Bad Astronomy
The entire universe in blog form

June 25 2015 3:23 PM

What Is Glittering at Pluto’s North Pole?

As the New Horizons spacecraft nears Pluto, more details are coming into view, and we are beginning to see surface features on the tiny world.

And that means we’ll see things that are … odd. Perhaps “as yet unexplained” is a better term, since we’re seeing these markings for the first time in human history. The press releases have been amazing, but the images released have been enlarged and processed in complex ways to bring out details.

But as the probe gets closer, we can see details without such means. The raw data are posted online within hours of them being transmitted back to Earth, and that means they are available for perusal.

I was looking at a pair of fresh ones taken just today, June 25, at 05:37 UTC (just after midnight, more or less, U.S. time), when New Horizons was just 22.9 million kilometers from Pluto. They’re amazing. Both Pluto and its large moon Charon show all kinds of features, as you can see at the top of this article (the only processing I did was a straight enlargement and a brightness/contrast fiddle). Overall, Charon is much darker than Pluto, but even then surface features are clearly visible.

But that bright spot on Pluto surprised me. That’s near its north pole, and it’s been seen before in earlier images, basically as a splotch. In this image it’s quite obvious.

I wondered if perhaps this was an image artifact, like a particle hit on the detector, but in fact it’s the same in the other image taken 30 seconds earlier. Here are the two shots side by side:

Pluto
Pictures of Pluto taken at 05:37:30 (left) and 30 seconds earlier (right), enlarged and contrast enhanced.

Photo by NASA/JHUAPL/SwRI

The spot is very small, probably on the same scale as a single pixel or two in New Horizon’s long-range camera. That means a slight change in the pointing can make its shape look different. Remember too this image is enlarged by a factor of about 10, which can play with the shape as well. While the shape you see may not be real, the brightness contrast is.

But the important thing to note is that it’s seen in both pictures. I’ll note too that Pluto was in a different spot in the camera’s field of view, too, so this isn’t some bad lone pixel either, messing with the shot. This bright spot is quite real. Measuring the pixel brightnesses, it looks to be about twice as bright as the surface around it.

Right now, Pluto is only a couple of dozen pixels across in the long-range camera’s view. New Horizons is moving so rapidly that in 10 days Pluto will be twice this size, and will double again five days after that. Features that are tantalizingly fuzzy now will continue to sharpen, and then we’ll see Pluto as it truly is.

Is this spot at the north pole a fresh impact? Is it nitrogen in its atmosphere freezing out as Pluto slowly moves away from the Sun on its elliptical orbit? Is it one big spot or a lot of little ones (like the weird ones we see on Ceres)?

Give it a couple of weeks. Because that's how close we are. After more than nine years and 5 billion kilometers of travel, New Horizons is about to give us quite a show.

Tip o' the lens cap to Karl Battams for noting new images had arrived.

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June 25 2015 12:56 PM

The 2015 Earth and Sky Photography Winners

The good folks at the World at Night—dedicated to preserving the night sky and raising awareness about light pollution—have announced the winners of the sixth annual International Earth and Sky Photo Contest, and as usual they are breathtaking examples of the art of astronomy.

They are all beautiful, and you should see them all, but I particularly liked “The Enchanted Forest” by Lyubov Trifonova (shown at the top of this article). The aurora sweep across the sky, set against snow-covered trees in Russia. The Moon illuminates the scene while the familiar stars of the Pleiades and Taurus hang nearby. This won first place in the “Beauty of the Night Sky” category. You can tell she had to endure some fairly inhospitable circumstances to get that shot.

I was pleased to see frequent BA contributor Brad Goldpaint take second place in this category as well.

All the images have been put into a video for ease of viewing:

The contest is open to people all ages anywhere in the world, a way to show that the sky belongs to all of us. I really do like TWAN and support them; check out their site and see what they do. The photographs they have there are surpassingly lovely and will give you an appreciation of the natural heritage of our night sky.

