Bad Astronomy
The entire universe in blog form

Oct. 3 2015 9:30 AM

Crash Course Astronomy: Multiple Star Systems

The stars are not as they seem.

The nearest one is tens of trillions of kilometers away, a distance so terrible that the might and power of Alpha Centauri is reduced to a faint spark that can be washed away by the lights of a nearby city.


Distance shrinks details, too. Alpha Centauri is not one star, but two: one very much like the Sun, though slightly larger, orbiting and orbited by another that is somewhat fainter, cooler, and more orange. There’s also a third star, Proxima Centauri, which orbits the pair, but is so faint it can’t be seen by the naked eye even though it is in fact the closest known single star to the solar system.

A large fraction of all the stars in the sky are actually multiple stars; binary, trinaries, or even more complex systems. That alone is enough to want to know more about such multiples; but once you look closer you find that such systems become critically important to our understanding of everything in the Universe.

And, contrary to my usual nature, that’s not an overstatement. Find out why in this week’s episode of Crash Course Astronomy: Binary and Multiple Stars.

I’m excited that this phase of Crash Course is airing: We’re traveling farther out into the Universe, even though we haven’t even left our cosmic back yard yet. But there are larger structures to explore, and grander things yet to see. Just you wait.

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Oct. 2 2015 9:15 AM

Behold, the Mess That Is Charon

Charon is so, so weird.

It’s also astonishingly beautiful. Look at it! The image above is a newly released high-resolution color photo of Pluto’s largest moon, taken by the New Horizons spacecraft when it zipped past the Pluto system in July 2015. It’s been enhanced to bring out the color variations more, but this also gives us an idea about the surface features, and how they vary across this strange little world.


There’s so much to see! The most obvious bit is the red splotch at the north pole, informally named Mordor Macula (macula means spot and is commonly used in planetary nomenclature to refer to a big dark region; Mordor is a place you simply don’t walk into).* Pluto is covered in red spots, and it’s thought these are tholins, carbon-based molecules created when ultraviolet sunlight breaks apart molecules, which then reorganize themselves into more complex structures.

Very little of the rest of Charon is red, prompting some scientists to conjecture that Mordor Macula is from some sort of transfer of material from Pluto onto Charon’s surface, possibly from Pluto’s extremely tenuous (but observable) atmosphere. Craters in Mordor are bright, indicating the red material is a veneer; thin enough that small impacts excavate brighter material (likely ices) underneath.

The next most obvious feature is that huge canyon separating the north and south hemispheres. The canyon is staggeringly huge, at least 1,600 kilometers long, making it four times longer than the Grand Canyon and in places far deeper. To scale with Charon, it’s similar to Valles Marineris, the vast canyon scarring the face of Mars.

By the way, the stretch of the canyon just to the right of center, to the right of that centered crater? That’s called Serenity Chasma, and it’s named that way for exactly the reason you think. Shiny.

There’s a big dichotomy between the hemispheres, too. The southern half of Charon has a smoother look—this area is dubbed Vulcan Planum, the Plains of Vulcan—dotted with craters and what looks like cracks or graben (downward thrusted rocks, usually due to faulting as the crust expands). The northern half looks more rugged, less smooth. Perhaps some ancient event caused cryovolcanism—ice volcanoes!—in the southern hemisphere, flooding the plains with ice.

We only have good images of this side of Charon, unfortunately, because the New Horizons mission was a very fast flyby. I’d love to know what the other side looks like in this sort of detail!

A high-res mosaic of part of Charon was also released. It’s well worth your time to peruse the whole thing, but there’s one spot I want to point out:

crater chain
A crater chain dots the surface of Charon.


See that linear feature just above center? That’s a crater chain, usually caused when debris from a big impact is ejected, and then falls back to the ground. But this one is a bit weird; the craters are very close together, almost overlapping, and they don’t seem to point to any other obvious big crater. I’m wondering if this is due to a small body breaking up before it hit, forming a long chain of objects that then hit one after the other along a line. This happened when the comet Shoemaker-Levy 9 hit Jupiter in 1994; Jupiter’s immense gravity ripped the comet into pieces, which hit one after another over several days. Neither Pluto nor Charon has strong gravity, so I’ll admit this seems unlikely. It’s an intriguing formation either way.

