The entire universe in blog form

Nov. 17 2014 7:30 AM

Philae Spotted Hopping Away in Photo of Comet

A few days ago, the world watched and cheered as the tiny spaceship Philae landed on the surface of a comet. However, it was quickly determined that the anchoring harpoons didn’t fire, and the lander bounced off the comet. It soared a kilometer high before falling agonizingly slowly back down nearly two hours later, only to take a second, shorter hop, ending up in comet incognita.

It took a little while, but images taken by the orbiting Rosetta spacecraft mothership (and assembled into a short video) were released by the European Space Agency showing where Philae impacted the first time. The video shows before-and-after images of where Philae smacked down. At the time, my friend/planetary geologist/Planetary Society blogger Emily Lakdawalla speculated that you could actually see Philae and its shadow in the “after” image, but the data were so noisy I was pretty skeptical.

Turns out, she was right.*

Here is a lovely animated gif showing the two images, with the impact site marked in the first image, and the lander (with shadow) in the second.

Photo by ESA/Rosetta/NAVCAM; pre-processed by Mikel Canania

Amazing! Astrophysicist Eamonn Kerins did this even better: He made a “difference image,” subtracting one from the other to show what’s changed between the two. It really brings out Philae and its shadow:


Photo by ESA/Rosetta/NAVCAM/Eamonn Kerins

You can see lots of bright pixels—most likely “hot pixels," overactive spots on the camera detector—with dark ones next to them, a product of how the images were processed. Note how the spot labeled as Philae is blurrier, and the shadow is several pixels below it. That’s pretty convincing to me.

I was initially skeptical because the “plume” stretching below and to the right of the impact site looked the same in both images, and was also mimicked by a similar feature to the upper right; both look like ridge shadows.

In the difference image those go away, so most likely they really are shadows, the lower one coincidentally right on top of where the lander bounced. That’s unfortunate, since it steered me away from what was really happening.

Before and after, in more detail.


Update, Nov. 17, 2014 at 15:30 UTC: Not long after I posted this, the ESA released a mosaic showing Philae before and after impact, seen moving across the face of the comet by the high-def OSIRIS camera on Rosetta! You can see Philae come in from the lower left, then move off to the right after it bounced. Amazing. 

And as a reminder of what you’re seeing: That’s an action shot of a 100 kilogram machine the size of a lounge chair that weighs less than an ounce in the local gravity hitting the surface of a four kilometer-wide dirty snowball almost precisely on target as seen by another spaceship that took 10 years and three planet flybys to achieve its goal of matching the 40,000 kph velocity and entering orbit around a comet … all of which is a first for humanity, ever.

So yeah. Cool.

*At least she was gracious in victory.

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Nov. 16 2014 9:46 AM

Epic 4K Sun Video, With Bonus Sunspot Tantrums

Not long ago, the ridiculously huge sunspot called Active Region 2192 ruled the face of the Sun. Bigger than Jupiter, it was easily seen by the (adequately protected) naked eye, and it was a distracting though extremely cool blemish during October’s solar eclipse.

A sunspot that big has a lot of storage space to stuff magnetic fields, and 2192 didn’t disappoint. Sunspots are essentially magnetic phenomena, and as the huge looping magnetic field lines in the spot tangled up, they sometimes violently snapped and reconnected, releasing their energy as solar flares. Dwarfing every nuclear bomb on Earth combined, the flares kept popping off as 2192 marched across the Sun’s disk, swept along with our star’s rotation.

From space, the Solar Dynamics Observatory keeps a close eye on the Sun, and watched in multiple wavelengths (think of them as colors) as 2192 did its thing. James Tyrwhitt-Drake, who has created interested scientific animations before, took 17,000 SDO images of the Sun in the ultraviolet, spanning Oct. 14–30, 2014, and created an astonishing video that shows 2192 in all its glory. The video is available in 4K resolution, if your bandwidth can choke that down, but it’s worth it to make this full screen:

The sound you hear is not real; it’s made from visible light data by SDO’s Helioseismic and Magnetic Imager, which maps motions on the Sun’s surface, which was then converted into sound by solar astronomer Alexander Kosovichev.