June 25 2015 7:15 AM

A Star Boils Away Its Own Planet, Turning It Into a Megacomet

Hey, remember last week when I wrote about a Neptune-sized planet (called GJ 436b) that orbits a nearby star, and how it may have an atmosphere that’s almost entirely helium? That’s really weird, since the bigger planets in our solar system have predominantly hydrogen atmospheres. We’ve got nothing like a helium-rich planet in our solar system.

I wrote that the planet seemed to have no methane in its atmosphere as it should; that could be explained by a lack of hydrogen, needed to make methane. Astronomers were guessing that the planet orbits so closely to its star that the lightweight hydrogen would get blown away by the star, and the planet’s gravity is too weak to hold onto it. Helium is heavier and the planet can hold on to it better.

But hang on. It takes a long, long time to strip a planet of hydrogen. Billions of years! So, if what these astronomers were supposing is true, maybe, just maybe, GJ 436b is still losing hydrogen now.

Yeah, about that.

Astronomers using Hubble have just announced that they’ve detected a huge cloud of hydrogen around the planet, and the long, curving tail-like shape to the cloud indicates it’s being blown away from the planet by the star.

Huh.

When I got the press release for this, I did a double take. You don’t usually get observational proof of an idea so shortly after it’s first announced! But here it is.

GJ 436b
The lack of hydrogen and organic molecules should make GJ 436b a dull gray in color, different than any other planet we've seen.

Artwork by NASA/JPL-Caltech

The planet GJ 436b is called a warm Neptune because, at 23 times the mass of Earth, it’s closer to Neptune's  mass than it is to Earth or Jupiter, and it orbits the star only a few million kilometers out. From our point of view it passes directly in front of the star, transits it, once per orbit. That’s how it was first discovered; once every 2.6 Earth days the starlight dims a bit as it’s blocked by the planet. The amount of visible light blocked is small, less than 1%, but measurable.

The astronomers observed the star, a red dwarf about 30 light years from Earth, before, during, and after such a transit. They used the Space Telescope Imaging Spectrograph (a camera I helped calibrate!) to observe the star in the ultraviolet, where hydrogen atoms just love to absorb light. What they found is that the amount of UV light they saw from the star dropped precipitously, by over 50%, starting about two hours before the transit, and lasting for three hours after.

Not only that, they could measure the velocity of the hydrogen atoms as they move around the star. Using 3D modeling, the best fit to what they see is a huge cloud of hydrogen around the planet, forming a comet-like tail sweeping out behind it. Here's a the video showing a depiction of the planet and cloud passing in front of the star. The graph below it shows how the UV light gets absorbed by the hydrogen over time.

Most likely what’s happening is that the lightweight hydrogen is very hot due to the planet being so close to the star. The atoms move so rapidly due to heat that they get flung far above the planet, where the light from the star can give them an additional push, freeing them from the planet’s gravity. That push isn’t terribly strong, so they don’t just fly off and away, but instead form a puffy cloud around the planet, and a long tail of material trailing the planet as it orbits. That’s much the same as how comets form long curving tails as they orbit the Sun, too. Anyway, that’s why they see a dip in UV before the planet transits (that’s from the puffy cloud) and for many hours after (that’s the tail blocking the light).

The image at the top of this post gives you an idea of what this looks like. The star is boiling away the planet! Well, part of it, at least. Calculating the amount of hydrogen they see, and how fast it’s leaving GJ 436b, it looks like it would take many billions of years for the planet to lose all its hydrogen (though it’s possible the loss rate was higher in the past). But still, the planet is already billions of years old, so this method has clearly caused a severe depletion of hydrogen, explaining the lack of methane in its atmosphere, too.

I love it when a plan comes together.

All in all, this makes me smile. What’s not to love? A giant planet, skimming the surface of its star, its atmosphere being slowly torn away and trailing behind it, leaving behind mostly helium… which, as I mentioned in the earlier post, will make the planet oddly gray in color.

