Phobos’ Googly-Eyed Transit
Phobos is weird for more reasons, too. It orbits the planet very low, only 6,000 km or so above the surface of Mars. It moves so quickly around the planet that it actually goes around faster than Mars rotates, so it rises in the west and sets in the east—twice each Martian day.
It just so happens that the rover Curiosity is in a location on Mars where things line up just right such that every so often Phobos passes directly in front of the Sun. I’ve written about these transits before, but I somehow missed this one from Aug. 20, 2013. Happily, Robert Krulwich on his NPR blog wrote about it, to my delight.*
The photo above shows two images of the transit, which I couldn’t resist because it looks a bit googly-eyed. Someone tell Anne Wheaton and Bonnie Burton!
But those are just two images; Curiosity took quite a few … and the folks at NASA’s JPL put them together into this amazing video showing the moon moving right across the face of the Sun:
I love this video because it shows the whole transit, because the transit isn’t partial (with the moon cutting a shallow chord across the Sun, say), and because it’s in real time! The frame rate was set so that what you see here is pretty much what Curiosity saw: a 37-second long event.
On Earth, the Moon and Sun are about the same apparent size in the sky, because in a cosmic coincidence the Sun is 400 times bigger than the Moon but also 400 times farther away. Phobos is smaller than the Moon, but much closer to Mars, so it appears about half the size of our Moon. But Mars is also farther from the Sun, so the Sun looks smaller there too, and Phobos does a decent job covering it up.
It’s really odd to see something like this, knowing that what you’re seeing isn’t an airplane or a cloud, but an actual rocky moon orbiting far overhead.
… and of course, that’s nothing compared with knowing that this sequence was taken by a machine sitting on the surface of another world.
*Correction, July 28, 2014: This post originally misspelled the name of NPR.
Let me tell you about a catastrophe. I don't use that word lightly: This event was monumental, an apocalypse that was literally global in scale, and one of the most deadly disasters in Earth's history.
It began about 2.5 billion years ago (though opinions vary). The Earth was very different then. There were no leafy plants, no animals, no insects. Although there may have been some bacterial life on land, it was the oceans that teemed with it, and even there life was far simpler than it is today. Most of the bacteria thriving on Earth were anaerobic, literally metabolizing their food without oxygen.
But then an upstart appeared, and things changed. This new life came in the form of cyanobacteria, sometimes called blue-green algae.
Cyanobacteria are photosynthetic. They convert sunlight into energy and produce oxygen as a waste product. Back then, the Earth’s atmosphere didn’t have free oxygen in it as it does today. It was locked up in water molecules, or bonded to iron in minerals.
The cyanobacteria changed that. But not at first: For a while, as they produced free oxygen as their waste, iron would bond with it and the environment could keep up with the production.
At some point, though, as cyanobacteria flourished, the minerals and other sinks became saturated. They could no longer absorb the oxygen being produced. It built up in the water, in the air. To the other bacteria living in the ocean—anaerobic bacteria, remember—oxygen was toxic. The cyanobacteria were literally respiring poison.
A die-off began, a mass extinction killing countless species of bacteria. It was the Great Oxygenation Event. But there was worse to come.
Up until this time, the atmosphere was devoid of the reactive molecule. But as oxygen abundances increased, some of it combined with methane to create carbon dioxide. Methane is a far more efficient greenhouse gas than CO2, and this methane was keeping the planet warm. As levels dropped, the Earth cooled. This triggered a massive glaciation event, a global ice age that locked the planet in its grip.
Things got so bad the cyanobacteria themselves were threatened. Their own numbers dropped, along with nearly all other life on Earth. The mass extinction that followed was vast.
But there was an exception: Some organisms could use that oxygen in their own metabolic processes. Combining oxygen with other molecules can release energy, a lot of it, and that energy is useful. It allowed these microscopic plants to grow faster, breed faster, live faster.
The anaerobic species died off, falling to the oxygen-burning plants, which prospered in this new environment. Certainly, anaerobes didn't vanish from the Earth, but they were vanquished to low-oxygen environments such as the bottom of the ocean. They were no longer the dominant form of life on Earth.
