Saturn’s Psychedelic Jet Stream
Saturn is a gas giant planet, nine times wider than Earth, and mostly atmosphere. We don’t see its surface as such, but the top of its clouds. That means we peer down on a wildly dynamic environment, in some ways like Earth and in others, well, alien.
And sometimes both. Sitting over the planet’s north pole is a vast circulation pattern of gas called the north polar vortex: 20,000 kilometers (12,000 miles) across, it forms a surprisingly regular hexagon, with winds and storms churning around inside it.
A new animated image above of the six-sided system was just released by astronomers, and is the first to show the motion of the vortex in color, and is the highest-resolution full view of it so far. We’ve seen spectacular shots of it before, but never the whole thing like this:
[Photo by NASA/JPL-Caltech/SSI/Hampton]
The images were taken by the Cassini spacecraft, which has been orbiting the ringed planet since 2004. In it you can see difference between the inside and outside of the hexagon; scientists can use these images to understand better what’s going on in Saturn’s complex atmosphere, including what material is in it, the sizes of the particles, and the temperatures of the gaseous constituents as well.
Incidentally, see that big whitish circle near the bottom of the vortex? That's a storm roughly 2000 km (1200 miles) across: comfortably larger than Texas. The huge hurricane in the very middle of the hexagon has also been seen in staggering detail before as well.
The hexagon looks freaky, but it’s actually not that surprising; we see similar things on Earth in our own jet stream (called Rossby waves). What I find most interesting is not that it exists at all but that it’s so symmetric and well-defined; on Earth it’s sloppier. Saturn spins far faster than Earth does (its day is about 10.5 hours long), so, coupled with its larger size, the Coriolis force is far larger there, helping define the vortex’s shape.
Images and animations like this help us understand what’s going on in that vast laboratory over a billion kilometers away. I am all for that; knowledge for its own sake is a wonderful thing. But we’re also trying better to understand our own planet, and it helps considerably to have something with which to compare and contrast it, even something seemingly so different. Inevitably with space science, looking out is very much the same as looking in. We try to understand the Universe so we can better understand our own environment.
A Volcanic Twofer... FROM SPACE
Regular readers know I love me a volcano picture from space, and today I have two.
The first is from one of my favorite volcanic hunting grounds, the Kamchatka Peninsula in eastern Russia. This forbidding region has several active volcanoes, and when they are covered in snow, they make for an extremely photogenic — if slightly terrifying — setting.
Klyuchevskaya (also spelled Kliuchevskoi) is one of a cluster of volcanoes on Kamchatka, and is pretty active. It’s a big one, reaching 4750 meters (15,500 feet) high, and has been continuously active for centuries. On Nov. 16, 2013, the International Space Station was 1500 km (900 miles) to the southwest of the stratovolcano when an astronaut snapped this highly oblique shot of it:
Ooooh, aaaaaah. The plume of ash and steam appears to be blown east by winds immediately after leaving the vent, and by the shadows I’m thinking it was early in the morning. I’ve written about Klyuchevskaya many times (like here and here and here), and every time it’s because of some amazing image of it taken from space. It’s truly lovely, if tremendously forbidding.
Note that essentially every large peak you see in that photo is a volcano. Yikes.
Let me now take you from the frozen north to the tropical southeast: Vanuatu, an archipelago of volcanoes east of Australia. Astronaut Mike Hopkins was flying over it in the ISS recently, and tweeted this spectacular photo of one of the islands in the chain:
He doesn’t say which one it is, but it didn’t take me long to figure out that it’s Ambrym, a shield volcano with a caldera about 12 km (8 miles) across — you can see the rim of it circling around to the left in the photo. It was created in a huge explosion around 50 A.D., one of the largest in recorded history. It’s still a very active volcano, with two cones in the caldera: Marum (the oval one on the left) and Benbow (right; in the picture north is roughly down). The picture is a little overexposed (you can see it in the plume) but it shows the vegetation and the lack thereof perfectly.
The island is lightly populated, but there have been several deaths due to eruptions in the past; people were killed by lava bombs and overtaken by flowing lava. Still, the location looks lovely, and one day I’d love to visit it. I need someone with more money than sense to fund me for a year to travel the world and visit amazing places; if I ever got to Vanuatu I’d very much like to see Ambrym, as well as Gaua.