As I mentioned, the picture of Charon is enhanced in color to show surface variations. Here’s one more picture, showing what it actually looks like in comparison with Pluto, with both bodies scaled the same way.

Pluto and Charon
The darkness and the light.


Charon is a lot darker than Pluto! That in itself is interesting. Charon most likely formed when an impact on Pluto blew some or most of its crust into space, which went into orbit and coalesced to form Charon (and perhaps the smaller moons, too). It seems to me that they may have started off looking similar, but subsequent events changed them, either brightening Pluto or darkening Charon, or both. Both show evidence of cryovolcanism or more recent resurfacing (the left side of Pluto’s “heart” is likely to be nitrogen ice that’s glacially flowed into lower elevations).

As more images and data trickle back from New Horizons, traveling the long, long emptiness stretching for five billion kilometers, we’ll learn more about the surfaces of these worlds. But every new picture shows something weird and wonderful, and while we get traction on some mysteries, others deepen.

Oh, how I love that! Science is fun.

*Features on Charon are informally named at the moment, but the agreed-upon nomenclature is that they are named after fictional destinations, ships, or voyagers.

Oct. 1 2015 9:30 AM

GOP Presidential Candidates, Science, and Reality

It’s time to not only face facts, but to call them out, too: This cohort of Republican presidential candidates isn’t exactly a brain trust.

Every time I see an article about something one of the GOP contenders has said, I’m stunned at just how much lower they can sink. It’s as if they’re scrambling on purpose to brag about the dumbest possible thing they can come up with.


Think I’m exaggerating? Here are some choice examples of ideas that have come out of the mouth holes of the remaining viable candidates:

None of this stuff is exactly rocket science … but when it comes to climate science, not a single one of these people is even close to planet Earth. They’re in their own alternate reality where up is down and, I suppose literally, hot is cold.

Let’s do a quick rundown of where they all stand:

I’ve been railing against the GOP’s party plank on climate change for years now, so none of this is surprising. But it’s upsetting. I disagree with almost all of the stances of the Republican Party these days, but in the past they at least used to embrace science. Now, though, if one of their candidates says the Sun will rise in the East, I’d lay better odds on the Earth’s rotation having reversed.

This stunning intellectual deficit, whether real or pandering, is wholly the fault of the party itself (and, to an extent, the American public for letting it slide this far). The abject dismissal of reality has become more and more mainstream in the party politicians, and its power soared upward like a hockey stick graph when the Tea Party gained congressional seats in the in 2010 election.

The fallout from this is as fascinating as it is maddening. For example, the Heartland Institute—or as I think of it, the Mos Eisley of think tanks—attacked the pope on his climate change stance, and even a Catholic congress person boycotted the pope’s speech. The internal paradoxes in the minds of these folks must be incredibly turbulent.

More examples can be easily found from other conservative groups. But there’s a glimmer of hope, a glimpse of the path back to reality for the GOP. As the pope showed, religious belief doesn’t necessarily lead to rejecting science; one need only look to outspoken climatologist and Christian evangelist Katharine Hayhoe for that as well. This reveals an underlying aspect of all this that seems to be forgotten: Belief in conservative principles doesn’t lead inevitably to the denial of science.

Conservative political parties in other countries don’t necessarily deny global warming either. It’s only endemic to the GOP. And while funding from the über-far-right Koch brothers clearly affects the way politicians vote in the U.S., not all wealthy donors are the same; Republican businessman Jay Faison has put the incredible sum of $175 million on the table to invest in climate-change–accepting Republican politicians.

The response to that was as predictable as rising temperatures: James “Snow disproves global warming” Inhofe, R-Oklahoma, denounced it. Of course he did; Inhofe is so far removed from reality he actually thinks the pope wasn’t discussing climate change in front of Congress.