In this view, south is up, so the Sun rotates right to left (I’m used to it the other way, but hey, in space there is no up, so fine). 2192 makes its appearance early on, announcing its presence with towering loops of magnetic energy over 200,000 km high—mind you, the Earth is a mere 13,000 km across—and dominates the view thereafter. It’s incredible.

You can watch as enormous prominences erupt away from it, hot hydrogen gas flowing along otherwise invisible magnetic field lines like beads on a wire. The gravity of the Sun is strong, and pulls the gas with a force nearly 30 times stronger than Earth’s gravity, but the magnetic field is strong, too, and the gas flows back to the Sun along curving, graceful paths. It’s mesmerizing.

As the Sun rotates, AR 2192 has come around again, returning on or about Nov. 12. But it decayed substantially when it was on the far side of the Sun from the Earth. It’s a shadow, so to speak, of its former self. It doesn’t look like it’ll last much longer. We may not get another spot like it for a long time; it was the biggest seen in decades. But the Sun is a complex beast, and predicting its behavior for things like this is a losing bet. We may not see another like 2192, or another might grow and swell into existence once again. We’ll have to wait and see.

Nov. 15 2014 7:30 AM

Hey, Galileo Was Right!

One of the funny things about being a human is that our intuition can steer us wrong, even on things that should be pretty obvious, things we see literally every day.

For example, if you ask someone what would fall faster, a bowling ball or a marble, I bet a lot of folks would say the heavier bowling ball falls faster. But in fact, if dropped from a meter or so off the ground, they’d fall at the same rate. Gravity accelerates them at the same rate, so they fall at the same rate.

Part of the reason our intuition is off here is due to air. As objects fall, the air pushes back on them. This depends pretty strongly on their surface area, how big they are, so a lightweight large object will in fact fall more slowly than a heavier, smaller one.

Dropping a bowling ball and a feather will yield results that will satisfy our intuition. But what if you removed all the air from the room and dropped them? What happens then?

My friend and physicist Brian Cox did just this for his new BBC TV series Human Universe. He traveled to NASA’s Space Power Facility at the Glenn Research Center in Ohio to test gravity. What happens when he does is pretty wonderful.

Lovely! With the air removed, the feathers and ball fall at the same rate, just as Galileo predicted and Newton showed mathematically. I assume the bit at the end of the video about Einstein is referring to the Equivalence Principle, which has to do with acceleration due to gravity—if you’re standing on the Earth’s surface, you feel this as your weight, the force due to Earth’s gravity on your mass—and is indistinguishable from acceleration due to some force (like being in a rocket under power). This idea has profound implications, and in part led to Einstein developing the theory of General Relativity. I’d love to see this show and find out how Brian follows that concept farther.

I’ve known Brian for quite some time, and I have to say it’s nice to see him finally get some recognition for his work. The poor guy has been languishing in obscurity for years

Nov. 14 2014 5:06 PM

Rosetta Spots Site of Philae’s First Bounce

Update (Nov. 14, 2014 at 23:00 UTC): Contact with Philae has been re-established! Data taken from the surface (including drill samples) have been sent back to Earth. Not only that, a command was sent to rotate the lander, and that worked as well! It rotated by 35°, enough to point a bigger solar panel up to the Sun. Reports indicate power is flowing, so the life of the mission has at the very least been extended somewhat. This is incredible work by the ESA team!

Update 2 (Nov. 15, 2014 at 00:00 UTC): While the move to rotate the lander was successful, the drain on the battery by the instruments on board was too much. At about half past midnight the voltage dropped below the critical point and the lander put itself into standby mode (no science being done; just communication with the Rosetta orbiter). HOWEVER, the point of the rotation was to get more power available. It's entirely possible that over the next few days, as the comet rotates around, enough sunlight will hit the solar panel to the battery enough charge to restart Philae. As usual, Emily Lakdawalla has more info on this. So Philae is not necessarily dead. It may just be sleeping, hibernating. We could very well hear from it again.

