Bad Astronomy Blog

The Latest Crash Course Astronomy Will Be Delayed

15 hours 9 min ago

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, August 6 at 21:00 UTC (5:00 p.m. EDT). 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 over two dozen other episodes online to keep you entertained and learning about our amazing Universe. Have fun!

Categories: Astronomy Headlines

Arc of Truth

Fri, 07/31/2015 - 04:30

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.

Categories: Astronomy Headlines

The Summer of ’82

Thu, 07/30/2015 - 04:15

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.

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.

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.

Categories: Astronomy Headlines

The Densest Galaxies Ever Discovered

Wed, 07/29/2015 - 04:15

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 incredible 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 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. In one of the new UCDs just discovered, it has far fewer stars — something like ten million — but it’s only about 20 light years across!

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 pre-disposed beliefs. Look around you! What are you missing? 

Categories: Astronomy Headlines

Sen: Is Kepler-452b Really Earthlike?

Tue, 07/28/2015 - 10:16

I recently wrote about the newly discovered exoplanet Kepler-452b. It’s bigger than Earth, but it orbits its Sunlike star in the habitable zone, where water could ostensibly exist on the planet’s surface.

The planet is actually 1.6 times the Earth’s diameter, and if I were a betting man, I’d wager it’s not Earthlike at all. Given what we think we understand about planets, it’s as likely to have a thick atmosphere like Neptune's as one like Earth's. Maybe more likely. But we just don’t know.

Despite this, a lot of headlines were screaming about an Earthlike planet found, calling it “Earth’s twin.” Feh.

In fact, I feel “feh” so strongly that I wrote all about this for my biweekly column for You can go there to get the details of my “feh”-ness. It’s subscription only, but that includes getting lots of articles by lots of good writers … and there are more to come. You’ll like it.

And to be clear: I am excited about the discovery of this planet, and its implications. I just wish stuff like this weren't overhyped.

Categories: Astronomy Headlines

Because Comets Aren’t Cool Enough: They Also Have Sinkholes

Tue, 07/28/2015 - 04:15

“No, no. We have already succeeded. I mean, what are the terrors of the Comet? One, the ice venting—no problem. There's a popping sound preceding each; we can avoid that. Two, the sinkhole, which you were clever enough to discover what that looks like, so in the future we can avoid that too.”

— The Dread Astronomer Westley Roberts

The comet 67P/Churyumov-Gerasimenko is heading toward the Sun, and as it does, it slowly dies.

But what a death. Underneath its crusty surface are icy deposits, and as the comet nears the Sun, these warm. The ice turns directly to gas and blows out of vents, forming gorgeous and delicate streamers of water vapor dozens of kilometers long. The picture at the top of the article shows the long-distance view of this; from 177 kilometers away, the Rosetta spacecraft sees quite a few of these jets.

But what do these do to the surface? Some of the vents have been seen in close-up views from Rosetta, and they come from pits that you might mistake for impact craters at first. It’s clear these are the sources of at least some of the jets, but a new study reveals they’re more than that: They’re sinkholes.

Sinkholes on Earth are relatively common; water (for example) can erode away material under the surface, and at some point gravity takes over, and the structural integrity gives way. The surface collapses, sometimes taking cars or even houses with it.

On a comet things are slightly different. For one, the gravity is only a tiny fraction of Earth’s. For another, sinkholes on Earth tend not to jet towers of water vapor out from them.

But the overall idea is the same. Heat from the Sun warms the comet. This heat leaks under the surface (possibly through cracks) and turns the ice into gas, which then leaks out. Eventually a large cavity is formed under the surface, so big that the “roof” of material over it collapses, forming the steep-walled sinkholes.

This allows light to flood in, which can heat the ice rapidly, causing an outburst of jetting from the comet. This has been seen on 67P, too. Eventually, the walls of the hole erode as more ice vaporizes, and the steep pits become more shallow. Quite a few of these are seen on 67P as well. This means the steep pits are young, and the shallow ones old.

While this result doesn’t surprise me—it’s been suspected since the first close-up pictures came back from Rosetta—it’s nice to see the whole story figured out, and an explanation found for the steep pits.

Comets are so cool. And this one has turned out to be a fantastic choice for an extended visit by Rosetta. We’re learning so much about these interplanetary wanderers, and, unsurprisingly, it’s all been really amazing.

Categories: Astronomy Headlines

Gardasil: Yup. Still Safe.

Mon, 07/27/2015 - 04:00

Through an article in Forbes I saw that a new study has been published about the safety of Gardasil, a vaccine for prevention of certain strains of human papillomavirus, or HPV.

HPV is a virus that can lead to genital warts, many types of cancer, and cervical cancer in women, which kills 4,000 women every year in the US alone.

The Gardasil vaccine, on the other hand, caused some people to faint after getting it, and others got mild skin infections — both of which occur somewhat rarely with other vaccines too, as you might expect.

Which sounds worse to you?

The study, published in The Pediatric Infectious Disease Journal, looked at the published data about effects from the vaccine, and found that it has a “favorable safety profile”. This study comes after many other previous studies that show essentially the same thing. There is no correlation between getting the Gardasil vaccine and seriously adverse effects such as “autoimmune diseases (including Guillain-Barre Syndrome and multiple sclerosis), anaphylaxis, venous thromboembolism, and stroke.”

Mind you, all these things and more have been used by people who attack vaccines as an argument against it. And, just like essentially every claim made by the anti-vaccination movement, these arguments are wrong.

That doesn’t stop them from making them, or from them getting attention by mainstream media; attention they most assuredly do not deserve.

