Bad Astronomy Blog
On July 5, 2016, at 03:18 UTC (July 4 at 11:18 p.m. Eastern US time), the Juno spacecraft will ignite its main engine. It will burn for 35 minutes, and when it’s done the spacecraft will be doing something a NASA mission hasn’t done in many years: It will be orbiting mighty Jupiter, the biggest planet in the solar system.
Oh my, yes, this is a big deal.
Juno’s mission is to investigate Jupiter, observing its dynamic atmosphere to determine its composition, temperature, and cloud structure. It will measure Jupiter’s ridiculously powerful magnetic and gravitational fields, and reveal what the interior of the giant planet is like. The overarching goal: Find out how Jupiter formed, and how it’s changed in the billions of years since then.
It’ll do this with a fleet of scientific instruments, including particle detectors, a magnetometer, cameras, and many others (SpaceFlight 101 has a great overview of all of them). One instrument, JunoCam, is designed to take color pictures of Jupiter, including its poles, which have never been seen before from above. I was amazed to find out that when Juno is closest to Jupiter (called perijove), JunoCam will have a resolution of 15 kilometers per pixel! Mind you, Jupiter is a staggering 140,000 km across, so we’re talking very high detail shots. We’ll get stunning views of Jupiter’s atmosphere and, hopefully, its aurorae. Emily Lakdawalla has a great write-up of JunoCam on her blog at The Planetary Society.
Before you ask, no, it won’t be getting any pictures of Jupiter’s moons to my knowledge. They’re not the focus of the mission, and besides they’re small and will be far away, so they wouldn’t look like much anyway.
This is an ambitious mission, made even more difficult by Jupiter’s radiation belt. Jupiter has an incredibly powerful magnetic field, and that’s trapped subatomic particles from the solar wind and emitted from its moon Io. These particles are accelerated to high energy and can damage spacecraft components. Juno’s hardware is hardened against this, but even so it limits the lifetime of the mission. The design is to last for 36 orbits of Jupiter; after that it is planned to do a deorbit burn and fall into the planet itself in 2018.
We’ve sent spacecraft to Jupiter many times, but with one exception they’ve all been flybys, brief but amazing. The exception was Galileo, which orbited Jupiter but suffered a hardware problem with its main antenna that prevented rapid downloading of its data, limiting the goals of the mission. It still worked, and did amazing science, though.
Another pretty cool thing is that the Juno spacecraft is powered by solar panels, which is something that until recently hadn’t been possible for outer planets. Sunlight is weaker out there, and it wasn’t until this mission that solar panels were efficient enough to power a spacecraft; on top of that the instruments are also very efficient with their power, allowing lower energy generation needs.
But why believe me? Here’s my pal Bill Nye to explain it:
I’ll be watching the Jupiter Orbital Insertion on July 4/5 live, and tweeting it. Emily Lakdawalla will as well, and she has a timeline of insertion events on her blog worth keeping bookmarked, too.
It’s been a while since we’ve seen Jupiter up close. This should really be amazing.
Part of the problem with being a vocal advocate for critical thinking is deciding just which facet of nonsense to spend time fighting. The forces of anti-reality present a huge number of fronts, making triage a necessity.
As an astronomer I of course have certain pet projects; I’ve taken on astrology, Moon landing deniers, cosmic doomsday promulgators, and Geocentrists. But a background in science allows me to broaden that approach, and I will happily help shoulder the load to debunk the claims of climate change deniers, anti-vaxxers, homeopaths, and young-Earth creationists.
Some of these present a more pressing need than others, of course. Astrology is a minor issue compared to, say, someone who supports abstinence-only education.
But they’re all there, all the time, creating a background buzz of hogwash, an atmosphere of denial of science, evidence, and rational thinking… and that can have devastating consequences.
We are awash in that miasma, where people can say almost anything, no matter how ridiculous, and not be confronted, not be challenged. Many of these purveyors of poppycock wind up surrounding themselves with throngs of people willing and eager to suspend their disbelief and support the foolishness. Cults certainly can form in such an atmosphere… and when the person spouting the nonsense is a politician, that’s when things get very sticky indeed.
And now here we are, with Donald Trump the nearly inevitable champion of the Republican Party.
This is no coincidence. An interesting if infuriating article in New Republic very clearly lays out how the GOP has spent decades paving the road for Trump by attacking the science that goes against their prejudicial ideology. I strongly urge you to read it, but one section jumped out at me in particular:There’s another factor at work here: The anti-intellectualism that has been a mainstay of the conservative movement for decades also makes its members easy marks. After all, if you are taught to believe that the reining scientific consensuses on evolution and climate change are lies, then you will lack the elementary logical skills that will set your alarm bells ringing when you hear a flim-flam artist like Trump. The Republican “war on science” is also a war on the intellectual habits needed to detect lies.
Yes, precisely. This is exactly what I have been saying for years now. When we erode away at people’s ability to reason their way through a situation, then unreason will rule. And not just abut scientific topics, but any topics. We see nonsense passed off as fact all the time by politicians, including Representative Lamar Smith’s (R-Texas) attacks on NOAA, Ted Cruz (R-Texas) claiming there’s been a pause in global warming, the GOP attacks on Planned Parenthood, and more. People will still believe what these politicians say, long, long after the claims have been shown to be completely false.
Months ago, early on in the Presidential campaign, I made light of Trump, saying that his particular candidacy would crash and burn when he inevitably said or did something so outrageous and horrific that people would flee his side.
I was wrong. I underestimated just how thoroughly the GOP had salted the Earth. Philosophical party planks of climate change denial, anti-evolution, anti-intellectualism, intolerance, and more have made it such that Trump can literally say almost anything, and it hardly affects his popularity.
The good news is that even the party elders are terrified to support him, and many seem to be accepting what looks like the inevitable wave coming this November, and instead are hoping to recoup in 2020.
Perhaps that will come to be. Trump’s numbers are certainly slumping, and I see no way he will be able to pivot toward anything resembling reality, no way for him to gather more middle-of-the-road votes. His racist, bigoted, misogynistic, xenophobic narcissism is too firmly entrenched for it to be otherwise.
The GOP isn’t to blame for Trump existing—we can lay that at his own feet—but the path he’s taking was certainly smoothed by them.
The fact is, this is the candidate the GOP has sown, and so shall they reap. My hope is that the majority of the electorate will see through the nonsense, the distortions, the lies, and use their critical thinking skills on November 8. Reality doesn’t give a damn about our beliefs, and so we must instead give a damn about reality.
Want to know more about how to think critically? I have some thoughts on that:
- How Critical Thinking Affects Society
- Qualia Soup: Critical Thinking
- How to Get Kids to Think Critically
- Vaccines: Opinions Are Not Facts
- Some Bad Science Cam Make You Laugh, and Some Kills
- The World Is Subtle, and That's Why It's Beautiful
Tip of the candle in the dark to Zack Kopplin.
One of the most difficult aspects of astronomy is distance. Even the Earth’s Moon is 380,000 kilometers away, a four-day trip by rocket, and that’s the closest object in the Universe to us!
Remote galaxies are a hundred million billion times farther away than that. That’s a soul-crushing distance, almost beyond human grasp.
Almost. We’re pretty clever, we humans, and we’ve found ways to figure out how far away cosmic objects are. One powerful tool we’ve found are “standard candles”: bright objects that all shine at the same luminosity. Think of it this way: Take two light bulbs you know are the same brightness (say, 100 Watt bulbs) and place them at different distances. The more distant one will be fainter, of course. But if you can measure how much fainter it is, you can calculate their relative distances. If you can measure the distance to the nearer one, you automatically know how much farther away the second one is.
We have various types of standard candles at our disposal. Supernovae are good ones; there’s a special kind of exploding star (called a Type Ia) that all explode with more or less the same energy. These are very bright and can be seen to tremendous distances. It turns out they have their quirks, so they’re not perfect candles, but we could adjust for inconsistencies. Once that was done, they allowed astronomers to measure distances all the way across the Universe, and even determine that the universal expansion is accelerating.
Still, it would be nice to have more than one ruler. Waiting around for a supernova takes a while, and even then they’re so faint we need huge telescopes to spot them. And while they let us see out to about 11 billion light-years—a very long way—that still falls short of the roughly 14 billion light-year distance to the edge of the observable Universe.
Is there anything that could fill that gap? The problem is you need hugely energetic events to be bright enough to see from all those billions of light-years away.
The good news is there are such hugely energetic events: gamma-ray bursts (or GRBs). These are ridiculously powerful blasts, so luminous they can even dwarf the brightness of a supernova. They were discovered in the 1960s, and we’ve learned a lot about them since then, including the amazing idea that they are the birth cries of black holes! If you want some background, I have a whole episode of Crash Course Astronomy about GRBs:
There’s a problem, though: No two GRBs appear to be alike. They explode with different energy, they have different brightnesses, they fade differently. Some have explosions that last for seconds, others for hours. There’s an expression in the GRB community: “If you’ve seen one GRB, you’ve seen one GRB.” That makes them terrible standard candles.
