Bad Astronomy
The entire universe in blog form

Aug. 5 2015 7:00 AM

Anybody Wanna Peanut Asteroid?

On July 25, 2015, at 04:55 UTC, the near-Earth asteroid 1999 JD6 made a decently close pass of our fair planet. We were never in any danger — at its closest it was over seven million kilometers away, 18 times the distance to the Moon — and it never gets much closer than that to us, so an impact isn’t a concern.

But it does get close enough that astronomers can get a good look at it. Mind you, it’s so small that at its closest approach it would only appear as a single pixel dot even to Hubble.


But using sophisticated radio telescope techniques, astronomers were actually able to get a pretty good look at 1999 JD6, and what they discovered is very interesting: It’s a gigantic cosmic peanut!

That video was made using observations from NASA’s Goldstone Deep Space Network antenna and the huge 100-meter Green Bank Radio Telescope in West Virginia. The ‘scopes worked together, acting like a mega-radar system, pinging the asteroid with pulses of radio waves which get reflected back to the Earth. By carefully measuring the timing and Doppler shift of the pulses, the size, shape, and rotation rate of the asteroid can be found*.

In this case, 1999 DJ6 is about two kilometers long, 200-300 meters wide, and spins once every 7.2 hours. But the most interesting thing is that shape: It’s a narrow-waisted peanut! Technically, it’s called a contact binary, with two major components (lobes) touching at a single point.  

Lots of objects are shaped like this, including the comet 67P/Churyumov-Gerasimenko, currently under intense investigation by the European Rosetta probe. 67P and many other such objects have a relatively thick neck between the two lobes. It looks like 1999 JD6 has a considerably thinner connection, but it’s hard to tell from these observations.

I find it interesting that 10 – 15% of all near-Earth asteroids are shaped like this. It’s not clear how they form, but it’s most likely due to slow-speed grazing collisions. After the impact shears off some material, the two objects slow even more relative to one another, and wind up coalescing into a single, if elongated, body. Here’s another video, showing a physical model of the process:

Nifty. I love how surprising the solar system is! I would never have guessed that such collisions could occur at all, let alone result in such fantastically shaped bodies, but as usual this is a lesson in the fact that Nature is more clever than we are. Its job is to do what it’s gonna do, and ours is to figure out how. The good news? We’re pretty good at our job, too.

* I’ll note that these are not images like those from optical-light telescopes; Doppler radar maps like this don’t actually take pictures. If you want the details, my friend Emily Lakdawalla has an as-usual excellent explanation on her Planetary Society blog.

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Aug. 4 2015 12:56 PM

Magnificent Earth

On July 15, 2015, the European Space Agency launched the fourth Meteosat Second Generation (MSG-4) satellite into orbit. This advanced Earth-observing bird will monitor our planet in a number of ways, including taking very high-resolution images.

MSG-4 is in its commissioning phase, being tested out to make sure it’s fully operational. Today, the ESA released this jaw-dropping picture of the Earth taken by the satellite:

Aug. 4 2015 11:15 AM

We Will Reboot the Suit!

I am very pleased to give y’all a quick update on the fundraising campaign to conserve Neil Armstrong’s Apollo 11 EVA spacesuit: We are fully funded! In fact, we hit the $500,000 goal in just five days, thanks to thousands of people who generously supported the Kickstarter project.

Wow. Thank you all so much! Know that you have helped contribute to preserving a historic icon and will also help millions of people learn about one of the most important moments in human history: when we first stepped on the surface of an alien world.


But we’re not done. The next goal is to reach $700,000 so that the Smithsonian’s National Air and Space Museum can perform the same good work on another space artifact: Alan Shepard’s flight suit that he wore when he became the first American in space in 1961.

Alan Shepard's suit
The spacesuit of the second human being in history to go to space.

Photo by the Smithsonian's National Air and Space Museum

Like Armstrong’s Apollo suit, Shepard’s Mercury suit will be photographed in high resolution to make (printable!) 3-D maps and to conserve as much about it as possible. It will also be displayed along with many other spacesuits at the museum.

We’re already halfway to the new stretch goal with just two weeks left in the Kickstarter campaign. And whether you pledge or not, please help us spread the word on social media using the #RebootTheSuit hashtag.

