Bad Astronomy Blog
I have so much to say about it, but really, just watch this (note: lots of bleeped swearing for comedic effect, including from a kid, if that kind of thing offends you):
There are so many great lines in this segment, but I think my favorite is this:You know how you know when climate change is real? When the hottest year on record is whatever year it currently is.
Yup. Well, that, plus when it keeps happening year after year. When we've had at least six months in a row of record-breaking heat, when the 16 hottest years since 1880 are all in the past 17 years, when 97 percent of climate scientists agree, and heck, when Sarah Palin thinks it’s wrong, then yes, we’re in serious trouble.
And yet the networks and media still think giving air to a climate change denier is a good idea. Incidentally, as Media Matters points out, there are more climate scientists in that Jimmy Kimmel video than were interviewed on ABC’s top news shows in all of 2015.
And this is why I still focus on the reality of climate change. Because too many people in charge of you getting your information won’t.
We can’t work on solutions until we get our politicians to admit the problem even exists. Remember: November is coming.
The search for Earth-like planets continues, as astronomers scour the sky examining stars for telltale clues of orbiting worlds. Most of the exoplanets found are big, like Jupiter, because they’re the easiest to detect. But our technology has become better and more clever over the years, and smaller planets have been found, including many roughly the size of Earth.
That search took a cool turn this week … literally. A team of astronomers announced they have found not one but three Earth-size planets orbiting a red dwarf, a tiny and cool star just 40 light-years away!
This is very interesting for many reasons: This is the lowest mass full-fledged star ever seen to have planets, it’s relatively close by, and all three planets are (more or less) in the star’s “habitable zone,” where temperatures might—might—support the existence of liquid water on the planets’ surfaces.
The European Southern Observatory put together a nice video explaining this, so give it a view:
The planets were discovered using TRAPPIST (short for Transiting Planets and Planetesimals Small Telescope). This is a 60 cm (24”) telescope that takes images of a select group of 60 nearby red dwarf stars visible from the Southern Hemisphere. The team looks for dips in the stars’ light that are caused by any planets orbiting those stars periodically blocking their host star’s light; this is called the transit method, and most exoplanets have been discovered this way.
TRAPPIST found evidence of planets orbiting a star, called TRAPPIST-1, and follow-up observations were made with much larger telescopes. Three planets were found in total, which is remarkable all by itself. But it gets better.
TRAPPIST-1 is an M8 dwarf, only 0.08 times the mass of the Sun; just barely massive enough to fuse hydrogen into helium in its core. If it were much lower mass we wouldn’t call it a star at all (we’d say it’s a brown dwarf). Its surface temperature is only about 2,550 K—the Sun is literally more than twice as hot—so it's informally called an "ultracool" star. And it’s tiny, only about 0.11 times the diameter of the Sun. That’s roughly the same size as Jupiter!
Yet this teeny star sports at least three planets. Called TRAPPIST-1b, c, and d, the exoplanets were detected as they blocked a small fraction of the star’s light. The sizes of the planets were found by seeing just how much of the starlight they blocked. The best measurements indicate they are 1.1, 1.05, and 1.2 times the size of Earth. We don’t know their masses, but if they have the same composition as our home world—rock and metal—then their surface gravities wouldn’t be all that different than ours.
So they’re Earth-size. But are they Earth-like? That is, nearly the same temperature and composition as Earth?
We have no idea what these planets are made of. They could be rock, metal, watery, airless … with our current technology we don’t know how to determine that. Finding the masses of these planets would be extremely difficult, so we’re out of luck there.
But we can estimate their temperatures. The temperature of a planet depends on its distance from the star and that star’s temperature, of course, but also on how reflective the planet is; a more reflective planet will be cooler than a dark, absorptive one.
Each of the planets orbits ridiculously close to the star compared with the planets in our solar system. In order, they’re 1.7 million, 2.3 million, and 3.3 million–22 million kilometers from the star (the observations of the third planet, d, don’t constrain its distance very well, so there’s a range of possible distances). Mind you, Mercury is 58 million kilometers from the Sun, so all three of these planets would easily fit inside Mercury’s orbit, with a tens of millions of kilometers to spare.
But remember, the star is very cool, so even at those distance the planets aren’t as hot as you might think.
Assuming very dark planets, the inner two would be about 125° and 70° C, far too hot for life as we know it. The outer planet’s distance from the star wasn’t as well determined, but it would likely have a temperature somewhere from -160° - +10° C depending on its distance. The warmer end of that range is close to Earth’s average temperature!
Remember, that’s assuming dark planets. If they’re more like Earth (which reflects about 40 percent of the light that hits it), they’ll be cooler. If they’re reflective enough, the inner two planets might be more like Earth, too (but the outer planet would be a frozen ball of ice).
That part is more speculative; we have no idea how reflective they are. It’s possible, though I’d think unlikely, that all three planets are somewhat clement.
Again, we don’t know much about them; they might be airless, or have thick atmospheres of carbon dioxide, or some other noxious combination, so don’t start looking into real estate on them just yet. And even if they are Earth-like, 40 light-years is 400 trillion kilometers. That’s a fairly long road trip. It would take 450 million years to drive there at highway speeds. Better pack a lunch.
But don’t be disappointed. The amazing thing to remember here is that these planets exist at all. Even dinky red dwarf stars manage to make planets, including ones the same size as ours. That’s incredibly exciting.
Another reason this is so exciting is because of the host star. Cool red dwarfs are faint and hard to detect, making these observations somewhat difficult, but they also make up the most populous class of star in the galaxy. If they have planets in the same proportion as more massive, hotter stars do, then planets orbiting red dwarfs will outnumber planets orbiting all other types of stars combined. And here we found three Earth-size planets orbiting one nearby.
It’s impossible not to ask, how many planets like Earth exist in the galaxy? We’re not sure, but various methods have been used to estimate that number, and even conservatively their numbers must be in the billions. Billions. In our galaxy alone.
And our tech is getting better. In the coming years we’ll have telescopes able to dissect the light from such planets, looking for the Earth-like conditions: oxygen in the atmosphere, say, and a temperature more like ours. We’ve found a few candidates for Earth-like exoplanets, but nothing yet that we can point to and confidently say, “Earth 2.”
So, SpaceX wants to land a spaceship on Mars in 2018.
Yup. Last week, Elon Musk, CEO of SpaceX, made the startling announcement on Twitter:
He wrote, “Planning to send Dragon to Mars as soon as 2018. Red Dragons will inform overall Mars architecture, details to come.”
My very first thought when I read this was, “He thinks they can land a three-ton uncrewed Dragon capsule on Mars in the next couple of years? Something heavier than any other payload ever dropped on Mars, and from a company that hasn’t even sent anything beyond low Earth orbit?”
Then I mulled it over for a moment. To my own astonishment, I realized, “Huh. Yeah. In fact they can do this.”
Now look, it won’t be easy, not by a long shot. But Musk’s claim isn’t out of the blue—SpaceX has been working toward this for years. What it comes down to is key pieces of technology still untested in flight but currently being developed, as well as SpaceX maintaining its current launch schedule.
But in the end, it’s feasible that by the closing days of 2018, a Dragon capsule may sit on the surface of Mars.
First, let’s take a look at the spaceship that would do the actual landing. The Dragon V2 is an upgraded version of the Dragon capsule currently being used to send supplies up to the International Space Station. Dragon V1 has been sent to space and back successfully many times already.