… maybe. Astronomers have been trying for quite some time to find some way to standardize them, account for their differences, so that they can be used as cosmic metersticks. And it appears that the first solid step toward that has been done: Maria Dainotti and a team of astronomers have just published a paper where it looks like they cracked the GRB code! They found a set of 122 GRBs that, when examined carefully, display a unique set of observable characteristics that allow them to be used to determine their distance.
The GRBs they examined were all of the long variety, with detectable energy that lingers for weeks. Each got very bright and then faded rapidly for minutes. After that they stopped fading, “plateauing” for a few minutes. Then, finally, they begin fading again, this time more slowly. Each of these GRBs also had an independent measurement of its distance (using its redshift; see Crash Course Astronomy Episodes 24 and 42 for more on that), which then allowed for the total energy emitted to be calculated.
What Dainotti and her team found is that when you look at that sample of GRBs and plot three of their characteristics—how luminous they are at their peak, how luminous they are during their plateau stage, and when the plateau phase ends—they all behaved in a nice, orderly way. Instead of being randomly scattered around, they all fall into an obvious pattern. They also found that if they exclude a few subtypes of GRBs the correlation is even tighter.
The beauty of this is what you can do with it. If you observe a distant GRB with these characteristics, all you need to do is plot it against the others, and the distance to it pops right out.
Well, it’s not that easy, but the point is this may be a new way to use GRBs to measure distances across the cosmos (and it’s telling us some physics about the GRBs themselves which is interesting). That’s pretty exciting. This is still new, but it’s a promising step toward being able to use these fickle explosions to probe the conditions of the Universe at much larger distances than we’ve been able to up this point.
I’ll note that this work would not have been possible at all were it not for the existence of Swift, a NASA satellite launched in 2004 designed specifically to rapidly find and observe GRBs. It’s cataloged more than 1,000 bursts now, providing a huge database that allows astronomers to look for trends. And it’s still going strong after all these years. I worked on the education and public outreach for Swift for many years, and seeing it supporting important work like this makes me pretty proud.
We didn’t understand GRBs much at all until the late 1990s, and now we’re close to being able to use them to take the measure of the Universe itself. That’s almost as amazing as GRBs themselves.
In the early morning of Tuesday, June 28, 2016, a small rock that is very likely a meteorite fell onto a house in Phitsanulok's Muang district, punching a hole in the roof and doing some minor damage inside.
Apparently many people in the area, including the owner of the home, heard a loud explosion some time before, which may have been the shock wave from the meteorite entering the atmosphere.
I don’t speak or read Thai, but there’s a video from the Matichon TV YouTube channel with some pretty interesting footage.
I’ll note that in September 2015 a somewhat larger meteor burned up in the same area and was caught on video, but that’s certainly a coincidence.
The rock from this fall will have to be tested to make sure it’s a meteorite, but it certainly looks like one to my eye; the gray interior is common in stony meteorites, and the outer dark shell may be a “fusion crust”, caused by the few seconds of intense heat as the meteoroid (what the solid piece of rock or metal is called before it hits the ground) passes through the air at high speed.
One part of the story gives me pause, though: The homeowner says the rock was hot to the touch when she picked it up. In general, a meteoroid is only hot for a few seconds as it rams through the air, decelerating from hypersonic speeds down to below the speed of sound. As it slams through the upper atmosphere around 80 – 100 km above the Earth’s surface, the intense pressure of its passage compresses the air violently, and that heats the air up, which in turn heats up the meteoroid. It gets hot enough to glow (the air glows too) and we call that part the actual meteor.
But it slows in just seconds, falling the rest of the way at a few hundred kilometers per hour, taking a few minutes to fall the rest of the way to Earth. Air is very cold that high up, so many meteorites should be very cold to the touch if they’re found immediately after hitting the ground. Perhaps the homeowner made a mistake, thinking the intense cold was heat (if you’ve ever touched something extremely cold, the sensations are very similar).
I’ll be very curious to hear about any tests run on the fragments. The homeowner says she’ll keep it, and that it will bring her good luck. I don’t know about that, but meteorites from known falls that hit objects on the ground can be extremely valuable to collectors. They’re called “hammers”, and this one has a mass of around 300 grams, so it’s easily worth thousands of dollars.
She’s lucky that no one was injured; at a hundred or more kph that would’ve hurt (it weighs twice as much as a baseball and was moving at least as rapidly as a fastball). Still, if I could choose to have one hit my house, I’d probably take that chance! What a story!
The odds are extremely low, of course. The Earth is ¾ water, and even the land area is mostly uninhabited. Meteorite falls over populated areas are rare, and having them hit objects even rarer. Very few injuries have been reported, and fewer verified (though a woman named Ann Hodges was hit by a meteorite in the 1950s in Sylacauga, Alabama, and that’s well worth your time to read about). It’s not something I worry about, to be honest.
Perhaps more meteorites from this fall will be found, too. That would be nice. A meteorite is in some ways a gift from the Universe to us, a piece of it that we can hold in our hands and examine in our labs, instead of just seeing from some huge distance away. Sometimes the Universe is pretty cool that way.
Want to learn more about meteors? Here's my episode of Crash Course Astronomy about them!
Tip o’ the Whipple Shield to Ron Baalke.
Using a fleet of telescopes both on the ground and orbiting the Earth, astronomers have discovered what is very likely to be a black hole only a few thousand light-years from Earth.
On its own that’s not terribly newsworthy; we know of lots of black holes in the Milky Way galaxy. What makes this one so very interesting is that it has been hiding in plain sight, located in the sky near a gorgeous globular cluster, masquerading as a distant galaxy.
And even that’s not the most interesting thing. The most interesting thing is what this implies for the total number of such black holes in the Milky Way. There could be a lot more than we first thought. A lot more.*
The object has the handy nickname of VLA J213002.08+120904 (a combination of VLA for Very Large Array, the radio observatory that discovered it, and its coordinates on the sky). It’s also called M15 S2, which I find amusing. Let me explain, because this is fun.
Globular clusters are collections of hundreds of thousands of stars in close proximity to each other. M15 is a glorious example of such a beast; about 30,000 light-years away, quite bright and well-studied. In 1996, a group of astronomers scanned the cluster using the VLA, looking for gas flowing into it. By accident they found a point source of radio emission in the outskirts of the cluster, but they weren’t sure what it was. Some astronomers thought it might be a distant galaxy coincidentally aligned in the sky with the cluster.
In 2014, another team of astronomers observed this object (which they designated S2, for the second unidentified point source of radio emission in M15) using a collection of radio telescope across the planet, and using parallax (the object’s apparent motion in the sky which is actually a reflection of the Earth’s motion around the Sun) found it was located about 7,000 light-years away—one-fifth the distance to M15! Clearly this was neither a distant galaxy nor a weird star in the cluster. That distance puts it firmly inside our own galaxy. The plot thickens.
Finally, another team of astronomers looked at observations from a variety of telescopes, hoping to nail down the identification of this thing. They found it in more radio observations from VLA, and interestingly Hubble Space Telescope observations show what looks to be a faint red source at that position. The kicker is that they also looked in data of M15 taken by the orbiting Chandra X-Ray Observatory, and found nothing; whatever it is, it’s too faint to be seen in even a 30-hour observation.
All this put together points toward a very peculiar object: a black hole orbiting a tiny red dwarf star. If the black hole has a mass typical of such objects, about 10 times the mass of the Sun, the red dwarf is about 0.1 to 0.2 times the Sun’s mass (also typical). It’s likely the two orbit each other very closely, with an orbital period of roughly one to two hours. That’s close enough together that the star is grossly distorted by the black hole’s gravity, and material is flowing from it to the hole.
When material does this, it tends to form a disk around the black hole called an accretion disk. It piles up there before falling in to the black hole. The disk can be very hot, glowing brightly in X-rays, and also blast out a wind of subatomic particles. In this case though, the disk appears to be very weak and not as hot, which is why it’s not bright in X-rays even though its wind (or possibly other structures called jets) generates radio emission.
Other types of objects can be bright in radio and quiet in X-rays, but each one of these was systematically eliminated from consideration by the astronomers; for example a planetary nebula would show fuzziness in the Hubble images, but none is seen. In the end, the best candidate is indeed a low-mass binary black hole system.
Assuming this truly is as advertised, it’s the first accreting X-ray quiet black hole binary ever seen outside of a globular cluster. It’s also one of the lowest mass black hole binaries known. And that has some very cool implications.
This object was found essentially by accident in a radio observation of a globular cluster. But it’s not in the cluster; it’s much closer and just happens to lie near it in the sky—that’s fortunate, otherwise it may never have been discovered! Given that one of these was found in a very small region of the sky observed, that implies there are a lot of them scattered throughout the galaxy. Using some simple assumptions, the astronomers find that there may be anywhere from 25,000 to 150 million such low-mass black hole binaries in the Milky Way alone!