The European Space Agency just released a great short video showing Rosetta's view on the comet where the Philae lander took its first kilometer-high bounce! [Note: If the video is blank, let it run to the end (it's only 12 sconds long), then hit the "replay" button in the video window. It should play normally then. Sorry about that. We're looking into the problem.]

If I've measured this correctly, the red circle is roughly 15 meters (50 feet) across. The "flight dynamics solution" is where the spot was predicted to be given Philae's trajectory, and as you can see they pretty much nailed it. 

It's hard to interpret exactly what we're seeing in the before and after. The dark streak looks like a plume of material, but I'm not so sure. Just above and to the right you can see another similar dark feature, and I'm leaning toward them both being shadows cast by low ridges as the angle to the Sun changed between the first image and the second. 

These images should prove useful in figuring out just where Philae is; its location is still unknown. As I write this we're still awaiting word that contact between the still-orbiting Rosetta and the lander has been re-established, and the data taken uploaded. Hopefully, samples of the comet have been analyzed by Philae, and we'll get a sense of what materials are on and just below its surface.

This is still very exciting! Certainly, it would've been far better had the lander stayed upright, and able to draw energy from the Sun, but even if that's not to be, it's still done an amazing job.

Nov. 14 2014 12:38 PM

Quick Philae Update

There’s more news this morning about Philae, the European Space Agency lander that is on the surface of the comet 67P/Churyumov-Gerasimenko. Recap: It set down on the comet yesterday, but the harpoons didn’t deploy. It bounced, twice, and came to rest a kilometer or so from the desired landing site. It’s not known precisely where it is, and it’s too small for the Rosetta spacecraft, still orbiting the comet, to easily find it.

Philae departs from Rosetta, on its way down to the comet.


Update, Nov. 14, 2014 at 18:00 UTC: The ESA Rosetta blog has posted an update, which has information about what the instruments on Philae have been doing so far.

Philae came to a rest on its side, unfortunately in a hole or an area surrounded by tall outcroppings. Because of this it’s not getting enough sunlight for its solar power cells to keep it charged. It has two batteries, but the instruments are using up that power rapidly. If nothing is done, it will run out of power soon.

If it does run out of power, all is not necessarily lost; as the comet nears the Sun the cells may receive enough charge to turn the lander back on. This is speculative, though.

The good news is the lander is working and taking data; dozens of high-res photos have been taken, for example, and are waiting to be transmitted up to Rosetta so they can be sent back to Earth. Contact between Rosetta and Philae is intermittent as the orbiter moves around the comet and the line of sight clears to the lander. The next good pass should be today around 21:00–23:00 UTC (16:00–18:00 Eastern).

I wondered yesterday if outgassing from the comet could dislodge Philae, but apparently it’s too dense for that to happen. One idea engineers are looking into is turning on the lander’s flywheel (a heavy, rapidly rotating disk that is used to rotate the lander)—Lander Manager Stephan Ulamec calls it “a very attractive idea”—which might provide enough torque to get Philae upright. There may not be enough power to spin it up though.*

I get the impression that, of course, people on the Philae team are disappointed at what happened, but are still really happy that it worked at all and got as far as it did. I keep hearing comments that anything they get now is “cream on top” of the amazing data they’ve already received. In other words, this mission was a success!

Let’s hope that the success it’s had so far is just the beginning, and not the end. And remember: Rosetta is still orbiting and going strong. That part of the mission has many months of discovery ahead of it.

*Correction, Nov. 14, 2014: This post originally misspelled the first name of Stephan Ulamec.

Nov. 14 2014 7:30 AM

Cymatics: Science v. Music

I’m about to make you very happy. Stop what you’re doing and watch this extremely cool video called “Cymatics: Science v. Music,” by musician Nigel Stanford. Seriously. Make it high-def, full screen, and crank up the volume.

Science! Music!

