very Large Telescope in Chile with some from a much smaller 32 cm telescope.

The cluster is young, only a few million years old. The brightest stars in it are massive, hot, luminous, and blue. They flood out light, illuminating and ionizing the gas in the cloud, which responds by glowing red.

I could go into details, but I already have in countless posts about emission nebulae, as well as in Crash Course: Nebulae. I’ll leave it up to you, Bad Readers, to determine how deeply you want to dive into those particulars by clicking those links.

But I want to point something out. Images like this are gorgeous, and always stop me in my tracks. The details, the colors, the structure of the gas … all of these combine to make such arresting images!

Still, it’s the science behind them that touches some atavistic part of my brain, giving me a chill that is both intellectual and visceral.

In many such nebulae, there are quite a few massive stars lighting them up, sometimes dozens of them. But in others, like NGC 6188, it’s only a few. In this case I mean that literally: The vast majority of energy pumped into the gas is being done by three stars.

In the center of the nebula you can see two stars, their cores blurred into a single smear, but their distinct presence revealed by the pair of X-shaped diffraction spikes coming out from them. Moreover, one of those two is itself a binary star, two stars in close orbit, so close they appear as one. So you’re actually seeing three stars there! One is a brutal O3 star, probably 50,000 times more energetic than the Sun, and the other two are O6, smaller but still beasts. All together they probably crank out 100,000 times as much light as the Sun does.

If you replaced the Sun with any of those three stars, the Earth wouldn’t last long. It’d be fried to a crisp.

But here’s the thing: The glowing part of that nebula, the gas energized by those stars, is roughly 20 light-years across. That’s 200 trillion kilometers! All that gas, probably several times the mass of the Sun, glowing due to the light of just three stars.

That made me wonder: How many photons are those stars emitting?

The math on that isn’t so bad. I won’t start from first physics principles, because that would take a lot of words. Instead, let me skip around a bit.

First, how many photons does the Sun emit? Well, the energy of a photon is defined by its wavelength or frequency. The Sun emits most strongly in the green portion of the spectrum, and that’s a wavelength of about 0.5 microns (or 500 nanometers if you prefer). The equation of the energy in a single photon is:

Energy = h x c / wavelength

Where h is Planck’s constant (just a number that has units of energy times time), and c is the speed of light. You can look those numbers up, but in the end the answer is that a single green photon has an energy of about 4 x 10-19 Joules (a Joule is a unit of energy; the energy stored in a single calorie of food is equivalent to more than 4,000 Joules).

The Sun emits about 4 x 1026 Joules of energy every second. That’s spread out over many different colors, each with their own energy, but I’m being really rough here, so assume they’re all green for math purposes. Dividing that total energy by the energy per photon gives us the number of photons the Sun emits:

4 x 1026 / 4 x 10-19 = 1045

Holy. WOW. That’s a lot of photons. Written out it’s:

1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 photons!

And that’s every second. The Sun has been doing this for 4.6 billion years, so I’ll leave it to you to figure out how many photons total the Sun’s given off since it was born (but it’s roughly 1062, and yikes).

Mind you, those stars lighting up NGC 6188 are 100,000 times brighter than the Sun, so they emit 1050 photons per second! They also tend to emit higher energy light, like ultraviolet. That kind of light is preferentially absorbed by the hydrogen in the gas cloud. That ionizes the gas, blasting the electrons off the atoms. When the electron recombines, it re-emits that energy as light, usually that characteristic red you see in the image.

That’s how (well, in part that’s how) just a few stars can light up gas for trillions of kilometers around.

Funny, too: As bright as those stars are, distance is more important. At 4,000 light-years away, they’re 250 billion times farther away from the Sun. So even though they blast out 100,000 as much energy, they’re just barely visible to the naked eye at that distance. I’m not sure what’s more unnerving: The energies involved, or the vast distances. Both are mind-numbing.

So in case you were wondering, when I see astronomical images, that’s the sort of stuff that goes through my mind. I’ve said it many times, but it bears repeating: There is great beauty in astronomy, but that’s dwarfed by what these cosmic artworks teach us about the Universe.

Categories: Astronomy Headlines

Astronomers X-Ray Colliding Galaxies to Find a Pair of Monster Black Holes

Tue, 10/25/2016 - 06:00

When whole galaxies collide, it’s a train wreck on a cosmic scale.

Usually there’s a near miss first, with each galaxy flying past the other. Both galaxies get distorted, their mutual gravity stretching them like taffy. They pull apart, but then their mutual gravity draws them together again, and the collision begins for real. What may have started as two lovely spiral or elliptical galaxies becomes chaos, the stars and gas clouds flung this way and that, and the resulting coalescing object a lumpy mess.

Eventually the two galaxies merge. We know that all big galaxies have supermassive black holes in their cores, million and even billions of times the mass of the Sun. After two galaxies collide, eventually their central black holes collide and merge as well, forming a bigger black hole (and blasting out gravitational waves). But that doesn’t happen for quite some time; during the actual galaxy collision each black hole is its own entity.

Not only that, but gas clouds tossed about by the collision can drop into the center of each galaxy, doomed to fall into the black hole there. When they do, the material piles up into a disk just at the edge of forever, swirling madly, heating up, and blasting out X-rays.

Which brings us to Arp 299, a pair of gorgeously colliding galaxies about 140 million light years from Earth. We know that the collision has been going on a while; the system glows brilliantly in infrared, putting out almost a trillion times the Sun’s energy output just in that one wavelength! That’s due to huge amounts of dust around their black holes, which absorbs a lot of the energy, gets warm, and re-emits it in the infrared.

The cores of the two galaxies are separated by less than 15,000 light years, which is pretty close on a galactic scale. That’s interesting, but it’s also irritating to astronomers: They’re so close together it’s been difficult to separate them using X-ray telescopes. And we know they’re emitting copious X-rays; the problem is knowing which black hole is emitting what.

Now, though, they’ve been teased apart. Using both NuSTAR and Chandra—two orbiting X-ray observatories—astronomers have figured out what each black hole is doing. In the image above, it’s the one on the right (Arp 299B) that’s pouring out X-rays, and is what we call an Active Galactic Nucleus, or AGN. The galaxy on the left (Arp 299A) is also emitting X-rays, and might be an AGN as well, but it’s only contributing about 10 percent of the total X-ray emission of the system.

The energy of the X-rays Arp 299A is emitting is also consistent with it having lots of what are called high-mass X-ray binaries (or HMXB), which consist of a high-mass star orbiting a black hole. In this case, the black hole in a HMXB is far smaller than the ones in the centers of the galaxies; it may have a few times the Sun’s mass, not millions of times. But it’s enough to draw material off its companion star, which then (like its supermassive counterpart) creates a disk of material that heats up and emits X-rays. But the way these emit rays is different then the cores of AGN, making it possible to distinguish between them (in general HMXB emit much higher energy X-rays than AGN).

Well, sometimes. In the case of Arp 299 it’s hard to be sure; the observations aren’t distinct enough to be certain Arp 299A is not an AGN. The astronomers who observed the system mention they plan on observing lots of other galaxies in this same way, specifically galaxies that are known to be rapidly forming stars. These tend to have more HMXBs in them, and that will act as a benchmark, helping astronomers distinguish between AGN and HMXB. The more “starburst” galaxies observed, the easier it will be to understand colliding ones as well.

All of this underscores a very important aspect of astronomy, science, and really just life in general: You have to observe things in more than one way to understand them. Using telescopes like Hubble or other big optical-light observatories is great, but they only give you part of the picture (literally), only tell part of the story.

Changing your viewpoint gives insight and perspective. That sounds like pretty good advice to me, whether you’re thinking about something scientifically or exercising a little bit of human compassion. In my opinion, we could use a lot more of both.

Categories: Astronomy Headlines

A Year of Record Heat

Mon, 10/24/2016 - 06:00

Every month since March 2016, I’ve posted an article that is almost exactly the same every time. For the nth month in a row, I’ve written, we’ve had a month that broke the temperature record historically. And even when I wrote the first one in March, we’d already seen record months since October of 2015.

And it’s happened again. September 2016 was the hottest September on record. That makes it the 12th month in a row this has happened.

After repeating the same article nearly word for word every month since March, I just can’t do it again. It seems too glib this time.

We’ve had a year of record heat. A year.

To be fair, this September just barely beat the previous record holder, by 0.004 degrees Celsius, putting it essentially in a statistical tie. But the previous record was in 2014, which again shows you that the world is heating up; all the record high temperatures are recent. The only way to even be a record high these days is to beat out some record from a year or two before.

The world is too damn hot. It’s a foregone conclusion that 2016 will be the hottest year ever recorded.