That’s a lot. It’s a wide range because of a lot of the uncertainties involved, but even on the low end, that’s three times more than predicted by looking at how stars are born and evolve over time (you need a low-mass star orbiting a high-mass one, so that the bigger one blows up and forms a black hole at the end of its life). And on the high end it’s thousands of times the number predicted.
How can the numbers be so far off? That’s a good question, and it’s not clear. Maybe this really was a very lucky observation, and just happened to spot one such object even though the odds were long. Maybe our stellar formation models are off. Either way, it shows us we need to search for more of these objects so we can figure out what’s going on. That’s not easy, as they’re usually found in X-ray surveys of the sky, and they’re X-ray quiet. Looking for the kind of radio emission these types of objects give off specifically will help, as will looking toward the galactic center for them, since they should be more common where there are more stars. A new generation of more sensitive X-ray telescopes coming soon will do well here, too.
I think this is all wonderful. It’s still possible to discover new objects by accident today and use them to learn important characteristics of the galaxy in which we live. And if it means more black holes to study, hooray! Getting a bigger sample of the weirdest objects in the Universe can only be a good thing for science and our understanding of the cosmos.
*Before you freak out, not to worry: Space is big, and even if there are zillions of these things out there, over the entire lifetime of the Universe the chance of any getting near enough to Earth to hurt us is essentially zero.
On Earth, we are keenly aware of gravity. It shapes and modifies everything we do, including our architecture, our behavior, and the landscape around us.
Comets, on the other hand, think of gravity as more of an afterthought.
The image above is from the Rosetta spacecraft, still traveling along with the comet 67P/Churyumov-Gerasimenko as it orbits the Sun. Both were about 474 million kilometers from the Sun and 449 million km from Earth when this shot was taken.
Rosetta was considerably closer to the comet than that, of course. It was just a hair under 30 km from 67P when it snapped this shot, and the resolution on the full-size image is a stunning 0.5 meters per pixel: around 18 inches!
I love the jagged peaks surrounding the flatter plain, towering shards a hundred meters high that clearly don’t have to deal with a whole lot of forces like gravity, wind, and the like (another angle on this same region can be seen here). You can see rocks resting comfortably at all sorts of weird angles, partially due to friction with the surface being more than enough to overcome any sliding due to the weak gravity, but also because “down” becomes a complicated topic if you’re standing there. The comet has two big lobes connected by a thin neck, and what you call “down” changes rapidly and strongly with position.
In general, if you were standing on the surface, you’d feel gravity something around 0.0001 times that of Earth. I’d weigh about a quarter ounce, as much a sip of water. A solid jump would fling you away from the comet forever.
The reason behind this is simple: Comets aren’t terribly big, 67P is roughly four kilometers across, and has a mass considerably less than a typical Rocky Mountain. This makes the force of gravity on the comet pretty weak, barely enough to hold it together.
Even though conditions on the comet seemingly defy the forces we deal with on the surface of our much larger planet, the comet is actually incredibly fragile. It’s made of rock and ice, and when it gets near the Sun on its 6.4 year orbit that ice turns into a gas. This can dislodge rocks, shift surface features, and generally erode things away (and also creating the iconic tail of a comet). In a relatively short time (millions of years? Less?) the comet will lose its structural integrity and fall apart. We’ve seen comets do this.
Such will be the fate of 67P as well. But in the meantime, there’s much to learn! Rosetta is still observing the comet, still sending back valuable data, and still helping us understand these bizarre frozen remnants of the solar system’s past.
My thanks to Emily Lakdawalla who helped me find the location of this shot on the comet’s surface. Follow her on Twitter!
Hey, I know just you want on a Sunday morning! A physics problem!
If it helps, think of it as a brain teaser. Like many such, it’s deceptively simple, but when you start to think about it a lot of concepts collide and it’s not as obvious as you might suppose at first glance.
Here’s my friend Dianna Cowern, aka Physics Girl, with the brain-stumper. I suggest you do as she recommends, and stop the video to think about it before she gives the answer.
Did you get it right? I will admit it: I did. For the right reason, too, which I almost had to laugh at; many times when I think about a physics problem like this I can argue it both ways depending on what angle I take on the problem. In those cases I know I’ve forgotten something in my deducings.
In this case, I knew that rock is denser than water (as long as it’s not pumice, I suppose), so in the boat the rock was displacing its weight, but in the water it was displacing its volume. If rock is denser than water, its weight in water is larger than its volume in rock, so it displaces less water when it’s actually in the water, and the level goes down.
That kind of reasoning can be hard to follow if you’re not used to doing it. One slip up loses the chain of logic. I was actually thinking that as I was going through the steps, and a part of my brain whispered to me, “Do an extreme case; it’ll be easier”. Then one minute later Dianna suggested just that and I did laugh out loud.
Extreme cases may not solve the exact problem you’re facing, but they really help with getting through the logic, because there’s an intuition you get living in the real world about how some physics works. You really do! For example, you may know that if you throw a ball at about a 45° angle it’ll go farther than if you throw it at a higher or lower angle. If you do the physics you find the equations are symmetric around that angle, meaning that really is the best angle to throw a ball for distance.
Extreme cases exploit that knowledge you’ve gained through just existing in a Universe bound by physical laws, giving you an answer that either makes sense or is absurd, allowing you to get a better grip on things. I use them all the time when trying to figure things like this boat puzzle out, and they really do help. Just remember they’re extreme cases, and may not represent the actual answer you want. Apply them carefully, and remember they’re a tool, not a solution themselves.
If you liked this problem and the video, Dianna makes lots of them and they’re really good. This one about mirrors is great, and generates a lot of interesting discussion (lots of people say the answer is obvious, but it clearly isn’t to a lot of people). I also like this one about hurricanes and soap bubbles.
Sometimes you just need to look at pretty stars.
That image was taken by the Hubble Space Telescope back in 2009 (but just released recently), using the Advanced Camera for Surveys. It shows a region of the sky very near the center of the Milky Way galaxy, where stars are packed pretty closely together—think of them as city lights, and you see more when you look downtown*.
Interestingly, the stars are displayed pretty close to their natural colors. Hubble cameras are equipped with a wide variety of filters that let through light of not just various colors, but also various bandpasses; that is, the range of colors. A narrow bandpass means you’re seeing a very thin slice of colors (say, centered in red), whereas a wide passband lets through light at a bunch of different colors. These filters have various uses; looking at gas clouds, for example, is usually better using narrow bandpasses to isolate the light emitted by specific elements.
In this case though, wide bandpasses were used. Specifically what you see displayed as blue is centered at 435 nanometers, which really is blue. Green is actually from a filter at 606 nm, which is closer to yellow-orange, and red is from 814 nm which is very red (technically I’d say it’s near-infrared). But when combined all together, the image is not a bad representation of the actual colors the stars emit.
And look at the variety! Blue, yellow, red… the color of a star is due to its temperature. Blue means hot, red means cool. In general you can’t tell the mass of the star without more info; a red star might means it’s a dim red dwarf that’s close by, or a mighty red giant blazing much farther away.
There’s something I want you to note, though. The stars seem more or less evenly distributed throughout the image, but you can still see some patches where stars appear somewhat less frequent. There’s a band of lower density running from the lower left to the upper right in the shot, which is subtle but definitely there. Here’s a close-up of a region near the lower left side of the big picture:
Notice anything? Ignore the brighter stars, and concentrate on the fainter ones. Can you see they’re mostly red? Now some of that is real; faint red dwarfs are the most common stars in the galaxy. But I have to think that we’re also seeing the effects of dust here. Dust is made up of tiny grains of silicates (like rock) or complex carbon-based molecules called polycyclic aromatic compounds, or PAHs—essentially soot.
Both tend to absorb visible light, but not only that, they scatter it. When light hits a teeny grain it bounces off in a random direction. Blue light scatters way better than red light; a star behind some dust will appear red because the blue light is absorbed or scattered away, while the redder light goes straight through. I strongly suspect that’s why so many of those fainter stars look red. They’re almost certainly brighter, bluer stars being affected by dust.
This is very common in photos taken of the sky near the galactic center; dust is strewn liberally throughout that region. It’s commonly made in older stars, and stars that explode, and those are more populous toward the heart of the Milky Way. My favorite example of this is the dark cloud Barnard 68, where the material is thin near the edge and thicker toward the center; you can actually see stars getting redder as you look from the edge toward the middle. I talked about this in my Crash Course Astronomy episode about nebulae, too (start at about 3:23 for the whole explanation).
As always, I love how astronomy provides both brain candy —beautiful pictures just for looking at— and brain nutrition—science that provides a better understanding of what you’re seeing. Art and science are two sides of the same coin.