The V2 upgrades are extensive, including adding the ability to carry seven astronauts to ISS. But as far as a Mars trip goes, the most important upgrade is the addition of SuperDraco thrusters; four sets of two engines around the outside edge of the capsule. These are powerful, designed to be able to rapidly carry away the capsule in case of rocket failure during flight. But they’re also critical for landing on Mars.
The atmosphere of Mars is very thin, but it’s there. You can’t ignore it if you want to land on the planet; at interplanetary speeds a capsule will burn up as it plows through the air if steps aren’t taken. Sending smaller probes to the surface (like early landers and rovers) used a combination of aerobraking (drag on the spacecraft to slow it down), parachutes, and in the case of Curiosity a rocket crane that slowed to a hover over the surface to deploy the rover.
A Dragon V2 is too big for any of these options; a parachute big enough to slow it down would be shredded under those stresses. Instead, the plan is to use an advanced heat shield on the bottom to slow it down enough that the SuperDracos can take over, landing the Dragon V2 safely on the surface.
This has never been done before, but SpaceX has been slowly learning how to do it, and you’ve probably seen it happen: the return of the Falcon 9 first stage boosters. To return to Earth, the booster flips around and does a “boostback burn” to slow its motion. Even though there have been many attempts to land the booster, and only two successes, that doesn’t mean all was lost. The data retrieved from all the attempts are precious steps toward understanding how to do a “supersonic retropropulsion” burn to slow a vehicle in air … under conditions very similar to the conditions a Dragon capsule will face entering the Martian atmosphere.
That’s no coincidence. Every booster return is like a real-life simulation of a Mars landing. So SpaceX has been amassing quite a bit of information on how to do this.
In fact, they’ve been sharing that data with NASA in exchange for technical advice on deep space planning and support. No money has changed hands, just the trade of information. NASA has also pledged communications and telemetry support using their Deep Space Network in exchange for the data from an uncrewed mission to Mars using the Dragon V2.
So it looks like the Dragon V2 can get down to the surface of Mars from space. But how does SpaceX plan to get it to Mars in the first place?
Right now, the company has contracts with NASA and other groups for launches using its Falcon 9, their workhorse two-stage rocket. The Falcon 9 is a capable booster. There have been 23 launches of Falcon 9 so far, with 22 successes and one failure (that last tracked to a faulty support strut inside the booster; those have been upgraded since that time).
It can even be used to send a payload to Mars, as long as that payload has a mass less than about 4,000 kilograms (8,800 pounds, or four tons). That’s not bad, but not nearly enough to get a Dragon V2 capsule down to the surface—a dry (unfueled) Dragon V2 has a mass of 6,400 kilos.
Clearly, they’ll need a bigger rocket.
Enter the Falcon Heavy: This beast is essentially three Falcon 9 first stage boosters strapped together, providing a much larger payload capability. It can hypothetically send up to 13,600 kilograms to Mars. That easily covers the mass of the capsule and fuel, and would still have a few tons of capacity left for scientific instruments.
So, great. Use the Falcon Heavy to throw a Dragon V2 at Mars, and use the knowledge gained over the past few years to drop the capsule safely to the surface.
Except, hang on. SpaceX isn’t quite there yet. While all of this makes sense on paper, they haven’t actually tested all this hardware in flight. The Falcon Heavy has never been flown. But at the Satellite 2016 conference held in March, Gwynne Shotwell, president of SpaceX, said that the first Falcon Heavy flight may be late this year, possibly in November. That launch, from Florida, is also planned to include recovery of all three first stage boosters, two on land and one on a floating barge in the Atlantic (this is basically a three-fold test of the single booster relanding after launch). Over the next couple of years there will be more flights as well, which will hopefully work out the bugs and build confidence in the rocket.
Of course, the Dragon V2 hasn’t flown yet either. However, it has been tested extensively on the ground, including a “pad abort test,” a NASA requirement for crew-rated vehicles to make sure it can take astronauts away to safety if there’s a launch emergency:
The capsule should be tested in flight this year as well. SpaceX has said it wants to send a crew to space on the Dragon V2 in the next year or so, and already has an order from NASA to send a crew to ISS (though no date has been specified, 2018 is a decent guess).
So, SpaceX being able to go to Mars depends critically on flight-testing both the rocket and the capsule lander. But both of those tests are in the works and may happen quite soon. And, if they test successfully, SpaceX will turn its eyes to Mars.
Which brings me back to Musk’s tweet. Red Dragon is the name of the mission to send a Dragon V2 to Mars. The information learned from that mission will then be used to figure out how to send larger and more ambitious missions.
And make no mistake, Musk is determined to put people on Mars; I interviewed him on this topic in 2015, and he stated plainly, “Humans need to be a multiplanet species.”
We’re not there yet. SpaceX isn’t there yet either; quite a lot rests on the successful tests of Falcon Heavy and Dragon V2—and more, for that matter. Details of the actual mission profile (for example, what kinds of potential payloads it might carry) haven’t been released yet; the company plans on discussing all this at the International Astronautical Congress in Mexico this September. Realistically, the 2018 goal may get pushed back a year or two due to inevitable delays; there’s a long way to go and a lot to do before this mission literally gets off the ground. But SpaceX is very serious about it.
And, in my opinion, it's quite capable of accomplishing it.
Post script: My colleague Eric Berger wrote two excellent articles on this topic: “Can SpaceX Really Land on Mars? Absolutely, Says an Engineer Who Would Know” and “Why Landing a Flying, Fire-Breathing Red Dragon on Mars Is Huge.” You’ll find a lot more details there. I’ll note we agree that SpaceX can in fact achieve this goal.
There are times when I glance at an image and right away I know something is peculiar about it. Such was the case for UGC 477, the very lovely but decidedly weird galaxy pictured above.
The image was taken using Hubble Space Telescope, and only shows two colors; usually these images are the more natural-looking three-color red/green/blue composites. In this case, what you see as blue is actually at a wavelength of 475 nanometers (teal or blue-green to our eyes), and red is 775 nanometers, just at or outside the reddest end of what we can see (it’s fair to call this near infrared). The blue highlights the young, hot, massive stars and red the old, low-mass, cooler stars in the galaxy.
To my eye the galaxy looks, well, raggedy. Most spirals seen edge on are smoother, or if they’re clumpy, the clumps have a pattern to them. This one looks like it just woke up in the morning and hasn’t had its coffee yet. It’s messy, disorganized.
It turns out that’s really the case. But it’s weirder than that: UGC 477 is what we call a low surface brightness galaxy, or LSB galaxy. As the name implies, these are pretty faint galaxies, sometimes actually much fainter than the night sky surrounding them. Our own galaxy is a disk, and would easily swamp the light from UGC 477 if the latter weren’t located well above our own galaxy’s plane, where stars and dust are less populous.
The galaxy is about as big as our Milky Way, 100,000 or so light-years across, and it’s 120 million light-years away. At that distance it should be bright and fairly obvious, but instead is much dimmer than you’d expect. This may be due to a lack of star formation in it; although you can see some bluish clumps where stars are being born, most spirals have big, splashy nurseries in them. UGC 477 seems to have a much larger gas to star ratio than other galaxies, unused material from which to make stars.