There are a couple of things I want to point out in particular. I laughed out loud when I saw the drummer’s spiraling water (starting around the 1:20 mark). His drumming makes the rubber tube vibrate in a circular motion, which sends the water flow out in a different direction over time, like a lawn sprinkler. You don’t see the hose move because the vibration is synched with the video frame rate; every new frame of video is taken when the hose is back to the starting position. I explain this in great detail in an earlier post about this effect (you really do want to see that post; it’s got very cool stuff in it).


I like the way the flames move starting around 3:30, too. There’s a speaker at one end of the gas tube, and as sound waves come out of it the gas in the tube gets compressed and rarefacted (the opposite of compression, so decreasing the density of something) by the waves. Standing waves are created in the gas, like the waves you get if you snap a rope at just the right rate. That’s why you see the flames going up and down in those graceful sine curves.

And I love the patterns of sand on the metal plates seen throughout the video. That’s an interference effect. Waves of sound travel through the plate, making it vibrate. Where the crests of those waves meet each other you get amplification of the waves, again related to standing waves. The patterns are complex because of the shape of the plate; the waves propagate through it and get their direction and shape changed by the edges and corners of the plate. I remember working through the math of this in my grad school mechanics physics class; it took days and many, many sheets of paper to solve the equations even to show how a circular drumhead vibrates, which is a pretty simple shape.

But out of complexity can come great symmetry and beauty. The patterns are lovely.

I really like Stanford’s music, too. The video was sent to me by Tom Lowe, an astonishingly talented astrophotographer. Lowe created the time-lapse videos “Rapture,” “TimeScapes,” and “Death Is the Road to Awe,” which are all stunning. Stanford did the music to “TimeScapes,” which is how this is all connected.

I can’t get enough of stuff like this. Astronomy, physics, science, math, music, video … they are all related, and the interconnectivity is, simply, art. 

Nov. 13 2014 11:03 AM

COMET UPDATE: Where is Philae?

Yesterday, the Philae lander separated from the Rosetta spacecraft, descended to the comet 67P/Churyumov-Gerasimenko, and then … what, exactly?

It was supposed to fire harpoons, reel itself down to the surface, then engage screws in the bottom of its landing legs to secure itself to the surface. However, the harpoons didn’t fire. Yesterday we knew it bounced, and landed somewhere else, but now we’ve learned more.

Image from Rosetta showing where Philae first hit (red cross). It then bounced and moved to the right, and now most likely sits inside the large, shallow crater.


First of all, it actually bounced twice! It probably hit, then rebounded nearly a kilometer off the surface in the tremendously low gravity—on the comet it weighs about as much as 10 grams would on Earth, the same as four ping-pong balls. The comet rotated underneath it, and then the lander slowly hit again some distance downrange, only to rebound again. This was a much lower bounce, perhaps 20 meters (60 or so feet) high, and didn’t last nearly as long, only about seven minutes.

where is Philae?
A map of the comet, showing where the lander originally hit (red square) and where it may have landed (blue diamond).

Photo by ESA via SpaceRef

Where did it land? It’s not clear. In the image above it hit in the red square, its original landing site, then bounced to somewhere in the blue diamond hundreds of meters away. There is a large, shallow crater on the top of the smaller of the two lobes of the comet (what looks like the rubber ducky’s head in the original pictures of the comet showing its shape) and it’s most likely in there somewhere. The high-resolution camera OSIRIS on Rosetta itself is busily taking images of the area to see if the lander can be spotted.

The bad news is it isn’t upright. It’s on its side, with one leg sticking up “in the air”—really into space, since there’s no air on the comet. The good news is that the folks at the European Space Agency are still in contact with Philae, and it’s sending back data, including pictures. 

surface of the comet
Detail from the first picture.

Photo byESA/Rosetta/Philae/CIVA

And the first one sent back (at the top of this post, and enlarged above) is dramatic, showing the weird, forbidding landscape. The lander appears to have come to against a flattish surface of some kind. The angle is confusing, since we know the lander is on its side. The picture was taken by the CIVA camera near the top of the barrel-shaped lander, and it looks down on the foot. Judging from the orientation here, this means we may be seeing the highly angular surface of the comet, though it could be a wall or side of a cliff. The material looks more solid, not powdery and soft, which might explain the lander bouncing.