* These images were not taken primarily for science; while another camera was investigating a cluster of stars nearby, this camera just happened to be pointed at this star field. Scientists don’t like wasting opportunities, so the camera was turned on to see what it could see. This is called taking “parallels”, and when I worked on Hubble I was fascinated by them; I wound up writing a short paper on an object we found in one.
So yesterday I wrote about Pluto possibly having a liquid water ocean under its surface, which is pretty amazing. But other worlds in the solar system have stuff going on too, y’know.
Like Neptune. It has a new dark spot.
Neptune is what we call an ice giant; bigger than rocky planets like Earth and Mars, but smaller than Jupiter and Saturn. It’s not literally made of frozen stuff; it’s called an ice giant because planetary scientists tend to call things like methane, ammonia, and water ices when dealing with outer worlds.
Neptune orbits pretty far from the Sun, about 4.5 billion kilometers out. That makes it pretty cold, and you might not expect the atmosphere to have much action. For a long time telescopic observations of it didn’t show much (it’s so far away that even though it’s nearly four times wider than Earth it’s not terribly big in telescopes), but in 1989 the Voyager 2 probe flew past it, revealing a gorgeous deep blue world with a banded atmosphere, and, very surprisingly, a huge dark spot which was somehow named the Great Dark Spot.
Since then our ‘scopes have gotten better and more of these spots have been found. We now know they’re anticyclones—high pressure systems—in Neptune’s troposphere, the deeper layer of atmosphere under its stratosphere. Since they’re high-pressure systems, we may be peering deeper into Neptune’s atmosphere when we see them.
Dark spots on Neptune tend to be associated with bright clouds around their rims, which may be from methane clouds condensing as air blows around and above the dark spots. This happens on Earth… well, with water instead of methane. Moist air rising up can condense to form clouds; we see this on the windward sides of mountains as the air lifts up to go over the obstacle. In this case, they’re called orographic clouds. With Neptune, the methane freezes, crystallizes, and becomes bright white to form the lovely thin white clouds around the dark spots.
Dark spots come and go. The Great Dark Spot had disappeared by the time Hubble looked for it in 1994, but other ones had appeared in 1995. This new one found is the first one seen in well over a decade. They can last for many years, because they spin in the same direction Neptune does. That sets up a stable feedback system that helps keeps the spot rotating (in that case it’s called a vortex). We see this on Jupiter, Saturn, and possibly other places on Neptune, too.
Why is this important? Well, to be frank, atmospheres are complicated. Planets spin, and warm up, and have different stuff in their atmospheres, and sometimes warming or cooling changes the layering and condensation and evaporation rates, and it’s a mess. Understanding them in terms of their physics is really hard.
In some ways the outer planets are simpler than Earth: They’re mostly air. But there are other complications, like gases in abundance we don’t have here (like hydrogen and helium). Also, while the major source of Earth’s heat is the Sun, the outer planets don’t get nearly as much sunlight. Plus, they still have lots of warmth leftover from their formations (yes, they’re still cooling after 4.56 billion years), and for Neptune that’s its major source of heat. So it’s warmed from the inside out, the opposite of Earth.
All these worlds are test cases for our understanding of how atmospheres behave, including our own. Plus, of course, just understanding things is good. Neptune is a huge, massive, complex world, and worthy of our attention just because it exists and is near enough for us to study it.
Before the New Horizons space probe zipped past Pluto in July 2015, we weren’t sure what to expect. A lot was known about Pluto in general — given its density it was likely a mixture of ice and rock, for example — but very little about was known about, say, the surface structure.
Then the little spacecraft flew by the little world, and our knowledge exploded. The close-up pictures were amazing, both beautiful to behold and tantalizing for the brain. There were lots of surprises, of course, including how diverse the surface was: There are frozen plains of nitrogen, mountains of water ice, dark and bright spots, huge fields of pits on the surface, and much more.
Scattered around the surface are another type of feature: Huge cracks, some hundreds of kilometers long and many kilometers deep. They’re pretty interesting, and their presence has led one group of planetary scientists to make an astonishing claim: There may be a liquid water ocean under the surface of Pluto!
If this is true, it’s a very big deal. Pluto is small and extremely cold, so the last thing you’d expect is liquid water anywhere with three billion kilometers of it. How can this be?
First, the evidence. The cracks are called extensional tectonic features, meaning you get them when the surface extends, expands. Imagine covering a balloon with mud. Let the mud dry, then inflate the balloon a little bit. What happens? As the balloon expands, it pushes the mud from underneath. Mud isn’t stretchy like rubber, so instead of smoothly expanding it cracks, allowing the pressure underneath to be relieved.
That may be happening on Pluto. The solid crust (mostly water and nitrogen ice) is feeling pressure from underneath, expanding, and cracking. But what could be causing the expansion? Liquid water. And lots of it.
Pluto is mostly ice and rock. However, there is likely to be some amount of radioactive elements in its core. Our own Earth has them, and the heat generated by the decay of these elements is a major source of our planet’s internal heat, even 4.56 billion years after it formed.
Studies show that even a small amount of such material (including uranium, thorium, and potassium) could produce enough heat inside Pluto to melt some of the water ice. I’ll admit this surprised me; my gut reaction is that Pluto is so small that it would lose heat faster than the radioactive materials could generate it.
The new research just published looks into that. They show that the rocky material inside Pluto insulates it, and keeps that heat from leaking away too quickly. The rock acts like a blanket, keeping the heat inside Pluto, and over time it could be enough to not only melt a substantial amount of ice, but keep it liquid even to today.
Well, mostly liquid. Pluto is pretty cold, and some of that water, especially closer to the surface, could start to freeze. When liquid water turns into ice, it expands, and it’s that expansion that’s proposed to cause the crust of Pluto to expand with it, creating the cracks.
How weird is that? Tiny, frigid Pluto, long thought to be a frozen ball of ice, may yet have some spring in its step.
And there’s more. The new research shows that if the ice shell covering Pluto is thick enough — deeper than about 260 km — then the water under the surface could form a strange kind of ice called ice II. It’s still made up of water molecules like regular ice, but under higher pressures (caused by the thicker shell) the molecules realign themselves, forming a different crystal structure than normal ice.
Ice II is denser than regular ice, denser even than liquid water. If it forms, the ocean under the surface would shrink, contracting to a smaller volume. If that happened, you’d expect to see compressional features on the surface of Pluto, like thrust faults.
However, none was found, so it’s unlikely ice II ever formed. That suggests the water under the surface is still liquid, even today. Incidentally, the cracks on Pluto are fresh-looking, with few craters marring them. This indicates relative youth, though it’s hard to know what that means on Pluto. Millions of years? Tens of millions?
Still, this is an intriguing idea. I expect there will be some back-and-forth on this, as the surface of Pluto is examined more closely. For example, there’s a mountain on Pluto that looks like it was pushed up, and then began to subside. If that’s the case, what does that tell us about the thickness of the crust there, and the forces underneath? Also, there are cracks on Pluto’s surface that aren’t linear so much as radial, as if whatever pressure under the surface were greater there than average. Maybe there’s material welling up there, pushing up on the surface.
And of course, there’s another thought. A source of heat, liquid water, and complex chemicals are three ingredients needed for life. Now have a care here: I am in no way saying there’s life under Pluto’s surface! My point is more subtle than that: We wonder if life exists out in the Universe, and the key to that is how commonly the necessary conditions arise. What we’re seeing on Pluto — and on Enceladus, and Europa, and Titan — is that these conditions at least in part appear to pop up quite a bit just in our solar system alone. Even in almost literally the last place you’d expect.
Oh Pluto, will you ever stop surprising us?
I certainly hope not.
Imagine you are on a large sphere.
Got it? Now imagine that sphere is spinning. As it does, two poles are defined: You can call them what you like, but “top” and “bottom” work. Halfway around the sphere from the top one toward the bottom is the sphere’s midsection. You can call it what you like, but “waist” works.
Now imagine there’s a source of light some distance off. Imagine too this source of light is carefully placed such that the axis of rotation of the sphere is perpendicular to the direction to the light. In other words, the sphere spins vertically. The light then illuminates half the sphere, but as the sphere spins every point on its surface will eventually get lit during one rotation.
If you stand on a pole, let’s say the top one, you spin in place, once per sphere rotation. To you, the source of illumination spins around the sky, neither rising nor setting. It just goes around. The same is true if you’re on the bottom pole, too.
If you’re on the waist, in one spin you make a big circle, the size of the circumference of the sphere. For half a spin the source of illumination is visible, but for the other half it’s behind the sphere and you can’t see it. The light rises, goes directly overhead, and sets again after half a rotation, then rises again a half rotation later. If you’re anywhere else on the sphere except a pole (and if the sphere is very large compared to you), the Sun will rise and set, but won’t go overhead.