LSB galaxies may be isolated from other galaxies, in regions of space called voids. This means they don’t suffer collisions as much, which is one way to build a giant galaxy, and to crash gas clouds together so they can form stars. It’s something of a mystery as to why LSBs can be so big then, though. Malin 1, another LSB galaxy, is a freaking monster, five times or more bigger than our Milky Way! Yet it’s far fainter than you’d expect for such a beast.
Interestingly, LSB galaxies appear to be dominated by dark matter, making them good test beds for models on how this affects galaxy formation, growth, and shape over time. We actually don’t know as much about these galaxies as we do normal ones, since they’re so dim they were only discovered recently, and they’re difficult to observe. Hubble is ideal for this kind of study, though, at least for nearby ones—but even its mirror is too small to collect enough light from ones substantially farther away.
But as telescopes get bigger, and our detectors more sensitive, we’ll learn a lot more about these odd denizens of deep space. What were they like when the Universe was young? Pretty much as they are now, or were they substantively different? Hopefully soon we’ll know, and put into place have yet another piece of the puzzle that is our Universe.
A new study just published in the journal Nature Climate Change reached an interesting, if not totally surprising, conclusion: The Earth has become significantly greener over the past 33 years.
The main reason? All the extra carbon dioxide we humans dump into the air.
Let me be clear right away: This is a kinda sorta good thing, but don’t celebrate the positive aspect of climate change just yet. The effect almost certainly won’t last, and this small positive is completely buried under a long, long list of negatives.
The research used satellites to examine vegetation growth over time, assuming that the extra green is coming from leaves on plants and trees. Using a computer model to estimate leaf growth, they find the extra greening is equivalent to adding about 18 million square kilometers of vegetated land to the globe, over twice the area of the mainland US. That’s pretty astonishing.
The growth is due to added CO2 in the air. Plants use sunlight for energy, and convert CO2 (plus water) into sugar, which is stored for food. In a naive sense, more CO2 means more food for plants (this is called carbon dioxide fertilization), so there’s more growth.
The good news, such as it is, is that this means plants are able to soak up more carbon from the atmosphere. The bad news is, it’s not nearly enough. This is made clear by a graph showing atmospheric carbon dioxide content, as measured at the Mauna Loa Observatory in Hawaii:
As you can see, the amount of CO2 in the air is still increasing, even with this extra vegetation. Worse, look at the increase from 1980 (roughly the start of the new study’s time range) to 1995. If you extend that slope, you’ll see that the increase has increased since 1995; in other words, we’re putting out even more CO2 per year than we did 35 years ago.
All that extra plant growth can’t keep up with the 40 billion tons of carbon dioxide humans dump into the atmosphere every year.
Incidentally, some of that greening is in the Arctic. That place usually covered with snow and ice, except warmer temperatures have been causing it to melt away. That’s a not a place we want to see green. White would be way better.
Of course, this hasn’t stopped the deniers, who tend to ignore inconvenient facts like that, and instead just tout how the Earth getting greener must be a good thing. World News Daily and the Cato Institute were two sources I found pretty easily making this fallacious claim. It’s cherry-picking in the worst sort of way, but then deniers have been making this ridiculous claim for a long time now.
What I find funny is that in the press release, one of the authors of the research pre-emptively smacks down the deniers [emphasis mine]:The beneficial aspect of CO2 fertilization in promoting plant growth has been used by contrarians, notably Lord Ridley (hereditary peer in the UK House of Lords) and Mr. Rupert Murdoch (owner of several news outlets), to argue against cuts in carbon emissions to mitigate climate change, similar to those agreed at the 21st Conference of Parties (COP) meeting in Paris last year under the UN Framework on Climate Change (UNFCCC). "The fallacy of the contrarian argument is two-fold. First, the many negative aspects of climate change, namely global warming, rising sea levels, melting glaciers and sea ice, more severe tropical storms, etc. are not acknowledged. Second, studies have shown that plants acclimatize, or adjust, to rising CO2 concentration and the fertilization effect diminishes over time," says co-author Dr. Philippe Ciais, Associate Director of the Laboratory of Climate and Environmental Sciences, Gif-suvYvette, France and Contributing Lead Author of the Carbon Chapter for the recent IPCC Assessment Report 5.
Of course, deniers gonna deny. Using this study to say that climate change is good is like getting in a massive car accident and being happy you don't have to vacuum out the car anymore.
But hey, if you’re willing to ignore rising sea levels, more extreme weather, melting polar ice, deoxygenation of the oceans, droughts, floods, acidification of the oceans and coral bleaching, more heat waves, and the displacement of potentially hundreds of millions of people, then y’know, a little more green in your life is just great!
Enjoy it while it lasts.
This is just too cool. Click in the video and drag it around. Hint: At the beginning, tilt up.
The Falcon 9 booster landing on April 8, 2016 was pretty amazing. It was windy out, as you can see from the video; once the booster made contact it slid a few meters. A while later, some SpaceX crew went out to the barge to weld it to the surface so it wouldn’t tip over if the seas got rougher. Bear in mind, that booster is over 40 meters tall. That’s taller than a 12 story building.
The video is neat. Being able to move it around like that is a relatively new thing for YouTube videos; we exploited it for an interactive Crash Course video tour of the solar system. Go play with that if you’d like. The narrator is a close friend of mine.
The next Falcon 9 launch (carrying a Japanese communication satellite) is scheduled for May 4, with a launch window opening at 05:22 UTC. A booster landing at sea will again be attempted, but it’ll be much tougher: The launch is to put the satellite in a geosynchronous orbit, which means the booster will be moving horizontally much faster than it did for the last landing, and will have less fuel to slow and maneuver to the barge. It’s likely not to be successful, but we’ll see.
Another day, another weird Facebook astronomy hoax.
The photo with the caption above have been spread around Facebook quite a bit the past few days; it shows Saturn looming huge in the sky over a city, with the annotation, “On 5/1/16 Saturn will be the closest it ever has been to Earth. It will look like this.”
I got a few notes from readers on Twitter about it. Unlike a lot of other wrong but possibly sincere memes, this one is clearly a hoax. It’s just silly and wrong on every level, so it couldn’t possibly have just been an honest mistake. It’s a joke.
What’s wrong with it? Well, two main things: Saturn isn’t the closest it’s ever been on May 1 (its closest approach to Earth this year is in June), and Saturn can’t get big enough to look like that, ever. Which is a good thing.
The closest Saturn ever gets to Earth is about 1.2 billion kilometers. That’s something of a hike. Saturn is big — 120,000 km in diameter, not including the rings which are 250,000 km across — but from that distance it’s not even big enough to appear as a disk to the eye. Through binoculars you can see the rings as a tiny ellipse, and through a smallish ‘scope you can more clearly see the planet as a disk and the rings circling it.
To be that big, Saturn would have to get as close to us as our Moon! In fact, that’s where the image comes from. It was easy enough to track down; a reverse image search on Google showed it’s from a Russian video intended to show what the sky would look like if the Moon were replaced with the other planets in our solar system:
It’s a fanciful idea, and as far as I can tell first done by my pal Ron Miller, a space artist, in 2012, and again by videographer yeti dynamics in 2013. In fact, yeti dynamics went ever farther and created a wonderful video showing what it would look like if Saturn were actually passing the Earth in the solar system:
As I wrote at the time, that would be the most amazing sight ever witnessed… and also the last thing you’d see. From that distance, Saturn’s gravity would inflict monstrous tidal forces on the Earth, causing apocalyptic floods, massive earthquakes, and generally dealing out death on a global scale.