I can make a laundry list of problematic GOP planks, but global warming is perhaps the single biggest threat facing humanity today. Faison’s move is a step forward, even if it makes some deniers froth and fume. Their staunch denial may yet lead to political extinction: A majority of Republican voters acknowledge the reality of global warming, and humanity’s role in it. That’s hopeful indeed.

And to those who still deny it, I’ll note that it’s better to take the carrot than the stick: Some people are proposing siccing the RICO Act on corporations actively suppressing global warming and climate change information. This isn’t fringe stuff; an investigation into Exxon revealed they allegedly knew about the threat of global warming for 40 years, yet still funded misinformation campaigns about it. Fossil fuel interests use the same tactics employed by the tobacco industry to downplay harm, and it was the RICO Act that brought those same tobacco companies low.

I’d rather not see things go this far, of course, but that’s the world we now live in: a planet that needs saving from those who would actively burn it down. And that, in sum, accurately describes the current crop of GOP presidential candidates.

Perhaps most sad is that it needn’t be this way. Republicans are supposed to be conservatives. Isn’t it about time they started conserving?

Sept. 30 2015 9:30 AM

Bloom With a View. Two of Them, in Fact.

Oh, I do so love a coincidence. And when it’s about imaging Earth from space, that’s even better.

I subscribe to NASA’s Earth Observatory Image of the Day (and you should, too!), which, oddly enough, posts an image of Earth every day. They’re almost always satellite shots, featuring various amazing portraits of our planet. As a satellite photo nerd I love it, and I learn a lot about Earth every time I see a new one. The cloud images alone are worth it.


One of the most spectacular and lovely kinds of photos they post are of phytoplankton blooms—huge bursts of growth (usually of cyanobacteria) in the ocean. Warmer waters can create conditions where nutrients and sunlight become abundant to the little plants, and they go forth and multiply. Blooms can be huge, hundreds of kilometers across.

The image above shows (a small part of) a bloom in the Baltic Sea, just north of Poland. It was taken by Landsat 8 on Aug. 11, and it’s not “true color,” that is, what your eye would see. The detectors used are sensitive to colors across a range of the spectrum, so the colors displayed are close to red, green, and blue, but there’s quite a bit of overlap (for example, the detector that sees in the green is also sensitive to yellow, and the blue one sees green as well). Still, the bloom is eerily beautiful. You can see airplane contrails and the wakes of ships in the original full-res image, too.

The spiral pattern is lovely, caused by eddies in the sea currents. Cyanobacteria are plants (more or less) so they flow along with the water.

The coincidence? The European Space Agency released a similar picture taken just a few days before, on Aug. 7, using the Sentinel-2 Earth-observing satellite:

Sentinel bloom
If you told me this was a radio map of a spiral galaxy, I might believe you.

Photo by Copernicus Sentinel data (2015)/ESA

Whoa. I’m not positive that’s the same swirl, but it’s from the same general area of the Baltic Sea (the Sentinel image is also part of a much larger image). Interestingly, both images from Landsat and Sentinel-2 show ships crossing their respective swirl; in each you can see the ship as a dot followed by a black trail.

Cyanobacterial blooms are important to study. They can rob water of oxygen and nutrients, and some phytoplanktons produce toxins that can be dangerous. And here we have two space agencies studying the same bloom at two different times with two different satellites! It’s really gratifying to see nations taking this sort of work seriously … especially when one faction of my own nation doesn’t.

We need to understand our planet as best we can. Not just because doing so produces such wonderful natural art, but because we are part of Nature ourselves, and we influence it just as it influences us. Understanding it is critical.

After all, Nature can live without us, but we can’t live without Nature.

Sept. 29 2015 9:30 AM

Global Epic Eclipse

Well, despite some baseless fears, we’re still here after Sunday night’s lovely lunar eclipse.