What a planet we live on! There are so many places to see, and so many things to learn about them.
A lot of tech is so ubiquitous you don’t even notice it anymore; it would be like a fish noticing the water in which it swims.
Google certainly fits that category; it’s not very often a company name becomes a verb. It’s second nature now to fire up a browser and type in a few words when I need some help pinning down a word or phrase, or to just get more info on a topic.
A while back, Google introduced autocomplete; if you start typing words into the search engine text field, it’ll make suggestions for words even before you’re done typing. I don’t find this feature particularly useful since I generally have a pretty good idea what I’m looking for when I’m searching. But I can certainly see its utility.
The suggestions are based on previous searches by users as well as page content, so the most common things people type in (weighted with with highly-ranked sites) are what Google offers up as helpful phrases. That makes sense; using the most common searches is statistically likely to match what you might need.
It’s not hard to imagine a downside to this, though. It can focus searching to a few popular sites, and can reinforce false information, since those pages may not be vetted for accuracy.
I was alerted to this when Lindacska126 on Twitter sent me the following tweet:
@BadAstronomer Have you seen what happens when you Google "Scientists are"? pic.twitter.com/xWf7hoKd4W
The link goes to a screengrab showing Google’s suggestions to her. I typed “Scientists are” into Google and got essentially the same results:
Ouch. That doesn’t seem to fare well for what people think of scientists.
I’ll admit, most scientists are liberal, or perhaps better described as progressive. In general that’s to be expected of someone who has an open mind, is ready for open inquiry, and willing to change their views based on evidence. But only in general; I know many conservative scientists who are quite brilliant. I’ve been labeled as liberal myself many times, which makes me chuckle; my views on most topics are a bit more subtle than can be assumed from such a blanket label.
But the “scientists are stupid” and “scientists are liars” suggestions are troubling. Can it be that most people really think this?
I decided to follow through, and see what pages are actually recommended by Google if you use these suggestions. What I found is that yes, many of the pages linked do make these accusations — and they come from the usual suspects, such as fundamentalist religion sites, or climate change deniers. No surprise there. And some are satirical pages, clearly meant as parody. But it’s not hard to find page after page, site after site, sincerely making these claims about scientists.
What do we make of this? Is all hope lost?
This is troubling, to be sure, but I don’t know just how bad it is. After all, we don’t know why people are using these terms. I search for things I know are wrong all the time, for instance, so I type weird things into Google every day. Of course, I tend to be looking for people making claims that are, um, not as reality-based as they could be, so maybe I’m not the best example.
I can think of a few other ways this may not be so bad, but I keep coming back to the fact that in the United States, roughly 45% of people outright deny evolution. Climate change denial is on the wane, but still, something like a third of people in the US deny that humans have played a role in it. And it’s not hard at all to find media pundits who froth and rail against science, as long as it doesn’t have the ideological stance they cleave unto.
Scientists need a better rep. Science is everywhere, all around you, all the time. You’re soaking in it. I can make all manners of arguments of why it’s important philosophically — and I have — but it’s also absolutely critical economically; our way of life in the United States, and the world, depends absolutely on scientific achievements. From better agriculture to medicine to communication to mitigating global disasters, science plays a fundamental role in each.
So what to do? In my opinion, there are two things that will help. One is to not let broad and ridiculous accusations about science and scientists go unchecked. I do that here quite often, of course.
The other, though, is if you love science, tell people. Write about it, talk about it, sing about it if you can (and Gawker? You're not helping; we should be encouraging people to look up the definition of "science", not making fun of them).
And if I may, let me suggest simply being a better person. I get this idea from my friend George Hrab, who has a segment on his podcast where he answers questions from listeners. Many times, he is asked by someone who is nonreligious how their reputation can be improved. George tells them to lead by example: be friendly, help out, do charity work. Then, later, if someone finds out you’re not a believer, it won’t color their opinion as much. In fact, it may change their mind about an entire group of people they otherwise would have written off.
I suspect the same can be done for science. If so many people truly think scientists are liars, scientists are stupid, then we need to show them otherwise. Don’t lecture; teach (or better yet, converse). Don’t insult or belittle; enlighten. Admit your mistakes, show where you learn from them. Talk about the joy and wonder and awe of truly understanding the Universe as it actually is!
Isn’t that why we love science in the first place?