It’s very frustrating; mounds of data show these vaccinations are incredibly low-risk, but it only takes a little bit of doubt and fear to make vaccine rates drop. For example, a young girl died tragically not long after getting the vaccine, and it got a lot of press, but it was later found that she died of a completely unrelated cause. This, sadly, is expected; over 178 million doses of Gardasil have been given worldwide, and given that huge number it’s a statistical certainty that some young people will die not long after getting them. But as the saying goes, correlation is not causation. The vaccines are not to blame here.

Even more frustrating about this vaccine is that it’s being fought by an unusual group of people; while most anti-vax leanings are not affiliated with any particular political persuasion, Gardasil gets attacked additionally by conservatives who think that girls getting it will become more promiscuous, since HPV is a sexually transmitted disease.

However, this has been shown to be false. Worse, these same people tend to promote abstinence-only education, which has been shown conclusively to be the worst possible sex education; kids taught his way tend to have more pregnancies and more STDs than ones who are taught progressive, healthy sex ed.

It’s like Bizarro world, where everything is backwards. All the evidence shows Gardasil to be safe and to be effective against a virus that causes horrific illnesses. It also shows that the claims made by anti-vaxxers are wrong, and that people fighting the vaccine because of their own sexual biases are making things far worse.

And yet they dig in. They insist real science is wrong, that their anecdotes are better, that the entire medical industry is on the take (which is silly beyond reason).

But that’s where we are. When it comes to health issues, especially ones tied to sexuality, reason goes out the window and emotions take over.

That’s why I am very, very clear about this: I and my family are all up to date with our vaccinations, and my daughter has had all three stages of the Gardasil vaccine (we’d have done that if she had been a boy, too). As a parent, as someone who knows and loves someone with an autoimmune disorder, and as a person who knows just how truly awful so many diseases are and how easily and safely they can be prevented, I am a strong advocate for vaccinations.

It’s your body, but it affects literally everyone around you. Don’t listen to the anti-vaxxers, who just want to scare you. Get the facts. And please, talk to your board certified doctor and find out if there are any vaccinations you need.

How many lives will you save when you do?

Tip o’ the virion to the Refutations of Anti-Vaccine Memes group on Facebook.

Categories: Astronomy Headlines

Journey From the Far Side of the Sun

Sun, 07/26/2015 - 04:00

Studying the Sun from Earth can be frustrating. From 150 million kilometers away, we can only see one side at a time. Sure, the Sun rotates, so we see the whole thing over the course of about a month, but sometimes you want to see it from different angles at the same time, like when it shoots out an explosive flare or coronal mass ejection.

What you want is a stereo view. Or STEREO.

STEREO is the Solar TErrestrial RElations Observatory, a pair of Sun-orbiting satellites; one is in a slightly smaller orbit than Earth so it travels ahead of our planet, and the other in a slightly larger one, so it lags behind. Over time, they get far enough apart to see the Sun from totally different viewpoints.

Right now, STEREO-A (A for Ahead) is almost directly opposite the Sun from us. In fact, it was behind the Sun for a few days, but even before and after that it was so close to our star that communicating with it was not possible.

The image above, taken in the far ultraviolet, was one of the first to come back from STEREO-A, on July 15 (around the same time New Horizons was sailing past Pluto 15 times farther away from us). At this wavelength, magnetic activity glows fiercely, and you can easily see the towering loops of the Sun’s complex magnetic field piercing the surface and arcing a hundred thousand kilometers above the surface.

This is the same magnetic activity, incidentally, that will not cause an ice age on Earth. Not that it isn’t dangerous.

STEREO has provided a huge amount of benefit to solar astronomers trying to figure out the ridiculously complicated behavior of our nearest tame nuclear inferno.

Sometimes, though, what it does is just plain cool… like the time it saw the Moon pass in front of the Sun. It’s a solar eclipse like you’ve never seen before.

We learn a vast amount of important, crucial, information from space-based astronomical observatories. But also, they just increase the coolness of our lives.

My apologies to Gerry Anderson for the title of this post.

Categories: Astronomy Headlines

Hey! It's Not Rocket Science!

Sat, 07/25/2015 - 04:00

I mentioned in a recent post that I met astronaut Chris Hadfield at Comic Con in early July. Chris is the real deal: He is a friendly, funny, warm, intelligent, and hard-working human being who truly and passionately wants to make the world a better place.

One way to do that is to get more people interested in science. To do that, he’s helping create (and starring in!) an animated comedy science series called “It’s Not Rocket Science”, which will premier this fall.

The series is being made with the help of his son, Evan. It was Evan’s idea for his dad to make the “Space Oddity” video, in case you’re wondering if Evan is up to the task (he edited it all together, too). Evan has also been helpful to me a few times pinning down some of the photos from space Chris took when he was on the International Space Station, too.

As for the animation, rest assured that’ll be great too. How do I know? Because my friends Tracy King And DC Turner are doing that! They made Tim Minchin’s brilliant song “Storm” into an equally brilliant animated video.

The animated series will be free on YouTube, but they’re supporting it via Patreon. If you pledge to it you can get lots of bonuses, like graphics, wallpapers, mention in the credits, and even signed swag from Chris.

They’re making ten videos, and I am seriously really excited to see them! This is a fantastic team of people, and I know the series will be great.

So throw some filthy lucre their way, and keep your brain ready for this. You’ll be glad you did. In the meantime follow Chris, Evan, Tracy, and DC on Twitter, to keep up with the news on the show.

And because why not, here's "Storm". It's amazing.