It was quite nice here in Colorado; the Moon was still very low to the horizon when it started to pass into the darkest part of the Earth’s shadow. I was just finished setting up my Celestron Regal M2 80ED spotting ’scope to watch when I saw an airplane approaching the rising Moon … and as I shot the video, to my surprise I got two planes transiting!


That was fun. The Moon was still yellowish as it rose due to atmospheric effects. It was just about the enter the darker part of the Earth’s shadow (called the umbra) but even then you can see the left side is darker and redder than the right.

I also did a live Periscope as the Moon darkened, winding up with more than 8,000 people watching at different points. I love seeing so many folks interested in what’s going on in the sky!

I think my video is pretty cool, but master astrophotographer Thierry Legault did me one better. Well, more than one: He caught the International Space Station transiting the Moon during the eclipse!

That is so cool. He told me that, to the best of his knowledge, this is the first time anyone has caught the ISS transiting the Moon during a lunar eclipse on video.

I want to share a couple of photos, too. As the sky darkened, the eclipsed Moon rose through several thin cloud banks, and I liked the feel of this one:

eclipse clouds

Photo by Phil Plait

You can see the eclipsed part of the Moon on the left. It helps sometimes to have something else in the field of view when you’re taking pictures like this. A cloud is nice, but sometimes something more recognizable can turn a nice shot into a fantastic one.

Like, say, this:

Eclipse and monument
Oh say can you see the eclipse?

Photo by NASA/Aubrey Gemignani

Wow. Yeah, sometimes it’s all about the framing.

If you want to learn more about these events, I talk all about them in my Crash Course Astronomy episode on eclipses. The next lunar eclipse visible to the U.S. won’t be until 2018, but August 2017 will bring the Great American Solar Eclipse. Stay tuned for more on that.

Sept. 28 2015 12:27 PM

The Big Mars News: Flowing Water on Mars, at Least Briefly

Scientists have found what they think is evidence of extant, if brief, flowing water on Mars.

In a NASA press conference on Monday, scientists claimed that images and spectra taken by the Mars Reconnaissance Orbiter’s HiRISE camera show what are called Recurrent Slope Lineae, or RSLs, straight dark streaks that run down the sides of craters and canyons on Mars. These features, which are a few meters across and hundreds of meters long, change with the seasons, becoming darker and more obvious in the spring and summer on the sides of crater walls facing the Sun. That strongly implies that warmth triggers the formation of the RSLs. The important finding: Scientists found evidence of salt deposits in these features, which in turn implies that briny, salty water is the force behind them. They think the darkening seen every spring is from water seepage!


If you want details, I wrote all about this Sunday in an article based on papers written by the scientists in question to be presented at a planetary science conference in Europe. I had not read the (embargoed) science papers, so what I wrote was based solely on those public papers, but it looks like I was right on the money.

Mind you, the detection of water here is indirect, through the dark streaks and the presence of salt. Still, the evidence they presented is very compelling, and their conclusions, in my opinion, likely to be correct. But there’s a problem, and it’s a big one: Where does the water come from?

We know there’s ice under the Martian surface. We see lots of evidence for it—it was seen directly by the Phoenix lander in 2008, and small asteroid impacts leave craters behind that excavate ice that can be seen. But Phoenix landed at high latitude, near the north pole where you’d expect ice, and the craters with ice only reach as far as midlatitude. But these RSLs are seen closer to the equator of Mars. Over time, the water ice there, to at least mild depths, should have disappeared, melting away.

Because of this, the authors of the work speculate that perhaps water is absorbed into the ground from the atmosphere, where it collects until there’s enough for it to flow—a process with the lovely name of deliquescence. The soil of Mars is loaded with a chemical called perchlorate, which is capable of absorbing water in this way, and perchlorates were found at the RSL sites.

So this idea ... holds water.

Still, the air on Mars is exceedingly thin, less than 1 percent of Earth’s. And there’s not much water in it, either, so it’s difficult to understand how enough water could collect to form these seepages. Although deliquescence is the preferred scenario by the scientists involved, they also admit the actual source of the water is still something of a mystery.