But now let’s tilt the sphere. It can go any way, but let’s say the top pole it tipped toward the light. If you stand on the waist, the light still rises and sets, but instead of going overhead it makes a lower arc in the sky, never quite reaching the overhead point. How much it misses depends on how much the sphere is tilted.
If you stand on the bottom pole, tipped away from the light, you’re still spinning in place, but you’re facing away from the light. The light is always blocked by the sphere, so you never see it. It’s always dark.
If you stand on the top pole, you’re still spinning in place, but now the light appears to go up and down over one spin. It doesn’t get blocked by the sphere, but it does get low, close to where the sphere blocks the sky (let’s call that the “horizon”). If you move away from the pole, down toward the waist by just the right amount, then the light will just kiss the horizon as it dips down before moving back up again. The distance you have to be from the pole for it to do this depends on the amount the sphere is tipped.
Now. If you’re on the top pole, what would that look like?
That wonderful time-lapse video was taken by astrophotographer Göran Strand just a little over a day ago. He was standing on a big sphere—the Earth. The Earth is tilted, by about 24°. It goes around the light source (the Sun) but the tilt stays the same, so at one point in that journey the top (north) pole is tipped as much toward the Sun as it can be. We call that point in its orbit the solstice.
Strand was just the right distance from the north pole, so that the path the Sun made in one rotation (one day) just barely stays above the point where the Earth blocks the sky (the horizon). He saw it make a big circle in the sky, taking one spin (one day) to go around.
Someone much farther away from the pole saw the Sun rise and set over the course of that day, but not Strand. Whereas it was the middle of the night for that person farther away, Strand never saw the Sun leave the sky.
And that’s why this phenomenon is called “the Midnight Sun”. Strand took that photo from just inside the Arctic Circle (24° south of the north pole), in Gällivare, Sweden, at just about midnight local time. Gällivare is at a latitude of 67°N, or 90 – 67 = 23° from the pole. Anyone there or closer to the pole never saw the Sun set that day.
And anyone inside the Antarctic circle, 24° away from the south pole, never saw the Sun rise that day. It’s always night there right now, and if you’re on the pole you won’t see the Sun rise until September*.
Think of it! You are on a tilted sphere that is madly spinning as it whirls through space around a distant light source, creating day and night and seasons and climate and weather, which over billions of years has impacted geology and sculpted life to adapt to the day/night cycle, the annual cycle, the change in light versus distance from the poles. We set our calendars to these cycles, our clocks, our very lives to these cycles caused by our rotating, oblique planet.
Don’t think science affects your life? Think again. It affects everything.
* Right now, two members of an NSF team there are very ill, and a rescue mission has been mounted to bring them back north for medical attention. It is always dark there, and very, very cold, so this is nothing short of a heroic effort. The plane landed there yesterday, and has begun the arduous journey back.
Two new exoplanets have been discovered, and they’re important milestones in our understanding of how alien solar systems behave. That’s because both are very young, both are massive, and both orbit their stars very close in, closer than Mercury orbits the Sun.
First, a quick intro to the problem: When astronomers first started finding planets around other stars in the mid-1990s, they were surprised to find that many were as big and massive as Jupiter but so close to their parent stars that they had orbital periods measured in days. Given that Mercury, the innermost planet in our solar system, is small and takes three months to circle the Sun, these “hot Jupiters” were pretty shocking. How did they get there?
Models of planetary formation show that it’s very unlikely a big planet can form so close to the star. Most likely, they form farther out and somehow migrate in toward the star. One way would be to interact with the disc of debris circling the star from which the planet formed. As it plows into this material, it can drop down to the star. It’s unclear if this happens very early in the life of the planet (like, within a million years or so after it forms) or much later, like right before the debris disk is blown away by the star millions of years later.
Another way would be for it to gravitationally interact with other planets in the system, which can affect their orbits. This method takes a while, though, and is slower in general than the debris disk method. The problem: Most planets found are old, a billion years or more, so it’s hard to know just when the hot Jupiter moved.
These two new planets change that.
One is called K2-33b and was found by the Kepler spacecraft, the one that has discovered so many alien worlds. The star, K2-33, is about 460 light-years away and is a cool red dwarf, only about 0.6 times the diameter of the Sun and shining at a feeble 15 percent as bright. It’s part of a loose cluster of stars called the Scorpius-Centaurus OB Association, which is known to be young. The colors of the star also indicate youth (it’s still very hot from its formation, so it’s bluer than you’d expect), and the smoking gun is the presence of lithium in the star’s atmosphere; that element gets destroyed by a star very quickly, so seeing any at all means the star is very young. All together, this points to an age of no more than 20 million years, and most likely closer to 11 million years.
Our own Sun is 4.56 billion years old, so this star is basically a wee bairn.
K2-33b, the planet (note the “b”) is roughly 60,000 kilometers across, a bit less than five times Earth’s diameter. It has no more than the mass of Jupiter, and likely has less—it’s more like a super-Neptune or a mini-Jupiter. It orbits the star every 5.4 days, so it’s close.
Given its youth, that strongly indicates that massive planets can migrate rapidly toward their star right after they’re born, perhaps even while they’re still forming.
But wait! There’s more! We have the other planet, too.
Before I even get started, let me say that this second planet has not yet been confirmed, but given the circumstances it seems very likely it’s real. I’d be happier with more independent evidence, but the authors indicate the probability of it actually existing is very high.
This one orbits the star V830 Tau, which has a mass almost the same as the Sun, but is twice the radius and about 20 percent more luminous. The planet orbits the star every five days at a distance of just 8.5 million kilometers—that’s very close indeed. Even better, the age of the star appears to be only about 2 million years, which is even younger than K2-33!
So, in both cases, we have a massive planet, which is orbiting very close to its star and is very young. That’s very exciting! They show that planetary migration can happen almost immediately, even as the planet and star are still settling down after their formation.
Mind you, this doesn’t mean planets don’t move later in life. In fact, we have evidence that planetary interactions do happen (some planets orbit their stars backward, in the opposite sense of the star’s rotation, which can happen if the planet has undergone a game of celestial billiards with other planets).
So what we now seem to find is that there’s more than one way to cook a Jupiter, and it can happen right away or it can take a while.
This is amazing. I’ll remind you that until 1995 we didn’t even know if other planets existed around other stars like the Sun. It’s only been 20 years, and we’ve learned so much about them! We have thousands to study, and they come in so many flavors: Big, small, hot, cold, puffy, compact … we see planets like the ones in our solar system, and ones that are entirely alien.
And we’re still just getting started here. We know of something like 3,000 planets right now, but there are likely hundreds of billions in our galaxy alone! With a sample size that vast, even something very unlikely is bound to happen. What other strange new worlds await us?
On Monday at 22:34 UTC (6:34 pm Eastern U.S. time), the Sun will reach its highest declination in the sky, its farthest point north for the year. That is the moment of the June solstice.
This means that, in the Northern hemisphere, we have the longest day of the year, and the shortest night. If you live your life standing on your head in the Southern hemisphere, it means you have the shortest day, and the longest night.
I enjoy writing about the solstices and equinoctes* when they happen, so you can read all about how and why they occur in past articles. I’ll note that Monday is not the date of the earliest sunrise and latest sunset though; that has to do with the Earth’s orbit being slightly elliptical, so I’ll make a special point of linking to this article last year where I explain why that happens. I’ll also note that some people call this the first day of summer (or winter for those in the south), but I disagree; I tend to think of it as actually the midpoint. You can read about that to your brain’s delight as well.
No, instead of spending time on that here, I’d prefer to point out something rather special that led to me wandering down a rabbit hole Sunday night as I researched it: Not only is the solstice Monday, but the Moon is full on Monday as well. That moment occurred at 11:02 UTC (07:02 Eastern; I’ll note it’ll look full all day and probably even Tuesday as well).
A full Moon on the same day as the June solstice (or the December one, for that matter) is relatively rare. As I thought about this Sunday night, I wondered just how rare it was. My first thought was that it probably happens once every 30 years or so, since the full Moon can occur on any day, and there are 30 in June.
But then I realized it’s not that simple. Sometimes in astronomy two cycles can beat together in unusual ways, throwing off what you might expect. So I dug into it. I found a list of solstice full Moon dates on the Farmer’s Almanac website, and perusing the numbers it appears that we get a full Moon on the June solstice roughly every 19 years or so … or multiples thereof.
Nineteen years? That sounded familiar. It took me a few minutes, but then it clicked: That’s the Metonic cycle! Let me explain.
The Moon goes through a full phase of cycles (from full to new and full again) in about 29.53 days. That all by itself is interesting, and I talk about that in the episode of Crash Course Astronomy on the phases of the Moon:
One Earth year is, on average, about 365.24 days long. But there’s a funny coincidence here: 19 years is 6,939.56 days, and that is almost a perfect multiple of 29.53! Nineteen years is almost exactly 235 lunar phase cycles. That means that when you have a full Moon on a given date, 19 years later it’ll be on that same date once again. That’s what’s called the Metonic cycle. This fact has been known for about 2,500 years, which is pretty amazing.