As much as I love looking at Saturn, I’m pretty happy it’s over a billion klicks away.
So where is Saturn right now? It’s currently about 1.37 billion km away, where it always is. It rises around 10:30 p.m. local time, and shines at a magnitude of about 0.2, making it one of the brightest objects in the sky. In fact, it’s very much worth going out and taking a look around midnight; very close to it in the sky is the much brighter and much oranger Mars, and the bright red supergiant star Antares, the heart of Scorpius. Face south and look low to the horizon for the trio; your outstretched fist can cover all three.
And if you have a telescope, well then what are you waiting for? Saturn is one of the most magnificent objects in the sky. Patience pays off, too: in early June it will be at opposition, opposite the Sun in the sky, which means it rises at sunset and it up all night. As an added bonus, that’s when it truly is closest to the Earth, and appears as big as it can. But then, that means it’ll be 0.3 arcminutes across: Only 1/100th the width of the Moon in the sky.
But through a telescope, it’s glorious. So forget the dumb Facebook hoaxes, and go see the real Universe for yourself. It’s way, way better.
The Universe is a bit bent.
You’d think that light would travel in straight lines, going directly from point A to point B. But it’s more complicated than that. Space is curved, warped, distorted by the matter lodged within it. It’s hard for our puny three-dimensionally-adapted brains to wrap themselves around (so to speak), but what we think of as space is actually a framework that can be bent.
Mass does that bending, and we perceive that bending as gravity.
But we can see the effects of this bending, too. Like a car following a curve in the road, light follows the gravitationally induced curving of space. We poetically call this effect “gravitational lensing”, because a lens bends light as well.
Sometimes the curve in space is profound, like when a black hole makes a warp so severe it’s almost a puncture in the fabric of reality. The path a beam of light takes can be whipped around quite viciously — we call this strong lensing — or even plunge down into the black hole, never to return. Clusters of galaxies can do this as well, warping light from even more distant galaxies into bizarre shapes.
Other times that curve is more gentle, when the mass is more spread out. Individual galaxies and some galaxy clusters are like that. Instead of an obvious distortion in the direction light takes, it’s subtler, only marginally changing the light’s path.
Although harder to detect, this weak lensing can tell us a lot about the mass doing the bending of space. And that’s why astronomers used Hubble to take that lovely image of the galaxy PGC 54493 seen above.
That galaxy dominates the view, our eyes drawn to magnificent spiral arms, the bar-shaped distribution of stars in its center, the blue patches where massive stars are being born by the thousands. But it’s not the most important thing in this image.
Look around it. See all the smaller, fainter galaxies? PGC 54493 is perhaps 500 million light years or so away, but these other galaxies are much farther. The light we see from them was emitted when the Universe was far younger, and has traversed billions of light years of space to reach us.
On that trip, this light passed near PGC 54493, traveling through the region of space subtly distorted by the galaxy’s mass. The shapes of these distant galaxies thus get distorted, too, the amount of change in their shapes determined by the amount of mass in the big spiral galaxy bending space. It’s difficult to determine that for any individual faint galaxy, but if you observe enough of them, you can show statistically how much they’re warped, and therefore where the mass of the intervening galaxy lies and how much there is.
That is critical. We know that normal matter — the kind of matter that makes up you, me, the computer you read this on, and essentially every visible object in the Universe — is in the minority. Dominating the amount of matter in the cosmos is a mysterious form of it that we cannot see, but which has mass, and therefore gravity. Dark matter can’t be observed directly, but its gravity warps space, and that distorts the light from those distant galaxies, and that we can indeed measure.
Astronomers have been mapping dark matter in this way for many years; perhaps most famously in the Pandora Cluster, which showed just how dark matter in clusters of galaxies can affect the light from more distant galaxies. They continue to observe other clusters to make even more maps of the distribution of dark matter in the Universe, and that’s why PGC 54493 was the target of these observations.
Although bright and beautiful, it’s the dark reach of that galaxy that concerns us, invisible matter making invisible bends in space, distorting more distant galaxies in almost, but not quite, invisible ways.
Sometimes the Universe is obvious, ostentatious, perhaps even gaudy. But other times it whispers, hints at us to follow the rules of math and science that shape it, and in so many cases it is following that path — distorted and subtle as it may be — that leads to seeing its underlying structures.
As our globe heats up, the effects of those rising temperatures are complex and varied.
Overall, we call these effects “climate change”, but that’s an umbrella phrase that covers a vast number of changes. Melting polar ice, glacial melt, changing weather patterns, more extreme weather, rising sea levels, ocean acidification… these are the topics we hear about quite a bit. But there are other changes going on, and these are every bit as much a cause for concern.
For example, global warming is strangling our oceans.
By that I mean that oxygen levels in the oceans are affected by global warming, too. This occurs in two general ways. One is that warmer water has a harder time holding on to dissolved gases — that’s a basic law of chemistry. So oxygen levels drop as water warms. The other is that as surface waters warm, they expand, and mix less with deeper water. Surface water gets most of its oxygen from phytoplankton that breathe it out. That water sinks, and mixes with deeper water. As the water becomes more stratified due to global warming, less of that oxygenated water gets to lower depths.
The question then becomes, when will we start to see the effects of global warming on the oceans’ oxygen content? Like so many other aspects of climate change, we’re seeing that deoxygenation due to human-generated global warming occurring now. Not sometime in the distant future. Now.
That’s the result of a new study done by a team of scientists led by Matthew Long, an oceanographer at the National Center for Atmospheric Research in Boulder, Colorado. He and his fellow scientists used a sophisticated computer model that calculates the amount of oxygen dissolved in the oceans over the globe and with ocean depth. The model accounts for a great number of factors, including air temperatures, water temperatures, layers in the water, sea ice, and much more.
Global warming changes the air temperature, which affects the model. In the past, global warming was small, and natural variations in the environment change the oxygen levels far more than human-made warming. But, as the world warms more and more, the effect of warming increases, and at some point becomes noticeable over the natural variations.
Think of it this way: Imagine being in a loud room, with many people talking, and someone nearby whispers at you. You can’t hear them at first over the ambient noise, but if they keep speaking more and more loudly, at some point you can distinguish their voice from the crowd.
The scientists running the model wanted to know when they could hear the voice of warming over the babble of the natural variations. They ran the model many times, varying the air temperature a small amount with each run. This gave them a range of outcomes that they could compare to physical measurements; that gave them a check to make sure they had real-world testable outcomes.
What they found is sobering. Deoxygenation due to human-made global warming is already detectable in the southern Indian Ocean, and in some regions in the eastern tropical Pacific and Atlantic. By 2030 to 2040 — two decades from now — they expect to see more and more widespread deoxygenation over the globe. By the year 2100 (which is how far into the future they ran the models) a significant fraction of the global oceans will see some deoxygenation due to human activity.
This is, obviously, bad. The amount of deoxygenation may not be very much, just a drop of a few percent. But as we learned with increasing carbon dioxide levels in the atmosphere, and rising temperatures, it doesn’t take much change to destabilize a system.
The worst effects will come from areas already low in oxygen, called hypoxic zones, where the levels can be as much as 70-90 percent lower than average, and in suboxic zones, where it’s even lower. In those regions, a few percent drop can mean the difference between life barely holding on, and death.