Opinion time: This is a wonderful discovery, and an important one. The origin of these features has been a mystery for a long time, and it does look like we’re finally starting to get a grip on it.

But it’s far from solved. Where does the water come from? How much is there? Is it just water, or are there other substances involved?

And what does this mean for the possibility for life on Mars? Well, in my opinion, it doesn’t change much. Not yet. We know Mars has lots of water ice, and it once had vast amounts of standing and flowing liquid water on its surface in the past. This doesn’t change that. Mars may once have had life, but we still don’t know, and don’t know if there’s life there now.

What it does change is the idea that there could be liquid water beneath the surface of Mars. This makes it less unlikely, I’d say, which I know sounds weak. But what we’ve seen here is temporary flowing water, not persistent liquid water. The bottom line is that we still don’t know if liquid water exists under the Martian surface or not.

But we’re learning. This is just one of many steps we’re taking in observing Mars. Remember, Mars is a planet, an entire world, with a rich history, diverse geography, and a lot of real estate. We’ve only just scratched the surface—in this case, almost literally—and there are great depths left to explore.

Sept. 27 2015 5:35 PM

Mars News: “Major Science Finding” to Be Announced Monday

By now, many of you have heard about some big announcement NASA is about to make about Mars. The news is embargoed until the press conference Monday (which you can watch live at 11:30 EDT), but of course speculation is rampant, especially since the press release says it’s a “major science finding.”

In the email NASA sent out, the names of some panelists were given: Alfred McEwen, Lujendra Ojha, and Mary Beth Wilhelm. McEwen is the principal investigator for the wonderful HiRISE camera on the Mars Reconnaissance Orbiter. Ojha studies recurrent features on Mars that look very much like they were carved from water, like gullies down the sides of craters. Wilhelm studies many things, including the habitability of ancient Martian terrain.


As many people have pointed out on social media, at a European planetary science conference on Monday, McEwen and Ojha are presenting results of a study showing that seepage in crater walls appears to be seasonal, and most likely due to water. Not only that, but Ojha and Wilhelm are presenting results that show the presence of salts in crater wall gullies, too, implying strongly they are due to water leakage.

I’m posting this now to hopefully extinguish rampant speculation (what I write here is based on evidence, so call it mild speculation). I assume these new results will be a major part of the news conference, but there might be more as well.

I also wanted to give a little bit of background on these gullies, since they’re pretty cool. As far back as 2007, NASA announced they might be from water, though a year later a study was released indicating many might be better explained as dry grains flowing downhill. In 2010 more gullies popped up that looked like they could be from liquid flowing, but the evidence was still a bit circumstantial. We know water once flowed on Mars, a long time ago, and there’s plenty of evidence for ancient standing lakes and even oceans. Also, even now there’s lots of water ice just below the surface across a wide range of latitudes, too.

Salty water melts at lower temperatures than fresh water, so if that’s what lurks behind crater walls, then in the spring sunlight can warm the ground and cause seepage. The results being presented at the European conference question the idea of water ice under the surface being the cause, and suggest it may be from deliquescence; absorption from the atmosphere in the ground until the water can break through. That seems unlikely, but we’ll get more info during the press conference.

Mind you, as of right now we have never seen any evidence for the presence of extant liquid water on Mars. Even the temporary existence of water in a liquid state is scientifically interesting, even exciting. However, it’s also been found that a type of chemical called perchlorates is widespread in Martian soil, which makes the hunt for life a bit more of a problem. I expect that will come up in the press conference as well.

I’ll be listening in and will write up the news as soon as I can. Stay Tuned.

In the meantime, because why not, here’s my Crash Course Astronomy episode on Mars. Enjoy!

*Correction, Sept. 28, 2015: In the caption of the photo, I originally misspelled Russell.

Sept. 27 2015 10:00 AM

Hey, I Can See My House From Here

I love posting pictures of the Earth from space. It’s fun to see things from a height, and get an overview of our planet. Volcanoes, lakes, deserts, cyanobacterial blooms … sometimes you need to take a step back (well, up) to see things for how they are.