My hope is that we can change Google’s algorithm, so that one day it will produce this:
Tip o' the beaker to Zach Kopplin for the Gawker link.
Time-Lapse: The Earth from Orbit
Stop whatever you’re doing (unless you’re performing brain surgery) and watch this astonishing and enthralling time-lapse video, showing the Earth from space using photographs taken by astronauts aboard the International Space Station:
You know the drill: Make it hi-res and full-screen, and thank me later.
The video was created by David Peterson, who also made a similar video called “All Alone at Night”. Some of the clips I’ve seen before, but many are new to me.
At the 29 second mark, I was thrilled to see a glory, a complicated optical phenomenon where light is reflected back from water droplets in the air, creating a circular rainbow beneath the observer. You can see it tracking along with the station as it orbits above the clouds.
At 1:00 in, you see the Sun dip between the station’s solar panels; I believe this sequence was shot in 2012 at the summer solstice. At that time, the Sun never sets for the ISS; it just dips down near the limb of the Earth and rises back up, much as it does at the Earth’s north pole.
At about 1:30, you can see two docked Russian spacecraft (a Soyuz in the foreground and a Progress in the back) with the Earth behind them. To my surprise, you can see the Progress firing its rockets twice, once on each side! The Progress rockets are sometimes used to maintain the ISS attitude (orientation to the Earth) and I had never seen video of them firing before.
At 2:00, Peterson put in a remarkable series of shots showing C/2011 W3 (Lovejoy), a spectacular Sun-grazing comet that sported an extremely long tail. Discovered in 2011, it was very photogenic, and astronauts on the ISS took many photos of it.
He ends the video with a series of moonrise shots, which I never tire of. You can also see astronaut Don Petit working in the cupola; he was a pioneer of taking beautiful photographs from the station, and is a fitting way to end the video.
Tip o' the spacesuit visor to astronaut Ron Garan on Twitter.
Three New Baby Planet Pictures
Very cool news: Three new planets orbiting other stars — exoplanets — have had their picture directly taken!
Seeing planets around other stars is hard. Planets are faint, and stars bright: From a distance, for example, the Sun is a billion times brighter than Jupiter. Most times, when we look at other stars, the planets are totally lost on the glare.
Sometimes, though, we can make things easier. Planets are warm, so looking in the infrared helps. Looking at younger planets helps, too, since they still glow with the leftover heat of their formation. Cooler, redder stars are dimmer, making planets around them easier to see as well. Finally, checking out nearby stars is a big plus, since that means we can more easily separate out the planet and its star (like looking at a distant car blurs the headlights into one glow, but when it’s closer you can separate them).
After all these years, only about a dozen planets have been directly photographed, and even then some are controversial; their ages aren’t well known, and that affects their measured mass. Some might be brown dwarfs, objects intermediate in mass between planets and stars.
But now we have three more exoplanets baby pictures! Here’s what we know about them.
FW Tau b
FW Tau is perhaps the most interesting of the three systems. The star is actually a binary, two stars orbiting each other. Both stars are cool red dwarfs, about a quarter of the mass of the Sun each, orbiting about 1.6 billion kilometers (one billion miles) apart, roughly the distance of Saturn to the Sun. The stars are a bit less than two million years old, and are 470 light years from Earth.
The planet was first noticed in 2001, but was not confirmed as a planet until recently. This was determined by what’s called proper motion: The stars’ physical motion through the galaxy can be seen over time, and the planet is clearly moving with them.
The planet, FW Tau b, orbits both stars at a staggering distance of 50 billion kilometers, over 300 times farther away from its stars than Earth is from the Sun. For comparison, Neptune is only 30 times Earth’s distance from the Sun, so this new system is ten times wider than our own. From that distance, the two stars combined would only be about as bright as the full Moon as seen from Earth.
The planet has a mass ten times that of Jupiter, and is still hot due to its age, probably around 1700° C (3000° F), so it’s not habitable by any means. But it exists, and we have the picture to prove it.
ROXs 42B b
ROXs 42B is also a binary star, with both stars smaller and cooler than the Sun. They’re a bit under seven million years old, and 390 light years from Earth. The planet is also about 11 times the mass of Jupiter, but is closer in to its stars, about 22 billion kilometers (14 billion miles) away from them. That’s still many times farther out than Neptune is from the Sun.