This latest record—all the recent records—are not individually critical. But we see so many of them that they should trigger warning bells in your head. And when you see the trend—a paper recently published by climate scientists claims that the Earth is hotter than it’s been in more than a hundred thousands years—those bells should be clanging louder than anything else. Global warming is an existential threat to our species.

So why is it we had three presidential debates with only barely a mention of this? And why do we have flat-out deniers still sitting in Congress?

Here’s a bit of good news: A total of 469 seats in the U.S. Senate and House are up for re-election on Nov. 8. Better yet, many vulnerable seats in the Senate are held by Republicans, the party that is far and away the most responsible for climate change denial in Congress. It’s literally in the party platform for the GOP.

That makes the Senate up for grabs for the Democratic Party, and a lot of the House as well. Even such stalwarts of GOP denial as Rep. Lamar Smith (R-Texas) are not looking as solid as they once were; for the very first time, in Smith’s home town the San Antonio Express-News refused to endorse him because he’s using his power as a congressman to bully scientists about climate change. His rabid denial has led him to abuse his position, and as the newspaper has shown, whether you agree with him or not, this alone is enough that he should be kicked to the curb. I’ll note that his opponent this election is Tom Wakely, a Democrat.

While Smith is probably safe, perhaps in two years a more moderate Republican who understands science will see his or her opportunity to unseat him. I dearly hope so.

I need not go into detail on the horrendous threat Donald Trump poses to our nation and our planet. But have no doubt that down-ballot candidates are every bit as dangerous. Denying global warming is as fundamentally wrong as saying the Earth is flat. It’s long, long past time to vote those flat-Earthers out of power.

Go out and vote. It’s not too late.

Categories: Astronomy Headlines

Mars Lander Impact Site Seen from Orbit

Sat, 10/22/2016 - 06:00

So, half of the European Space Agency’s ExoMars mission went well the other day. The Trace Gas Orbiter is now circling the planet, and appears to be healthy and happy.

Unfortunately, the Schiaparelli lander didn’t do so well. Instead of gently touching down on the surface, an as-yet undetermined problem shut the landing rockets off while it was still two to four kilometers above the ground. It impacted at an estimated speed of 300 km/hr. That’s 180 mph. Oof.

The image above is from NASA’s Mars Reconnaissance Orbiter, and shows the impact site. The lander’s planned descent was very similar to that of NASA’s Curiosity rover. Its heat shield took the brunt of first slamming through the atmosphere and then was ejected. After that a parachute slowed it further, then it and the back shell attaching it to the lander were ejected. Finally, the lander itself would slow using rockets and drop down to the surface.

In the image near the bottom you can see a bright spot below the cluster of pits to the lower right; that’s likely to be the parachute and back shell. And near the top is the, um, rather large black spot. That smudge is 15 x 40 meters in size, or about half the size of an American football field. The lander’s rockets would disturb the surface as it came down, but not nearly that much. It’s far more likely it’s an impact site.

This animation shows it better:

From telemetry, it seems that the thrusters switched off far too early. That means the fuel tanks were nearly full of propellant, so it’s likely they exploded upon impact. That would explain the size of the impact disturbance. It’s not clear why it happened, but engineers are poring over the data and hopefully will figure it out soon.

This is pretty disappointing, but it’s important to note that that lander was a technology testbed, literally designed and built to test the tech needed to land a future rover or other equipment on Mars. For the most part, the lander was a success! Most of the hardware and software worked, but obviously a very important piece did not.

And more importantly, the Trace Gas Orbiter is doing well. This is an extremely sensitive observatory that will look for methane in the atmosphere of Mars. Methane is a simple carbon-based compound that breaks down easily in the atmosphere. It’s been detected in the air of Mars before but it’s very diffuse and difficult to nail down. Methane can be created both by geological activity (outgassing from the interior) and by biological action. Obviously, the question of life on Mars looms large, and if it exists and is anything like life here, it might make methane. Detecting the gas is a big clue.

TGO will not only map methane, it will also look for different isotopes of it. A carbon atom usually has six protons and six neutrons. An isotope of an atom has a different number of neutrons; for example carbon-13 has seven neutrons, not six. Biologically made methane usually has more C12 in it than C13, so mapping the various isotopes can give us clues about the origin of the gas as well.

So let me stress again that TGO is ticking along. And hopefully engineers at ESA will learn enough about what went wrong with Schiaparelli to make sure the next attempt will go a little bit more gently.

We humans have sent a lot of probes to Mars, and nearly half have failed in one way or another. Space exploration is hard. But it’s so very worth it. I hope the folks at ESA working on this remember this as they continue to strive to better understand the Universe around us.

Categories: Astronomy Headlines

Twinkle Twinkle, Little Star, Who Wrote You? ’Twas Not Mozart.

Fri, 10/21/2016 - 06:00

“I never made a mistake in my life. I thought I did once, but I was wrong.” –Charles Schulz

Despite being a beloved internet personality, I have my flaws. Sometimes—rarely, of course—I make mistakes. I know. You’re shocked. Take a moment to recover, if you need one.

But it happens. If it’s small and doesn’t impact the writing in an article I fix it and move on, or (because TPTB at Slate are quite strict about such things) I issue a correction in the article itself. Sometimes the mistake is extensive, or worth diving into more fully, or as happens often is illustrative of an interesting issue, and in those instances I’ll write a separate follow-up article.

Sometimes it’s more of the “Oh. Huh!” variety. Such is the case here.

In my first book, Bad Astronomy, I offhandedly mention that the tune for “Twinkle, Twinkle, Little Star” was written by one Wolfgang Amadeus Mozart. Perhaps you’ve heard of him, and perhaps you’ve heard this claim as well.

However, it appears I and everyone else who repeats this little factoid are wrong. In an article at Woot, professional smart person Ken Jennings corrects this common misconception. It turns out the tune did not come from Mozart, but instead is actually a French folk song that dates from before him. I urge you to read Jennings’ article for details, as he mentions how Mozart got saddled with the credit.

Jennings also calls me out specifically for making the claim, especially and ironically in a book I wrote trying to correct misconceptions. Mea culpa. I remember writing that claim back in 2000 when I was drafting the book, and I even vaguely remember both thinking to myself that I should check its veracity, and actually doing so. However, I must have found some article that confirmed my own bias about the song’s authorship and went with it. Unfortunately, no one else in the editorial process caught it either, most likely simply assuming the old claim was correct.

Ah well. If you buy my book and are saddled with existential conflict due to this error, I suggest you take a pen, cross out the offending portion, and smile knowingly as you have gained more knowledge, a noble goal.

And if you’re the kind of person who delights when someone in my position makes an error, I  suggest you buy somewhere between 10 to 20 copies of the book and distribute them among your friends, so that you may all gather and bask in my factual wrong turn.

Of course, none of this affects another book, Astronomically Correct Twinkle Twinkle, written by my friends Henry Reich and Zach Weinersmith, which is quite delightful. Ironically, I suppose, I fact checked their book, and came up empty of errors. But then, they’re both smarter than I am, and combined they possess fierce intellect.

Now, for penance, I’m going to go listen to “The 1812 Overture,” which I hear was written by Francis Bacon.

Categories: Astronomy Headlines

The Lone Icy Volcano of Ceres

Thu, 10/20/2016 - 06:00

It’s hard to pick the one weirdest thing about Ceres. It’s the largest object in the asteroid belt between Mars and Jupiter. Most of the billions of chunks of debris in the belt really are leftover rubble from the early solar system, but some grew larger by the power of their own gravity, drawing more material in.

As it happened, Ceres was well on its way to becoming a planet before it ran out of material to feed on. Bigger than an asteroid, but smaller than a planet, scientists call it a protoplanet.

Out past Mars, the early solar system had lots of ice, and Ceres trapped this material as well. Its surface is dotted with white spots, what are now thought to be salt deposits left over as briny water leaked to the protoplanet’s surface and sublimated away.

The surface is heavily cratered, of course, and hilly. But one features stands out… and I do mean literally.

Ahuna Mons is the lone true mountain on Ceres, and it’s far and away the tallest: It towers an amazing four kilometers over the surface, and is 18 km across at its base. Nothing else on Ceres even comes close to it.

But Ceres doesn’t have tectonics like Earth does. So what could possibly create such a huge feature?

Ice. And lots of it.

We know salty water is oozing up to the surface because we see those shiny spots. Most of the spots are small, indicating low flow. But apparently that’s not the case for Ahuna Mons. New research just released analyzed data from the Dawn spacecraft, which has been orbiting Ceres since March 2015.

There must have been a lot of salty water under the surface at the location of Ahuna Mons, and it kept pushing its way up and out. Mixing with the rock and dust of Ceres, it piled up over time, forming the mountain out of muddy brine.