It was perhaps the first of the mass extinctions life would face on our planet, and its impact resonates through the eons (and of course there is quite a lot of detail to this story). To this day, our atmosphere is rich in oxygen, with most multicellular life on Earth descended from the upstart oxygen breathers, and not the anaerobes.
It's an interesting tale, don't you think? The dominant form of life on Earth, spread to the far reaches of the globe, blissfully and blithely pumping out vast amounts of pollution, changing the environment on a planetary scale, sealing their fate. They wouldn't have been able to stop even if they knew what they were doing, even if they had been warned far, far in advance of the effects they were creating.
If this is a cautionary tale, if there is some moral you can take away from this, you are free to extract it for yourself. If you do, perhaps you can act on it. One can hope that in this climate, change is always possible.
The Glory of Guadalupe
You just never know what you’ll see when you take a picture of the Earth from space. German astronaut Alex Gerst must’ve been pretty surprised when he looked out the space station window and saw a 35-kilometer-long seahorse blowing a rainbow bubble!
That image was taken on June 21, 2014, and—not to burst your bubble—actually shows the island of Guadalupe, located about 240 kilometers off the coast of Baja California. It’s essentially two volcanoes that overlap in the north/south direction, and has ridges running along it that reach a maximum height of about 1,300 meters (0.8 miles).
In the photo (which is part of a series Gerst took), north is toward the upper right. The winds tend to blow from the west (upper left), and you can see the webbed pattern of (what I think are) stratocumulus undulatus clouds around the island. Guadalupe’s elevation splits the wind, which flows around the island, disrupting the stratus formation near it. That’s why there’s a clear spot around the island.
I suspect the clouds to the east (lower right) are flowing back toward the island due to eddies in the winds as they move around the island. You can also see a small vortex a little farther to the east, which can sometimes form in such situations. Sometimes long streamers of vortices appear downwind from such islands; these are called von Kármán vortices, and I’ve written about them many, many, many times. They’re extremely cool.
But what about that rainbow effect? What’s that?
That’s what’s called a glory. It’s an optical effect where light from the Sun gets refracted (bent) back toward the observer. To see one, you need to have the Sun directly behind you (so in a sense you’re looking down into your own shadow), and there has to be water droplets suspended in the air to bend the sunlight. As far as I can find, the exact physics going on is not terribly well understood (as opposed to what happens in actual rainbows, which is quite well known).
I see them every now and again when I fly in airplanes; I got video of one on a recent trip home from Texas:
The engine noise was loud, so I posted a transcript.
Since there’s a glory in the picture of Guadalupe Island taken by Gerst, we know the Sun must have been directly behind him as he looked down at the island. Another picture he took within minutes of the other shows the glory in a different spot. If you connect the two points, they go right over the north part of the island (the “seahorse head”). Anyone standing there and looking up would’ve been able to see the space station pass directly in front of the Sun! That would’ve made for a pretty dramatic picture itself. And what would that have looked like? Why, this:
That was taken by Thierry Legault in 2010, and shows the ISS in transit across the Sun.
I would love to see a pair of photos like these taken at the same time: A glory shining around some spot on the Earth, and at its center a photographer looking up to capture the station in front of the Sun. Of course, the presence of a glory means the sky would be cloudy for the photographer, but if the clouds were thin stratus, you’d see the Sun right through them. It’s possible.
Someone get on that, OK?
How the Universe Works: Season 3
I'm very pleased to let you know that the Science Channel astronomy documentary series How the Universe Works is back on the air. The third season began a couple of weeks ago with the episode "The Sun," which focuses on the journey of a photon, a packet of light, as it makes its way out from the core through the 700,000 kilometer deep abyss of our nearest star. The second episode is "The End of the Universe," a topic near and dear to me.
Before I go on, I have to admit to being a wee bit biased about this show: I'm on it. They interview quite a few scientists in each episode, and they've been kind enough to include me now in every season of the show. I have to admit it's a lot of fun to spend a day getting barraged by questions from the producer, answering them in my own style. The overall narrative of the show is already outlined before the interviews, but we get to answer the questions the way we want. Our answers are then woven into the storyline.