Categories: Astronomy Headlines

New Horizons Looks Over Its Shoulder at Pluto

Fri, 07/24/2015 - 12:00

I’ve been expecting—and seeing—amazing images of Pluto from the close approach flyby of the New Horizons probe from mid-July. And even though I knew the images taken once the spacecraft was past Pluto would be lovely, I still wasn’t quite prepared for just how awe-inspiring they would be.


Oh, WOW.

That was taken when New Horizons was about 2 million kilometers (1.2 million miles) past Pluto, when the tiny rock and ice world was very nearly between the spacecraft and the Sun. New Horizons looked over its shoulder, back at Pluto, to capture this breathtaking picture.

The ring of light you are seeing? That’s Pluto’s atmosphere! Light passing through that cold, thin, nitrogen gas gets scattered, bent, and we see it as a halo surrounding the night side of Pluto.

This image is surreal; both familiar and alien. We see a similar sort of photo every time there’s a solar eclipse. But as rare and lovely an event that is, this is no moon … it’s Pluto. Five billion kilometers from Earth, we see the dark side and eerie atmospheric glow of another world.

This image is more than just art. The brightness of the halo tells scientists how thick Pluto’s atmosphere is, how high it reaches. It also reveals the presence of haze, particles of ethylene and acetylene, in the atmosphere that extend up to 150 kilometers above the surface! That’s unexpected; haze was expected lower in the atmosphere, but not so high up. Another mystery for scientists to ponder. Could this be pointing to weather, albeit ethereally thin weather, on Pluto?

Not only that, but another detector on New Horizons showed that the surface pressure on Pluto has decreased hugely over the past two years: The atmosphere has lost about half its mass! Pluto orbits the Sun on an ellipse, and is currently heading away from the Sun, getting colder. Its axis is tipped by 120° to its orbit (compare that to Earth’s 23° tilt), so it has extreme seasons as well. Did a huge amount of Pluto’s atmosphere freeze out over the past two years as parts of Pluto chill? That’s possible, but this is only one data point. We’ll be getting more data from the probe sent back to Earth over the next few months, and hopefully they will reveal what’s going on in Pluto’s air.

Art and science. Hand and hand, as always.

But there’s more.

This image makes me very very happy. It shows the northern part of Sputnik Planum (the upper left part of the heart-shaped feature on the surface), the ice plains we’ve seen in earlier images. I speculated that the area looks very much like there’s been fluid flow, flooding or seepage, where liquid has lapped up and filled in low lying areas near the hills and mountains nearby.

I was very close! Look specifically at the darker gray area where the flat region meets the hilly one. You can see swirls in the pattern, which is exactly what you expect if viscous ice has flowed around obstacles. What you’re seeing there is glacial flow on Pluto! But the ice in this case is not water ice, but nitrogen ice. At Pluto’s temperature, nitrogen ice should flow glacially much as water ice does on Earth.

That’s incredible.

Here’s another image, a mosaic of the Sputnik Planum region, this time to the south:

Again, powerful evidence that there’s bulk motion of fluids on Pluto. The infilled crater in the middle fills me with delight; the depression in the surface has been filled by nitrogen ice flowing into it. The glaciers appear to have flowed around and filled in the lower areas around the Hillary Montes as well.

The thin ice sheet is fascinating too; the polygonal shape to the segments indicates it can’t be too thick, which may be due to the surface cracking and making segmented sheets as the ice below it moves around.

Alan Stern, the New Horizons principal investigator, said that if the ice is thick enough (tens to hundreds of meters) it could liquefy underneath, so the ice is moving on top of liquid nitrogen. This is not at all clear yet though.

All of this may be easier to see if you watch this amazing 3-D flyover animation made using the geometry deducted from these images:

Amazing. Simply amazing.

And as always, let me say that these are still a drop in the bucket of the data we’ve received so far from New Horizons. These are still relatively low-resolution images; the high-resolution data still sit on the probe’s hard drive, slowly being transferred across the vast distance of the solar system back to Earth. It’ll be months before it’s all down, and as it dribbles in we’ll see more and more incredible features on Pluto, and in much more detail than we have now.

This is all still a taste of what’s to come. And even then, this will be the best data we’ll have of Pluto for decades to come. Scientists will be planning their careers over these data.

As well they should. There are lifetimes' worth of science to explore at Pluto. 

Correction, July 24, 2015 at 19:40 UTC: I originally said this was a solar eclipse at Pluto, but in fact the Sun was slightly off to the side in this shot, so Pluto was not physically blocking the Sun in the picture.

Categories: Astronomy Headlines

Full-On Pluto

Fri, 07/24/2015 - 09:47

While I’m waiting for a press conference on Pluto in a couple of hours (18:00 UTC), I thought I’d show you this beautiful image of Pluto’s face released by NASA this morning. It’s a composite of high-resolution data from the black-and-white (well, grayscale) LORRI camera combined with color data from the Ralph camera.

The colors have been enhanced to bring out overall patterns and regional differences. The images were taken on July 14, when New Horizons was 450,000 kilometers from Pluto—not much farther than the Moon is from Earth!

Several things strike me right away. We see lots of craters, many of which look eroded from time. It looks like there are faults or canyons running here and there across the surface. Also, some of the colors appear as “streaks,” making them look wind-blown or the result of some kind of fluid flow.

Having said that, I am totally guessing here. We must have a care not to overinterpret low-res data like this! Also, I’m no expert, but I hope that the experts today will comment on some of these features. No doubt more detailed images will be released soon, so stay tuned!