This is nothing at all like any planet we have here in our neighborhood. That’s so cool! The goal of science may be to learn as much as we can about the Universe, but the motivation for so many of us is the weird, the spectacular, the alien, the amazing.

This planet is all of those, and more.

June 24 2015 12:44 PM

Dancing Lights Against the Sky

When you look up in the sky enough, you'll see some really, really weird things. 

YouTube user QuadeM13 was out riding his bike and noticed a strange light beam flashing and twisting around above a cloud. He stopped and took some video of it, and it's, well, really really weird (warning, some NSFW language is muttered therein):

So what is this thing? An alien beacon? Thor going back to Asgard?

Nope. It's ... ice crystals.

Seriously. What's happening here is a wispy cirrus cloud, made up of ice crystals, is being impinged upon from below by a rising cumulus cloud. If the ice crystals in the cirrus are long and needle-shaped, they'll align themselves with the electric field of the lower cumulus cloud, which is generated by up- and downdrafts inside the cumulus cloud. When the electric field suddenly changes (due to, say, lightning discharges inside the cloud), the ice crystals can snap into a different orientation, reflecting and refracting sunlight in a different direction (note that the plume in the video is the same color as the Sun). They do this as a group, making it look like huge coherent structures are suddenly changing shape.

In the video the flare is pretty bright, and I imagine it would be easy to be freaked out by it. I watch clouds a lot and I’ve never seen this, so I doubt it’s terribly common; you need the right circumstances of the cumulus cloud rising into an icy cirrus layer as well as the right geometry to get the sunlight flashing of the crystals.

Back in 2011, I wrote this very odd phenomenon. I had to do some sleuthing to find out what was going on, but what I didn't know at the time is that they're called “crown flashes.” That would’ve made it a lot easier to find out more!

I found a letter to Nature magazine from 1971 describing the phenomenon, so people have been seeing this for a while. A Web search on “crown flash” turns up lots of interesting pictures and videos, too.

The Internet makes finding weird things like this so much easier. I’ve been able to identify iridescent clouds, pileus clouds, and many other weird atmospheric phenomena with just a few clicks. Like any other tool, the ‘Net can be used for ill or for good. I’m glad that it can help us see—and understand—the amazingness all around us all the time.

Tip o’ the Faraday cage to photographer Jerry Lodriguss.

June 24 2015 7:30 AM

Like a Sci-Fi Sunset: Three Crescent Moons Over Saturn

Every time I think I’ve seen the most amazing picture from the Cassini Saturn probe, it sends back something even more devastatingly spectacular.

Like this shot of three crescent moons huddled in the black sky!

Are you kidding me?

Wow. This image was taken on March 25, 2015. The big one is Titan, the one to the upper left is Rhea, and the little one is Mimas. Titan has a thick atmosphere, thicker than Earth’s, composed mostly of nitrogen (also like Earth’s). Sunlight hitting that air gets bent around, sent around the limb, so the crescent appears to wrap farther around the moon than it would otherwise. Mimas and Rhea are airless, so their crescents look much like the familiar one we see every month from our own Moon.

All of Saturn’s big moons orbit the planet almost exactly above its equator, so when the spacecraft’s orbit crosses that plane, the moons can appear to be close together due to perspective even when they’re hundreds of thousands of kilometers apart. The Sun is just off to the lower right in this shot, setting up the correct angles to get this spectacular and breathtaking scene.

Seriously, this looks like it came right out of a sci-fi movie. But it’s real. Those are worlds, real actual places, ones we can explore and understand.

And we have: Titan has a methane cycle on it much like Earth’s water cycle; the simple molecule can be found in clouds over the surface that rain it out as a liquid, forming rivers and giant lakes, where it evaporates to form clouds once again.

Mimas has a gigantic single crater named Herschel that makes it look like the Death Star. Though it was almost more like Alderaan: Had the impact that formed Herschel been much larger, it would’ve shattered the moon.

Rhea has deep canyons covering one hemisphere, giving it a wispy fairy-tale look, but they are actually the walls of steep canyons caused by deep fractures in the surface. 