I think it's a pretty good show, which is why I've agreed to come back again on it. It doesn’t overreach, sticking with a few simple themes and explaining them. The narrative storyline is fun, and the basic concepts are gone over well enough that anyone with an interest in science and a little bit of knowledge shouldn't have too much trouble understanding the show. The graphics are stunning, and whenever I watch an episode I'm amazed at what's possible to show viewers.
It's also a kick to see old friends interviewed as well. Alex Filippenko, Hakeem Oluseyi, Michelle Thaller, Sean Carroll ... these are good people I've known a long time, and I'm really happy they still get on the air. Their joy and sense of wonder shines through, and I think that's a crucial factor that makes a TV show successful. We talk about this stuff because we study this stuff, and we study this stuff because we love this stuff.
I think you will too. How the Universe Works airs weekly on the Science Channel, Wednesdays at 9 p.m. Eastern time. Check your local listings, of course. It gets repeated fairly often, so you shouldn't have any trouble catching it.
And before you ask: When you see the segments I'm in, yes, that is my telescope in the background (a Celestron C8-SGT XLT), the same one I use to capture images of the Moon, Mars, and more. If you like the show, remember: The Universe is out there, and you can observe it too. Once you're done watching TV, step outside and look up. All those things we talk about are up there.
That's one of the many, many reasons I do, in fact, love this stuff.
Space Rocks for Two Science Promoters
I am very pleased to say that two of my friends have been honored with asteroids named after them! To give a hint on who they are, the asteroids are (274860) Emilylakdawalla and (249530) Eugeniescott.
Regular readers know both of these people. Emily is a science communicator, blogging for the Planetary Society—in fact, I’ll just redirect you to her thorough and typically excellent post on her asteroid.
Genie is more than a friend of mine: She’s one of my heroes. I don’t use that term lightly. She unflinchingly defends science against those who would try to tear it down, and she did so for many years as the executive director of the National Center for Science Education. She has done battle with young-Earth creationists and climate change deniers, and was one of the people who won the day in the Dover evolution trial. And while doing all this, she has been calm, genial (perhaps her name is apopros), and even downright friendly.
But don’t mistake that for weakness. She’s tough and has weathered withering attacks from promulgators of anti-science. Her asteroid orbits the Sun out past Mars, and has withstood a billion years of solar wind and impacts from other asteroids.
It seems fitting, doesn’t it?
The idea to name an asteroid after Genie came from Bob Blaskiewicz, a skeptic and, like me, an admirer of Genie. He approached me a while ago asking if it were possible to name a space rock after her. Having friends in high places, I then called Amy Mainzer, principal investigator of NEOWISE, a space telescope that scans the skies looking for asteroids. Amy got right on it, and amazingly it only took a couple of months for the paperwork to go through. Amy’s the best.
So now Emily and Genie join the group of science advocates with asteroids named after them. I’m still tickled to be in that group myself and hope someday to observe my namesake through my own telescope.
It’s a peculiar and wonderful thing to know that hundreds of millions of kilometers away, cold and silent, a rock a kilometer across (in my case, or a few kilometers in the cases of Emilylakdawalla and Eugeniescott) glides through space. Will humans ever venture there some day, centuries hence? Will they wonder why the asteroid they’re visiting has the name it has?
It’s a nice thought. And with Emily and Genie, it’s a wonderful tribute to two people who try—and succeed—to make science available to everyone.
Congrats to them both.
WANT Part XX: Hubble Lego Edition
I have a soft spot in my heart for the Hubble Space Telescope. I got my Ph.D. using observations from the venerable observatory (literally signing on to the project two weeks before the ‘scope launched into space), then got a job helping build, calibrate, and use a camera called STIS that was installed onboard Hubble in 1997.
So when I got a tweet from Gabriel Russo about getting a Lego model of Hubble officially approved, my reaction was immediate.
If you can’t figure out what it was, then reread the title of this post.
Russo’s model is amazing, and extremely cool. However, it’s not a real thing just yet. He’s submitted it to Lego’s Ideas site, which is where people can turn their ideas into real Lego kits.