Again, thank you. This has been amazing so far, and we’re just getting started. 

Aug. 4 2015 7:00 AM

Mike Huckabee: Exactly Wrong About Global Warming

When it comes to science, it seems that every time former Arkansas Gov. Mike Huckabee opens his mouth, falsehoods and nonsense fly out.

His latest ridiculousness was uttered when he was interviewed by Katie Couric on Yahoo! News (the exchange starts at 24:07):


Here's the part about global warming (transcribed by me):

Couric: Climate change: Do you believe in it?
Huckabee: I think climate has been changing over the entire history of the Earth.
Couric: Do you believe Man contributes to global warming?
Huckabee: He probably does, but a volcano in one blast will contribute more than a hundred years of human activity.
Couric: That’s very nice, but do you think that Man contributes basically to climate change.
Huckabee: Could be. Y’know, I don’t pretend to know. Here’s what I do know: When I was in college we were told that climate was changing but we were about to enter a deep freeze and if we didn’t make urgent changes in the way we live we were all gonna be Popsicles within another single generation.

In less than a minute Huckabee is able to say two completely and egregious false howlers.

The first is about volcanoes. He’s completely wrong there. First, in a single year, human activity puts a hundred times as much carbon dioxide into the atmosphere as volcanoes do. I’ve written about this false denier claim many times. The idea behind it is to say that Nature does far more to change the climate than we do (note he starts off saying that climate has always been changing, another line of denier baloney*), and this sows doubt that we puny humans can do much compared with that. 

And it’s even more ironic: Volcano eruptions launch sulfur dioxide and aerosols into the atmosphere that reflect sunlight, and so they actually cool the Earth overall. Huckabee is not only wrong, he’s exactly wrong.

Second, his global cooling comment is also just so much fertilizer. If I had been there, I would’ve asked him who, exactly, made the claim we were “about to enter a deep freeze”. Because even back then, the majority of published scientific research pointed toward warming, not cooling. It was the media that trumped up the cooling idea (and they had to cherry-pick data to do it), and of course it’s the Republican climate change deniers who keep beating that drum, as ridiculous as it is.

And it hardly matters; that was 40 years ago. Today, with better measurements, better understanding, and far, far more research into the problem, the overwhelming majority of climate scientists agree: The Earth is warming, and it’s human activity causing it. At least 97 percent of climate scientists agree with that statement, and the actual consensus may be even stronger.

And Huckabee is wrong in another way (in case you’re not used to it yet). He says he “doesn’t pretend to know” about climate change, but that’s exactly what he’s doing: pretending to know. If he listened to any scientists who actually study our climate he wouldn’t have to pretend any more. He’d know for a fact the planet is heating up.

Tip o’ the caldera to Christian Walters.

*To be clear, of course the climate is always changing. But deniers use this line to downplay the fact that the Earth is currently warming almost entirely due to human influence. They say it's the Sun, or Earth's orbit, or whatever—anything but our use of fossil fuels. 

Aug. 3 2015 7:00 AM

What a Comet Looks Like … From 9 Meters Away!

The European Space Agency has just released some fantastic close-up images taken by the Philae lander of the comet 67P/Churyumov-Gerasimenko. This release came out along with a passel of scientific papers (in Science magazine behind a paywall; here’s a summary) about results from the Rosetta probe’s lander, too.

When I saw these images the hair on the back of my neck stood up. These photos may not look like much at first, but when you realize you’re seeing the surface of a comet hundreds of millions of kilometers from Earth, and can see objects as small as a centimeter across … well, I hope your brain gets that same electric shock mine did.


Here’s the story.

landins spots
The many touchdown sites of Philae (labeled TD in the image).

Photo by ESA/Rosetta/Navcam

On Nov. 12, 2014, at 15:34:06.471 (± 1 second), the Philae lander made contact with the surface of the comet 67P/Churyumov-Gerasimenko.

The first time. Two malfunctions (a cold-gas jet system designed to push the lander down onto the comet’s surface didn’t fire, and neither did the harpoons meant to anchor Philae to the comet) occurred, and instead of landing and staying secured to the surface, Philae bounced high into space, only to land again, bounce again, and finally skid (that is, make multiple shallow, short bounces) to a stop many hours later, and many hundreds of meters from its intended destination.