I love science fiction. It’s inspired me over the years, given me a glimpse into places we can only imagine.

But I love science more. It shows us these places as they actually are, and reminds us that clearly, Nature is far, far more imaginative than we are.

June 23 2015 11:58 AM

Pluto Grows in Size While Its Moon Sports a Dark Cap

New Horizons is approaching Pluto and is now just over 20 days from closest approach. Every day the tiny world looks a wee bit bigger to the space probe, which is screaming toward Pluto, getting closer to it by 14 kilometers each and every second.

New images just released are showing more detail, as you can see in the images above. These have been carefully processed to enlarge and enhance those details. Note that Pluto is almost certainly very round, but it looks misshapen due to darker features near the edge blending into the black background.

Pluto is severely tilted with respect to its orbit around the Sun; while the Earth is tilted by about 24°, Pluto is flipped over at about 120°. Because of this and its approach angle, New Horizons doesn’t see the entire surface of Pluto, but it does see more than half as Pluto rotates. Projecting forward, scientists know which part of Pluto will be under the probe’s cameras when it passes, and they can see that part of the surface is richly diverse, sporting lots of different features. This promises some pretty exciting pictures come July …

But we’re learning more all the time. Charon is Pluto’s big moon, more than half the diameter of Pluto itself. Yet it’s very different; as you can see in the video above it’s far darker than Pluto, and therefore likely to have less ice on its surface to reflect sunlight. Also, weirdly, its north pole is darker than the average of the rest of its surface! That’s very interesting. On Earth, water and land are dark, but ice is bright, and the icy poles are brighter than average. Pluto too has a bright north pole (it’s not certain what it is, but it could be frozen nitrogen, not water). Why is Charon’s pole so dark? What different processes are at work there than on its larger partner?

Charon
Pluto's moon Charon on June 18, 2015, shown as the camera sees it (left) and processed to bring out details (right). At the time, New Horizons was 31.5 million km away from Charon.

Photo by NASA/JHUAPL/SwRI

We’ll find out soon enough. Right now, New Horizons is less than 25 million kilometers from Pluto. At closest approach it’ll zoom over the surface at distance of less than 14,000 km! And every day, every hour, between now and then this new world grows under the spacecraft’s eye, getting larger and revealing more detail, more secrets invisible from Earth. 

June 23 2015 7:00 AM

What Do We Do About Misogyny Online?

Not surprisingly, the issue of misogyny on the Internet has hit the news again.

The blatant and horrid misogyny women face online has been an issue for as long as there’s been an Internet. Recently, though, with the advent of Gamergate, it’s been amplified to a terrifying degree, with women receiving organized attacks, including death threats.

There’s also the problem of doxxing (publically listing a person’s information like phone number and address), which has also led to Swatting: calling the police with a fake claim of (say) a hostage situation and giving the address of the person you’re targeting. The police raid that person’s house, and this can lead to incredibly dangerous situations, and severe psychological harm.

John Oliver did a typically brilliant report on all this for his show Last Week Tonight on HBO on Sunday.* Watch:

I’m very glad he tackled this; it gives this issue a wide audience, and I think it’s very important that people with a soapbox use it to help those who may not have as loud a voice.

There’s a trick in our brains that makes all this hard to fight: We tend to listen to people who are like us, and not listen (or not listen well) to those who aren’t. In this case, that means that some men may not hear this message from women talking about it. But if a man says the same thing, it gets traction. I hate that this is the case, but it means these groups can use vocal advocates, allies, among men.

That’s why I write about this as well. I’m a middle-aged white guy, and pretty much the bull’s-eye demographic for a lot of the problems faced by women, minorities, and other marginalized groups. My hope is that if I speak up, others will as well.

As I’ve done before, I’ll make this simple. Men (and anyone, of course): Don’t do this. Don’t threaten, harass, doxx, or SWAT. It’s grossly, morally wrong.

I’ll note it’s also massively ironic, since it so face-palmingly proves the point that we really do need feminism.