On Earth, when material flows out of the interior and forms a mountain, we call that mountain a volcano. But on Ceres, the material isn’t lava, it’s ice. So, Ahuna Mons isn’t just a volcano. It’s a cryovolcano. We know of several objects in the solar system with cryovolcanism, including moons of the outer planets, and even Pluto.

And this gives us another piece of the puzzle that is Ceres. Clearly, ice plays a role locally in the surface of Ceres. However, another bit of research shows that its role is less important over long stretches of terrain.

While the surface of Ceres is loaded with craters, it seems to have a deficit of truly big craters; several are expected to have formed from impacts, but only a couple exist (and even those are faint and hard to trace). It looks like the crust of Ceres is weak on the large scale, so that material in big craters can flow around and erase them, but still relatively stiff on local scales, allowing smaller craters to exist.

All of these data are clues to how Ceres formed, how it changed over time, and why it came to look and behave the way it does now. Astronomers and planetary scientists are like sleuths, mulling over the evidence to figure out whodunit. And how.

We’ve only been studying Ceres up close for a year and a half, and look how amazing it is! I wonder what else we’ll find there as we hold our magnifying glass to it.

Categories: Astronomy Headlines

How Big Is Proxima Centauri’s Planet?

Wed, 10/19/2016 - 06:00

Earlier this year, astronomers announced amazing news: The closest star to the Sun, called Proxima Centauri, has a planet! Not only that, but the planet’s size is roughly the same as Earth’s, and at its distance from Proxima it gets about the same amount of heat as the Earth does from the Sun.

In other words, we’re looking at a potentially Earth-like planet.

Potentially. The problem is that we don’t really know how big the planet is; and I mean that literally. Its diameter is unknown, and we need that to get any kind of understanding of what the planet may be like.

Why? Because if the planet (called Proxima Centauri b, or just Proxima b) is small and massive that means it’s dense, and so is will probably be composed of mostly metals and rock. If it’s large and massive it’ll be far less dense, and could be rocky with lots of water. Somewhere in between means it could have the same overall composition as Earth. These are three very different outcomes, and they all depend on the planet’s size. My friend Ian O’Neill has a good article outlining this.

The only way we know to measure the physical size of a planet is if it transits its parent star; that is, the orbit of the star is edge-on as seen from Earth, so we see the planet pass in front of the star once per orbit. When it does that the star’s light drops a bit, and the amount it drops depends on the size of the planet: A big planet blocks more light than a small one. If we know the size of the star (and we generally can determine that) then the amount the light dips tells you the size of the planet.

Knowing this, some astronomers observed Proxima using the Microwave and Oscillations of Stars Telescope (or MOST), a ‘scope with a 15 centimeter mirror that orbits the Earth. MOST is tiny; it only has a mass of 53 kg (that’s less than the mass of a typical adult human) and has a relatively small mirror, but being in space means it’s very stable. It doesn’t have to worry about peering through Earth’s atmosphere, which is wiggly and wavy. That means even a small ‘scope can make very precise measurements of a star’s brightness.

They observed Proxima for more than 40 days, looking for any tell-tale dip in its brightness. And they found one! Better yet, it was about what you’d expect from a planet the size implied by Proxima b’s mass. But the problem is the data are a bit noisy, and the transit inconclusive. It’s possible, even likely, it’s just a statistical fluctuation in the data, and so in the paper they say the odds are actually against the transit being real.

That’s disappointing. But not really unexpected; if the planet is roughly the size of Earth, the orbit has to be almost exactly edge-on for us to see a transit. Even a small tilt means it would appear to pass above or below the star from our viewpoint. The chance of a transit was only expected to be about 1.5 percent anyway.

Helpfully, David Kipping from the Cool Worlds group—and also the lead author on the Proxima transit paper—has made a video explaining this, too:

By the way, that tilt affects the mass we find for the planet, too. The planet’s existence was found because as it orbits Proxima, it pulls on the star with its gravity. While the planet makes a big circle around the star, the star also makes a smaller circle. We call that reflexive motion. The more massive the planet, the bigger the reflexive motion of the star.

In the research that found Proxima b, they found the likely mass of the planet is about 1.27 times Earth’s. But that depends on the tilt of the orbit! If the orbit is edge-on we see the reflexive motion maximized; if we see the orbit face-on we won’t see any reflexive motion at all. So the mass we find is the minimum for the planet; it could be larger if the orbit is tilted.

The thing is, at around twice the mass of the Earth, a planet starts to look more like Neptune than our fair world. It has enough gravity to accumulate a thick atmosphere, and would not be Earth-like as we think of it. So knowing the exact mass is important. And we don’t know it.

But there’s hope. As the paper authors point out, observations in the infrared, light outside the range our eyes can see, would help. Proxima is several hundred times brighter in the infrared, making the observations easier. Also, like many red dwarfs, Proxima is a flare star, blasting out huge stellar storms due to its magnetic activity. That makes observing it very difficult; it keeps changing its brightness, and that interferes with planet transit hunting. But in the infrared flares are much dimmer, again making it easier to observe there.

Mind you, the odds of Proxima b actually having an orbit that allows it to transit are long. But not zero! I think it’s worth a big infrared telescope’s time to look for a transit. This is, after all, the closest known planet in the Universe outside our solar system.

I think it’s a good idea to get to know our neighbors.

Categories: Astronomy Headlines

A Spiral Galaxy Defying the Cosmic Flow

Tue, 10/18/2016 - 06:00

I’d like to introduce you to an interesting galaxy today. The reason it’s interesting is because it’s surprising, and in a way that caught me off guard.

It’s called M 98 (or NGC 4192; every object in the sky is in multiple catalogs and has multiple handles), and it’s a spiral galaxy much like the Milky Way. It’s located about 50 million light years away, which isn’t exactly close on a cosmic scale but isn’t all that far away either. If I had to make an analogy, it’s like it’s in the next town over.

We see M 98 at a pretty low angle, so it appears nearly edge-on to us; spiral galaxies are pretty flat, and can have wildly different appearances depending on our viewing angle. Still, the spiral pattern is obvious enough, and you can see bright blue regions where stars are being born; those trace the arms. There is also lots of patchy dust along the arms; molecules of silica and aluminum as well as complex carbon-based molecules that are more like soot than anything else.

I like the central region of the galaxy; it’s bright but from this angle is cut in half by a dust lane, distorting the apparent shape of the usually elliptical hub.

All in all, it’s quite lovely, and that shot by the New Technology Telescope really shows it off.

But in that way it’s like a zillion other spirals. So what makes this one special?

Unlike nearly every single other galaxy in the Universe, this one isn’t moving away from us. It’s moving toward us.

There’s no danger of a collision! At its speed of 150 km/sec, it would take a hundred billion years to get here, so don’t wait up. Also, it’s probably not heading directly at us, because it’s part of the Virgo Cluster, a grouping of about  thousand galaxies bound by their own gravity. It’s the closest true cluster to us, and our own small Local Group of a couple dozen galaxies is like a small town near a bigger one. M 98 is part of the Virgo cluster, so it’s in orbit around the cluster center. We’re way outside the cluster, so it can’t hit us.

Here’s the fun bit. The Universe, as you may know, is expanding. One way to think of it is that space itself is getting bigger, and as it does galaxies are swept along with it. Galaxies aren’t really moving away from each other, they’re just floating along with the local flow.

But in many ways it’s like they really are moving away. One way is that their light is redshifted; the wavelength of the light they emit is stretched (it’s very similar to the Doppler effect that makes a motorcycle go EEEEEEeoowwwwwww as it passes you, changing the pitch of the noise). Practically every galaxy in the Universe shows this redshift, and in fact that’s how all this was discovered in the first place. The farther away a galaxy is, the more it’s light is shifted.

But not every galaxy shows it. Close by galaxies have much lower redshifts, and if the galaxy itself is moving rapidly through space (and not just with it), that local velocity will get added to or subtracted from the recession velocity.

One example of this is the monstrous Andromeda Galaxy, which is headed toward us at high speed. We actually will collide with it, though not for quite some time (like, four billion years). But it shows a distinct blueshift in its light; it’s moving around faster than space is expanding.

M 98 is doing the same thing. That surprised me when I saw it in a catalog; it’s far enough away that the Universal expansion should make it recede from us at about 1000 km/sec.

But then I saw it was in the Virgo Cluster, and I understood. The massive gravity of all those galaxies means they orbit the center at a decent clip, so some galaxies are redshifted more than average as they head away from us, in the part of their orbit taking them to the other side of the cluster. Some have lower velocities because they’re headed toward us in their orbits.