Like FW Tau b, it’s moving through space bound to those two stars, and its that motion which gave it away as a planet orbiting them. It’s also quite hot, about 1900°C (3400° F).
The mass is somewhat hard to determine for this object, and may be anywhere from 6 – 15 times the mass of Jupiter. At the lower end it’s definitely a planet, but at the higher end it’s more like a brown dwarf. Some of this depends on the distance of the star from Earth; if it’s farther away, the planet must be more massive to be as bright as it is. The authors of another study of ROXs 42B b (published just two weeks before the other one, thouhg made public in October) are a bit conservative in the planet mass, but it seems to me that it’s likely to be part of a known and nearby cluster of young stars, meaning the planet is on the lower end of the mass scale.
ROXs 12 b
ROXs 12 is also a cool red dwarf, and also about the same distance as ROXs 42B is from Earth, 390 light years. The planet is bigger, about 16 ± 4 times the mass of Jupiter. As it happens, anything bigger than about 13 times the mass of Jupiter is more in the brown dwarf category; with the uncertainty in the mass of this object it’s not completely clear if it’s a planet or not. But it’s close, and for now (until better measurements are made) I’ll grant it, given the caveat. Either way, it orbits the star at a distance of about 31 billion kilometers (20 billion miles).
Interestingly, both FW Tau b and ROXs 12 b may have a disk of material around them, meaning they are still actively in the process of forming. The observations show they both glow in the light of warm hydrogen — with very young planets, that’s generally indicative of a disk. If so, we’ve caught them in the act of gathering material, building themselves up even more. That’s pretty cool (even if it means ROXs 12 b may be pushed out of the planet category as it gains mass).
I’m fascinated by these direct images of planets. For now, given our technology, the ones we see this way are young, hot, and massive. But we’re getting better at this. As we make bigger telescopes equipped with better detectors, and use more sophisticated techniques in our observations, more planets will be found. I have no doubt that we’re getting closer to being able to physically see a planet like the Earth, orbiting some nearby star. It may yet be several years away, but that time is coming.
I wonder how it will be, to gaze upon the light of a planet like that? To know that from there, our own planet would look much the same?
China (Again) Shoots for the Moon. We Should Join Them.
Over the weekend, the Chinese government did something that has not been attempted in nearly 40 years: Launch a spacecraft for a soft landing to the Moon.
On Dec. 1, 2013, the Chang’e 3 lander and rover launched successfully from the Xichang Satellite Launch Center in Sichuan, China. It’s on a direct orbital insertion path, meaning it heads straight from Earth to the Moon (sometimes, long, looping paths are taken to utilize Earth’s gravity for maneuvers to save fuel). It should enter lunar orbit on Dec. 6, orbit for a week, then land in an area called Sinus Iridum (“Bay of Rainbows”) on Dec. 14.
I have some thoughts on this, but first, there’s a launch video that — as is usually the case with launch videos — is very, very cool.
Launch occurs one minute into the video (although I have to say, a few seconds earlier when they cut to the shot of the bottom of the rocket, with the small fins and engines bells sticking out, I had a momentary flashback to watching Gerry Anderson supermarionation TV shows as a kid). Other key moments are at 1:29, when they cut to the external rocketcam, 3:19 when the external boosters cut out and fall away, 3:33 when the second stage ignites after the first falls away, and 6:38 when the third stage booster ignites and the second stage falls away.
The rocket used was the biggest and heaviest of China’s Long March boosters, powerful enough to fling the 1200 kilogram (2600 pound) rover and lander to the Moon. Once they land, the rover will deploy and wander the surface to make scientific measurements. The instruments include the usual sorts of things for a rover: cameras, surface probes, mineralogical testing devices, and a far-ultraviolet telescope; UV light is absorbed by Earth’s atmosphere, so the airless Moon is a good platform for such an astronomical device.
The mission has a three month nominal lifespan, and is a testbed for future and more ambitious rovers. You can read more about all this at Emily Lakdawalla’s blog at The Planetary Society.
So what do we make of this?
First, China has been launching rockets since 1970, and has done quite a bit of space exploration. It seems like a straightforward enough assumption that they will continue to aim for the Moon — they’ve launched two orbiters, Chang’e 1 and 2, already — with an eye toward eventual crewed mission. They’ve already been building space stations in low Earth orbit (the Tiangong space station in the movie “Gravity”? Yeah that’s real), and have invested a lot of cash into space; they have four main launch sites and are clearly serious about this next step in human exploration.