Categories: Astronomy Headlines

Crash Course Astronomy: Stars

Fri, 07/24/2015 - 04:00
You’re the only star in heaven, You’re the only star that shines, You’re the only star in heaven, Now that only star is mine.             Frankie Goes to  Hollywood, “The Only Star in Heaven”

Stars are the building blocks of the visible Universe. They’re the fundamental unit, like atoms in matter. Stars make up galaxies, and galaxies make up the Universe.

They are also why we’re here, quite literally. Stars make planets, and stars make the elements that make you and me. We owe our existence to stars.

So understanding them is kinda critical to understanding, well, everything. Wanna know more? Then do I have a Crash Course Astronomy episode for you!

Mea culpa: In the “Focus On” segment, I say that the Sun’s spectrum peaks in the green. To be fair, it peaks in the blue-green part, and atmospheric absorption makes the light that hits the ground peak more in the blue. But when you add it all up, the Sun emits more green than blue light, which is what I meant. I should’ve been more clear.

I wrote about why there are no green stars in a post a few years back. Not that there aren’t green objects in space. But those are different. Comets can look green too.

And don’t confuse any of this with Hank Green in space. That’s a completely different topic.

Categories: Astronomy Headlines

Astronomers Find a Near-Earth-Size Planet in the Habitable Zone of a Very Sunlike Star

Thu, 07/23/2015 - 10:13

One of the biggest goals in the search for exoplanets—alien worlds—is finding an Earth-size planet orbiting its star in the “habitable zone,” where liquid water might exist on its surface. In other words, finding another Earth.

So far, a dozen such planets have been found. All of those planets may be very much like Earth (we can’t be sure, as I’ll get to in a sec), but they orbit smaller, cooler stars than our Sun.

On Thursday, astronomers announced they have found another planet in its star's habitable zone: Kepler-452b. But this one is different: It orbits a star much more like the Sun. The star and planet are about 1,400 light-years away.

The planet was discovered using what’s called the transit method; as it orbits its star, we see that orbit edge-on. Once every orbit, the planet passes directly in front of the star and we see a tiny dip in sunlight. The size of that dip tells us the size of the planet, and the time it takes tells us the planet’s orbital period.

Kepler-452b orbits its star at a distance just 5 percent more than Earth orbits the Sun, with a year 385 days long. While the star is similar to the Sun, it’s older, and stars brighten as they age. That means Kepler-452b actually receives more heat from the star than we do from the Sun, so it’s likely warmer than we are.

Note, though, that a couple of billion years ago the star was cooler, pretty much like the Sun is now. That means that a long time ago, 452b was getting the same amount of light and heat we do. Interesting.

This doesn’t mean the planet is Earthlike, though. For one thing, it’s bigger than we are: Its diameter is 1.6 times that of Earth. We don’t know its mass, unfortunately, and without that we can’t know its density. The density is what gives us our first clue about what the planet’s made of; water has a density of 1 gram per cc, but iron is 8. Rock is 2–3.

If the planet has the same stuff in it as Earth does, it’ll be more massive; four times Earth’s mass*. In that case, its surface gravity would be 1.6 times Earth. If you weighed 100 pounds on Earth, you’d weight 160 pounds there. But only if it’s rock and metal like we are. If it’s less dense (more rock) than, the surface gravity will be lower; if it’s denser (more metallic), it’ll be even higher.

It’s not clear what that means for a planet’s atmosphere. All other things being equal, more gravity means it can hold on to more gas, so the air there could be much thicker. If so—and remembering it’s receiving more light and heat from its star than we do—it might be suffering a runaway greenhouse effect. Or, it may not have any air at all. Or or or. Without more information, we can only guess.

This is an exciting discovery, since this is the first exoplanet roughly Earth-size in the habitable zone of a star so much like our own. The last time we found one this good was Kepler-186f, which orbits a red dwarf. That planet is much closer to our size than 452b is, and may be more similar to us. It’s not clear there how orbiting a red dwarf would make it different. Would the atmosphere be different? If life existed there, how might it look?

I’m a little torn about this discovery. For decades we had no idea if other planets even existed around other stars. Now we know of thousands! And we also know of many that are the size of our Earth, meaning they aren’t too hard to make. In fact, we think there are billions of Earth-size planets in our galaxy alone! Most will be too hot or cold for life, or have other issues making them likely to be uninhabitable.

Searching for a planet with conditions as close to ours is a clear goal here. Kepler-452b is a big step in that direction.

But it’s not perfect. It’s bigger, the star is hotter, and so on. I suspect 186f might be more Earthlike, but again we can’t know for sure. So I don’t want to overhype this discovery.

We need bigger telescopes, ones capable of teasing out the planet’s light from the star’s, taking its spectrum, and analyzing that spectrum for tell-take signs of chemistry. From that we can gauge its temperature better, what it’s made of, and even if there are biological markers (like, say the presence of oxygen molecules, which are hard to keep around without biology). Until then, we just don’t know enough about these planets to say much more about them with certainty.

And I think what may be even more important is to see just how diverse Earth-size planets are! Some bigger, some smaller, some hotter, some cooler. The interesting point here is that nature is cooking planets with all sorts of different flavors here, and while looking into the heavens and seeking out one that looks like us is natural, we should also be careful to delight in the varying recipes out there.

The big question we ask is, Are we alone? The answer, I suspect, hangs on what you mean by “alone.” We are in a galaxy brimming with planets, many of which look like us, and many of which don’t. But even the ones that look different at first may be more like us than we know.