But M 98 is still unusual because it can completely overcome the recession of the cluster, and actually be physically headed toward us. That’s almost certainly because it’s recently interacted with another galaxy in the cluster; when galaxies pass each other one can be flung away at high speed, something like a slingshot effect. M 98 may very well have done this, and that’s why it’s blueshifted, not redshifted.

As you look to more distant clusters this gets rare or nonexistent, because at that distance the cosmic expansion dominates, and it doesn’t matter how fast the galaxy is moving: It can’t overcome that recession. All galaxies past a certain distance are redshifted, which is yet another reason (among many, many others) that we know the Universe actually is expanding.

That’s pretty cool. I like surprises when I’m reading up on lovely astronomical objects; that means I’ve learned something. M 98 is headed toward us, a rare blueshifted galaxy. Huh. That just adds to its beauty and intrigue to me.

It’s a really beautiful Universe, and it’s also a really interesting one. I’d say that’s its best quality.

Categories: Astronomy Headlines

NASA Sets Sight on Mars. I Just Hope Its Aim Is True.

Mon, 10/17/2016 - 06:00

Last week, President Obama reaffirmed that NASA will put humans on Mars “by the 2030s.” In an editorial on the CNN website, he wrote about an initiative that will help enable it: deep-space crew habitats designed by private companies for the long-duration mission. NASA is pitching in $65 million over the next couple of years for the companies to create prototype modules on the ground that can be used to develop the understanding needed to do the real thing.

My response to this is: OK. Sounds cool.

I know, that’s a bit tepid. But I’ll admit I’m conflicted about all this.

First, let’s clear up a small misconception I’m seeing here and there: NASA has been talking about putting people on Mars for years now, and we’ve known for a while their goal has been sometime in the 2030s. The president’s announcement isn’t really about the date; it’s just letting people know that important steps are being taken.

I’m actually pretty happy about this intermediate step. There are a lot of moving parts to a Mars mission, and a critical one is keeping your astronauts alive and happy during the monthslong voyage. Going to the Moon only takes three days, so a small capsule might be a bit cramped but won’t drive the passengers stir crazy.

On a trip to Mars, which’ll take six months or more, you need something roomier. These habitats have to be big enough to give the crew some elbow room, some space (if you will), but also not be too big to get into space in the first place. One of the companies in the running, Bigelow Aerospace, is looking to make inflatable habitats, for example. That might sound odd, but a lightweight and strong material could be packed into a small space for launch, inflated upon reaching orbit, and provide good protection against radiation and small meteoroids. They’re testing one version on the space station right now.

I love this idea; it’s innovative and could very well be the best way to protect people in space for months at a time. It might be how we go to Mars. But the other companies (like my local Colorado’s Sierra Nevada Corp.) will be working on this as well.

But still … going to Mars relies on the Space Launch System, or SLS, rocket and the Orion crew capsule, and as I’ve written many times, I’m not a fan. They are incredibly expensive, won’t fly often, and have a huge political albatross tied around their necks.

On the other hand, as my space-writing colleague Eric Berger points out, SLS and Orion are almost certainly inevitable. They have baggage, yes, but they’re being built, right now, and should have a first launch test in 2018 (I’m still skeptical on that, but we’ll see; I’m happy to be proven wrong).

On the third hand, though, both SpaceX and Blue Origin have plans to build very large and powerful rockets. SpaceX has had a series of unfortunate events lately, and the Heavy is behind schedule, but I’d lay odds it’ll be flight-tested before the SLS is upright. Blue Origin is taking slower, more methodical steps (its slogan is gradatim ferociter, “step by step, ferociously”), but it also may very well have a huge booster ready to go by the time SLS takes humans into orbit.

I understand NASA’s desire to have a rocket independent of those—and certainly there’s considerable pressure from Congress on them to build one as well—but I still wonder if it makes more sense to focus instead on private rockets than government ones. And the process through which Orion and SLS came to be leaves a bad taste in my mouth.

That may be why my enthusiasm has been somewhat restrained for NASA’s Mars plans. Sure, as Berger states, it may be time to learn to love SLS, as long as NASA is committed to use it wisely. NASA does seem to understand it needs to fund commercial crew heavily as well, so perhaps in time the right balance will be found. If they find a way to not have to spend the $3-4 billion a year currently used for the space station, that’ll free up a lot of funds for other ventures. A NASA official has talked publicly about handing it over to private ventures as early as 2024, the date when the current budget for ISS operations ends, and has already talked about opening up the station to commercial company use.

But there is more. Another issue I have is that NASA hasn’t really been as forthcoming as I’d like on details of how it plans to go to Mars, and what it plans to do after that first mission. I certainly don’t want a “flag and footprints” mission, framed like the Apollo space race. That doesn’t support sustainability, and if we go to Mars, by damn we should go to stay. What I’m hearing does sound more like a long-term plan for many missions, so that’s good. But some more details would be nice.

I’ll note that in his op-ed Obama mentioned the Asteroid Redirect Mission, which will cost a lot of money and has somewhat nebulous goals. I was for it initially—moving a seven meter asteroid into orbit around the Earth or Moon sounds amazing, and will be useful scientifically—but I cooled on it after I found out it’ll cost well over a billion bucks … and that’s only to retrieve it. To send astronauts to it and study it will cost billions more. I’m not convinced it’s worth that kind of money; smaller, robotic missions make more sense to me at this point. I sometimes wonder if ARM was invented just to give SLS and Orion something to do.

And surrounding all of this is the issue of funding. President Obama can make these statements, but Congress has to approve them. I don’t think it’s too much to note that things are about to change in our government. Certainly Obama will be leaving office, and perhaps Hillary Clinton will take over. While she’s stated she plans to sustain SLS, I really don’t know how firm her commitment is to Mars. As for Trump, if he’s president the least of my worries is NASA. Not so incidentally, the face of Congress may change in November as well, and who knows what it will look like in the late 2020s? Incidentally, for an excellent review of this, once again Eric Berger is your guide.

Look: I am all for going to Mars (and, better yet, going to the Moon first). I’d love to see a human boot print on Mars, especially sometime in the next couple of decades. It’s possible Elon Musk and SpaceX will do it first, though his Interplanetary Transport System is big on flash and short on some important details (at least details we’ve seen). He may very well get there first, and I will applaud if he does. As I’ve said before, I wouldn’t bet against him.

But, to be honest, I like to see NASA being the innovator in situations like these. Let them pave the way, and make it easier for others to follow. I’m glad they have the Red Planet in their sights!  I just hope the path they’ve plotted is one that’ll get us there.

Categories: Astronomy Headlines

The Sky Is Filled With Galaxies

Fri, 10/14/2016 - 06:00

A new paper just published in the prestigious Astrophysical Journal makes a stunning claim: There are ten times as many galaxies in the Universe as we previously thought. At least. The total number comes in at about two trillion of them.

Two. Trillion. Galaxies.

Now, let me be clear. This doesn’t meant the Universe is ten times bigger than we thought, or there are ten times as many stars. I’ll explain — I mean, duh, it’s what I do — but to cut to the chase, what they found is that there are lots of teeny, faint galaxies very far away that have gone undetected. So instead of being in a smaller number of big galaxies, stars are divvied up into a bigger number of smaller ones.

What the astronomers did was look at extremely deep images of the Universe taken in surveys, for example the Hubble Ultra Deep Field. Hubble stared at a single point in the sky for nearly a million seconds —that’s over 11 straight days— just seeing what it could see. The result is an image that is staggering in both its beauty and profundity. By counting the galaxies seen in the image, and then extrapolating to the whole sky, you can calculate that there are roughly 100 billion galaxies in the observable Universe.

That’s a lot of galaxies. But wait. It turns out that in this case, there really is more.

Surveys like the UDF are limited. Galaxies that are very faint are hard to see. We know there are small, faint galaxies in the Universe; there are lots of them close to us. Even then many of them are barely detectable because they have so few stars. Remove them to a distance of a few billion light years and they’re faint. Even Hubble can’t see ‘em.

The astronomers who did this research had an interesting problem. If these galaxies are too faint to see, how do you count them?

The answer is two-fold. One is to look out as far as we can to see all the galaxies we can, and then add up all the galaxies we can see in a given volume of space. By carefully observing these galaxies, we can lump them into bins according to size. So, you find at a given distance there are so-and-so many galaxies with a mass of ten billion times the mass of the Sun (the mass of the Sun is referred to as a “solar mass”, and it’s a handy unit) in a given volume. In that same volume there are more galaxies with a billion solar masses, and fewer with 10 billion.

Those numbers change with distance. When we look at galaxies really far away, we see them as they were when they were younger, because it takes a long time for their light to reach us. Galaxies really got started forming a few hundred million years after the Universe itself formed, but most were small. Over time they merged together to form bigger galaxies like ours (the Milky Way). So you need to carefully count up all the galaxies in a given volume of space at a certain distance from us, and then do that again for a region of space farther away, and so on.