Philae panorama
A panorama made from several images from Philae, including a drawing of the lander superposed on it to show the orientation. Sideways is better than noways. The fan of light at the top is reflected sunlight inside the camera.

Photo byESA/Rosetta/Philae/CIVA

The lighting is worrisome; if the lander is in shadow for long periods of time the frigid cold might affect it, and the solar panels may not be able to supply enough energy. Hopefully at the next ESA press conference they’ll be able to fill us in on that situation.

So while this isn’t ideal, let’s keep in mind the real situation and what we’re seeing here: The Philae lander is down, on the surface of a comet, it’s working, sending back data, and will still be able to carry out much of its mission.

That counts. This mission was already a success yesterday, and now everything we get back from it just makes things better.

Nov. 13 2014 7:15 AM

Shmutz in Jupiter’s Pupik

I remember when I was in grad school, running a telescope observing lab. I was setting up the telescopes, and Jupiter was well placed in the sky, so I was using it to align the finderscopes and get things focused. By coincidence, one of its moons, Io, happened to be just on the edge of Jupiter’s broad face when I looked. Over the course of the three hour lab, we all took turns going back to that ’scope to see how much Io had moved. By another sheer coincidence, Io takes about three hours to cross Jupiter’s disk, so the transit ended just as the lab did.

It was mesmerizing. But it was nothing like this:

If you didn't freeze, get crushed, be poisoned, and asphyxiate, this would be a pretty good place to see a total solar eclipse.

Photo by C. Go and theHubble HeritageTeam (STScI/AURA)

That’s how Hubble sees Jupiter, which is way better than my old (otherwise very nice) 25 cm ’scopes did. You can see the broad bands and swirly festooned storms all over its cloud tops. But what really gets you is the ridiculously huge Great Red Spot, big enough to swallow the Earth.

And as if even that isn’t cool enough, there’s a big black spot on it: That’s the shadow of the moon Ganymede, which happened to fall right across the Spot when the shot was taken.

Jupiter’s moons orbit the planet above its equator, and Jupiter has almost no axial tilt (unlike the Earth, where our spin axis is tipped about 24° to the plane of our orbit). That means Jupiter’s moons pass directly between the planet and the Sun every orbit, casting their shadows on the clouds (Jupiter doesn’t have a solid surface; we only see the top of its dense atmosphere, which is tens of thousands of kilometers deep).

I’ve seen moon shadows on Jupiter many times through telescopes, but I’ve never seen one throw its shadow over the Spot! That’s really cool. And what really strikes me is how big Ganymede’s shadow is compared with the Spot. There are two reasons for that: One is that Ganymede is big, 5,270 km across—bigger than the planet Mercury! So it casts a huge shadow.

But also, the Great Red Spot over the years has become somewhat less Great. It’s shrinking. In the past 40 years it’s lost more than 30 percent of its width, and no one knows why.

Incidentally, another mystery is why the Spot is red. Is it from material upwelling from deep within Jupiter's atmosphere, or is it from something else? A new study indicates that it might be due to gases and other material in the upper atmosphere of the planet that get smacked by solar ultraviolet light, changing their chemistry. In the lab, such a process has created a red gas similar to what's seen in the Spot. I can't say if it's conclusive, but it's an interesting step in solving this long-standing enigma.

Anyway, the picture above, released the week of Halloween, was being sold as “Spooky Shadow Play Gives Jupiter a Giant Eye.” I am a master observer of pareidolia, and I’m not buying this. It looks a little like an eye to me, but the placement and relative dimensions don’t look right. If pressed, I’d say it looks more like a jovian belly button.

So maybe, instead of using Hubble, they should have taken this picture with the Naval Observatory.