* The volume of a sphere increases with the cube of the radius. Since Kepler-452b is 1.6 times the radius of Earth, its volume is 1.6 x 1.6 x 1.6 = 4.1 times Earth's volume.

Categories: Astronomy Headlines

Space Walking at Comic Con with Adam Savage

Thu, 07/23/2015 - 04:00

Every year, I go to San Diego Comic Con, the annual nerd bash where something like a mole of people converge on the town to celebrate pop culture. It’s a lot of fun, and one of the joys for me is to get together with friends I don’t get a chance to see otherwise.

I’m also privileged that all of my friends there are supremely talented, smart, and interesting people. One of them is My Close Personal Friend Adam Savage™; we’ve known each other for many years (so much so that he is starting to look like me).

As you might know, Adam is something of a celebrity, and getting around at the con can be a challenge for him; the huge crowds guarantee he’ll get stopped, and once that happens it’s all over. That’s how he got the idea of “Adam Incognito”, where he wears a full head-to-toe costume that conceals his identity. He then walks the exhibit hall of the con (where tens of thousands of fans visit exhibitors, goods dealers, artists, and more), and anyone who spots him and correctly IDs him wins some sort of prize, usually a VIP pass to one of Adam’s talks at the con.

This year he walked as Judge Dredd. But he threw in a twist: The next day, he decided to do it again, but this time bringing along a very special guest. The whole thing was recorded for Entertainment Weekly and, and it’s pretty fun. Watch!

Commander Chris Hadfield is a Canadian astronaut; he worked three stints on the space station (commanding it the third time), covered David Bowie while up there, and is an all-around nice guy—I highly recommend his book, too.

I’d never met him, so when I got a note from Adam asking if I’d like to sit behind the scenes and watch them prep for the con walk, I said YES. On the Saturday morning of the con I headed over to Adam’s hotel, met Chris, and watched with some amusement as they suited up. I wasn’t able to walk the con with them (Adam eschews anyone going with him, since it might give away the show, though in this instance they happened to run into Andy Weir, author of The Martian (soon to be a major motion picture) and they let him tag along) but I was around when they got back to the hotel room.

The suits were amazing, as you can see in the photos here. I put together an album of pictures on Flickr for your perusal as well. I think my favorite part of all this, besides the coolers Adam built to prevent them from overheating (a lesson he learned last year in his full-blown Alien space suit, complete with face-hugger), was the fact that they made sandwiches for the trip as well. That’s right out of the Moonbus scene from 2001, where Heywood Floyd and the other travelers eat lunch on the way to seeing the Monolith. Adam even made sure the crusts were cut off, an homage to the sandwiches in that scene!

Full disclosure: I ate the last sandwich. It was better than astronaut ice cream. As is everything.

And that wasn’t the end of it: That evening Adam did a one-hour Q&A on stage in the huge Room 6 of the exhibit hall, and asked several friends to come on stage and ask him questions as special guests. I was first, then Andy Weir, then Alton Brown, and finally Chris came on. It was a huge amount of fun, as you can see:

It was an honor to be able to watch this unfold and to be a part of it. Commander Hadfield really is as nice as he seems, a wonderful thing to behold. He is a true gentleman, and someone who honestly and openly wants to share his joy of the world with that world. Adam is the same way; erudite and charming, he just loves what he does, and his enthusiasm is as infectious as his smile and laugh.

Although I wouldn’t say it’s a requirement, it’s a great bonus that my friends inspire me to be a better person, to work harder, to just do more. To all of them, I say: thanks.

And special thanks to Will Smith and Norman Chang of Tested for their patience, and for taking some of the pictures in the album.

Categories: Astronomy Headlines

More Pluto! And Two Weird Moons. Well, It’s All Weird. It’s Pluto.

Wed, 07/22/2015 - 04:00

On Tuesday, the folks at New Horizons released more images, this time of Pluto’s surface and two of its smaller moons, Nix and Hydra.

The Pluto image shows an area to the west of Tombaugh Regio, the heart-shaped pattern. Like the earlier release, this shows mountains surrounded by flat plains of ice. The mountains aren’t as tall as in the other area (1–1.5 kilometers high, as opposed to more than 3 kilometers), but there’s something new in this one: craters.

Unlike the first close-up showing no craters at all, here you can see circular features that look very much like old impacts filled in by ice. This lends credence to the idea that the mountains are old, and the plains younger, possibly due to something that flooded (or seeped) into the lower topography. You can really see where the older, darker material had the younger, brighter stuff fill in the lower areas.

Finding craters is very important, as that helps geologists figure out just how old the surface is; more craters means the surface has been out there for longer, exposed to space.

I can’t wait to see detailed spectra of the surface so that we can know why some places are dark and some bright. Spectra will give more information on the composition of the surface.

I have to note: Some of the craters well inside the dark region have bright floors, as if some of the material got in there as well. That’s a bit harder to explain with just flooding or seepage. I can almost see gullies leading to them … but the resolution is just barely too low to tell.


This next shot shows the moons Nix and Hydra. Displayed roughly to scale, Nix is about 42 x 36 kilometers in size, and Hydra is 55 kilometers long. The best images we saw before were very pixelated, so these are fascinating to see.

Nix is red! Or it has a big red spot. It appears to be whiter near the edges, but I can’t be sure if that’s a real border to the spot or an odd effect caused by the curve of the moon’s horizon (note that the red hue in the photo has been amplified in processing to show it better). Either way, it’s a sure sign that some chemistry has been going on there. How?