Even when the change isn’t so dramatic, it can be devastating. You might think of the ocean as one big fish tank, but it’s actually incredibly diverse, depending on water temperatures, currents, pressure, and more. Changes in oxygen levels in the water reduce marine life habitats, stressing the inhabitants there. Changes in regional oxygen levels have caused migrations of fish, and even massive die-offs. Besides the effect on the life there, this has an impact on human activity including fishing, on which many countries depend.
Mind you, about half the oxygen we breathe comes from ocean phytoplankton. Messing with their habitat is like setting fire to your own house. Which is pretty much what we’re doing.
So you can add this to the list of deleterious effects of global warming to our planet. And don’t forget that the past six months have all had record-breaking high temperatures, with many scientists already expecting 2016 to be the hottest year on record globally, and carbon dioxide levels still rising.
Global warming is our future, but it’s also our present. It’s now. Once again, Americans, I implore you to consider this, what is perhaps the greatest long-term threat facing humanity, when you go to the voting booth in November. And for the rest of the world, know that most of us here in the US are aware of the problem and doing our best to urge our leaders to take action as well. We can minimize the damage of global warming, but first we have to make sure our government is facing reality.
Well now, this is very cool: Astronomers have just announced that Makemake has a moon!
Makemake (pronounced MAH-kay-mah-kay; it’s named after a Rapa Nui god who created humanity) is a Kuiper Belt Object (or KBO), a large icy world orbiting the Sun way out past Neptune. It’s what’s called a “classical” KBO, because its orbit is far enough from Neptune’s that it can orbit the Sun stably for billions of years (Pluto actually gets closer to the Sun than Neptune does, but their orbits are timed such that they never get very close together). At 1430 km across, it’s the biggest known classical KBO, and the third biggest such body known past Neptune. Only Pluto and Eris are bigger.
We know quite a bit about Makemake from previous observations. It takes about 7.77 hours to rotate once, and must have a very reflective surface. Spectra show it has a lot of frozen methane on it, too, more than any other object out past Neptune. Its orbit is elliptical, taking it as close to the Sun as 5.8 billion km and as far as 7.9 billion km out. Right now it’s almost at aphelion, the point in its orbit when it’s farthest from the Sun.
It’s been observed many times, but until now no moon had been found. The discovery was made using Hubble Space Telescope, which observed Makemake exactly one year ago, on Apr. 27, 2015. The moon — which for now has the cumbersome designation S/2015 (136472) 1 — was seen very close to the KBO, almost lost in its glare.
That may be why it hasn’t been seen before. For one thing, it’s much fainter than Makemake, making it hard to detect. The astronomers who discovered it also propose that we may be seeing its orbit edge-on, which means it spends much of its time too close to Makemake to easily detect from Earth.
The observations were split into two “visits”; one on Apr. 27 and the next on the 29th. The moon was seen in the first visit but not the second, meaning it was too close to Makemake to see in the second set. Each visit consisted of six long exposures, and the moon was seen in all six images on the first visit.
The problem is, the time between the first and last images in the first visit was only a couple of hours, which was not enough to show any motion of the moon. That means the orbit isn’t well known. The best the astronomers could do was say that the orbital distance is at least 21,000 km, but may be as much as 300,000! For comparison, the Moon orbits the Earth at a distance of about 380,000 km. The moon orbits Makemake with a period somewhere between 12 and 660 days.
Those are pretty wide ranges. And that’s too bad, because the orbit of a moon is really critical: It tells you the mass of the object it orbits. Gravity depends on mass of the primary object and the distance to the moon, so if the orbital period of S/2015 (136472) 1 had been measured, the mass of Makemake could have been found.
What makes this even more frustrating is that we know how big Makemake is, because in 2011 it passed directly in front of a star as seen from Earth; the length of time it blocked the star combined with its known orbital speed yielded the diameter of 1430 km. With that number, plus the mass, its density could be determined, and that gives a huge clue about what it’s made of. Rock is denser than ice, for example, so just knowing Makemake’s density would constrain its composition.
However, the good news is that now that we know the moon exists, more observations can be made. It may take Hubble to see it once again — Hubble’s really good at spotting faint things near bright things — but it can be done. And if carefully planned (which it will be) the moon’s orbital period and shape can be found.
There are some interesting implications of this, too. Earlier infrared observations of Makemake indicated the surface had at least two different materials on it, which had different thermal properties (darker material, for example, gets warmer than more reflective stuff). If that were the case, though, the brightness of Makemake should change enough to measure as it spins, but no such change was seen.
The moon may solve this problem! If it’s darker than Makemake then that would throw off the infrared observations. Those telescopes couldn’t separate the moon and the KBO, so they merged together, confusing the interpretation.
I find that very interesting indeed. As you may remember from last year, Charon, Pluto’s moon, is much darker than Pluto as well. If this new moon is indeed dark, that might indicate a similar origin story. Future observations with the James Webb Space Telescope, due to launch in 2018, may help figure this all out; it has the keen vision in the infrared to separate the two objects and determine how reflective the moon is.
Just the fact that the moon exists is interesting, too. Pluto has a moon, as does Eris and Haumea (another large trans-Neptunian object a bit smaller than Makemake). Are they ubiquitous? Two other such objects, Sedna and 2010 OR10, have no known moons. Perhaps we just haven’t seen them because they’re too close to their primaries. Clearly, more and deeper observations are needed.
And let’s not lose sight of the more general nature of this: We’re still learning basic information about our solar system! Finding a moon like this gives precious insight into what the outskirts of our celestial neighborhood are like, a region that is terribly far away and dark, and very difficult to explore. Each discovery about it is a clue to how it came to be, how it changed over time, and why it looks the way it does now.
All of this tells us more about our existence, and informs us about our own world. A cold and distant moon orbiting a smallish iceball may not seem like much, but it’s another piece of the puzzle, one worth investigating and understanding.
I’ve said many times that there are no green stars, but that doesn’t mean there are no green objects in space.
My pal Babak Tafreshi makes this point beautifully in his phenomenal photograph of the night sky over the Paranal Observatory in Chile:
Oh my. Isn’t that gorgeous? In the foreground is one of the four smaller auxiliary telescopes that make up the Very Large Telescope Interferometer, a sophisticated piece of equipment that can take observations with far higher resolution even than Hubble. And by smaller, it’s a 1.8-meter wide mirror; that’s only small when compared to the 8.2 meter behemoths that make up the Very Large Telescope!
But that sky. To the right of the telescope blazes the billions of stars of Milky Way, our home galaxy, partially obscured by dark dust lanes and punctuated by the pink glow of hydrogen in the Lagoon Nebula.
But that green fuzzy glow above the telescope somehow manages to steal the show, perhaps because its color makes it stand out in stark contrast to the other objects in the sky. That emerald blob is the comet 252P/LINEAR, which passed the Earth in mid-March at a close distance of more than 5 million kilometers.
Many comets glow green; it’s due to the presence of a molecule made of two carbon atoms (C2), so that’s not a big surprise. But that’s about the only nonweird thing about 252P.
It turns out it was full of surprises. For one thing, it was followed closely by another comet, P/2016 BA 14, which had a very similar orbit, sparking hypotheses that they were once the same object that split. Both passed very close to Earth (the fourth and seventh closest passes of comets in recorded history).
This gave astronomers a chance to observe BA 14 with radar and lead to another surprise: BA 14 was way bigger than first thought. From its brightness it was at first estimated to be less than 200 meters across, and probably much less. But the radar observations showed it was more like a kilometer across! It turns out the solid nucleus of BA 14 is incredibly dark, reflecting less than 3 percent of the light that hits it. That makes it fainter than expected, which is why astronomers thought it was small.