At the same time, these faint galaxies are easier to see close to us, and harder farther away. So to get an idea of the number when we can’t actually see them, the researchers looked at individual galaxies nearby and figured out what kinds of stars they’re expected to have in them. Most have a few really bright, massive stars, and lots of smaller, fainter ones. The ratio tells you how bright a given galaxy is.

They calculated this for all kinds of galaxies, right down to really small ones with about a million times the mass of the Sun. Galaxies don’t get much smaller than this; objects with lower masses are more like clusters of stars in bigger galaxies, not galaxies themselves.

They can then combine these two pieces of information: How many faint galaxies there are near us and how bright they are, with how many galaxies of a given mass are in a volume of space. When they did that, they could extrapolate to figure out how many really faint galaxies there are at the most distant reaches of space, up to a distance of over 13 billion light years. When the light from those galaxies left on their journey to us, the Universe itself was only about 650 million years old!

And that’s how they found that there are at least two trillion galaxies in the Universe.

Mind you, just because we don’t see 90 percent of the galaxies in the Universe doesn’t mean this explains dark matter or anything like that. We know that’s not made of any kind of normal matter like the stuff that makes up stars, planets, you, and me. These unseen galaxies are extremely far away, and made of stars and gas and dust just like galaxies here are. It’s just that they’re faint.

And it doesn’t mean the Universe has 10 times more mass than we thought. The mass is the same, it’s just distributed differently than we thought. It’s like knowing there are a million people in a city, and finding out they live in 100,000 buildings when you thought they were only in 10,000. There are more buildings, but not more people.

As the authors themselves say,

The total number of galaxies in the universe is an interesting scientific question, although it may not reveal anything fundamental about the cosmology or underlying physics of the universe.

So yeah, this is cool, but not necessarily critical knowledge.

But it does say some pretty interesting things. It means that we should expect to find a helluva lot more galaxies when we take deeper surveys, perhaps with observatories like the James Webb Space Telescope, which should launch in 2018. And it lends a lot of support to the idea that small galaxies formed first in the Universe, and grew large as they ate each other. We kinda knew this already, but it’s nice to see independent evidence of it.

And yes, even I have to admit that in the end it’s still just cool. Two trillion galaxies is a lot.

A whole lot. A Universe worth.

Oh, there is another thing, and this one is the coolest of them all. Because we now know how many galaxies there are, how they’re distributed throughout the Universe, and roughly how big they are physically, it’s possible to calculate how much of the sky is covered in galaxies. Think of it this way: If you’re in a very thinly populated copse of trees, you can look around and see things outside the copse; buildings and such in the distance. But if you’re deep within a forest of trees, everywhere you look you see trees.

So the researchers did this, and they found an astonishing thing: Given all the numbers they calculated, it looks very much that every single part of the sky is covered at least in part by a galaxy!

Do you see what this means? No matter where you look — up, down, left, right — and no matter how much you magnify the view through a telescope, at some point wherever you’re looking there’s a galaxy. It might be close by, or more likely crushingly far away, but it’s out there.

The sky is literally covered in galaxies.

How about that? It gives me a chill just to write that. Wow.

But when I read things like this — once the scientific wonder sinks in — I am always struck by a much deeper and far more wonderful notion: That we can know these things! We look up and we think about what we see, and we use math and science and engineering and we count the very essence of the Universe itself.

We are a part of the Universe, we are driven to understand it and ourselves, and that makes us mighty.

Categories: Astronomy Headlines

Earthrise, From the Moon

Thu, 10/13/2016 - 06:00

If you go outside over the next few nights shortly after sunset and look east, you’ll see the waxing gibbous Moon rising. In the twilight you can see quite a few details on its surface with your naked eye. For example, most obvious are dark “seas”—actually called maria, gigantic impact sites that filled with dark basaltic lava.

But looking through Earth’s atmosphere limits our view of the Moon, causing the view to boil and waver. Even our largest telescopes can’t see features much smaller than 100 meters or so across.

And that’s why we send probes there: to see our nearest neighbor even nearer, and plumb its secrets from up close. In September 2007 the Japanese space agency JAXA sent the SELENE probe to the Moon. Nicknamed Kaguya, it took high-resolution images as it circled the Moon in a polar orbit. Twice a year, the orbit of the spacecraft lined up in such a way that it could see the Earth itself rising above the horizon. It took images so rapidly that a movie could be made from them. JAXA just released a huge set of that data, which contained enough images to make such a movie.

So photographer Nicolaus Wegner did just that. The result? Sheer, gorgeous art.

Holy. WOW.

Wegner touched up the imagery a bit, speeding up the frame rate and doing some color balancing. But for the most part what you’re seeing here is what the spacecraft itself saw as it orbited the Moon.

And it’s so beautiful! The lunar surface is so rugged and barren, yet capable of astonishment. There’s so much of it! I didn’t recognize any features until the Tsiolkovsky crater swung in to view at the 1:14 mark, its floor covered in dark basalt like the maria.

But for all the beauty, it’s the Earth that captures our imagination in these views. It’s far brighter than the Moon, reflecting four or more times as much sunlight as the Moon’s surface. And the color … while the Moon is dull and gray, the Earth positively radiates blue and white. My heart aches seeing how familiar it looks over that unfamiliar rocky moonscape.

… but then the end of the video shows the crescent Earth setting and rising, with the glare of the Sun swamping the scene, flooding it with light. That thin crescent may be home, but its phase reminds us that it’s a planet, a world floating in space just like countless others.

There a great many benefits to exploring space, have no doubt. But perhaps the most important, the one reason we must do it, is that it maintains our perspective. It forces us to see our planet and ourselves from literally a different angle, and shows us just how small we are, and how great we can be.

Categories: Astronomy Headlines

S Marks the Spot of a Planet Being Born Around Another Star

Wed, 10/12/2016 - 06:00

About 450 light-years from the Sun, in the constellation of Ophiuchus (yes, that Ophiuchus), lies a young star. If it were off by itself somewhere it would be an unremarkable star, a red dwarf roughly half the mass of the Sun. The galaxy is lousy with them.

But it’s not by itself. It’s sitting in a vast dense cloud of gas and dust sometimes called the Ophiuchus star-forming region. Stars are being born in this huge nebula, and Elias 2-27, as the star is called, is one of them. Stars form as pieces of the cloud collapse under their own gravity (generally instigated by some sort of event that disturbs the cloud like a nearby supernova or a collision with another cloud).

A clump of material shrinks, and flattens into a disk (I describe this in Crash Course Astronomy: Intro to the Solar System; start at time 5:36). The star forms in the center, and out from the center clumps of material form, stick together, grow, and become planets. Sometimes the gravity of a planet can attract enough material from around it that it carves a gap in the disk, similar to the gaps in Saturn’s rings.

Theoretically, a planet forming can cause spiral patterns in the disk, like the spiral arms of a galaxy. One has never been directly seen in a protoplanetary disk, but there have been hints.

That’s changed now. Using the Atacama Large Millimeter/submillimeter Array, or ALMA, which observes light with much longer wavelengths than our human eyes can see, just such a spiral has finally been detected directly. Elias 2-27 has a beauty, too.

The star itself is buried by dust in the center, too enshrouded to be seen (actually, the dust in the Ophiuchus cloud blocks all the visible light coming from the star and the disk; the submillimeter wavelength light can penetrate that junk and be picked up by ALMA). Just outside that is a classical flat disk, seen as the yellowish ellipse in the center (it’s probably close to circular in real shape, but we see it at an angle). Outside that is a dark gap, which is exactly what you’d expect from a forming planet. The planet itself isn’t visible.

The spiral starts just outside the gap, and the arms extend to about 10 billion kilometers from the star (Neptune orbits the Sun about five billion kilometers out, for reference). This sort of structure is called a density wave pattern; it’s not really a physical structure, it’s regions where the gravity of the disk sets up conditions that particles are denser there. So the spiral arms don’t wind up!

It’s more like a traffic jam. Cars can enter the jam from behind, stay it a while, then move out the front. The jam persists, even as the individual cars move in and out of it; I describe this as well in Crash Course Astronomy: The Milky Way (start at 4:58).

This is just what you’d expect from a planet in that gap; the gravity disturbs the disk, and the density wave pattern arises naturally from there. Given that the arms start there, I’d bet cold cash there really is a planet or other massive object in or very near that gap.

While this structure has been expected to exist in these star- and planet-forming disks, none has ever been seen before, and this shot is so clear! It’s wonderful. ALMA has been a powerful tool for astronomers, peering deep inside clouds, at galaxies, at material surrounding black holes, at objects in the distant solar system, at dying stars (yeah, click that; the image is amazing), and at quite a few forming stars.