I’ve written my thoughts about this a few times in the past, usually when China makes progress, or when NASA’s future is threatened yet again by Congress, the White House, or its own Administration. The bottom line is this: I want humans to live in and explore space. If those humans are Chinese, or Russians, or what-have-you, then I’m glad, because it significantly improves the long-term survival chances of our species.
But I’m an American, and there’s some amount of pride in me. This country has always been a leader in pushing back the boundaries of space, and inspiration is no small part of that. I want to see my own nation continuing that pioneering spirit, but instead I see it all-too-commonly mired in bureaucracy and politics, and stunted by a lack of vision.
I am not interested in another space race. This needs to be articulated clearly: Such things tend to be all flash and no substance. In the 1960s it led to many Soviet and American disasters, and to a too-well-defined and specific goal: Landing humans on the Moon. Once those footprints were there, we turned on backs on the Universe, or at least the human exploration of it. A race has a finish line, and once you cross that line, you’re done.
That is precisely the opposite philosophy we should have right now. Exploring space is a long-term goal, one with many paths, many achievements along the way, and not one shining endpoint where, once we get there, we can rest.
What I hope to see from this latest Chinese effort is a rekindled sense of desire in America, a strong sense that once again we should be leaders in this grandest of all adventures. We need to achieve a balance between good-natured national competition and cooperation, so that all humans can benefit as we reach for the sky. And the benefits are many.
My congratulations to the people of China as they strive for the Moon. I hope that in a few years, there will be many others of us joining them.
Monoceros is a constellation of faint stars not far from Orion and Sirius, visible in the winter sky. I’d expect it to have a better rep than it does, given the Internet’s obsession with what it represents: a unicorn.
Still and all, there’s another reason you should know about it. Lurking in its borders is an astronomical mystery, an object of incredible beauty, terrifying power, and bizarre origin. Best of all, it’s a puzzle, since we don’t really understand what it is or what it’s doing.
It goes by the cryptic name V838 Monocerotis (which sounds like a horrible disease). It’s been observed by Hubble many times, and those data are available to the public. Telecommunication engineer Roberto Colombari took his hand to those observations, and created the best image of V8238 Mon I’ve ever seen:
Yegads! How weird, and wonderful.
This is combination of observations taken at three colors, approximately blue, green, and red. Colombari had to do some serious fiddling to get this final image; the camera itself has a gap between the detectors which leaves black lines across the images (you can see it in the inset raw image below). He combined several images in each color, including some rotated by 45° to fill in the gap. In the end, he was able to make a smoother image with a darker background than I have seen of V838, which adds substantially to the beauty.
But what the heck are we seeing?
There are a few things we know for sure. In 2002, the star underwent a truly epic eruption, brightening from obscurity to nearly naked-eye visibility, despite its soul-crushing distance of 20 quadrillion kilometers away. It blasted out radiation at level a million times that of our Sun, and was briefly one of the most luminous stars in our galaxy. The material around it is mostly dust; this stuff heavily reddens light passing through it, and in fact the Hubble images using the blue filter don’t even show a hint of the cloud. Not only that, but images taken in the years since the star’s outburst show the dust changing considerably.
It turns out though, that the dust cloud isn’t physically changing! It’s normally dark, and the blast of light from the star is lighting it up. Since light travels at a finite speed, we see some parts of the material being lit before others; this is called a “light echo”. So it only looks like the cloud is growing; in reality it’s hardly moving at all.
Studies indicate that the dust existed before the eruption, part of a huge star-forming cloud, and is probably only about 3 – 10 million years old; a blink of the cosmic eye. Still, if the star is extremely massive, that’s enough time for it to start dying.
That was my first thought when I initially saw this object. Stars live their lives in a delicate balance; heat generated in their cores due to nuclear fusion tries to expand them like hot air balloons, but their immense gravity tries to squeeze their octillions of tons gas into the core. If something happens to that balance, the star can react poorly. For example, it can undergo epic paroxysms, blasting out vast clouds of gas and dust.
But it turns out that’s probably not what’s going on here. That would explain the star getting bright, but we don’t see the sort of expanding shells of material associated with such an outburst.