Nov. 12 2014 3:12 PM

When We Reached Out Into Space and Grasped a Comet

Today, Nov. 12, 2014, at 16:02 UTC, a tiny robot landed gently down onto the surface of a comet.

Five hundred million kilometers away, millions of humans on Earth rode along with it.

After 10 years of travel through the depths of space, and at least that long beforehand filled with meetings, designs, construction, and a launch in 2004, the Philae spacecraft was successfully released from its Rosetta mothership. Then, seven hours later, it made history.

We have flown by eight comets before, impacted one with a 370 kilogram block of copper, and, now, for the first time ever, have landed on another. The robotic proxy of humanity sits on the surface of the comet 67P/Churyumov–Gerasimenko.

landing site
From 3 km up, the comet landing site swells beneath the lander's camera. You're looking down on the small lobe of the rubber ducky–shaped comet; the bigger lobe peeks around the top and right. One of Philae's landing legs is stretched across the upper right corner as well.

Photo by ESA Rosetta/Philae/Rolis

But only barely. For reasons yet unknown, the harpoons failed to deploy, so the lander may not be firmly anchored in place. In fact, from the telemetry received, it appears to have slowly hit the surface, bounced, spun a bit as it was over the surface (possibly due to the rotation of an internal flywheel used to change the attitude of the spacecraft), then landed again.

But it is down, and very nearly in the center of the planned target area. And if only for this reason, the mission has been a success.

It’s difficult to overstate this achievement. The comet is moving on an elliptical orbit that takes it just outside the orbit of Jupiter (850 million kilometers from the Sun) and as close as 186 million km sunward (just inside the orbit of Mars). The Rosetta spacecraft had to travel for a decade through space to catch up to its target, flying past two asteroids—Lutetia and Steins—as well as getting a gravitational boost by swinging past Mars and even Earth. It was a long, cold journey, which finally brought it alongside 67P in August 2014.

After that it slowly approached the comet, taking mapping images along the way, searching the bizarre terrain (cometain?) for a landing site. After much deliberation a suitable site was chosen. Rosetta moved in, dropped Philae, and the rest is history.

landing site up close
The landing site, moments before contact.

Photo by ESA/Rosetta/Philae/ROLIS via CNES

Except, again, we’re still waiting for more information. Philae is definitely down, and definitely working. It returned a few images, and engineers are still receiving telemetry from it. But it’s not clear what will happen next. The gravity on the comet is terribly weak—about 0.01 percent that of Earth—and the lander weighs half an ounce on the surface. That wouldn’t be a problem in the vacuum of space, except the comet is outgassing: The ice on and below the surface is warming as the comet approaches the Sun, and turns directly from a solid into a gas. This is a gentle wind, to be sure, but when you weigh less than a sheet of paper does on Earth, it doesn’t take much to set you flying again.

Philae has screws on the bottoms of its landing legs, and they did appear to deploy, but it’s not known how well the lander is secured. Nothing is clear right now. The European Space Agency held a press conference to give an update, but it won’t be until tomorrow that they know enough to take the next step. As soon as I know, I’ll let you know.

But, despite this sobering news, there is still joy and wonder to be had. The technical prowess to achieve this landing is nothing short of awe-inspiring. Math, science, engineering, even management and teamwork—in this case, across many countries in Europe—produced a breathtaking result: We have sent our work and our minds and our hearts across space, and done something truly remarkable.

Congratulations to ESA, to everyone involved with Rosetta, and yes, to all of us who care about exploring the Universe. It’s one of the noblest things we do.

Nov. 12 2014 6:00 AM

Watch Humanity Touch a Comet

Update 4, Nov. 12, 2014 at 16:05 UTC: T O U C H D O W N!!! At 16:02 UTC (11:02 Eastern) the European Space Agency's Philae lander made contact with the comet 67P/Churyumov-Gerasimenko, launching its harpoons into the icy surface and attaching itself. For the first time in human history, we have reached out and grasped a comet. We expect close-up images of the surface from Philae soon, so stay tuned.