The equipment available to astronomers today is nothing short of stunning. We are looking farther and better into the Universe than we ever have before, and what we’re finding is remarkable. Understand: When we look at objects like Elias 2-27, we’re seeing what the Sun may have looked like 4.6 billion years ago!

It’s easy to think of astronomy as looking outward, away from ourselves. But it’s the opposite; the more we look out, the more we see in.

Categories: Astronomy Headlines

Time's Arrow Explained by Minute Physics

Tue, 10/11/2016 - 06:00

Why does time flow from the past to the future?

That’s an extraordinarily deceptively simple question. It seems so, well, straightforward. But when you start to really investigate it, you wind up going down a rabbit hole of twisty, complicated physics.

When I first started reading about this, I was surprised to learn that it’s tied to entropy. That’s a concept in physics that has a lot of different ways to think about it, but the most common colloquially is to say it’s the degree of disorder in a system. The pieces in a completed jigsaw puzzle are highly ordered, but those same pieces when you first open the box are highly disordered. So the latter has higher entropy.

What does this have to do with time? My friend Sean Carroll —a cosmologist who spends his time thinking about, um, time— and Henry Reich, who draws Minute Physics, collaborated on a series of videos explaining this. As I write this article the first two are out, and they’re intriguing. Here’s the first one:

And here’s the second:

I can’t wait to see the rest! They’ll be out soon. In the meantime, Sean has books on this topic: From Eternity to Here, which is excellent, and The Big Picture, which I am currently reading right now. It’s also very, very good.

I’ve always struggled with the concept of things like entropy, time, and Boltzmann Brains. Talking with Sean has helped, but reading his books and watching those videos will go a long way, too. It’s amazing to me, as he explains in the video, that the second law of thermodynamics is the only (or one of the only) basic macroscopic physics equations that has time in it explicitly as moving from past to future. Why? Entropy.

It’s like dealing out a hand of five playing cards. There are roughly 2.6 million different hands you could get this way. But only a handful of them have what we would think of as value. A straight, for example, or a flush. If you get 2 3 4 5 6 of hearts, that’s a straight flush, and is extremely ordered. That means it has very low entropy.

Another hand, like 3 6 8 J K, with different suits, is not ordered at all. It has high entropy. Those high entropy, unordered hands are far more common than low entropy, ordered hands. That’s why we value the latter. The odds of getting a straight flush in five card stud are about 1 in 72,000, but 50 percent of the time you won’t even get a pair.

So if you shuffle the cards and deal them, you are far more likely to get a disordered high-entropy hand than an ordered, low-entropy one. That’s why they call it gambling.

Another way to look at it is to imagine a container full of gas. On the molecular level, the molecules of gas are distributed more or less randomly. If you swap two molecules with each other the gas looks pretty much the same, and that’s also true if you move a molecule a little bit, say, to the left or right. The number of different ways you could swap or move molecules without changing the nature of the gas is immense, which means it’s incredibly high entropy. If you cool the gas so much it becomes a liquid, or a solid, there are far fewer states each molecule can occupy, so the entropy, the state of disorder, is lower.

If you sit around and watch that gas for a bazillion years, chances are it will always look pretty much the same, even as the molecules move around. The chance of them suddenly liquifying, or all moving to the left side of the container, is extremely small. High entropy states are hugely more likely than low ones. And if you find yourself in a low-entropy state, after a moment the odds are you’ll be back in some high-entropy one.

That’s what Sean and Henry are outlining in those videos. We’re in a relatively low entropy Universe right now. We see it expanding, we see stars dying, we know eventually matter and energy will be more randomly distributed. We’re moving toward a higher entropy Universe, which strongly implies that it was lower entropy in the past. That’s the Big Bang.

Eventually, the Universe will become so disordered that entropy will be maximized. At that point, time has little or no meaning. After all, if you move stuff around and it looks exactly the same, how do you measure time? Time is a measure of the change in events. If everything is the same, time has nothing to measure.

Mind you, I’m still exploring all these concepts, and I’m no expert. But maybe, after watching those videos and reading this, you’l get a taste of just how deep this runs. It goes straight to the heart of our most basic philosophies, of some of the biggest questions we can ask. Why is there something rather than nothing? Why is that something —the Universe itself— the way it is, and not some different way? Why does time exist, and why does it flow into the future? Why don’t we remember the future and predict the past?

These are heady questions, and I’m thankful that there are people like Sean trying to figure them out, and people like Henry helping the rest of us come along for the ride. It’ll be interesting to see where this goes. Or where it went. Either way.

Categories: Astronomy Headlines

Would You Vote for Someone Who Thinks the Earth Is Flat?

Mon, 10/10/2016 - 06:00

Think about this for a moment: Would you vote for someone running for Congress —or to be President of the United States— who thought the Earth was flat?

And I don’t mean someone who’s just flirting with the idea, but someone who really, truly believes the Earth is a flat disk floating in space. Someone who refuses to accept any and all scientific evidence to the contrary no matter how obvious, someone who is proud of their belief, who campaigns on it, who actually holds hearings about it, condemning scientists and even threatening their careers because those scientists say the Earth is round. What would such a person do with legislative power over, say, NASA?

Can you imagine yourself voting for them?

Now imagine casting your ballot for a climate change denier. Someone like Lamar Smith (R-Texas) —who currently is the Chair of the House Committee on Science, Space, and Technology— or James Inhofe (R-Oklahoma), Donald Trump, Mike Pence, or practically every single sitting Congressperson with an R for their political affiliation (although there is hope some bipartisan work an be done).

At this point in our understanding, I see very little difference between denying climate change versus someone who thinks the Earth is flat, or that the Moon landings were faked. All these people deny the overwhelming evidence and substitute their own fevered imaginations and biases for reality.

There will always be people like that, of course. Denialism will never die. But that doesn’t mean we have to give them power over us.

Many climate scientists feel the same way. Michael Mann and Stefan Rahmstorf, for example,  were interviewed for a video by Earth101 called “How Dead Is Denial?”, and they cut right to the chase:

I agree with Dr. Mann; there will always be people who will deny reality even when they’re standing chained to the railroad tracks with a train ten meters away and bearing down on them at full speed. Especially for those who receive a whole lot of funding to stick their fingers in their ears and yell “LALALALALALALA” at the top of their lungs.

And when it comes to climate change, we’re chained on the tracks with them. We’ve been trying for years to get them to take their fingers out of their ears and open their eyes, and it’s long past time to admit this isn’t working. They refuse no matter what we do.

We need to cut ourselves free of them, and replace them with people who understand that we need to step off this track.

Vote. For yourself, for everyone you know, for future generations: Vote. If we want to stop the train, the first thing we must do is elect politicians who at the very least understand that  it’s real, and that the danger we face is very real as well.

Tip o’ the voting booth lever to Michael Mann.

Categories: Astronomy Headlines

Deep Sky Colors: A Gorgeous Astrophotography Book

Sat, 10/08/2016 - 06:00

I don’t plug stuff much on the blog for a lot of reasons, but one is that I only want to endorse things I truly, actually like. If I just shill for a bunch of stuff there’s not much reason to trust me, but if I save it for the really special stuff, well then, you’ll know it’s special.

This is special.

Rogelio Bernal Andreo’s book, Deep Sky Colors, is a ridiculously stunning collection of his astrophotographs. Andreo’s work is simply phenomenal, and basically you should just go and buy both that book and his other, Hawai’i Nights, because your brain will love you for it. Both are available on his website. You can even grab a free PDF of Hawai'i Nights, too.

When he asked me to write the foreword for Deep Sky Colors, I didn’t even hesitate. It was an easy decision, and easy to write: His photos have had quite the effect on me.

With his permission, I am posting what I wrote for the foreword. I’ll leave you with it, and with this: The holidays are coming. Wouldn’t it be nice to have at least some of the shopping done this soon?