But then you get a picture of some place you recognize, and suddenly it becomes personal.

To wit: On April 29 an astronaut on the International Space Station took a picture of me

Sept. 26 2015 9:00 AM

Crash Course Astronomy: Black Holes

OK, so here’s the thing about black holes: They’re weird.

Well, that’s not the only thing about black holes. And that’s the problem. There’s a lot to know about black holes, and it goes from simple to brain-melty pretty quickly. I had big plans for the Crash Course Astronomy episode about black holes, covering so many of the cool things about them.


After writing more than 3,000 words on them—the equivalent of about 25 minutes of footage—I realized I had a problem. A lot of stuff had to go. So I went through and cut this, excised that. What was left is, I hope, a pretty good primer on black holes, with the info you need to understand the basics.

The good news? Most of the stuff I cut will show up in later episodes. I’m pretty good about recycling electrons. If you’re impatient and want to know more about them now, then try these articles:

Oh, one more thing: In the video, at about the 8:30 mark, I talk about the perception of time near an object with gravity, and how it slows down. I say that someone near a black hole perceives time as moving more slowly than someone far away does. I should have phrased that differently; both people observe time to flow normally. To them. But they see each other's time flow rate change. Someone far away from the black hole sees the time flowing more slowly for the person near the black hole while the person close to the black hole sees the person's time far away flow more quickly. Time is relative; grammar isn't. I should've been more clear.

Sept. 25 2015 9:00 AM

Pluto. Oh My, Pluto.

I was going to write a big flowery introduction to preface this new image of Pluto from the New Horizons spacecraft, but screw that. 

Just look at it. Seriously. Look.


That ridiculously gorgeous picture is actually a combination of three images shot by New Horizons, one each using a blue, red, and near-infrared filter. So this isn’t what you’d see with your own eyes if you flew past Pluto (and weren’t dead from hypothermic anoxia), but it’s still simply amazing. By the way, this is a very, very ensmallened version of the picture; click it to get a 2,000 x 2,000 pixel version.

Or, you could grab the 8,000 x 8,000 pixel shot. Y'know. If you want.

As usual, Emily Lakdawalla does a great job explaining all this. In a nutshell, it was taken by the Multi-Spectral Visible Imaging Camera. It has several detectors on it, three of which are dedicated to seeing blue, red, and infrared. They use what’s called the “pushbroom” technique to take images, basically sweeping across an object like a scanner does when you scan a document. It’s a commonly used technique for spacecraft, so you don’t have to build a huge detector.

What can you say about this shot, though? Pluto is gorgeous! You can see the heart-shaped Sputnik Planum feature in the middle, and some terrain on the left that’s highly reflective in infrared (colored red in the photo). Those highlands are pocked with craters, in contrast to Sputnik, which is smooth—that’s an indicator of relative age; smooth terrain has probably been resurfaced, and so it’s younger.

I’m pretty interested in the higher surface features you can see that define the left side of the heart. What could cause such tall mountains so close to lower terrain? 

And check out this close-up of a region near the leftmost part of the heart:

Pluto Terrain
Taking pictures of Pluto has its ups and downs.


Whoa. Mountains pop up higher than the nitrogen ice plain below … which isn’t as smooth as I first thought. It appears almost corrugated, like it’s stippled with dunes. There’s no word yet on what’s actually causing that; the ice might be sublimating (turning directly into a gas), which could cause a rippling effect. 

Again, Emily has more close-ups and discussion, care of Alex Parker, the astronomer who created this jaw-dropping image. NASA has a few more detailed shots as well, including the highest-resolution map ever made of the surface of Pluto.

Remember, too, that new raw images are released every week on the New Horizons website. You should check there to see what’s hot off the interplanetary presses; it’ll take the better part of a year to get all the data back from the spacecraft. These marvels are just the beginning. It’s a whole new world out there on the edge of the main solar system. A lot more wonder awaits.