Around the same time, 252P had a huge outburst, suddenly becoming 100 times brighter in a short period of time. It went from obscurity to becoming naked-eye visible, though unfortunately for us in the Northern Hemisphere it was too far south to see. But that was good news for Babak, who was able to capture it in the photo above while he was visiting the European Southern Observatory facilities.
It’s rare, but sometimes comets flare in brightness. This can happen if they clave (split off a piece), which can release a lot of ice that turns into gas; that reflects sunlight and makes the comet brighten. In 2007 Comet Holmes underwent a tremendous outburst that made it easily visible to the naked eye even though it was out past Mars; it’s brightness increased by a factor of a million! I was fortunate to be in a place where I could see it, and it showed a disk easily to the naked eye; the cloud was more than 1 million kilometers across. I’ve never seen anything like that before, nor since.
Which goes to show you, it always pays to keep your eyes on comets. Sometimes they fizzle, but when they perform, they can really perform, and all the time spent watching them can suddenly pay off.
Aloha! I’m pleased to announce registration is open for Science Luau 2016, a five-day vacation on the Big Island of Hawaii, with a special bonus: SCIENCE.
My wife and I run a company called Science Getaways, where we take people on vacations that are already really nice and add science to them. For this trip, we’re spending Sep. 19–23 on the Big Island, in the lovely and luxurious Mauna Lani hotel on the Kohala coast.
We have several special extras planned. We’ll take a trip to the Kilauea volcano with an expert tour guide, ending in a stop at dusk at the summit crater, Halema'uma'u (ha-LAY-mah-oo-mah-oo), to see the lava pool glowing and illuminating the sulfur plume huffing and puffing out of it. We’ve chartered a boat to go to some coral reefs for snorkeling, and then we’ll go night diving with manta rays. We’ll also be taking a hike through a dry forest with another expert guide to look at the amazing native Hawaiian trees and wildlife.
I know a thing or two about astronomy, so I’ll be bringing my solar telescope to show you what our active Sun is doing that week. On top of all that, there will be talks by experts about what we’ll be experiencing; I’ll be giving an astronomy talk as well.
We’ve been doing these Getaways for a few years now, and they have always been a lot of fun, with honestly wonderful people (many have made lifelong friends on these trips). We went to the Big Island last year and it was so popular we decided to do it again.
I hope you’ll join us. All the information you need is on the Science Getaways page. Mahalo, and see you in paradise in September!
Sometimes geologists have it easy.
In astronomy, you can have two stars right next to each other, maybe even born in the same cluster, but you can’t be sure they’re the same age, or which one is older than the other. Differences can be really subtle, and have to be teased out of the data.
Geologists, on the other hand, get stuff like this:
WOW. That is a scene on Mars, taken by the wonderful HiRISE camera on the Mars Reconnaissance Orbiter. Its shows a small portion of Ganges Chasma, a huge, sprawling channel cut into the surface of Mars, probably due to catastrophic flooding a billion or more years ago. The violent rush of water cut through the landscape like God’s trowel, carving out the chasm.
Over time, erosion, weakness in the walls, or subsequent floods would have caused the walls to collapse inward further. Eventually, though, all that stopped, leaving behind the tableau we see now.
In the shot above, a crater about 3.5 kilometers (2.2 miles) across had the misfortune to be too near the flood. The surface just south of it collapsed, slicing the crater nearly in half.
But this is good fortune to Terran geologists! The crater was obviously there first, sitting in the surface from some ancient impact, minding its own business when the world collapsed next to it. The edge of the crater over the canyon is clean and sharp, and the crater itself quite nicely formed. If the crater had occurred after the flood, the shape would be distorted by the edge of the canyon.
The crater itself is interesting. It’s terraced, with circular ledges inside the main rim. Quite a few of these are seen on Mars. This can happen when there’s a layer of material under the surface with a different strength, like ice under rock. The shock wave from the impact carves out the main crater, then slams into the layer underneath and creates a smaller crater inside the first one. There are also smaller craters dotting the interior, and you can even see rippling sand dunes in the upper left of the floor.
Speaking of layers under the surface, using Google Mars to get some context, you can really see more of what happened after the channel formed:
The crater is arrowed. Note the weird raised features in the canyon floor; those are likely muddy or possibly dry material flows that happened when sections of the canyon wall collapsed. These landslides can create scalloplike indentations in the wall; many of them look like impact craters. But the featured crater here is clearly from an older impact.
Yegads. That really drives home the size and scale of this catastrophe.
Not that this in any way makes me less jealous of geologists, who sometimes have the timeline of events spelled out right in front of them. It’s a little ironic. Studying Mars used to be astronomy, and in some ways it still is. But now we go there, now we explore it, now we send robots to the surface to drill into it and zap it with lasers and sift through the dust to determine what it’s made of and what its history is.
Mars used to be astronomy, but now it’s a world, a place. Handing over the keys to the planet to geologists is hard, but oh, it’s so rewarding.
Sometime you see a photograph that’s just so wonderful you can’t wait to show it to other people.
It was taken by Petr Horálek, a European Southern Observatory Ambassador — the Ambassadors are a group of excellent photographers who shoot pictures of the ESO observatories for public outreach.
The photo was taken on April 6, 2016, just minutes before sunrise. Smack dab in the center is Venus, cruel twin of the Earth, covered in clouds so reflective they make the planet the third brightest natural object in our skies.
Below it is the crescent Moon, less than a day before its new phase. The crescent is so thin it’s almost an afterthought. Amazingly, the rest of the Moon’s surface was unlit by the Sun. So why can we see it? Earthshine! Light from the Sun hits the Earth, reflects off of it, illuminating the Moon, which then reflects it back into space, and to Earth. Our planet is very bright in the lunar skies, 50 times brighter than a full Moon. That’s enough to softly bathe the surface of our satellite in light.
Note too the Moon looks a little squished. That’s an effect of our atmosphere, which curves along with the Earth’s surface. Near the horizon, the light from the bottom of the Moon goes through a thicker layer of air than the top part of the Moon. The air acts like a lens, bending that light, making the Moon look flat.
Horálek timed this photo perfectly, getting the shot just as the Moon cleared the distant mountains. Had he waited much longer the Sun would have lit things up too much anyway. This was a time exposure, too: You can see the faint stars of Pisces surrounding the Moon and Venus.
And let’s not ignore the foreground! The silhouetted dome houses the 1.2 meter VLT Auxiliary Telescope, part of the Very Large Telescope array. See the two people crouched nearby? That’s my friend Babak Tafreshi on the left and Yuri Beletsky on the right, wrapping things up after a long night of photography in the incredibly rich and dark skies of this remote location in the high desert of Chile. I’ve featured both their works on this blog many times; click their names to fill your eyes and brain with delight.
I dream of capturing a photograph like this some day. But I just dabble in this; Horálek, Babak, and Beletsky are professionals. I might feel a pang of jealousy seeing shots like this, but it evaporates rapidly as I take in the sheer beauty. I’m glad there are so many people out their willing to collect the few photons the Universe graces us with, and share them with the world.
Photographer Michael Shainblum is a wonder. His photographs are just stunning, one after another. I’ve been following his work for years, and every time he posts something it’s awe-inspiring.
Oh, you want an example? Then how about this for your eyeballs?