It fell to rest on its side, shadowed by an overhang of ice and rock. Contact became intermittent, and a few days later the battery fell below levels needed to keep the probe awake. It went into hibernation.

Then, months later, it woke up! The solar panels had collected enough energy to turn the lander back on. Contact was again intermittent, and the future of the lander’s lifespan is still unclear. But it performed like a champ, taking images, spectra, and other measurements that have returned unprecedented knowledge about the comet back to us on Earth.

9 meters
The comet from 9 meters up, seconds before first contact.

Photo by ESA/Rosetta/Philae/ROLIS/DLR

This shot was taken when the lander was a mere 9 meters—30 feet—from the surface of the comet. The area you’re seeing is 9.7 meters across, about the size of one half of a tennis court. It shows that the surface is covered in a coarse regolith (loose material that hasn’t consolidated into a solid mass; we see similar surfaces on airless bodies like the Moon), and rocks of various sizes, ranging from centimeters to meters across. You can also see material of different darkness; some are quite dark while others are reflective.

Some of the rocks are smooth, and some sharp. In one of the papers published (Mottola et al.) they analyze the images, speculating that the smooth rocks may have once been embedded in ice or boulders, and then freed after the material they were embedded in disaggregated. The rougher ones with flat faces may be from bigger rocks that fell and shattered. Some of these chunks are partially buried in the regolith; are they being buried as the looser stuff piles up or being exhumed as the material moves away? Static pictures make that difficult to discern.

48.5 meters up
A wider shot taken from 48.5 meters up.

Photo by ESA/Rosetta/Philae/ROLIS/DLR

From higher up there’s more of an overview; the shot above was taken when Philae was still 48.5 meters from first impact. The area seen is about 50 meters across, half the length of a football field. The big rock, nicknamed Cheops, is about 5 meters in size. It may be an individual piece, or an outcropping of bedrock below. What’s very interesting about it is the arrowhead-shaped depression is sits in (the point is to the right), and the fine-grained material piled up on its left. That’s a wind-blown feature! Material immediately upwind of a rock gets picked up and blown around the rock, leaving behind an arc-shaped moat, and a pile of finer grains on the rock’s downwind side.

A rock 5 meters in size sticking up out of the regolith.

Photo by ESA/Rosetta/Philae/ROLIS/DLR

What could cause this? My first thought was ice turning into a gas (sublimating) as the comet warms up on its approach closer to the Sun. But I didn’t think this could be right; that gas would expand so rapidly that it wouldn’t have much effective pressure very far from the vent. It turns out that may be right; Mottola and his co-authors note that as well and wonder if perhaps this is caused by temporary gusts of material from impacts as the comet moves through space. I like this idea, though it seems that this would take a long time, and a comet’s surface doesn’t last long as the ice beneath it sublimates. However, it would also explain some of the erosion features seen as well. Hopefully as time goes on we’ll see more work in this area. Remember, these are first, initial results!

before and after
Now you don't see it, now you do.

Photo by Biele et al.

I love the image above (from Biele et al.): It was taken by the Rosetta probe itself and is a before-and-after picture of where Philae initially hit the comet. The left image was taken 15 minutes before impact, and the one on the right 25 minutes later, about 10 minutes after Philae bounced. You can see the impact craters from the lander! The two pits marked B and C are from the lander, and are 10 and 20 centimeters deep, respectively (the feature marked A is probably just a coincidental small undulation in the surface, casting a shadow that makes it look like a crater). This shows the regolith on the surface is at least 20 centimeters deep, too.

Knowing how deep the craters are and how dense the material is, scientists estimate about 180 kilograms of material was ejected at impact, which is more than the mass of the lander itself (100 kilograms). That’s interesting. All the data from the first impact indicate the material must be incredibly soft, like talcum powder. However, the surface there probably doesn’t have extremely fine-grain stuff in it, so whatever it is must be very loosely packed to have such weak compression strength.

This is very different from where the lander eventually wound up, where the surface is more like solid rock. A comet’s surface varies considerably from place to place. Interestingly, another experiment on Philae (which sent electromagnetic signals through the comet) indicates the interior of the comet’s small lobe is actually homogeneous over all.