Methane is abundant in the outer solar system. On Earth it’s fragile; in the presence of oxygen it’s easily burned (one reason it makes a useful fuel), forming carbon dioxide and water. But in the absence of oxygen, like out Pluto's way, ultraviolet light from the Sun can break down the molecule, and instead of forming water and CO2 it can build up to make more complex molecules. Called tholins, these are reddish in hue, and we see that a lot past Neptune.

The question is, why isn’t everything out there red? Pluto is reddish, but the big moon Charon is not. These are all clues telling us about the history of these objects. Were some objects more abundant in methane than others, or did something happen over millions of years to rob (or overfill) methane (or tholins) from some and not others? I’m totally guessing here. It’ll be interesting to see what the experts can tease out of the data.

The Hydra image, though not in color, is equally interesting. The moon is irregular in shape, looking like it has a huge bump on one end. I wonder though: That dark spot on the upper right might just be a big depression, and the rest of the bump in shadow. Perhaps more images will give us a better idea of the shape.

Two big craters are obvious; the one at the top (with a bright spot, probably a specular reflection—a glint—of sunlight off something shiny like ice) and the dark one at the bottom. I think at the bottom, that part of the moon is flattish and edge-on to the Sun; a possible crater rim can be seen on its left, and that would explain why the floor is in complete darkness. The crater on top is angled more toward us and the Sun, allowing sunlight into it.

Again, just seeing those craters is important. The more bodies we see with them, the better we can do at estimating their ages. How old is old, how young young? A hundred million years, a billion?

As usual, the first images of an unexplored place raise more questions than yield answers. But as we get more photos from New Horizons, we’ll see more of this territory and in higher resolution, too. The fun in the mystery isn’t in knowing the answer, it’s in finding it.

We’re on that journey now.

Categories: Astronomy Headlines

The Half Earth Catalog

Tue, 07/21/2015 - 09:29

Oh, that planet of ours.

On Feb. 11, 2015, a SpaceX Falcon 9 rocket launched with the Deep Space Climate Observatory, or DSCOVR, on board. The sat was slowly eased into an orbit 1.5 million kilometers (just under a million miles) away from Earth and toward the Sun, into a gravitational soft spot called the L1 point. There, the gravity of the Earth and Sun balance (if you account for the Earth’s centrifugal force as it moves around the Sun too).

Safely ensconced at this height, DSCOVR looks earthward, taking images of our planet using 10 different color channels, allowing scientists to monitor climate change among other important gauges of Earth. From that distance, very nearly 50 percent of the planet can be seen, and the camera was built to fit all that magnificence into one straight shot. As the Earth rotates, over the course of a day or so the entire surface will be seen and photographed. Starting in September, the images will be available to the public in just a day or so after they’re acquired.

Given that the camera has a 4 megapixel detector, they should be routinely gorgeous … as the image above testifies. That is a red-green-blue picture, showing pretty much what our eyes see. Centered on Central America, you can see the continents, cloud patterns, and the aqua waters around the Caribbean. The milkiness around the edge is probably due to atmospheric effects—haze and other stuff in the air mucking up the view. When you look toward the Earth’s limb this way you’re looking through more air, so the effect is more pronounced.

I’ll be very interested in seeing the infrared images, too, which will show how well the Earth reflects incoming sunlight. While DSCOVR has many mission goals, one is to monitor indicators of global warming, and looking in the IR is a good way to keep track. That is, after all, the root of the problem: Sunlight warms the Earth, and the Earth radiates away that heat as infrared light. Carbon dioxide in the air absorbs a small fraction of that heat, so the Earth doesn’t dump it as efficiently, and the planet warms up.

The satellite will also monitor solar weather—subatomic particles streaming from the Sun. But of all the things it does, I suspect its constant streaming of pictures of our planet to the public may wind up being its long-remembered legacy. There is something transformative about seeing Earth from space, something that touches a part of us deep in our brains.

That’s home. And, for now, it’s the only one we have. Keeping a close eye on it is a smart thing to do.

Categories: Astronomy Headlines

SpaceX Falcon 9 Rocket Lost Due to Internal Strut Failure

Tue, 07/21/2015 - 04:00

On June 28, 2015, disaster hit an uncrewed SpaceX Falcon 9 rocket 2 minutes 20 seconds after launch. Video made it clear something went wrong in the second stage, and at a press conference on Monday, CEO Elon Musk announced the most probable cause: a strut failure that led to the loss of the vehicle.

As fuel is used up during launch, high-pressure helium is fed into the liquid oxygen tank to maintain the pressure in that tank. The helium is kept at 5,500 PSI inside a bottle.

During launch, a strut holding the helium bottle down snapped. Counterintuitively, during the high acceleration of launch the helium tank feels a large force upward, because the helium in the tank is highly buoyant. The larger the acceleration is, the larger the buoyant force gets, and the more force the helium tank feels upwards.

The strut that snapped was designed to hold the bottle down against this force. When it snapped, the helium tank shot upward, slamming into and rupturing the liquid oxygen tank. The super-cold oxygen then boiled, expanded rapidly, and breached the second stage walls.

In the video, you can see that what happened was not technically an explosion; there’s no fireball, but you can see the expanding vapor from the oxygen tank flying away.

These struts are certified before launch, but Musk has promised that they will do a second test individually on each strut from here on out; this will mean a slightly higher cost for each launch but not a significant one.