Russo has done the first step, but the next step is to get 10,000 supporters to get his model reviewed by the powers that be at Lego (he doesn’t need money, just votes). He’s about halfway there, and I know there are 5,000 people reading this blog who can take a minute to register with Lego (it’s free) and give him an upvote. I did.
If it gets approved, he might be able to get it made by 2015, the 25th anniversary of Hubble’s launch. I think this model would be great for kids, adults, classrooms, space enthusiasts, and pretty much everyone. And yes, I’m doing this for selfish reasons, too.
I really want one.
Related Posts — All my WANTS
WANT Part XIX: Mercury Globe Edition
WANT Part XVIII: The Stars Underfoot Edition
WANT Part XVII: Galaxy Rug Edition
WANT Part XVI: The DANGER WILL ROBINSON Edition
WANT Part XV: Moon Credenza Edition
WANT Part XIV: Citric Acid for Blood
WANT Part XIII: Moon Throw
WANT Part XII: Earth Globe Fire Pit
WANT Part XI: To Boldly Slice
WANT Part X: The TARDIS. A REAL TARDIS!
WANT Part IX: Levitating TARDIS Edition
WANT Part VIII: Zen and the Art of Apollo Maintenance
Want: Part 6
Want: Part V, Lunar Furniture Edition
Want: Part IV
Want: Part III
Want: Part II
What Is This Mystery Object in an Astronaut’s Photo?
And sometimes we get a mystery. I have one of those for you today.
This started when I got an email from Nahum Mendez Chazarra, who had been going through pictures taken by astronauts from the ISS. In a batch taken on July 15, 2014, at about 11:57 UTC, he found three in a row that showed a curious thing. Here’s one of them:
Spectacular! The ISS was south of Australia at the time, so the green glow is the aurora australis, the southern lights. The ISS solar panels stick into the shot from the upper right (seen nearly edge on), and the Earth dominates below.
But look to the Earth’s limb, just below and to the right of the brightest part of the aurora, and just above the solar panel. See that streak? It’s clearly some sort of moving object.
It’s in the two pictures taken just before this one as well. I added them together and zoomed in on the object so you can see it better:
Some things to note: The first picture had an exposure time of 0.2 seconds, the second one was 0.4 seconds, and the third 0.8. Measuring the length of the streak, it looks like the object is moving at a constant apparent velocity (the last streak is four times longer than the first, and twice as long as the second, as you’d expect from the exposure times).
Here's an animation I made to show the motion more obviously:
Chazarra suspected it was a meteor, burning up in the atmosphere below the ISS. At first I disagreed, thinking it might be a satellite. But then I wondered … so I sent a note to my friend Jonathan McDowell, who is an expert on things in orbit. He noted it was consistent with a satellite or a meteor, and added it could also be a small bit of debris much closer to the station; for example, a piece of ice just a few dozen meters away.
Arg! How to distinguish between these?
Well, one way would be to look at pictures taken just before and just after this set. So I did, and found that the object is not in pictures taken just three seconds earlier, nor is it in the next set taken three seconds later!
If it were a satellite or a piece of debris moving at a constant speed, then I’d expect it to be in at least the first picture taken after this set of three, down in the lower right. I looked carefully; it’s not there. That makes a satellite or piece of debris less likely (though still more likely than some alternatives). Also, note how in the picture above it crosses over the face of the Earth; that means it must be in a lower orbit than ISS. If it were up higher then it could never be seen against the Earth like that. The ISS is at a height of about 415 kilometers (260 miles), which is pretty low. There aren’t many satellites orbiting appreciably lower than that height. This doesn’t preclude it being a satellite, but a priori it makes it less likely.
That leaves meteor. That does fit most of what we see; it appears suddenly, disappears just as suddenly, and moves at a relatively constant rate. If it were small bit of rock it wouldn’t necessarily flare up and get hugely brighter, which has been seen before when a Perseid meteor burned up as seen from ISS:
The object does seem to be brighter in the longer exposure, which is interesting. Since it’s moving, each pixel should be about a constant brightness; a longer exposure just means the streak is longer, not brighter. If it’s actually brighter per pixel, that means the object itself was getting brighter, as a meteor would. However, a longer exposure also means the Earth and other stationary background objects get brighter, and their light would add digitally to the object’s, making it look brighter even if it isn’t.