But looking at the Farmer’s Almanac, you see it doesn’t seem to happen every 19 years. Why not?
This is where I really started to dig deep. I looked at leap years, and fractional leftovers between the lunar phase month (called the synodic month) and the Earth’s year, and on and on. That can account for some of the reason the full Moon doesn’t always fall on the same calendar date every 19 years.
Then I realized something: time zones.
Astronomical sites list the times of the solstices and full Moons in Coordinated Universal Time (UTC, similar to Greenwich time). That makes it easy for everyone, since you can just look up how far off your time zone is from that (for example, right now the East Coast of the U.S. is on Eastern Daylight Time, UTC – 4 hours).
But that can mess up the full Moon June solstice cycle. Why? Because the exact moment of the solstice changes year to year, and can even occur on different days! It can be on June 20, 21, or sometimes even 22. If the solstice occurs on June 21 at 23:59, and the full Moon two minutes later, technically they’re on different days!
Worse, that’s UTC. In the U.S., where it’s four to seven hours earlier than UTC, both would occur on the same calendar day. So it’s possible (and even likely) that one place in the world would see a full Moon on the same calendar day as the solstice, and another part of the world wouldn’t. What a mess!
Look at Monday’s solstice: It occurs at 22:34 UTC. For someone a couple of time zones east of the U.K., that means it happens on June 21. For them, they don’t get a full Moon on the day of the solstice. The exact moments of the solstice and full Moon are independent of time on Earth (the solstice occurs at the same moment for everyone on the planet, for example), but because we bin time up into days, that can throw off the days on which we say those events happened. Weird.
Going back to the Farmer’s Almanac, you may notice that while the solstice full Moon doesn’t happen every 19 years, it does appear to have a cycle of multiples of 19. For example, there was one in 1796, then the next in 1834, a gap of 38 years, 2 x 19. Other such gaps can be found. The gaps happen because the full Moon missed the calendar day of the solstice by some hours. Not only that, but that table is for the U.S. East Coast, so it doesn’t work for the whole world.
The root of this problem is using calendar days, which are arbitrary to some extent. There’s an overall 19-year cycle, but because of time zones it can get thrown off. A better way to do this would be to ask, “How often does a full Moon occur within a day of the solstice?,” or better yet within 12 hours before to 12 hours after the moment of the solstice.
In that case, I’d expect the 19-year Metonic cycle to be more obvious. However, looking that up using calendars for the full Moon (like this one) and the solstices (like this one) is difficult and tedious. The best way would be to run the calculations specifically looking for that, which I thought of too late to ask anyone to do for Monday’s events. I’ll leave that as an exercise for the reader.
Anyway, my point is … well, I guess I don’t have a point except that numbers are fun to play with and the cycles in the sky are neither always obvious nor simple to grasp.
But they’re there, and if a full Moon falling on the solstice is interesting enough to people that they go outside and take a look for themselves, then I’m all for it.
So happy full Moon June solstice! Enjoy it, because the next one won’t be for a while—June 21, 2062, in fact … if you use UTC.
*Equinoctes is the actual plural for equinox. Some dictionaries say that’s a bit old-fashioned, and equinoxes is now used, which is fine by me. Languages change over time. But I rather like the way equinoctes sounds, and I like using it. So I do.
March … I Mean April… I Mean May 2016 Is the 6th … I Mean 7th… I Mean 8th Temperature Record-Breaking Month in a Row
October. November. December. January. February. March. April. And now May.
For the sixth seventh eighth month in a row, we’ve had a month that has broken the global high temperature record. And not just broken it, but shattered it, blasting through it like the previous record wasn’t even there.
According to NASA’s Goddard Institute for Space Studies, March April May 2016 was the hottest March April May on record, going back 136 years. It was a staggering 1.28°C 1.11°C 0.93° C above average across the planet.* The previous March April May record, from 2010 2014, was 0.92° 0.87° 0.86° above average. This year took a huge jump over that.
Welcome to the new normal, and our new world.
As you can see from the map above, much of this incredible heat spike is located in the extreme northern latitudes. That is not good; it’s this region that’s most fragile to heating. Temperatures soaring to 7° or more above normal means more ice melting, a longer melting season, loss of thinner ice, loss of longer-term ice, and most alarmingly the dumping of billions of tons of fresh water into the saltier ocean which can and will disrupt the Earth’s ability to move that heat around.
What’s going on? El Niño might be the obvious culprit, but in fact it’s only contributing a small amount of overall warming to the globe, probably around 0.1° C or so. That’s not nearly enough to account for this. It’s almost certain that even without El Niño we’d be experiencing record heat.†
Most likely there is a confluence of events going on to produce this huge spike in temperature—latent heat in the Pacific waters, wind patterns distributing it, and more.
And underlying it all, stoking the fire, is us. Humans. Climate scientists—experts who have devoted their lives to studying and understanding how this all works—agree to an extraordinary degree that humans are responsible for the heating of our planet.
That’s why we’re seeing so many records lately; El Niño might produce a spike, but that spike is sitting on top of an upward trend, the physical manifestation of human induced global warming, driven mostly by our dumping 40 billion tons of carbon dioxide into the air every year.
Until our politicians recognize that this is a threat, and a very serious one, things are unlikely to change much. And the way I see it, the only way to get our politicians to recognize that is to change the politicians we have in office.
That’s a new world we need, and one I sincerely hope we make happen.
*GISS uses the temperatures from 1951–1980 to calculate the average. The Japanese Meteorological Agency uses 1981–2010, which gives different anomaly numbers, but the trend remains the same. Realistically, the range GISS uses is better; by 1981 global warming was already causing average temperatures to rise.
† You may have noticed that the actual temperature anomaly for each month over March through May appears to be dropping; 1.28 to 1.11 to 0.93. That may be due to El Niño weakening, but it’s hard to know over such a short time period. Even if the trend continues, I’d bet 2016 will be the hottest year on record.
When you spend a lot of time and effort to send a spacecraft to another planet, it’s a nice benchmark when that spacecraft first spots it.
The image above is Mars, as seen by the Trace Gas Orbiter, part of the European Space Agency’s two-pronged ExoMars program (the first mission is the TGO plus Schiaparelli, a lander that will test technologies for future missions, including the 2020 ExoMars rover). TGO and Schiaparelli were launched on March 14 and were about 41 million kilometers from its destination when this shot was taken.
Mars is only about 6,800 kilometers in diameter, so from that distance it was only a dozen or so pixels across in the camera of the Trace Gas Orbiter. That’s pretty small, which is why it’s hard to see much here. But it shows the camera works! To make the picture a little more clear, here’s a slightly (3 pixel Gaussian) blurred version of it:
The image release notes that the Tharsis region of Mars was facing the camera when the shot was taken. Tharsis is a huge area of Mars known for its four massive volcanoes, including Olympus Mons, the largest such beast in the solar system. I poked around and found a Mars picture by Hubble that more or less matches the ExoMars shot:
That was taken in 2003 and isn’t an exact match but it’s close. Olympus Mons is the big splotch at the top center, and the dark southern region below it is called Terra Sirenum. Out of curiosity I shrank it to roughly the same size as the ExoMars picture, rotated it, and blurred it a bit to compare them:
Not bad. Not exact, but you can see the similarities. This first ExoMars mission will reach Mars in October, and once in orbit the camera (called CaSSIS) will be able to spot objects on the surface as small as 10 meters across—the size of a small house. So expect far more interesting picture than this coming this winter!
On Sunday, June 19, 2016 at approximately 14:15 UTC (10:15 a.m. Eastern time), the private rocket company Blue Origin plans to launch their New Shepard rocket for the fourth time. As with the three previous tests, it’ll launch straight up, deploy the crew capsule, and then come back down vertically. The crew capsule will come back much more slowly, using parachutes to descend gently (and a retrothrust system to make sure the landing isn’t too rough).
Except this time, the company has rigged it so that only two of the three parachutes will open.
This test is being done on purpose to make sure they can still safely land in the event of single parachute failure. As Blue Origin CEO Jeff Bezos said, “Works on paper, and this test is designed to validate that.”
This should be an exciting test. In a very different move for the company, they have announced they’ll be streaming the event live on their website (it starts at 13:45 UTC, a half hour before the launch). I find that very interesting; in general the company has not done that; they release video after the flights, and rarely even announce when the launch tests will be. I wouldn’t say they’re secretive, but they tend not to actively seek publicity.
I have to wonder if the live coverage of SpaceX launches is behind this decision. Obviously, SpaceX has captured the lion’s share of the public’s attention when it comes to rocket launches. SpaceX has carefully cultivated an excellent public outreach effort, and the result is that their launches are watched live by a lot of folks. I imagine Blue Origin wants a piece of that.