[Animation of the lander's descent images. Photo by ESA/Rosetta/Philae/ROLIS/DLR]

And what’s the comet made of? A chemical analysis experiment on Philae (called Cometary Sampling and Composition) was going to drill and sample the comet, but it obviously couldn’t. However, the impact did excavate material from under the surface, and some of this flew into the sampling tubes of the experiment (they call this “sniffing mode”).

It found water, methane, HCN, CO, methylamine, and 11 other types of molecules, many of them organic (that is, containing carbon; don’t confuse this with output from biological processes!). These were probably built up from simpler molecules by ultraviolet light from the Sun and subatomic particle impacts, which break up simple molecules and allow them to build up more complex chemistry. The nitrogen probably came from ammonia, which has been depleted to create these more complicated molecules.

Many of these chemicals are pre-biotic, not biological themselves but necessary ingredients for life. They are used to build sugars, amino acids, and even nucleobases (the building blocks of RNA and DNA). That’s fascinating! It doesn’t mean that these chemicals were brought to Earth by comets necessarily, but it does mean they are not terribly hard to manufacture via natural processes. We knew this before, really, but it’s good to see it confirmed from measurements taken right there at a comet.

One thing I was excited to see in one of the papers (Kofman et al.) is that the likely landing site of Philae has been narrowed down to an area of just 21 x 34 meters! This was done using measurements by the Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) experiment. The rough position was triangulated along a strip about 150 meters long, and then narrowed down to this area by using signals from the lander that passed through the comet itself. Images taken from Rosetta have not been able to nail down the position of the lander unambiguously, so hopefully these results will allow that.

I’m glad we’re finally seeing so much of the science from Philae; most of it has been under wraps for months as the scientists poked through it (and a lot of it still is, awaiting more data to come down to make a complete set so that context can be gleaned).

And as much as we’ll eventually learn from studying 67P, one thing that’s important to remember is that every comet is different! We’ve visited quite a few now, and their diversity is amazing. Some have lots of water ice, some very little. Some are active, some quiet, with different structures, different compositions, and more. As I read the papers and looked at the data, I was struck by how much information we now have on 67P … and how much we still have to learn about comets as a population.

Aug. 2 2015 7:00 AM

Colorado High

If you ever wonder why I love living in Colorado, well, maybe this’ll help.

That video was shot by Daniel Lowe as he drove through western Colorado and eastern Utah. Where I live, there’s substantial light pollution, but out by Gunnison the skies get dark (one of the many reasons my wife and I held a Science Getaways there), and the stars are magnificent.


And the geology! Some of it is lifted up, some of it eroded down, but there’s a billion years of history tucked away in the American Southwest. This is an astonishing place to live.

And that spillway/waterfall at 01:20? Lowe told me that’s south of Ouray on U.S. Highway 550. That’s a bit of a haul from my neck of the woods, but if I’m ever out that way, I’ll have to stop and see. This planet is a source of unending delights.

Aug. 1 2015 7:00 AM

The Latest Crash Course Astronomy Will Be Delayed

My apologies, everyone: After we put up this week’s episode of Crash Course Astronomy (about exoplanets), we found an error in one of the animations that got past us.

In some cases where a mistake is found we can simply annotate the video and move on. However, in this case the animation was explaining an important concept that couldn’t simply be corrected in the video itself. Faced with this we decided to take it down, fix the animation, and re-upload the video. Given the time that will take, we also decided to simply wait until next Thursday to re-release it, to keep the episode order on track.


So, the exoplanets episode will go back up Thursday, Aug. 6, at 21:00 UTC (5 p.m. ET). Again, I’m sorry about this, but we’d rather be late than keep a fixable mistake in the series! Thank for your patience, and I hope it’s worth the wait.

And in the meantime, we have more than two dozen other episodes online to keep you entertained and learning about our amazing Universe. Have fun!

July 31 2015 7:30 AM

Arc of Truth

I was out strolling recently on a cloudy day, and—as I always do—I took a quick look around the sky to see if anything interesting was to be seen.