This strut failure is hard to test for on the ground. As Musk pointed out, boosters are tested strapped down on the ground, so they only ever feel 1 g of acceleration (due to gravity). This failure happened when the rocket was undergoing 3.2 g, which cannot be realistically tested except in launch. This is a “really odd failure mode” and “quite a puzzle,” Musk said. The root cause of the failure still isn’t known; the strut failed at well under the rated stress level (it’s rated for 10,000 pounds of force, and failed at 2,000).

They are continuing to look into the telemetry; this series of events is the preliminary conclusion of the failure, not the definitive one.

Musk also said this will delay the next uncrewed flight (probably until September), and the loss of revenue to SpaceX will likely go into the hundreds of millions of dollars. Still, this probably won’t delay crewed flight, since that pace is being set by developing the next generation Dragon V2, which will likely take longer than fixing the strut issue.

Speaking of which, the Dragon capsule (filled with supplies for the space station) on the Falcon 9 survived the initial event, and in fact they were getting telemetry from it until it dropped below the horizon, but it was certainly lost when it impacted the ocean at high speed. Every indication was that, had the software triggered the parachute deployment, Dragon would have survived its fall into the ocean. However, that software has not been used on this Dragon version; it is supposed to be first implemented on the Dragon V2. Given that the capsule could have been saved, the new software will now be used on the current generation of Dragon capsules.

Incidentally, the next generation Falcon Heavy rocket demo flight has been delayed as SpaceX concentrates on the Falcon 9 issue. The Heavy demo will now probably occur in spring 2016.

Happily, no other problems have been seen in the telemetry. They’ve had 20 successful launches in a row, which is excellent, but as Musk notes, “a passing grade for rocket launches is 100 percent ... this is an important lesson and something we will take with us in the future”.

This is a huge setback for SpaceX, but Musk asserts that the company is on it and working to fix it for future launches. I certainly hope so.

Categories: Astronomy Headlines

Reboot the Suit!

Mon, 07/20/2015 - 08:28

Every now and again I get involved in a project I’m truly, deeply excited about, and honored to be a part of. This is one of those times.

The Smithsonian’s National Air and Space Museum needs your help for a fantastic project. They need to conserve and preserve one of the greatest icons in American History:

Neil Armstrong’s Apollo spacesuit.

This is the spacesuit he wore when he made that one small step, forever dividing history into two eras: One where humans had not yet set foot on another world, and one where we forevermore became a spacefaring species.

Today — on the 46th anniversary of that first Moon landing — Smithsonian has announced a project to help raise the funds needed to preserve the suit, and they asked me to be a part of it. We made a video introduction to the project:

You can read more about all this at the Air and Space Museum's blog

The Kickstarter page has details on the different avenues that will be taken to conserve the suit, and also has the long list of rewards you’ll receive at various pledge levels… including access to files that will allow you to make a 3D printout of the suit after it’s been digitized in high resolution!

The scale of this kind of project means it doesn’t come cheap. It’ll take $500,000 to fund it. But an artifact this important, this iconic, needs to be taken care of, and if this gets funded the experts at the Air and Space Museum will do so with professionalism, care, and love.

We are just passing through history. This:

This is history.

I was overwhelmed to be invited into the back corridors of the Udvar-Hazy Center in Chantilly, Virginia to see the spacesuit for myself (I have bigger versions of the pictures you see here, plus a few more, in an album on Flickr). I walked past workbenches and open areas with priceless treasures — the wheels from the Spirit of St. Louis, a snuffbox given to passengers who flew on the Montgolfier brothers’ hot air balloons, and the original Enterprise model from Star Trek (!!!) — and was able to stand next to and peer into Commander Armstrong’s suit.

It was, quite simply, one of the high points in my life. To be able to see it up close, to talk to its caretakers, see how they work with it and other priceless historical items… it was profoundly moving.

This suit, with its human inside it, walked on the Moon. For 2.5 hours, the suit traversed the lunar surface, allowing Armstrong to breathe and survive in one of the harshest possible environments. Along with Buzz Aldrin he set up scientific instruments, took pictures, and collected precious samples of the regolith and rocks around the landing site.

I’ve met some of the Apollo astronauts, and looked at other Apollo suits in museums. But this one? It was the first. The very first.

As Americans, as human beings of Planet Earth, it is more than our responsibility to maintain that spacesuit. It’s our duty. That’s why I jumped at the chance to participate in this project, and why I’m asking for your help.

If you have ever watched the footage of Armstrong stepping on the Moon, if you ever thought in awe of the grand adventure of traveling the 400,000 km gulf separating it from our planet, if you ever gazed up at the Moon in the sky and wondered what it would be like to go there, and when we’ll be heading back again, then please, throw a little bit of money at this project.

My own dream is that, in a generation or two, a little boy or girl will be taking their first trip to the Air and Space Museum, and they will see that suit. It will make them wonder about their own history, and where their future will take them. And when they go back home, back to the colony in Mare Tranquillitatis, they’ll look back toward Earth, and past it to Mars, to the asteroids, and to the stars.

But it starts here. Please help us Reboot the Suit.

I don’t ask this for much, but I will now: Please share this post and the Kickstarter link on any and all social media, and when you do use the hashtag #RebootThe Suit. Smithsonian’s Air and Space Museum has a broad presence in social media as well.

Thank you.

Categories: Astronomy Headlines

Venus, Jupiter, the Moon, and the Heart of the Lion

Mon, 07/20/2015 - 04:00

I was perusing Twitter on Saturday and someone mentioned that Venus and the Moon would be close together in the sky that night. I checked my Sky Safari software, and sure enough they’d be about 1° apart at sunset for me. Given that the Moon’s width on the sky is about 0.5°, that’s a nice, tight pairing.