… or is it? In this view, a panorama, the Milky Way spans the frame. Our galaxy is a thick disk, and we’re inside it, so we see it as a broad splash across the sky. The central region bulges outward, and that can be seen off to the right. The colors are interesting; probably not what your eye would see, but that happens when the contrast is stretched in a photo when you’re trying to bring out faint details. Still, very pretty.
The orange glow is from humans; the horizon commonly shows light pollution from towns sometimes hundreds of kilometers away (Fresno is only about 100 km south of Half Dome).
But what the heck is that green glow? You might guess it’s the aurora — a few people on Facebook did think that, in fact, when he posted the picture — but it’s not; Shainblum was facing south when he took this shot, not north.
That emerald radiance is actually airglow. During the day, sunlight hits atoms and molecules in the upper atmosphere, 100 km above the Earth’s surface. The energy can be stored, then released slowly at night in a process called chemoluminescence. Green is a strongly favored color due to oxygen atoms (similar to why many aurorae are green).
I love how perspective makes those parallel ripples in Shainblum’s photo appear to converge on the horizon, right behind Half Dome! You couldn’t hope for a better bit of placement.
A couple of weeks ago I posted a dramatic shot of the comet 67P/Churyumov-Gerasimenko backlit by the Sun, taken by the Rosetta spacecraft from a distance of a few hundred kilometers. I mentioned how the spacecraft was on a long looping path that would soon take it back to the comet, passing directly between it and the Sun at a distance of about 30 km, which should make for some very pretty pictures.
Well, here you go: As promised, the image above shows that exact event! Rosetta was 29.9 kilometers above the surface of 67P when it took that shot on April 12, 2016, using the OSIRIS wide-angle camera. As you can see, shadows are nearly non-existent, and only appear where there’s a sudden change in the topography of the comet (cliffs, shelves, and the like) near the edge of the comet.
And that glowing spot left of center is real, too! There are lots of fancy names for it, including the zero phase effect and heiligenschein, but I think my favorite is “opposition surge”. Poetic and scientific, all at the same time.
There are two reasons for it. One is that from the spacecraft’s view, the Sun is directly behind it, so the Sun’s light is shining straight down on the comet. At that spot directly below the spacecraft you don’t see shadows, so the surface looks brighter. Not only that, but some types of terrain bounce sunlight straight back in the direction it came. If you’re on that line, you see that spot on the ground being brighter than the area around it.
The Sun is in the opposite side of the sky as that spot, hence the term “opposition”, and the surge is pretty obvious. Heiligenschein means “halo” in German, and if you’ve ever seen a faint glow around the shadow of your head as walk past a patch of dewy grass, you’ll understand that term, too.
As for zero phase, the technical term for the angle between the source of light, the observer, and the spot illuminated is the “phase angle”. When they’re all on a line that’s defined as zero. The term should actually be familiar to you in another guise: The angle between the Sun, you, and the Moon defines the Moon’s phase! Surprise! You know more technical stuff than you probably thought.
By the way, the Rosetta shot is looking up at the flattish “underside” of the comet, the broad region across the wider of the two lobes making up 67P’s rubber ducky shape. You can see part of the smaller lobe, the “head” on the left. The shape looks funny when shadows go away; it’s hard to tell what’s what. Shadows actually help us understand the terrain, and can be used to make 3D maps of the surface. But this zero phase angle helps too; the surge can be used to understand better the surface on much smaller scales; different sized grains of ice or other materials change the brightness of the surge.
Fantastic! Science and geometry come together to form beauty. As they often do.
On April 24, 1990, the Hubble Space Telescope was lofted into orbit onboard the Space Shuttle Discovery. Sunday is the 26th anniversary of this grand event, and to celebrate, the good folks at the Space Telescope Science Institute have created a new and simply spectacular image.
Get a load of this!
That is the Bubble Nebula, aka NGC 7635. It looks almost delicate, doesn’t it? Like a thin soap bubble floating in space.
But that's a lie. Nothing about this tremendous beast is delicate.
What you’re seeing is the gas blowing outward from a massive star. Called SAO 20575, it’s the brightest star in the image, near the left edge of the bubble. And by massive, I mean somewhere between 10 and 40 times the mass of the Sun, so it’s a real bruiser. It’s already used up all the hydrogen in its core and is fusing heavier elements to generate energy. The vast amounts of energy generated in the core when this happens heats the outer layers so much that they get blown away from the star, forming the nebula.
The star is incredibly bright; it emits something like 400,000 times as much energy as the Sun does! If you replaced the Sun with SAO 20575, we’d have about one second before regretting that decision. The Earth would be cooked. Good thing SAO 20575 is 8,000 light-years away.
Because the wind is so fiercely powerful, the nebula itself is huge. When a star like the Sun dies and blows a similar (but far less energetic) wind, the nebula it makes might be one or two light-years across. Because the distance isn't well constrained, the exact size of the Bubble Nebula isn't well known, but measured from Hubble images it's something like five to eight light-years in diameter. That’s 50–80 trillion kilometers across! Put simply, that’s ridiculously big.
The Bubble really is a bubble, too: The wind blows away in a sphere, but winds up being bright around the edge because of an effect called edge brightening; when we look at the nebula, we see more material near the edge than when looking through the middle, making the edge look brighter. This can be reinforced if the nebula is expanding into gas that was previously outside the star; the material gets snowplowed up, adding its own brightness to the nebula’s.
You may have noticed the star blowing the bubble is way off-center, far to the left. That can happen if the star is moving rapidly in space, so fast it moves away from the center of the nebula it blew. The star’s motion has been measured and is in the right direction to account for this.
There’s also another possibility. The interstellar material surrounding the bubble is pretty thick; massive stars don’t live long and don’t usually get very far from the cloud of dust and gas from which they were born. The star is so bright that its ultraviolet light is evaporating that material, which is thickest to the upper left as seen in this image. That created a density gradient in the gas, a change in its density from one side to the other. If that’s the case, than the wind from the star can expand more easily in the direction away from the denser gas, making the bubble off-center from the star.
If that’s the case the Bubble may not actually be spherical; we just happen to see it looking down its elongated axis (that’s the case for the famous Ring Nebula, which looks round but is actually more barrel-shaped).
There is still some uncertainty about how this object was sculpted in this way. We’re still learning about it. The Bubble was observed before by Hubble, in 1998 and in 1999, the best images ever taken at the time, and you can see how much clearer our view is now.
And I can’t think of a more fitting tribute to Hubble itself. Launched more than a quarter century ago, it’s opened up so much of the sky to us, and brought the beauty of the heavens to humanity in a way never done before. Over time it’s been upgraded, with new and more powerful cameras installed, sharpening our view and our understanding of the cosmos.
And it’s not done yet. There’s still so much to see, so much to learn. Hubble has brought us a long way, but—happily—this is a journey that never ends.
If you look up into the sky long enough, you’ll see the weirdest things.
Astrophotographer Grahame Kelaher was in Western Australia late at night on Feb. 6, 2016, and he saw the odd, fan-shaped blue glow in the photo above moving across the sky. He wasn’t surprised, though: He planned for it!
That’s not some nebula — it’s actually the glow from fuel dumped into space by the Centaur upper stage of a United Launch Alliance Atlas V rocket! The Atlas launched from Florida on April 5, carrying an Air Force Global Positioning System satellite GPS IIF into orbit.