In the end, I’m leaning toward this being a meteor, but I cannot be positive. It’s still something of a mystery, as promised.
So, BABloggees: What do you think? What did I miss? Is there more (or less) here than meets the eye? I think that throwing this out to the Hive Mind might bring some insight to the puzzle.
What is this thing?
Rocketcam Video of the SpaceX Falcon Booster Splashing Down in the Atlantic
The private company SpaceX has been making amazing strides in making it easier and cheaper to access space. Besides three missions to resupply the space station under its belt, it’s also looking for ways to reuse the first stage booster of the Falcon 9 rocket.
Engineers there have been testing hardware and software to do a soft vertical landing of the booster after it’s used to loft a payload into orbit. Their last vertical take off and landing test earlier this year was a success, reaching a height of a kilometer before safely touching back down.
They did a flight test of this in April, but the video was unfortunately corrupted. But a second attempt, during a launch on July 14, 2014, went better. The mission was to put a collection of global communication satellites in orbit, but there was also a test of the soft landing system as well. The test went pretty much according to plan, although the impact of the booster into the ocean damaged the hull. They’ve released a pretty cool video of the test:
The re-entry engine burn, landing burn, landing leg deployment, and soft landing went well, and the booster even tipped over into its “water saving state” correctly. Even if the hull ruptured, they are saying they got enough information to move forward on this technology to make it work.
Another such test will happen in a launch planned for September (flight 13 for the F9), but it’s expected to have “a low probability of success” since they’re still working on the tech. However, the next two flights after that will be attempts to land the booster on land. If that works, it’ll be nothing short of spectacular, and the video will be very, very cool. Stay Tuned.
Tip o’ the nose cone to my pal Alan Boyle.
My 2014 Comic-Con Schedule
Starting tomorrow is the madhouse that is San Diego Comic-Con, and I’ll be there. I’m moderating two panels and participating in a third, and it’s always way more fun than I remember it being (and I remember it being a lot of fun). Just in case any BABloggees are going, here’s my schedule for your edification:
Thursday, July 24 at 12:45 p.m.: Behind the Scenes of Sci Fi in Movies and on TV (Room 6DE)
I’m moderating this panel of four incredible people: Nicky Perlman (co-writer of Guardians of the Galaxy), Amy Berg (Caper), Jane Espenson (80 bazillion things like Firefly, Once Upon a Time, and Husbands), and Gale Anne Hurd (producer of things like, oh, say, Terminator, T2, Alien, Aliens, and Walking Dead). We’ll be talking about new ways we consume media, and what it’ll mean for the people who create it.
Friday, July 25 at 6 p.m: The Science of Science Fiction (Room 7AB)
This is always a great panel, featuring people who write and consult on TV and movies, where we discuss how science is treated (or mistreated) in sci fi. Trust me, if you’re at SDCC you want to attend.
Saturday, July 26 at 1:30 p.m.: Marvel's Avengers S.T.A.T.I.O.N. Superhero Science Analysis (Room 5AB)
I’m really excited about this one: I’m moderating a panel of several of the science advisers for the Marvel superhero movies, and we’ll be discussing the science behind the Avengers. We’re going to be running it in a very fun way, but before his death ex-Director Fury has made it very clear to me I’m not at liberty to disclose how … but if you read the description you’ll get a hint. Still, in general I’m not inclined to argue with Fury. Even posthumously.
As for the con itself, I’ll be running around meeting up with friends, attending posh parties, hobnobing with celebrities, y’know, the usual. I’ll be at w00tstock for sure (not onstage, but watching) and I hope to make it to the Geek and Sundry lounge, as well as Nerd HQ.
And, of course, wandering the exhibit hall buying stuff I don’t need but desperately want. If you see me, come say hi!