If you’re worried about doxxing and swatting, then I suggest you bookmark the Crash Override Network website—created by harassment survivors—and especially their resources page, which focuses on prevention and supporting victims.

Here are other articles I’ve written on this issue. Some advice: Don’t read the comments, unless you need yet more proof of Lewis’ Law.

*Correction, June 23, 2015: This post originally misstated the name of John Oliver’s show as This Week Tonight. It’s called Last Week Tonight.

June 22 2015 1:07 PM

A Ceres of Weird Events

Ceres keeps getting weirder.

Those white spots on the surface we’ve been seeing for months are still mystifying, and we can now add another bizarro surface feature to the list: A huge 5 kilometer tall mountain sitting in the middle of an otherwise relatively flat part of the asteroid.

Um. Why is that there?

On Earth, mountains can form for several reasons. Continents crash together, creating wrinkles in the surface. That’s what the Himalayas are. Of course, Ceres doesn’t have plate tectonics! That wouldn’t form a solitary mountain anyway.

Volcanoes? Well, we do see that happening on Earth. But we don't see any other features like this at all nearby, making it unlikely to be from a weak spot in the crust. Devil’s Tower in Wyoming is similar to this feature, though; that tower may have been created by upwelling magma seeping into prehistoric sedimentary layers. But clearly that’s not going to happen on an asteroid! Sedimentary rocks would be, I expect, rather difficult to produce. 

Mountains on airless bodies like asteroids (or our Moon) can be made in several ways as well. Giant impacts have mountain ranges around their rim, created by rocks lifted up at the edge of the crater. But this mountain on Ceres is alone.

Smaller craters can get central peaks, where the rock rebounds upward after the initial impact (similar to the drop that splashes up in the center of a glass when you pour milk). But there’s no obvious crater around this mountain. Maybe other forces filled it in, or subsequent impacts eroded it away. There's evidence of landslides on the surface as well, which could eventually erase the features of a crater. This seems most likely to me. We've seen other craters on Ceres with central peaks, but I don't think any yet this size. Given all the evidence, though, this is the way I'd lean.

But I’m simply guessing. We’re just now seeing this strange feature, and it’ll be a while, I suspect, before planetary scientists can get enough data to understand it better. Note that Dawn, the spacecraft now orbiting Ceres that took this picture, is still in a relatively high surveying orbit, 4,400 km above the surface. It’ll be dropping down to get much higher resolution images in the coming months.

Hopefully then we’ll get some definitive answers to these mysteries. Ceres is odd. We know there’s ice under the surface, and there’s evidence it also has geysers, eruptions of water, from its surface. That might explain the white spots, too, but there’s still a long way to go to figure all this out.

white spots on Ceres
Yes, the white spots are still there too. This image was taken on June 9, 2015.

Photo by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Ceres is the largest asteroid in the asteroid belt (some call it a dwarf planet; I find the term not terribly useful). It’s unique in that sense, and big enough to have geological processes on it and in it we haven’t fully grasped yet. It’s not Earth, for sure, but it’s far more than a simple monolithic rock in space.

It’s a world. And with a surface area of nearly 3 million square kilometers, there’s a lot of it to explore.

June 22 2015 7:15 AM

Are Volcanoes Still Erupting on Venus?

There are a handful of known currently tectonically active objects in the solar system: Earth, of course, plus Saturn’s moon Enceladus, Neptune’s moon Triton, Jupiter’s moon Io (the actual most active body known) and (most likely) Jupiter’s moon Europa.

And now we may be able to add Venus to that list. New evidence strongly suggests there are currently active volcanic vents on the surface of Earth’s sister planet.

I’m actually pretty chuffed about this. We’ve had tantalizing evidence for years that something is bubbling and brewing just beneath Venus’ surface. The top of the mountain Idunn Mons is clearly hotter than surrounding terrain, for example. Lava flows have been seen to be warm as well, and they are certainly less than 2.5 million years old, and possibly far less. Sulfur dioxide, a known volcanic gas, has been seen to spike in abundance then fade with time, which looks very much like a volcano outgassing (though it could simply be due to shifting winds).