I do so love that habit. This particular time, I was greeted with a most unusual sight: a rainbow segment, just a small arc levitating in the clouds. It was raining in that direction, so there were raindrops in the air, a critical component to make a rainbow.


But the other half of that recipe is sunlight, and that day was almost completely overcast. Almost. In the west there was a small break in the clouds, enough to let a single shaft of sunlight through. That illuminated the suspended raindrops, refracted, and created the partial bow.

What I love about this, though, is that you can see that shaft of light! Haze, raindrops, and other particulates in the air scattered that light, reflected it back to me, lighting up in the path of that sunbeam, contrasted with the storm clouds behind it. And you can tell that the opening in the clouds to the west wasn’t fully open; there must have been a small cloud in the middle to account for the shadow ray piercing through the light shaft and arc.

Mind you, there was no other hint of a rainbow anywhere else in the sky. That was it, the only clear sunlight available. And it was only those raindrops, seen at just the right angle, that allowed me the view of the broken spectral arc. Someone a kilometer away in the wrong direction wouldn’t have seen anything at all. I was at the right place at just the right time.

But even then, it all would’ve been for naught had I not looked up.

Oh, that sky we live under. Wonderful, isn’t it? You should look at it more often.

July 30 2015 7:15 AM

The Summer of ’82

David: You knew enough to tell Saavik that how we face death is at least as important as how we face life.

Kirk [sadly, resigned]: Just words.


David: But good words! That's where ideas begin.

In June of 1982, I found myself waiting in a long, long line at a mall. I had just graduated high school, and was spending the summer doing what innumerable kids my age had done for decades: eagerly and nervously anticipating going to college in a few months, working at my part-time job (for me, slogging through the brutally humid Virginia weather at 5 a.m. to deliver the Washington Post to more than 100 of my neighbors), hanging out with friends, reading sci-fi books, going to the mall to play video games, and watching movies.

And oh, those movies. The summer of 1982 was magic. Magic! The science-fiction movies that came out in those few short months would change the way movies were made. Think I’m exaggerating? Here are a few of the movies that came out in 1982: Blade Runner. The Thing. Poltergeist. E.T, the Extra-Terrestrial. Tron

And, of course, one of my favorite movies of all time, Star Trek: The Wrath of Khan. When the first movie (Star Trek: The Motion Picture) came out, we hardcore arrogant and smug fans hated it. It was long, boring, and preachy. It was mocked unceasingly and mercilessly for years. But then Khan came out, and all was forgiven; faster paced, big battles, great tension, and far more personal, Khan was what we had craved.

Wrath of Khan
Oh, how my pulse raced when I saw this on the screen.

Photo by Paramount Pictures

I’m older, less of an ass, and hopefully wiser now, and appreciate the first movie far more than I did as a hot-headed kid. And yet, Khan still touches something primally Trek in me. The music still sings to me (I had the soundtrack on vinyl, copied it to cassette so I could listen in my Walkman, then on CD, and now digitally; a dynasty that’s lasted for electronic generations), and the scenes in the Mutara nebula still put me on the edge of my seat.

All that was ahead of me, though, as I stood in line at the mall with 100 people ahead of me. Over the course of an hour I was joined by my friends, coincidentally, a chunk of my graduating class wanting to see Khan on opening day. By the time the box office opened there more over a dozen of us (100 people from the front of the line), eagerly chatting away with nervous excitement.

Plait 1982
Your host in 1982. Most of that hair was left somewhere in Virginia.

Courtesy of Phil Plait

I had no idea at that moment what lay ahead of me in my life: a disastrous first year at college, dropping out because I wasn’t nearly ready for it emotionally, an ego-stomping year of living at home with my parents as I got my act (partially) together, then finishing out college, going to grad school, meeting my future wife, having a daughter, and everything else that life delivers that is simultaneously mundane and glorious.

I’m not sure any of that would’ve registered with me anyway. I was an immature kid, wrapped up in the excitement of seeing Kirk and Spock on the big screen again.

Why am I thinking of all this now? Lots of reasons, actually. I just got back from Comic-Con, where I saw old friends again, met new ones, and bumped into some of the people who made the stories that so shaped my own life.