The Atlas was configured for this launch as a two-stage vehicle. The lower, first stage, lobbed the upper stage, called a Centaur, and the GPS sat high above the Earth. The Centaur then burned to put itself into an elliptical “parking orbit”, then it burned again to achieve the desired near-circular orbit 20,450 km from the Earth’s center (roughly 14,000 km above the surface).
Once that happened, it performed three tasks: It released the satellite, it made a “collision avoidance maneuver” to make sure it wouldn’t accidentally hit the satellite, and then dumped the remaining fuel in its tanks into space for safety.
These events occurred when the Centaur was over Australia, and Kelaher captured them on video!
In the video you can see the plume of gas lit by the Sun (it was 03:00 local time, but the Centaur was high enough up to be in sunlight). Because it’s essentially a vacuum that high up, the gas cloud expands without friction, and moves along with the Centaur and satellite. You can see (what I presume is) the GPS satellite moving along with the plume, just to the lower left.
Because the launch time and orbit were known in advance, Kelaher could know in advance to see them… as he had been hoping and planning to for six years!
Patience pays off.
I’ve never seen anything like this, though I once saw a rocket booster burn up in re-entry many years ago, and it was amazing. This would really be something to observe! Rocket launches can create all kinds of truly spectacular and bizarre sights. And I’ll add that you can see many satellites with the naked eye (check Heavens Above for local listings of visible satellites), and it can be a real kick to spot one and identify it.
Going out under the night sky is never time wasted. The rewards are many, and if you do it enough the bonuses can be pretty nice, too.
Are you a) a science enthusiast, 2) a science-fiction fan, and γ) live near Washington, D.C.?
Then you’re going to love this weekend: Smithsonian magazine is holding a festival called “The Future Is Here,” from Friday to Sunday, April 22–24. It’s a celebration of science and science fiction and how they interact. It’ll be a lot of fun.
Most of the events are free, but some require tickets (which are on sale now). The speakers range from NASA scientists to actors, writers, and producers of television sci-fi. For example, one speaker is a guy named William Shatner, of whom you may have heard. Also speaking is Chris Carter (creator of The X-Files), NASA Deputy Administrator Dava Newman, explorers Céline and Alexandra Cousteau, Arc Attack (Tesla coils playing music!), and seriously a much longer list of very cool people.*
Also, me. I’ll be there in two capacities. On Friday night I’ll be moderating the 12 Monkeys panel, with co-creator Terry Matalas and stars Amanda Schull, Aaron Stanford, and Emily Hampshire. 12 Monkeys is a new series on Syfy, a part of the network’s notable and in my not-so-humble opinion highly successful campaign to put out some seriously high-quality television shows (like The Expanse).
12 Monkeys is loosely based on the movie of the same name, about a group of scientists from the future who use time travel to try to prevent a global plague that wipes out nearly all of humanity. The first season has already aired, and the second started this past week. It’s a really good show, atmospheric and clever, and I dig it. On the panel we’ll be discussing the mechanics and philosophy of time travel, how the writers keep up with alternate timelines, and how the actors and crew keep up with what must be a bonkers filming situation. Multiple timelines and multiple time eras can’t be easy to track.
In my second role at the event, I’m very pleased to be interviewing Dava Newman on stage, one on one, about NASA: where it’s going, how it’ll do it, what their plans are. I’ll also be giving a very brief presentation on what NASA means to me, introducing several other NASA speakers, and then also bringing in, via Skype, Andy Weir, the author of the best-selling novel The Martian, which you also may have heard of. I hear a pretty good movie was made about it.
I am very much looking forward to the festivities! I’ve been a science-fiction fan my whole life, and (obviously) also a science aficionado. The two are inextricably linked for me, each urging on and inspiring the other. The recognition this symbiosis gets now warms my heart and makes me hope for the future.
In many ways, that’s what both are about.
So please join me and all these fantastic guests for a weekend of looking up, looking out, and looking forward.
*Correction, April 20, 2016: This post originally misspelled Chris Carter’s last name.
So it’s been a while. Where are we now with the aliens-building-megastructures star?
A quick recap: As you may remember, citizen astronomers combing through Kepler spacecraft data found a very weird star. Kepler stares at thousands of stars looking for dips in their light, indicating a planet passing in front of the star. This is called a transit and is a massively successful way of finding such exoplanets.
Usually, the light from a parent star will have one dip every few days or weeks or so, as the planet orbits it. But the amateurs looking at the data from the star KIC 8462852 found something very different: Lots of little dips happening at irregular intervals, and the occasional big dip. And by big, I mean like 20 percent or more of the star being blocked. That’s colossal, and doesn’t make a lot of sense at first blush; even a huge planet might block only two or three percent of a star’s light.
The citizen scientists looking at the data were part of a team from Planet Hunters, an effort to get more people looking at Kepler science. They contacted their team leader, Tabetha Boyajian, who then published the data with a series of possible explanations, including perhaps a swarm of comets passing the star and blocking its light. More on that in a sec.
Another explanation is that aliens live on a planet orbiting that star, and are building giant solar collectors to generate the energy needed to sustain an advanced civilization. To be clear, we know this is incredibly unlikely to be the case, but it’s an intriguing idea. SETI even aimed its radio telescopes at the star to see if they could pick up any signals, but nothing so far.
Boyajian herself gave a TED talk about this star, and it’s well worth watching.
Still, Tabby’s Star, as it’s now colloquially called, is intriguing. I’ve never been convinced by the comet explanation. It seems the least unlikely explanation — faint praise! — but a new paper has come out giving it a bit of a boost. The researchers find that a swarm of comets could explain the clusters of smaller dips of starlight. It would take a few hundred comets if they’re each around 10 km across, or a few dozen if they’re 100 km across.
Their explanation actually works pretty well for the small dips, but it still makes me wonder. The comets would be very hard-pressed to explain the two very large dips in light seen in the star, meaning something else would have to be invoked to explain those. That’s not very parsimonious.
And a swarm of comets isn’t a stable thing; after a few thousand years it should break up. For this to work, you’d need a huge object, like the size of Ceres, breaking up for some reason (a huge impact?) with the pieces becoming these comets. Or it could be that we happened to catch the start of a bombardment, a long period of comets dropping down from the outskirts of their solar system, perhaps disturbed by the gravity of a passing planet.
Scientists don’t like coincidences; they’re like a magic wand, too easy to use to solve problems. But they do happen. And it’s worth remembering that we are seeing something very weird happening at this star, something we’ve ever seen before, and all the other explanations are even less likely. We might not like picking the least bizarre explanation, but this star is really blowing the curve on what’s normal.
Interestingly, another astronomer found that the star appears to be dimming slowly, over the course of the past century or so at least. I have to wonder if that could be tied to the comets; they tend to be surrounded by clouds of gas and dust which might contribute to an overall dimming. But other observations showed no signs of these clouds.
So, to answer my first question: Where are we with this star? Still scratching our heads, I think. Comets may explain some of it, but not all. It may be several related things happening at once, or maybe different things happening around the same time. Or it may be just one thing no one has thought of yet.
It’s a mystery, but a fun one. What’s going on? We just don’t know. But more observations (not just of this one star, but as many others as possible, too, to see if Tabby’s Star is unique), and more people thinking about it are the way to go. The aliens idea may make this seem silly, but the data are real. Something is going on around this star. I don’t know what it might be, but what I can guarantee is that when we do figure it out, it’ll be something pretty amazing.