But new results from an old mission provide what may be the most important evidence yet that Venus is still puffing away: The ESA Venus Express probe, which completed its eight-year mission last year, found several hot spots on the surface of the planet, and they were all located in rift zones; radial cracks around a volcano where, on Earth at least, magma is pushing up on the surface and flowing out.

Better yet, these hot spots flashed into existence and then faded away over the course of a few days. This is exactly the sort of behavior you’d expect from ongoing volcanism.

Venus volcano map
NASA’s Magellan probe data was used to generate this perspective view of the volcano Ozza Mons (red, in the center) with the rift zones (purple) radiating away. Venus Express saw several hot spots in these valleys.

Photo by Ivanov/Head/Dickson/Brown University

Observing the surface of Venus is difficult because of its thick, opaque atmosphere (a product of a runaway greenhouse effect). The observations were at the limit of what the camera could do, but Venus was accommodating by providing really big temperature spikes: One may have reach more than 800° Celsius, 350° higher than the surface average.

The camera’s field of view is large, so the resolution is low, but it’s possible these hot spots may be as small as a square kilometer. All in all, these really sound like lava eruptions to me. I’m no expert, of course, but then the people who did the research are.

Studying Venus is important. In many ways it’s very much like Earth. It’s roughly the same size and mass, which means the same density, and that implies we have similar compositions. So why is Venus so blisteringly different? Compared with us, we can ask, “What went wrong?” Why is its crust so thick? Why did the greenhouse effect run away there, and not here? Why does Venus appear to have a surface that’s everywhere the same age, as if a globally catastrophic event repaved the entire planet?

Looking to other planets to understand our own is a critical part of planetary science, and given the current state of Earth’s atmosphere, it’s something we must do. Together with studying our own planet (something the current congressional majority is dead set against, for some odd reason) these are matters that are critical to our own survival.

That’s why these new results of an extant volcanic Venus are so exciting. That, plus the more purely scientific reason that it’s just plain cool. Venus gets closer to Earth than any other planet in the solar system, yet still hides many secrets. What more is there to learn about it?

I’ll leave you with this, my episode of Crash Course Astronomy about Venus. I wonder how many of the questions raised in it will be answered in the coming years?

June 21 2015 10:15 AM

To Pluto

Why is it so many of us are excited about the New Horizons mission to Pluto?

This. This is why.

That video was created by Erik Wernquist, the brilliant mind behind Wanderers, what I consider one of the best paeans to exploration ever made.

And like Wanderers, all the places in the New Horizons video are real. We see Venus; Mars (flying over Valles Marineris; a rift valley that dwarfs the Grand Canyon); volcanoes of sulfur erupting over the moon Io as Jupiter and its Red Spot hover into view; the two-faced ice moon Iapetus, stained with organic compounds, revealing the magnificence of Saturn as we slide by; Uranus, its atmosphere a teal green from the presence of methane; Neptune and its moon Triton, with its geyserlike eruptions of nitrogen blasting into its extremely tenuous atmosphere …

… and then Pluto. As I write this, just over three weeks before the New Horizon probe pierces the tiny world’s region of space, we still only have fuzzy pictures of Pluto, a mere dozen or so pixels across. Astronomers have many ideas on what we’ll see when the spacecraft sends back its images over the staggering vastness of 5 billion kilometers of solar system, but the bottom line is we don’t know exactly what we’ll find.

If we did, it wouldn’t be exploration.

You can follow along with this journey using the Pluto Safari app, and of course by keeping tabs on the New Horizons website.

This is more than just terra incognita. It’s spatium incognita. Whether you think Pluto is a planet or just the biggest of the Kuiper Belt Objects, it’s a marvelous step in our exploration of the solar system.

And we’ll be seeing it for the very first time in the history of all humanity, very, very soon.

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