The Longest Year
I don’t usually write about newly discovered record-breaking objects found by astronomers, because in general it’s not long before that record falls. But in this case, I’ll make an exception for Kepler-421b. It has the longest year—that is, it has the longest orbital period around its star—for any exoplanet yet seen crossing in front of its star.*
That by itself is enough to make this an interesting object, but even cooler (literally) is where that puts this planet: Far enough from its star that it may have formed in a different way from the other planets we’ve detected around other stars. It may very well be an ice giant, like Uranus or Neptune, and not a gas giant or rocky planet.
First, let’s go through the basics: The host star is Kepler-421, a star much like the Sun but a bit smaller and cooler. It’s located about 1,000 light years away, which is a fair ways (the Milky Way galaxy is 100,000 light years across). From Earth, that makes the star pretty faint.
The planet, Kepler-421b, was discovered by the Kepler observatory, a space-based telescope that has found so many of the recently-discovered exoplanets. It uses the transit method to find planets; if we see the planet’s orbit around its star edge-on then every time the planet passes between us and the star it blocks a bit of the star’s light. It’s tricky; for example Kepler-421b only blocks about 0.3 percent of the star’s light. But with modern detectors, that sort of dip in light is detectable.
Generally speaking, you need three transits to be sure you’ve got something. If you see just one it could be a starspot, or some other nonplanetary object interfering with your observations. A second transit tells you the orbital period (the year) of the planet, but it could still be a coincidental starspot. If you get a third transit at the right time interval after the second, then you can be more confident.
For Kepler-421b, the astronomers only saw two transits, which made me suspicious, but after reading their paper I’m more inclined to think they got it. The shape of the “light curve” and the incredible match between the two transits make it very likely they did find a planet. For the rest of this article I’ll just assume it exists, but remember that it has yet to be confirmed independently.
Kepler-421b is about four times the diameter of Earth (judging from how much of the starlight it blocked), and has a year that’s 704 Earth days long. That’s amazing; most exoplanets found have much shorter periods, like days or weeks. That orbit puts it about 180 million kilometers (110 million miles) out from the star. Since the star is cooler than the Sun, the planet actually receives about one-fourth the light from its star as Earth does from the Sun. That’s even less than Mars gets, so the planet is pretty chilly.
And that brings us to the second cool thing about this planet. Planets form from broad disks of material orbiting the star when it’s young. Close in it's hot (duh) so you don’t get much gas or ice. The material in the disk is mostly metal and rock. Farther out there’s still metal and rock, but water is in the form of ice (this distance is called the “snow line,” a term I like), and there’s lots of it. Giant planets that form at least that far out have a lot more ice than ones farther in, and we call them ice giants. To be clear, these aren’t giant ice balls; they look a lot like gas giants but have more ice in them as opposed to rock and denser stuff.
In our solar system, Uranus and Neptune are ice giants. Given Kepler-421b’s location, it should be one as well. If we assume it’s about as dense as Uranus, it has 16 times the mass of the Earth. That will likely give it a thick atmosphere (and it’s very cold, remember) so it’s not Earth-like at all.
But it’s the first ice giant seen orbiting another star. We’ve seen other planets with similar masses and sizes, but they orbit closer in, and are likely gas giants. Ice giants may very well be pretty common among exoplanets, but they’re pretty hard to detect. For one, the long period means you have to wait a long time to confirm them. Also, the bigger the orbit is, the less likely it is we’ll get a transit — a planet close in to its star can be seen to transit from a wide range of viewing angles, but a more distant planet needs a more tightly constrained viewing geometry (the orbit has to be more precisely edge-on) for us to spot it.
Finding Kepler-421b means that astronomers may be able to start finding more. Seeing one planet might be an anomaly, but if you find 20 more like it you can start categorizing them. This means they can use physics and models to understand better how planets form, especially that far from their parent star. We’re still figuring that out for our own solar system, so having other examples with which to compare and contrast is very helpful.
And so that’s why I’m willing to write about a record-breaker, even if that record is soon broken. As usual in astronomy, I hope it is! That turns this planet from a weirdo into the first member of its class, and that means we get to learn stuff. And astronomers love learning stuff.
*Correction, July 23, 2014: This article originally stated that Kepler-421b has the longest year of any known exoplanet. It has the longest year of any exoplanet found by the transit method.