Also, as it happens, this clip of a news segment got posted to a friend’s timeline on Facebook. Watch it:

The mundanity of the descriptions belies the changes that were about to happen. (This was before the Spoiler Alert, obviously.) Watching that clip from 33 years ago (!!), seeing it as if I were that young once again, catching the 5 o’clock local news, made me smile. It was a great summer.

There’s a lot to be said for the present, too. My daughter somehow caught the Trek bug, and is now a full-fledged Federation dork. I’m bouncing in my seat waiting for her to finish watching the original series so we can see the movies together. I cannot wait to see Khan once again, chewing up the Enterprise as thoroughly as he did the scenery, Kirk’s tactics, Spock’s final (heh) scene.

I wonder how much of the movie I’ll spend sneaking peeks at my daughter’s face, to see how she reacts. Passing down our stories is part of what makes us human, and seeing it with her will, I think, make me feel young, as when the world was new.

July 29 2015 7:15 AM

The Densest Galaxies Ever Discovered

I think one of the most interesting facts in astronomy is a simple one to state: Galaxies are cannibals. They eat each other.

The Milky Way grew huge this way; our galaxy is in the top tier of spirals in the Universe. (Many are bigger, but the vast majority are far smaller.) It got that way by colliding and merging with smaller galaxies, enlarging its ranks over time. It’s actually in the process of eating several dwarf galaxies right now. Like, literally, at this very moment.


But what of these smaller galaxies? What happens to them?

Some merge completely with the bigger galaxy, a completely digestible meal. But sometimes parts of the smaller galaxy survive. If the center is compact and dense enough, it can make it through the ordeal.

We’ve seen these here and there, but now astronomers have found a new class of such objects: Ultra Compact Dwarfs, or UCDs. And it turns out they’ve been hiding in plain sight.

These galaxies are small and luminous, and incredibly dense with stars. Through ground-based telescopes they’re so small they look like foreground stars, and through Hubble their dense nature but slightly visible fuzzy halos that make them look like distant galaxies. That’s how they avoided discovery for so long: They slipped between the cracks.

These objects are the densest galaxies known. Our Milky Way has hundreds of billions of stars, but they’re spread out over a hundred thousand light-years. One of the new UCDs just discovered has far fewer stars—something like 10 million—but it’s only about 20 light-years across!

NGC 6934
NGC 6934, a typical globular cluster. A UCD would be about the same size, but have 10-to-100 times as many stars in it.

Phto by ESA/Hubble & NASA

That’s really weird. I mean, really weird. It has the size of a typical globular cluster (a spherical cluster containing a hundred thousand stars or so) but is a hundred times denser!

Another UCD found is less extreme but still pretty amazing: It’s about 200 light-years across and has a hundred million stars in it. That’s far larger than a globular cluster, with a lot more stars.

It’s their incredibly compact nature that helped them survive being a galactic snack. This video should help make that clear:

The small galaxy is in a tight orbit around the center of a much larger galaxy. Tides from the big galaxy strip the outer stars off the smaller one; in a sense the gravity they feel from the bigger galaxy is larger, so they get peeled away from the smaller one. Stars closer in to the center of the small galaxy are more tightly bound, and stay together.

After a few passes all the outer stars are ripped away, and what’s left is just the compact nucleus of the smaller galaxy: an ultra compact dwarf. In fact, spectra taken of the UCDs show they resemble the cores of galaxies.

You’d expect to find these objects near bigger galaxies, and sure enough both of the new objects are physically close to much beefier galaxies. Note only that the larger galaxies show signs of recent disturbances (basically, weird overall shapes) indicating they recently underwent a collision and merger.

This work is impressive. It’s not often you find a new kind of astronomical object, especially when examples of them are sitting right in images that have been around for years. But their borderline nature between star clusters and proper galaxies effectively hid them.

I’ve long said that we have to be careful and not let our prejudices blind us to objects that are neither one thing or another (cough cough Pluto cough). In this case, I’m glad this team was able to see these UCDs for what they are.

And I have to add: The astronomers who found them were undergrads, students at San José State University! They combed through archived data taken by several different telescopes to identify potential ultra compact galaxies, then followed up using observations to nail down their characteristics. It’s quite an accomplishment!

And a reminder to not always dismiss something just because it conforms to your own predisposed beliefs. Look around you! What are you missing?