A leading idea — and get this — is that the central star is the result of two big stars colliding and merging! That’s an extremely rare event, but it would explain a lot of what we see. It would cause a huge blast of energy, for one. It would also produce X-rays, which were seen in other observations. The star would expand a lot, causing it to become very red, which is the obvious color in the Hubble pictures.
That’s pretty weird, but we don’t see too many stars like V838 Mon, so a rare event may be called for. They may have been two stars in orbit around each other, perhaps on a very long elliptical path, and over time finally merged. It’s just good we happened to be looking so we could see the 2002 flare up. Astronomers are still watching the star; if it has another such outburst then we may need to find another explanation; a collision is a singular event and we wouldn’t expect a repeat. But nothing on that scale has happened to the star in the past decade.
Before this, I never would have guessed something like this could happen; star collisions really are extraordinarily rare. But the Universe is vast, and time is deep. If you look long enough, you’re bound to see exceptional events. And when they are this stunningly beautiful, why, it makes the search that much easier to do.
Comet ISON Post Mortem
Or… “That time I was right, then wrong, then probably right again like I was in the first place, more or less.”
The other day I wrote up a synopsis of the life and possible death of comet C/2012 S1 (ISON). Karl Battams, who runs the SungrazerComets Twitter feed and the Comet ISON Observing Campaign page, has an excellent summary of what we know so far (with a couple of very cool animations, too). The bottom line is that it’s been one surprise after another, with it getting bright, then dim, then bright again, then dim.
But, as we get more images of the comet as it heads away from the Sun, its ultimate fate is perhaps a little easier to see. The NASA / ESA spacecraft SOHO has been observing the comet since it entered its field of view on Nov. 28, and has told an interesting if somewhat head-scratchy tale. The solid nucleus of the comet started out about two kilometers wide, and got very bright. It faded rapidly as it approached the Sun, pretty much the opposite of what you might expect. But then it got bright again after it rounded the Sun, though not nearly as bright as before. And now it appears to be fading without stop.
Here’s a video I put together showing the comet starting on Nov. 28 at 07:00 UTC (02:00 EST), and ending 44 hours later on Nov. 30 at 04:00 (Nov. 29 at 11:00 p.m. EST):
You can see the comet head was so bright at the beginning it was saturating the SOHO detector, but then faded fast (I wrote a brief explanation of what you see in SOHO images in an earlier post). The other thing to note is that now, days later, the comet has faded substantially; there is no nucleus to be seen, and we can even see stars right through the comet (the image at the top of this post was taken on Nov. 30 at 20:42 UTC, and makes that clear; ISON is on the upper right and is now pretty well dispersed).
So what happened? A video from a different viewpoint may help. The STEREO spacecraft are twin probes moving around the Sun in opposite directions. They are on the other side of the Sun from Earth, so they have a very different perspective on what happened. Here is a (low-res) video from STEREO A showing the same events:
At about 10-11 seconds in, as ISON is about to swing around, you can see it starts to emit a thin puff of something (it looks like a flash, a sudden thing, but I suspect that might be an illusion due to the comet happening to cross a bright region in the solar atmosphere, making the comet look brighter). This may possibly have been a disruptive event, breaking apart the nucleus. That would explain why it faded. Heating and expansion of the material would cause it to glow briefly, which would be why the comet brightened after perihelion, and then as it dispersed it would thin, so overall the comet would fade.
Mind you, the SDO and PROBA2 spacecraft did not see the comet; if a lot of ice were blown out they should have seen it. Also, at the end of the videos you see a cloud of material blow out and sweep around the comet; that is likely fine dust blown out by the solar wind. So it may be that the disruption event shook out a lot of dust, and what we’re seeing now is a big cloud of debris moving away. Maybe we’ll know better when Hubble can take a look, but that won’t be for a few weeks (Hubble cannot look near the Sun, so we have to wait for orbital mechanics to bring the comet farther out). It may be there are still some decent sized chunks, and these could still brighten. I wouldn’t get my hopes up though.
As I’ve said many times, though, there's a lot of stuff going on here, and it’s not at all clear what happened. I’m guessing based on what I’ve seen, experts I’ve talked to, and my own experience observing comets.