They deserve it. New Shepard (named after astronaut Alan Shepard, the first American in space) has launched successfully three times, and each flight has tested different aspects of the process, including a quick restart of the engine only a kilometer above the ground before landing. It’s actually pretty amazing.
What SpaceX is doing and what Blue Origin is doing are, at the moment, very different. SpaceX is launching a very large rocket into orbit, meaning it has to go sideways (usually to the east) very rapidly to go around the Earth. Blue Origin’s flights are suborbital; the rocket goes essentially straight up, past the arbitrary but generally agreed-upon 100-km altitude marking the beginning of space (at that height, there’s almost no air and no drag on the rocket). That’s far easier than going into orbit.
But not easy. Going up that high, releasing a capsule, having that land safely, and landing the rocket itself back down vertically on its tail is incredibly hard. Blue Origin has shown they’re getting the hang of it, though.
And while there’s a good market for suborbital flights (even a few minutes of free fall can be very useful scientifically), the plan is to use the knowledge gained to create a more powerful rocket capable of orbital flight. This is how SpaceX did it with the Falcon 1 rocket that led to the Falcon 9, and Blue Origin has similar ideas. Their BE-4 engine, currently being tested, should have enough oomph to do this. United Launch Alliance, which makes the Atlas and Delta rockets, has partnered with Blue Origin to develop this engine for use with their next generation Vulcan rocket. That’s being created as a competitor for SpaceX’s Falcon series, and I’ll be very interested indeed to see how this goes.
I’ll be getting up early Sunday morning to watch this fourth New Shepard test flight, and live tweeting it, too. Rocket launches are fun and exciting, and these tests are the first steps toward a bigger and better arena for commercial spaceflight. I have a lot of hope for this new chapter in space exploration. A lot, and I think it’s been earned.
There’s an (apocryphal) curse: “May you live in exciting times.” I don’t think it’s a curse. I think it’s the best time to be alive.
The Earth has one satellite, right? That fact is so solid, we just call it the Moon with a capital M.
But due to a trick of gravity and timing, there are other objects out in space that aren’t really moons, but do travel along with Earth through space. I guess “companions” would be a better name.
One of them was just discovered recently by astronomers: the asteroid 2016 HO3. It’s small, probably 40 – 100 meters in size, and let me be clear: It orbits the Sun, not the Earth, so I wouldn’t call it a moon. But its orbit is such that it always sticks near the Earth, and from our point of view even seems to go around us!
Here’s how that works. The asteroid was first seen in April 2016 in observations of the sky taken by the Pan-STARRS observatory, designed to look for asteroids and comets that get close to Earth. That’s recent enough that a really good orbit for it is hard to determine, but it turns out it was seen in older observations (those can be found by tracing the orbit backward and checking if any observations of it were archived), providing a much longer baseline and therefore a better orbit.
What they found is really interesting: The orbit of HO3 is very Earth-like! It’s very slightly elliptical, and tilted by about 8° with respect to Earth’s, but the average distance of the asteroid from the Sun is just a hair more than Earth’s, and it takes 365.93 days to orbit the Sun. That’s just 16.6 hours longer than Earth’s 365.24 day-long year!
Because it’s moving on a tilted and elliptical orbit, sometimes it’s a wee bit closer to the Sun and moving a bit faster than Earth, and sometimes it’s a wee bit farther out and moving a bit more slowly. But it never gets closer than about 14 million kilometers from Earth or farther than about 40 million kilometers.
That’s hard to picture, so I made an animation using the JPL Small Body Database Browser. It shows the inner solar system, and keeps Earth centered as it and 2016 HO3 orbit the Sun (HO3’s orbit is blue; light blue for when it’s north of (“above”) the Earth’s orbit, and dark blue when it’s south (“below”)). As time moves forward, you can see HO3 moving faster and ahead of the Earth, then slowing and lagging behind, but never getting very far away:
So as you can see it’s clearly orbiting the Sun, but never straying far from Earth. If you map its motion relative to Earth, it actually appears to go around us, like a moon! That’s shown in the diagram at the top of this article.
But it gets weirder. Because the orbit is slightly longer than Earth’s, you’d expect it to drift away over many years, lagging behind Earth more and more every year. But that’s not the case! Earth’s gravity tugs on HO3, changing the orbit slightly every time they pass. That keeps HO3’s orbit in line with Earth’s, so it never gets too close or too far away. It’ll be our companion for at least the next few centuries.
If you’re wondering how we’ve missed it all this time, I’ll remind you it’s small and still pretty far away in terms of actual kilometerage. Even at closest approach it’s at about 21st magnitude, or just one-millionth as bright as the faintest star you can see with your unaided eye. It takes a decent telescope to see it at all.
I find things like this delightful. The Universe is so surprising! Due to the law of gravity our solar system is in many ways like a clock, each object like a gear ticking away in time with the others.
But there’s more than fanciful analogies to be had here: Because of its similar orbit, HO3 is moving relatively slowly compared to Earth’s motion through space. That makes it a rather tempting target for a space mission, where how much fuel you need to get from point A to point B depends on their relative motion. HO3 is moving just a few kilometers per second relative to Earth in some parts of it orbit, making it much easier to send a probe there. Or maybe, someday, humans.
How about that? One of the best targets we could hope for, and we just discovered it a few weeks ago. The Universe really is surprising.
1.4 (or so) billion light years from Earth, two black holes were on a dance of death. One was about 14 times the mass of the Sun; the other eight. For a long time their orbits had been decaying, approaching each other ever more rapidly. And then, finally, so close they were whipping each other around at very nearly the speed of light, they merged. The event was catastrophic, sending out a blast of energy that literally shook the very fabric of the Universe itself.
Eons later, that death cry was seen by astronomers here on Earth. By the time it got here it was vanishingly feeble, but strong enough to shake the sensors in LIGO, the Laser Interferometer Gravitational-Wave Observatory. Two facilities comprise the observatory, one in Livingston, Louisiana, and the other in Hanford, Washington. Each one uses a system of lasers to measure the distance between a set of mirrors, and when the rippled in spacetime emanating from the black hole merger passed through the Earth, they changed the distance between mirrors ever so slightly.
Perhaps I’d better explain. In fact, I already have, when the first event was announced in February 2016:One of the outcomes of Einstein’s General Relativity theory is that space and time are two facets of the same thing, which we call spacetime. There are lots of analogies for it, but you can think of it as the fabric of space, a four-dimensional tapestry (three of space and one of time) in which we are all embedded. Remember, it’s not literally like this; we’re using an analogy. But it’ll help you picture it… … if a massive object is accelerated, it will cause ripples, waves, to move away from itself as it moves. These are actually ripples in the fabric of spacetime itself! Spacetime expands and contracts in complicated ways as a wave passes, a bit like how ripples will move out from a rock dropped into a pond, distorting the surface of the water.
In other words, when a massive object accelerates, it emits what’s called a gravitational wave that quite literally stretches and shrinks space. The more massive the object and the higher the acceleration, the more powerful the gravitational wave is, and the more space gets distorted. Most objects in the Universe are way too placid to do this, but when two black holes merge, the masses are high and the acceleration fierce.
Even then, by the time the waves get here (moving at the speed of light across the Universe), the ripples are incredibly tiny. The ripples from this new event, called GW 151226 (for the gravitational wave source detected on Dec. 26, 2015), stretched space by only a factor of about 10-22 by the time they reached Earth. That’s so small it’s hard to imagine, so let me put it this way: If you had a ruler a kilometer long, as a ripple passed through it would change its length by less than the width of a proton!
Still, that’s measurable! Barely. As I described in my earlier article LIGO is designed to see incredibly small strains in the fabric of spacetime. The biggest problem is noise; in this case the detectors are so sensitive that they can detect molecules of air hitting the mirrors!
It’s taken many years, but last year LIGO was finally made sensitive enough to detect the more powerful gravitational waves passing through it. The first detection, made on Sep. 14, 2015, was from two pretty beefy black holes, roughly 36 and 29 times the mass of the Sun. The event lasted two-tenths of a second.
In this second case, the entire detected event lasted about a full second. As the black holes fell in those last few kilometers, their fierce gravity swung them around faster and faster, causing the gravitational waves to increase in frequency and strength. When sound waves do this you get a sharp, short “chirp”, and that’s what astronomers call this event, too.
The detection itself is pretty amazing. Automated software checks the signal from the LIGO setup and was the first to notice something was up. It alerted astronomers, who checked to make sure the signal was real. Part of that was looking at the signal from both facilities in Washington and Louisiana, and they both saw it (it was first seen in Louisiana, then in Washington 1.1 milliseconds later; that has to do with the speed of light and the angle to the merging black holes).
Note that in the plot above, each up and down cycle you see is one orbit of the black holes around each other. These objects combined are 20 times the mass of our entire star, but they were whipping around each other hundreds of times per second before the end.