Update 5, Nov. 12, 2014 at 17:00 UTC: Uh-oh. It appears that the harpoons did NOT fire, and Philae is not currently moored to the comet. It's not clear what's going on, and the data are confusing. We should know more soon. 

Update 6, Nov. 12, 2014 at 17:50 UTC: Some good news: The first picture of the comet from the Philae lander has been returned to Earth! Taken by the ROLIS camera, the landing site can be seen directly below, on the "top" of the smaller lobe of the two-lobed comet (you can see part of the bigger lobe above and to the right, as well as part of the lander hardware). Although we're still not sure what's going on with Philae as far as attaching itself to the comet, it's great that we're getting telemetry and the cameras at least are working.

comet form Philae
First image from Philae of the comet as the lander descended. Expect more like this soon!

Photo by ESA Rosetta/Philae/Rolis

Update 7, Nov. 12, 2014 at 18:20 UTC: Another amazing picture from Philae, this time taken moments before touchdown. The scale is unknown (I'm awaiting official word), but you can see boulders and rocks dotting the more-or-less smooth surface. Images like this may prove crucial in understanding what the lander is doing now. There's still no word on the harpoons and the state of the lander.

Moments before touchdown, the Philae lander took this astonishing image of the landing site. Individual boulders and smaller rocks can be seen (the scale is as yet unknown). This image is a screen capture from the CNES news feed.

Photo by ESA/Rosetta/Philae/ROLIS via CNES

At approximately 16:03 UTC (11:03 Eastern) Wednesday, Nov. 12, for the first time in human history, a spacecraft is expected to physically land on a comet.

As I write these words, less than a day before the event, the lander Philae has not yet separated from the Rosetta probe. As you read these words—and assuming no roadblocks messed things up—that should have occurred on or about 09:03 UTC (04:03 Eastern time). Philae will then slowly approach the comet 67P/Churyumov-Gerasimenko, taking data and images along the way, and at the right moment will fire harpoons into the comet's surface and then reel itself down. 

Update, Nov. 12, 2014 at 14:15 UTC: Philae separated on time! It is now approaching the comet. Everything looks good, except for one small problem: A gas thruster on the top of the lander, designed to absorb some of the rebound after the lander (softly!) impacts the surface, isn't working. Philae will have to rely on its harpoons to make sure it sticks its landing.

Rosetta from Philae
The first picture from the Philae lander after separation shows the Rosetta spacecraft backlit by the Sun.

Photo byESA/Rosetta/Philae/CIVA

Update 2, Nov. 12, 2014 at 14:30 UTC: Philae has released its first image! It shows the Rosetta spacecraft, to which its been attached for 10 years, with a bright sunstrike—a reflection of sunlight on the camera—in the middle. This shows the camera is working, and ready for its historic rendezvous which is on schedule for just after 16:00 UTC (11:00 Eastern time) today!

Update 3, Nov. 12, 2014 at 15:15 UTC: The incredible image below is of the Philae lander shortly after separation, taken by the high-res OSIRIS camera on Rosetta. It shows that the landing legs and instruments have deployed, which is great news. Remember, Philae has been essentially dormant for nearly all of the decade it's been on the way to the comet, so it's very nice to see these mechanical parts deployed. My thanks to Emily Lakdawalla for posting it.

Philae from Rosetta
Incredible shot of the Philae lander on its way down, taken by Rosetta.

Photo by ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA via Emily Lakdawalla

These events happen over night for most of the United States, making it difficult for me to cover everything live. So first, I suggest following my friends Emily Lakdawalla and Karl Battams on Twitter; they are at Rosetta HQ and tweeting everything as they hear it. Emily has posted a very useful timeline of events as well.

Second, I'm embedding a live feed from the European Space Agency. It's not clear when new images will be released, but if you're up you might get a chance to see them. I plan on getting up early so I can find out what's what, and when I do I'll update this post. Think of this as a placeholder until then. But stay tuned! I'll have images as soon as I can get them.

And remember, the times listed here are approximate, so you might want to tune in early so you don't miss anything!