And while I won’t make any firm predictions, because that path leads to ruin (or at least frustration), it does seem like this is the comet’s last gasp. The ethereal nature of the material in the SOHO images from Saturday makes it look like it won’t recover from this latest waning.
But who knows? When the comet started fading before perihelion I thought it might be dying, and I was more sure when it really smeared out. Then it came back, and we thought it survived, but now it’s looking more like that was a last gasp. This comet (and our estimation of what it’s doing) changes its story on an hourly basis, it seems.
So assume none of this is written in stone (or ice). We will certainly learn more as scientists analyze the data returned, and we get even more observations in the coming months.
Playing the Cosmic Odds
There is something to be said for perseverance, for persisting until the last moment you can. You can make a lot of moral and emotional arguments for it, of course, but there’s also a mathematical one: If you stick around long enough, sometimes the odds, stacked against you as they may be, will break your way.
Scott Rinckenberger is a photographer from Seattle. He was in Joshua Tree National Park, finishing up a five-week trip shooting scenes in the American west. I don’t want to spoil the whole story — he tells it well on his own website — but on the last day of the trip he threw the dice one last time… and they rolled his way:
This phenomenal shot shows the campsite where he and his friend were staying. It’s a lovely foreground, and the sky itself lent a fine photogenic backdrop. But as luck would have it, a meteor shot across the field of view during the short 30-second exposure.
That’s actually a fairly common occurrence; shooting stars happen several times an hour, especially if you’re in a dark site and can see the fainter ones. But this one was hardly faint! As you can see, it streaked in from the upper left, and shortly before burning out it flared brightly several times.
What we call meteors are actually tiny bits of rock (or sometimes metal) that blaze as they ram through our atmosphere. When you compress a gas it heats up, and when an object moving dozens of times faster than a rifle bullet plows through the air, it violently compresses the gas ahead of it. The air heats up so much it glows. At the same time, the meteoroid — the solid bit of material — itself is undergoing extraordinary pressure. The rock can flatten, pancaking, and crumble under the strain. When it breaks apart there are suddenly several rocks compressing the air ahead of them, which means more surface area to heat up, and more light is generated. Those rocks can also break up, until they are so small they either decelerate and no longer glow, or burn up entirely.
This all happens in a fraction of second at these speeds, and the velocity is so high the energies can be quite large. I expect the rock that Rinckenberger caught with his camera was perhaps no bigger than a grapefruit, but at 30 or more kilometers per second, that’s all it takes to make a very bright flash in the sky. He caught the whole thing, including the breakup, just barely fitting into the frame.
And not only that, it provides some balance to the picture, offsetting the big rock in the foreground and the airplane seen on the right in the sky.
I’d say he was lucky, but in this case, luck = (low chance of event) x (plenty of time spent looking). Sometimes luck breaks your way, but if you’re ready for it, and keep plugging away, then you can make the big score.
There is something to be said for perseverance.
ISON After Perihelion: The Undead Maybe Somewhat Ex-Comet
Yesterday, comet C/2012 S1 (ISON) zoomed over the surface of the Sun, barreling through the star’s intolerable heat and light. We all waited on the edge of our seats to see what would happen, and amazingly, a few hours later, something came out the other side.
But what, exactly? We’re still not sure. But here’s my guess, based on what I’ve seen and heard.
Let me give you a quick overview first. The comet itself was a chunk of rock, gravel, and dust held together by ice, smushed into an object perhaps two kilometers (a bit over a mile across). It came from the Oort cloud, a vast repository of such icy chunks well outside the orbit of Neptune. The orbit of ISON is extremely close to an escape trajectory for the solar system, meaning this is likely its first and only dip into the neighborhood; it may not ever return, and instead be ejected into interstellar space (or at least not be back for many, many, millennia).
As it approached the Sun on Nov. 28, it suddenly got very bright, which could have been from an outburst (perhaps due to solar heat seeping under the surface, reaching a pocket of ice, changing it directly from a solid to a gas, and triggering a sudden expulsion of that gas as it expanded), or even a disruption event. Since the ice holds the comet together, losing that ice means losing the infrastructure of the comet itself. It can break apart into smaller chunks, like other comets have in the past.
Still, it looked solid enough as it kept heading for the Sun… for a while. But a few hours later (but still before closest approach) it had faded considerably, and images from the NASA/ESA spacecraft SOHO showed it looking more smeared out. The trail of stuff narrowed toward the tip, but we didn’t see a single, bright spot there, which is what we expected for an intact comet. Those of us who were punditing at the time were, understandably, becoming convinced ISON was breaking up.