I also knew that Jupiter was still nearby, slowly separating from Venus after their very close encounter a couple of weeks ago (which I only caught glimpses of through thick clouds here after sunset EVERY SINGLE DAY in Colorado, grrrr). Once the Sun set I was outside snapping away. I took about 150 photos, and one really stuck out for me:

That turned out well! The Moon is obvious, with Venus nearby. Jupiter is off to the right, and the bright star Regulus (the “Heart of the Lion”, the star marking the chest of Leo the Lion) above. It’s nice that sometimes the Rocky Mountain foothills provide a dramatic silhouetted backdrop, too.

I have a pretty basic DSLR camera and lens (Canon T4i and a 135 mm telephoto) so my shot is OK, but not fantastic. But when you have great equipment and real talent, you get something like this:

That breathtaking shot is from César Cantú, an astrophotographer in Mexico. He used a star filter to produce the spikes, and was able to get a bit more of the Earthshine on the Moon than I could. He seems to be unhappy with the clouds where he was, but I think they add a lot of beauty to the picture. I like it when there are terrestrial reminders in wide-sky astrophotos. It gives them more of a sense of presence.

The best terrestrial reminder of all is the Earth itself, especially if the shot is taken from space:

Space Station Commander Scott Kelly took that one and posted it on Twitter. So yeah, location, location, location.

A lot of folks tweeted lovely photos they took to me after the event, too. Searching Twitter can be a pain, but if you look through my mentions around that date you’ll see the photos. Thanks to everyone who took the time to share!

An added bonus to this whole thing is that Venus and the Moon were showing similar phases, too. I had a few people asking why Venus has phases, too, and the good news is this guy explains it pretty well:

It’s funny to me that I might’ve missed this event (or more likely seen it late and then having to scramble to get shots) had I not seen it on Twitter; I’m usually more on top of sky shows. I’m glad I saw it early in the morning too: Venus is bright enough to be seen during broad daylight, but it’s tough. With the Moon nearby, they’re easier to spot. Given they were more than 30° from the Sun, I knew I could look for them without blinding myself. The irony is I found Venus easily in binoculars, but high cirrus blocked the Moon. It would’ve been nice to see them together, but there’s always a thrill seeing Venus in the middle of the day.

Venus is getting lower every day; it’s getting closer to the Sun in our sky, and will be gone by sunset in just a couple of weeks. To make up for it, Mercury is getting higher at sunset, and on August 6 will pass about a half a degree from Jupiter! That’ll be very pretty, so keep your eyes open for it. The pair will only be a few degrees above the horizon at sunset, so it’ll be a tough observation (especially if you have mountains to the west like I do!). I’ll be out with binoculars hoping to see that.

Remember, there’s a lot going on over your head all the time. Try not to miss it.

Categories: Astronomy Headlines

The Two Tails of Comet Pan-STARRS

Sun, 07/19/2015 - 04:30

I somehow didn’t hear anything about the comet C/2014 Q1 (Pan-STARRS), which isn’t to surprising: It never got bright to northern hemisphere observers. The comet’s orbit kept it mostly in the southern hemisphere’s skies, and it only recently got brighter once it swept past the Sun in its orbit.

But if you do live south of the Equator, it’s putting on a decent show. It’s still naked eye visible, and is close enough to the Moon in the sky to make for a pretty airing… as astrophotographer Yuri Beletsky proves with this astonishingly lovely shot:

He took this photo from a valley in northern Chile on July 17, 2015. He told me he had to climb a hill to get the shot he wanted, since the area is surrounded by mountains. I think he found an ideal spot.

The picture is HDR, or High Dynamic Range: It’s a composite of different exposure times, to compensate for twilight, the bright crescent Moon, its much dimmer dark part lit by reflected Earthlight, and of course the comet itself.

The comet is sporting two very different tails! Pointing straight up is the ion tail, made of gas that sublimated away from ice in the comet and which was subsequently ionized by the Sun’s ultraviolet light. Ionized gas is missing one or more electrons, giving the atoms or molecules a positive charge. The Sun’s solar wind blowing past the comet carries its own magnetic field, which sweeps up the ions and carries them away. The solar wind is typically blowing at several hundred kilometers per second, far faster than the comet, so the ion tail points directly away from the Sun.

In the meantime, as the ice holding the comet together turns to gas, it also loosens dust in the comet. This leaves the solid nucleus, and gets hit by sunlight. This gives the dust particles a little bit of energy, changing their orbits much more gently than the ions. The dust tail curves away from the comet, leaving in in very nearly but not quite the same orbit.

In general ion tails are green or blue (the glow of carbon or carbon monoxide molecules dominate there), while dust tails are orangey or yellow (reflecting and scattering sunlight). The ion tail of Pan-STARRS appears to have a lot of structure in it as well.

If you live Down Under and want to see this for yourself, Universe Today has a good article with maps. If you’re north of the equator, you’re out of luck. By the time it’s in our skies again it’ll have faded to invisibility.

Oh, and the comet’s unusual name? The designation has to do with when it was discovered and what kind of comet it is, and Pan-STARRS is the name of the observatory where it was discovered: the Panoramic Survey Telescope and Rapid Response System. This observatory surveys the sky looking for moving objects, and has found quite a few comets. Get used to hearing its name; it’ll be finding many such dirty snowballs for many years to come.

If you want to learn more about comets, then do I have a video for you: My Crash Course Astronomy episode all about them.

Finally, you should also check out Beletsky's astrophotos on 500px and follow him on Facebook. His stuff is really, really good.

Categories: Astronomy Headlines