The exact shape of that signal is predicted by Einstein’s Theory of General Relativity. Using computers, the astronomers then generated literally millions of theoretical signals, comparing them to the observed one. They change the masses of the black holes, as well as many other parameters, giving them a range of values for their masses and distances. In the end, the masses found were 14.2 ± 8.3/3.7 (so as much as 8.3 more and 3.7 less) and 7.5 ± 2.3/2.3 times the mass of the Sun, and the distance roughly 1.4 billion light years.
This means the black holes were probably created in the usual way. A long time ago, two very massive, hot stars were in orbit around each other. One blew up, expelling its outer layers, and its core collapsed to form a black hole. Sometime after that the second one blew, creating the other black hole. They would have orbited each other stably forever, but Einstein has something to say about that: As they moved, they emitted those gravitational waves. The emission was very weak at first, but it removed energy from the system, and the black holes spiraled every so slightly closer together. As they got closer they moved faster, were accelerated more, and emitted more waves. This was a positive feedback loop, and when they got close enough together, BLOOP! They merged.
The 14 and eight solar mass black holes combined to form a single black with 21 times the mass of the Sun.
Of course, 14 + 8 = 22. What happened to the missing mass? That mass was converted into the energy of gravitational waves.
I’m not going to lie to you: Just writing that gave me a chill down the back of neck.
That amount of energy is beyond staggering: It’s equivalent of all the energy the Sun emits over a period of about 15 trillion years. That’s a thousand times the lifetime of the Sun! Or, if you prefer, it’s about the same amount of energy emitted by a billion galaxies like ours over the same time interval as the merger.
And now you can see why astronomers are so excited by this. These are among the most energetic events in the Universe, and until last year we were completely blind to them.
The first event showed we could do it. This second event shows that the age of gravitational wave astronomy is truly here. Mind you, both events were detected just a few months after LIGO became sensitive enough to detect them; many more will be seen, and soon. As data are gathered, well learn more about this entirely new field of astronomy, one completely divorced from the usual detection of electromagnetic waves — light. Certainly, conventional telescopes will help; it’s suspected there may be a brief flash of light accompanying the release of gravitational waves, but it’s not certain. And just on their own, gravitational waves yield a treasure of information.
This is an amazing event. Predicted by esoteric physics a century ago, detected by physics even older than that, we finally have the technology that allows us to hear the faint whispers the results from these deafening roars. And it will allow us understand the universe in a whole new way.
When a star dies, it can be lovely.
When a star dies with another nearby, it can be amazing.
The image above shows Hubble 12 (also called HB 12 for short), what astronomers call a planetary nebula, the gas and dust thrown off by a star as it ends its life. When the star runs out of fuel in its core needed to generate the energy it uses to sustain itself, the outer layers of the star can be thrown off in a series of winds, like a solar wind on steroids.
But HB 12 has an extra ingredient or two. One of them is that the star in the center isn’t one star, but two. They orbit each other pretty close together, their orbital velocities high. This can help shape the wind blown out by the one star that’s dying; it adds a component of centrifugal force. Most of the material flung out goes out along the orbital plane of the two stars, forming a disk. Other stuff hits this disk and flows up and away, forming the hourglass figure.
Another ingredient is the fact that HB 12 sits in a region of the galaxy thick with interstellar gas and dust. Some observations indicate there’s quite a bit of it surrounding the stars, and the wind is plowing into that material, which confines it. That may be why the edges of the shapes you see in the image are so well defined. It also makes the nebula denser, and therefore brighter; HB 12 has one of the highest “surface brightnesses” of any nebula—that means any given piece of it is pretty bright compared with the same size section of another nebula.
But there’s a lot more going on here. If you look at the inner nebula, the part that looks like a butterfly, you can see brighter rings going around the cone-shaped “wings” (reminding me of the old Rocketdyne F-1 engines used on the Saturn V rocket). Each one of these may have been due to a gust of wind from the star, an episodic hiccup that temporarily increased the amount of material blown out. Given the spacing in the rings, they probably occur every 50 years or so. So twice a century the star went through some sort of event that increased its outflow. It’s not clear what that event might be.
Those outer structures, though! What a mess. But if you look carefully, you see symmetry. For every U-shaped structure you see, there’s an upside-down U to match it. That’s because every time the star blows out material, it does so in both directions, up and down. That might be more clear in a grayscale version of the image:
The exact cause of all these structures has me scratching my head, though. The eye-shaped oval in particular is weird. I’d expect that to be an ellipse, a circle of expanding material seen at an angle (like looking at a water glass from an angle makes the circular opening appear like an ellipse). However, in this case it has sharper cusps on the left and right. That might simply be due to a weird perspective; the gas here is thin, and you can see through it, so you’re seeing the front and back side of the nebula on top of each other.
So that wide open structure on the outside is probably much like the inner, bright butterfly structure. Perhaps it’s just older and has had more time to spread out. If that’s the case, I see at least three such structures here, which hints that the dying star has had a lot of increased activity over the years.
And this I find particularly interesting: Just outside the central bright point marking the star’s position, you can see two parallel circular features, one just above and one just below the star. That reminds me very strongly of NGC 1514, another planetary nebula:
As I wrote then, such features aren’t well-understood. What shapes them, why are they on opposite sides of the star like that, why are they so bright? It’s not clear.
Actually, there’s a lot that’s not well known about this object. We’re not even sure of its distance! Various methods to measure that yield wildly different results; everything from 7,500 light-years to more than 25,000 light-years! I suspect it’s probably on the closer end of that range, but who knows?
Here’s another interesting thing: This nebula is young. Measuring the speed of the expansion of the features and then tracing that back,* the age of the nebula is probably more than 1,000 years. That’s consistent with what we know about such objects; the gas is thrown out pretty quickly, and the planetary nebula stage of a dying star lasts millennia at most. The expanding gas becomes too thin and too distant for the star to light up, and the nebula fades.
I love planetary nebulae; I studied them both for my master’s degree and Ph.D. Very little was known about them before the advent of digital cameras, they’re pretty faint and small. But now we have extremely sensitive detectors and telescopes like Hubble, capable of imaging their fantastic structures.
And one last thing: The images you see here of HB 12 were processed and constructed by Judy Schmidt, who likes to reprocess data from the Hubble Space Telescope and create beautiful images. Her work has been featured here on the blog many times, and you can also see her creations on her website and on her Flickr page. Follow her on Twitter to get the latest updates, too. We had a fun conversation about this nebula, and I hope she tackles more such objects in the future.
*It’s a bit like knowing how far you’ve driven knowing your speed and how long you’ve been on the road. If you know the size of the nebula and how quickly it’s expanding, working the math backwards gives you the age.
In May of 2016, Elon Musk announced that SpaceX would be sending a Dragon capsule on its way to Mars by the end of 2018.
That’s pretty ambitious. After all, 2018 is soon.
But is it too soon? I wrote an article about Musk’s plan to go to Mars, and I still think SpaceX can do it. But can do it isn’t the same thing as will do it. The problems are essentially two-fold: The hardware they’ll use to go to Mars (mostly the Falcon Heavy rocket and the upgraded Dragon capsule) is still untested, and the fact that, to coin a phrase, stuff happens. By that I mean the winds of chance: a launch delay, a wonky part that refuses to be diagnosed, a Congressperson who has a NASA rocket facility in their district and doesn’t want the competition… these can all add weeks or months to the countdown.
So when Taylor Quimby of the New Hampshire Public Radio show “Word of Mouth” called me to talk about it and settle a bet he had with his colleague Sam Evans-Brown, I tried to explain this all carefully.
In the end, the distinction I’m trying to make is that yes, SpaceX can get to Mars, and possibly even launch the mission before December 31, 2018. But it seems to me, given the reality of the situation, it’s quite likely it’ll happen in 2019 or later.
Ask me again after the Falcon Heavy goes on its first voyage, and the upgraded Dragon is built and tested, too. Once SpaceX gets those up and running, well, the sky’s no longer the limit.
As I said in the interview, the real question is: Who will put humans on Mars first, NASA or SpaceX?
NASA’s plans to go to Mars are a bit vague, but rely on the Space Launch System to do it (full disclosure: I’m not a big fan of SLS). Like the Falcon Heavy, SLS has not yet launched, and the first flight is planned for late 2018 (barring delays, of course). NASA doesn’t plan to have humans on board an SLS flight until at least 2023, with a Mars flight perhaps sometime “in the 2030s”. Musk recently announced he wants to put humans on Mars by 2024, another ambitious but potentially doable deadline. Even if delayed several years, SpaceX would have an edge over NASA.
The situation with SLS and Falcon Heavy is complex, and more than I want to dive into here; a longer, more thorough post will come where I lay out my current thoughts on it. But in the meantime, to be clear: The deadlines Musk has laid are ambitious but achievable, and even if they aren’t met, the ability of SpaceX to go to Mars and eventually put humans there should not be discounted.
It’s the way to bet.