Pining for the Fjords
Then it got too close to the Sun for SOHO to see it (SOHO uses an occulting mask, a disk of metal, to block the fierce light of the Sun and allow it to see the fainter environment around our star; that’s why you see a black spot in the images, and the long bar to the upper right which holds the disk in place). We waited.
At some point after perihelion I made a decision. I drew a line in the sand, saying I thought this was an ex-comet. But then, not long after, like Lazarus or a zombie, ISON came back from the dead.
But Wait! What Light Through Yonder SOHO Breaks?
By 19:48 UTC, a little tadpole was visible in the inner SOHO images. Within a few hours it was clear something had made it around the Sun. But was it an intact comet, or just a dust cloud of debris ripped apart by the terrible forces it experienced?
That brings us to now. What of the comet? Well…we’re not really sure. The latest pictures do show a condensed blob of something, and it doesn’t look quite as much like a debris cloud as it did.
Best guess: As it rounded the Sun the solid nucleus fell apart. It may have released a lot of junk — dust, gas, whatever — but a sizeable chunk remained. That itself is still being heated by the Sun, and so is surrounded by a fuzzy coma of material. We can clearly see a tail of dust following behind it in the same orbit, and another tail of fine dust getting blown out by the solar wind (multiple tails of different compositions are common in comets).
So I wouldn’t say the comet survived, so much as some of it wasn’t destroyed. A subtle difference, perhaps, but clearly something is still there.
Interestingly, both the Solar Dynamics Observatory and the European PROBA2 spacecraft did not see any hint of ISON as it passed the Sun. That’s extremely puzzling; PROBA2 has a very sensitive camera. Both are easily able to detect oxygen atoms released by the comet, which should glow in ultraviolet light (and the oxygen would come from water, an abundant substance in the comet). It’s not clear at all why the comet was invisible; it may be more evidence it did mostly break up. But again, we’re still seeing a tail (which means it’s blowing out material), so the only thing we can be sure of is that there’s more to this story than we’ve figured out in this short time.
I’ll note the trajectory of the comet hasn’t changed. Gravity is far and away the dominant force steering the comet, and it’s still on its way out. It’s still bright, though not nearly as bright as it was. And it’s still very close to the Sun, just a few degrees away, so it won’t be visible just yet.
However, after a few days, if it stays bright, it may be visible in the pre-dawn sky. I wouldn’t bet on it, but geez, I wouldn’t bet against it either with this comet. Look low to the eastern horizon while the sky is still dark; you may need binoculars. As far as I can tell, the tail (if any) will stick more or less straight up away from the horizon (depending on your latitude). It may be visible after sunset in the west-northwest as well, but the angle of the tail won’t be as good.
I do NOT suggest trying to see it while it’s still near the Sun; it’s too faint and the chance of eye damage (if you use optical aids like binoculars or a telescope) is too high to risk it.
My advice is to wait a few days to see if it’s visible to the eye before dawn, and in the meantime delight and be puzzled by the fantastic images we’re getting from space.
The comet, or what’s left of it, will make its closest approach to Earth at the end of December, when it will be 60 million kilometers away. A few weeks later, it’s possible that we’ll pass through the debris trail from ISON, and see some meteors from it. At this point, given the capricious nature of the comet, I’d score this one as a firm maybe. We’ll know more in the coming weeks. I don’t think there’s any real danger from big pieces, since the comet itself will be millions of kilometers away at the time, so don’t fret. We should be safe from needing Bruce Willis’s help here.
This comet has been a weirdo since Day 1, and continues to surprise and fascinate astronomers. And normal people, too. I was overwhelmed with the response I got yesterday both during and after the NASA video Hangout, as well as on Twitter, where I was trying to keep up with this iceball as it performed its merry pranks for the planet to see. My tweets got hundreds of replies, in many different languages, showing how this event touched people all over our own small world.
I’ve said it before, and I’ll say it again: Comets and cats are equally predictable. It’s a losing game to be firm with them; your best move is to watch, wait, and enjoy the show while it happens. That’s my plan, for sure.
Tip o' the Whipple Shield to my pal Craig DeForest for the PROBA2 news.