I remember when I first saw one of Rogelio Bernal Andreo’s photographs. It was in 2010. I don’t remember how I found him; probably someone sent me a link to his work. I write a lot about the beauty and majesty of the skies, and love to feature the work of so-called “amateur” astronomers, many of whom have a dedication to the sky and the talent to photograph it unsurpassed by anyone. Over the years, the hardest part of writing about these photos is simply picking them; there are so many accomplished astrophotographers out there, and it gets to the point where I only want to feature something unusual — an odd framing of a familiar object, some deep sky galaxy usually unseen, or a balance of filters and exposures not generally used. So I probably “ho-hummed” to myself as I clicked the link to Rogelio’s mosaic of Orion; after all, who hasn’t seen a million photos of this constellation? When his photo came up on my screen, I may have choked on my morning coffee. It’s magnificent. And truly unique, showing a depth and beauty I had literally never seen before; the nebulosity strewn across the constellation sharp and colorful, every color balanced, the stars spread like jewels on polychrome velvet. It was, quite simply, the most beautiful astrophotograph I had ever seen. That’s why I chose it as the Number 1 photo of 2010 on my blog. It really is that amazing. In the time since then Rogelio has been kind enough to let me use his photos on my blog and in educational videos as well. They’ve improved my own work hugely. It’s surprising to me that a good, deep photo of the Virgo Cluster of galaxies is difficult to find online. When we needed one for the Crash Course Astronomy video series I turned to Rogelio, and sure enough he had the exact, perfect shot for it. He graciously allowed us to use several more as well, and the series was the better for it. The ridiculously beautiful book that follows these words is a showcase of Rogelio’s work, and is a powerful reminder of how much beauty exists in the world and above it. It takes a sharp eye and imaginative brain to be able to display it as he does, and we get to enjoy all his hard work. If there is a match made in heaven — or in the heavens — it’s Rogelio and the night sky. The photos in this book will prove it.
Categories: Astronomy Headlines

As Hurricane Matthew Hits Florida, What Will It Do To NASA?

Fri, 10/07/2016 - 06:00

Hurricane Matthew is a monster. It went from a run of the mill tropical depression to a full blown hurricane in less than a day, strengthening explosively as it drew energy from deep, warm waters. It passed over Haiti, doing vast damage and killing over 300 people, and now its sights are set on the east coast of Florida and points north.

I will not downplay this storm. With top wind speeds of over 220 kph (140 mph) the damage it can do is not to be underestimated. Its path along the coast is guaranteed to do a lot of hurt.

Beside the obvious worries, I’ve seen a lot of questions and speculation on social media about what the hurricane might do to NASA’s Kennedy Space Center and launch facilities; while they aren’t on the direct path of the hurricane eye, it’ll pass close. As Eric Berger points out at Ars Technica, most of the buildings there are built to withstand hurricane winds over 160 kph, and some more. But Matthew has winds exceeding this, so it may very well damage the center.

The facility has been evacuated, with only a very thin skeleton crew on hand to ride it out. Mind you, several launch pads could be damaged as well. The working SpaceX pad was already damaged when a Falcon 9 rocket exploded while fueling in September. It’s unclear what the hurricane could add to it. I’ll note it’s safe to assume that all rockets and other equipment at the center have been secured.

As hard as it is, we’ll just have to wait and see what this thing does. Having lived through a few hurricanes, I’ll say it can be terrifying. I hope everyone reading this in that area stays safe, and that our nation’s space assets are safe as well.

As an aside, I’ll note that this hurricane seems to have the fingerprints of global warming all over it. As climatologist Michael Mann notes the deeper layer of warm water fueling it is a product of extra warming going into the ocean, and there has been a trend of the most powerful recent storms getting stronger. I worry that as powerful as this hurricane is, we will probably see more like it in the coming years.

For more information, I recommend keeping an eye on Weather Underground, which is an excellent source of information. And again, folks: Be safe.

N.B. Before anyone accuses me of politicizing a tragedy, let me note that science is not in itself a political thing, but it certainly can be a pawn to it. Also note that it already has been politicized by the usual right-wing deniers like Matt Drudge and Rush Limbaugh, who, even for them, have stooped unusually low, including possibly putting lives at risk. My main concern now is with the immediate threat and the safety of people, property, and ecosystems; there will be time later to go into more depth about the causes of this storm.

Read more Slate coverage of Hurricane Matthew.

Categories: Astronomy Headlines

Blue Origin Tests Its Rocket Escape System in a VERY Dramatic Way

Thu, 10/06/2016 - 06:00

On Wednesday, Blue Origin had a helluva day.

After a handful of short holds, the company’s New Shepard rocket lifted off for the fifth time from the Texas desert proving grounds, heading up into space. Like the previous four test flights, this was to be a short suborbital hop: Straight up, pass the 100 kilometer line that demarcates the arbitrary but agreed-upon border of space, then back down to land vertically again.

But even for this rocket, this was no ordinary flight.

As I wrote earlier in September, this test flight had pretty good odds of being the last time we’d see this five-time booster intact. The reason was that the crew capsule’s emergency abort rocket was to be tested in flight. Roughly 45 seconds in, when New Shepard was undergoing maximum pressure as it rammed through Earth’s atmosphere, the powerful rocket motors along the bottom of the crew capsule would ignite, blasting it away from the booster underneath. This abort system is set up in case there’s a problem during the flight, and the crew needs to get away fast.

It was expected that this escape procedure might destroy the booster, kicking it sideways or otherwise putting huge stress on it. Full of fuel and off-balance, it might have exploded or fallen to the ground to explode there.

Instead, everything went pretty much perfectly. And it’s still incredibly dramatic! Watch (start at the 51:18 mark):

Holy wow! At T+45 seconds, the rockets kick in and the crew capsule roars away. Amazingly, the booster hardly even notices; it just keeps on thrusting up, up, and away. The crew capsule had a bit of a wild ride, oscillating almost upside down at one point after the rockets under it quit, but soon enough the drogue ’chutes popped out and it stabilized, and then the main ’chutes opened to give it a smooth ride down to the ground.

Then, amazingly, the booster comes back and lands on its tail like it was no big deal at all! That was stunning to watch.

It’s hard to overemphasize how important this was. For one thing, no other rocket on Earth has been launched into space and landed on its tail five times like this one. For another, there hasn’t been an emergency escape sequence like this tested since the Apollo days in the 1960s! For a third, this shows that Blue Origin can have an emergency escape and retrieve both parts of the rocket safely.

Altogether, that’s a pretty big deal. Blue Origin just showed the world that it can make big plans and execute them. I’ll note that until very recently they were very secretive about their work and even their launches, not releasing information until after the tests were done. Their holding live webcasts now shows just how confident they are on their path.

And their path is big. I wrote about Elon Musk and SpaceX’s plans to go to Mars just last week. But not long before that, Jeff Bezos released Blue Origin’s plans to build much bigger rockets. Their New Glenn rocket will be quite capable of achieving orbit. Note the names of the rockets: Alan Shepard was the first American in space, on a suborbital flight. John Glenn was the first American to orbit the Earth.

Bezos also said the next line of rockets after New Glenn will be the New Armstrong. I wonder what his plans are for that …?

Blue Origin is creating a new rocket engine, the BE-4, which is very powerful. Seven of these will power New Glenn, which will make it a rival of SpaceX’s Falcon Heavy. Both companies have plans for bigger and more powerful rockets yet. Both have their sights set on getting out of Earth orbit, and into interplanetary space.

I’ve said this before, and I’ll say it again now: People say it’s a curse to live in exciting times. Those people are wrong.

Congratulations to the folks at Blue Origin! As you say: Gradatim Ferociter!

Categories: Astronomy Headlines

Arctic Ice Reaches Second Lowest Extent on Record

Wed, 10/05/2016 - 06:00

Some records are best not broken. Especially when it’s the record for least amount of Arctic ice remaining after a summer of melting.

So it’s good that 2016 did not break that record. But when you look more carefully, you’ll find that’s hardly a relief.

The Earth’s boreal ice cap melts every summer as our planet’s north pole tips toward the Sun in spring. The days get longer, the Sun gets higher, and the increased warmth melts the ice. This is a natural cycle and has been going on for a long time. In general, September of every year is when the ice reaches lowest amount.

This year, 2016, the ice reached its lowest extent* on Sep. 10. On that day, it had an extent of 4.14 million square kilometers, or about half the area of the contiguous United States. That’s very low. So low, in fact that it’s the second lowest extent ever measured, in a dead tie with 2007.

The all-time record low measured extent was in 2012, which was 3.41 million square km. But there are a couple of important things to note here.

One is that 2012 was very unusual. A dam made of ice in northern Canada broke, allowing warm water to mix with the Arctic ice, melting the ice far more than usual. That, at least in part, is what led to the record low extent of that year.

2016 had no such anomaly that is known. In other words, we just hit the second lowest amount of ice ever seen, and nothing unusual caused it.

Well, unless you don’t count fierce global warming as unusual. Sadly, it is the new normal.

The other thing to note is that all these records have occurred very recently. That too is because our planet is heating up. Every year we get just a bit hotter, and more records fall (in fact, as you’d expect, far more high temperature records are broken than lows). The record in 2012 has stood because it was caused by global warming plus more rare events like the ice dam breaking. But every year we get a bit hotter, and soon we won’t need those unusual events to break 2012’s record.

So I don’t expect 2012 to hold on to its status much longer. Arctic ice is in a death spiral, and it won’t be long (even on a human timescale) before we get an ice-free summer. Most predictions put that event in the mid-2040s. Even now, enough ice melts every summer to allow ships to ply the Northwest Passage.

Mind you, the Arctic still did break a record this year: It had the lowest maximum extent back in March. Every year in winter the the water freezes, reaching its maximum area in early spring. When you compare the area at maximum extent over the years, that’s dropping too.

Not only that, but as Tamino points out at the blog Open Mind, 2016 is on its way to having the lowest average annual extent ever measured as well. Having the smallest maximum and near-record minimum makes that one pretty easy to understand.

This is all important because the difference in temperature between the poles and the equator drives much of Earth’s weather patterns. Warm water from the equator flows toward the poles, cools, sinks down into the oceans, then flows back to the equator to start the cycle again. This conveyor belt of heat is thought to help power the jet stream. As the poles warm, the difference in temperature across the latitudes shrinks. This weakens the jet stream, letting cold air from the Arctic drop down, bringing those “polar vortices” and their frigid temperatures into the US.

So yes, you can get colder weather with more global warming. An ice-free Arctic means a lot more than just easy passage across the northern Canadian ocean. It means a destabilization of the delicate balance of our water, atmosphere, and land, disrupting everything.

As I now point out every time I write an article like this, not all is lost. But we cannot do anything until we get politicians to at the very least recognize the danger we are in. Too many do not, flatly denying the science acknowledged and understood by the vast majority of climatologists.

The first step we need to take is vote those people out. Your voice matters. Vote.

* “Extent” is technical term that is more or less equal to the area covered by ice; scientists divide the Arctic into bins, and a given bin is said to have ice if more than 15 percent of it is frozen.

Categories: Astronomy Headlines

How Big Can a Black Hole Get?

Tue, 10/04/2016 - 06:00

Black holes are everywhere in the Universe. A typical galaxy might have millions of stellar-mass black holes, ones created when a massive star explodes (this is usually the kind you think of when you think “black hole”).

But some black holes are true monsters, with millions or even billions of times the Sun’s mass. We think that every large galaxy has one of these supermassive black holes in its core. Study after study has shown that these black holes have a symbiotic relationship with their host galaxies, too, growing along with them as each formed billions of years ago.

We know galaxies can get pretty big. It has to make you wonder: How big can these black holes get?

It’s a good question, and surprisingly hard to answer. Although there are a number of ways to “weigh” a black hole (really, measure its mass), but given the sheer number of galaxies out there these methods can be hard to implement on a large scale (I almost wrote “mass produced basis” but figured that’s pushing the pun too much). Despite that, we've found a few really big ones, and that can help us figure out what the upper limit to their size might be.

Now mind you, theoretically there isn’t an upper limit to them. You could, if you had godlike powers, collect every single bit of matter in the Universe, cram it into one spot, and have a truly and literally cosmic black hole with a sextillion times the Sun’s mass. More or less.

But realistically, that’s not possible. Matter is distributed throughout the Universe in the form of stars, gas, dark matter, and so on. The biggest black holes that actually exist today would probably need to be born big, and then grow over time. So the more practical question is, what’s the biggest black hole practically possible right now?

Some astronomers looked into this, and found what may be the answer: The most massive black holes likely to exist in the Universe today are about 10 billion times the mass of the Sun.

That’s still pretty dang massive. The supermassive black hole in the center of the Milky Way, our home galaxy, is around 4 million solar masses, so these monsters (called ultramassive black holes, or UMBHs) could be more than 2,000 times more massive!

How can such beasts exist?

To answer that, the astronomers looked at how black holes form in the first place, and how they could grow. In the early Universe, when it was less than a billion or so years old, things were different. Galaxies were in their earliest stages of formation, and the Universe was mostly gas and dark matter. The dark matter was distributed along huge filaments, and its gravity pulled normal matter toward it. These were the early structures, the scaffolding, upon which galaxies would form.

… and big black holes, too. Under these conditions, there are two ways supermassive black holes could’ve formed. The first is that the gas collected into huge stars, far larger than can exist today, with more than 100 or possibly even 1,000 times the mass of the Sun. These stars can’t exist today; the presence of heavy elements makes the stars too hot, and anything more than 100 or so times the Sun’s mass gets so energetic it would tear itself apart. But in the early Universe those heavy elements weren’t created yet (they form inside massive stars, as it happens), and all that was around was hydrogen, helium, and a smidgen of lithium. These primordial stars would’ve lived very short lives, blown up, and then formed huge black holes when their cores collapsed. Over time, these first black holes would draw in matter around then, growing huge.

The second way huge early black holes could form was using dark matter as a funnel. Those huge filaments of dark matter would channel normal matter down into tight knots of material. The flow could’ve been so fast that there simply wasn’t time to form a star first; instead the matter collapsed directly into a black hole. In this sense, the black holes were formed from “seeds”; a black hole was born and then grew rapidly.

Both scenarios—stars and seeds—are physically possible, and can produce a black hole with a billion times the Sun’s mass in a billion years after the Big Bang.

But that’s just the start. To get as big as we see them today, they have to grow. They can do that by simply eating more material (the dark matter that fed them initially can help there). But remember, not long after they were born these black holes had galaxies growing around them. Given longer timescales, galaxies can collide and merge. When they do, the black holes in their centers can merge as well. In clusters of galaxies, there can be thousands of galaxies all bound together by their gravity. Given reasonable growth rates, the theoretical models predict black holes can grow to 10 billion times the mass of the Sun over the age of the Universe.

And that’s how we could get ultramassive black holes today. Still, that’s theory. What about observations?

To check these numbers, the astronomers in the new study compared what they expect to see today versus what’s actually observed in galaxies. How do you measure a black hole? Indirectly: As black holes feed on matter, the material forms a swirling disk around it. This gets very hot, and glows. If the temperature reaches millions of degrees (which, terrifyingly, it can and does) it will emit X-rays, and those can be seen out to huge distances.

We see lots of these “active galaxies” in the early Universe, and they were pouring out X-rays, meaning their central black holes were feeding voraciously. During that time they were very efficient at gaining mass, and could grow huge. But how huge? And how many huge ones do we expect to see today?

There have been surveys of black holes in galaxies taken, and, for example, one of them found a handful of UMBHs out of the thousands of galaxies they looked at. It turns out that’s a problem: Assuming that brighter galaxies means more big black holes, the astronomers doing the new study predicted there should be thousands.

Obviously, something was wrong. They think that their assumption that you can simply extrapolate brightness to black hole growth doesn’t work on the high end. One explanation is that we know black holes are sloppy eaters. The tremendous amount of light the disk emits can blow a vast wind of particles outward, and that can choke off the flow of matter inward. If black holes try to eat too fast, their food dries up!

When they accounted for that, the astronomers found their numbers aligning better with observations. Interestingly, those observations indicate that the most massive black holes we see today really are about 10 billion solar masses, about what the models predicted.

How many of them do we see? Running the numbers, they predict there should be one UMBH in a volume of space encompassing 3x1026 cubic light years: a cube about 700 million light-years across one side.

That’s a ridiculously staggeringly huge volume of space, which means there aren’t too many of these monsters. There are roughly a million galaxies within this distance of us, and odds are only one has a UMBH in it.

Still, we should see a few of these monsters if we probe the Universe more deeply. That work is being done now, looking at the biggest and brightest galaxies we can, and no doubt will continue for a long time. Investigating the biggest black holes in the cosmos is enduring work. There are a lot of them to find, and they’re probably really far away.

And it’s important work, too. If the Universe limits the sizes of things, then there’s a reason for it. Maybe there wasn’t time for black holes to grow any bigger. Maybe their overall growth rate is limited. Maybe bigger ones exist and they’re so rare we haven’t seen them yet.

All of these facts tell us about the conditions in the early Universe, and how it’s changed since then to today. And all of that plays its role in the bigger picture of science itself: trying to understand how we got here, and why the Universe is the way it is. I find it positively enthralling that we can ponder and attempt to solve such problems.

And being able to think of the biggest black holes in the Universe as puzzle pieces in this bigger picture is pretty cool, too.

Oh, one final note: These UMBHs are the size they are now because the Universe is only about 14 billion years old. But time goes on, and over the next few trillion, quadrillion, and octillion years—even more—eventually these black holes will consume most everything in their galaxies, and grow huger still. They’ll outlast the stars, and possibly even matter itself! In a future so distant the numbers are almost meaningless, they will be the only large objects in the entire cosmos … and even they will eventually die. I talk about this in Crash Course Astronomy: Deep Time. If there’s a life lesson in there, feel free to ponder it.

Tip o’ the accretion disk to Randall Munroe, who mentioned this study in a What if? comic about, of all things, fireflies.

Categories: Astronomy Headlines