It’s a little early for me to start thinking about my annual Top Ten Astronomy Pictures, but I have a feeling this one will make the cut: the actual glowing trail of plasma left in the wake of Atlantis as it entered Earth’s atmosphere, as seen from space by astronauts aboard the space station!
Amazing! Oh yes, you want to click to embiggen.
Atlantis undocked from the International Space Station on July 19, and two days later the ISS was in position to coincidentally catch a view of the Orbiter as it made its final descent. This shot shows the plume of ionized gas left behind as Atlantis descended, as well as clouds, parts of the ISS itself, and atmospheric airglow: the faint glow of molecules and atoms high in the atmosphere as they slowly recombine with electrons and emit light.
This shot is simply spectacular. Since the stars aren’t trailed, this must be a fairly short exposure, not more than a few seconds. The trail you’re seeing is therefore not actually the Orbiter streaking across the Earth! The plasma trail behind it fades with time, so the trail is brightest near the Orbiter’s position and fainter as you backtrack along its path. Think of it as an afterglow of the passing of Atlantis.
Why does this happen? The air gets heated by the Orbiter’s ramming the atmosphere at 20+ times the speed of sound. And contrary to popular belief, it’s not friction that heats the air, but compression. When you compress a gas it heats up (like when a bicycle pump gets hot when you use it a lot), and the Orbiter is screaming through the atmosphere at hypersonic speeds. That compresses the air a lot. A shock wave forms in front of the Orbiter, and the air begins to glow as it gets heated up to temperatures as high as 1260° C (2300° F).
That’s what you’re seeing above: the shocked, rammed, and glowing air as Atlantis pounded through it at several kilometers per second. And it did this many, many times over its life… until this one final time, caught on camera by astronauts high above the Earth.
Related posts:
- … and then there were none.
- Southern lights greet ISS and Atlantis
- ISS and Atlantis seen in broad daylight!
- Atlantis goes head over heels
July 22nd, 2011 at 6:11 am
You’re right, I did want to click to embiggen. That is a remarkable picture. Would this have been visible from the ground, and roughly where would have been the best viewing locations?
July 22nd, 2011 at 6:17 am
fantastic picture. I’m so jealous that these great men and women had/have such extraordinary experience.
We on the other hand keep on doing our little jobs…damn it…
July 22nd, 2011 at 6:21 am
I’m puzzled. If the trail is brighter near Atlantis, why does the end nearer the ISS and appearing higher above the Earth appear brighter? Perhaps the fainter part of the trail is more related to its distance away from the ISS and the fact that it is being viewed through more of the Earth’s tenuous outer atmosphere?
Or am I looking at the trail wrong?
Clear skies, Alan
July 22nd, 2011 at 6:23 am
Yes, you are looking at the trail wrong. It is going away from camera, slightly down toward the Earth.
July 22nd, 2011 at 6:52 am
Yup, I was. To me, it looked like the brighter part was closer to the ISS and farther from Earth.
Clear skies, Alan
July 22nd, 2011 at 6:56 am
The first shuttle launch I saw in person was the Challenger disaster. I have seen many launches since then, but he last few pics you posted of Atlantis have brought tears to my eyes…
July 22nd, 2011 at 6:56 am
I see it the same was as Alan D does, but after staring at it for a while it suddenly switched around and made more sense. Very cool picture, probably literally the only one of its kind. Here’s hoping there’ll be a chance in the future for many more similar pictures.
July 22nd, 2011 at 6:59 am
Daniel,
Thanks! I see what you mean, and got it to switch and look like the brighter end was farther away from the ISS.
Clear skies, Alan
July 22nd, 2011 at 7:21 am
I know there must be something wrong with my thoughts here, but …
If it’s compression that causes the heating, then after the shuttle has passed by, why doesn’t the rarefaction restore the original pressure and therefore the temperature *immediately*?
After all, the compression is just a temporary phenomenon caused by the temporary presence of the volume occupied by the bulk of the shuttle.
July 22nd, 2011 at 7:33 am
There’s a visible kink in the descent path about half way along, visible in all the photos. Presumably this is where the air was thick enough for the shuttle to start active pitch/roll/yaw control (http://spaceflight.nasa.gov/shuttle/reference/shutref/events/entry/), which in turn suggests the steepening curve isn’t just a perspective effect…
Oh how I wish I was there!
July 22nd, 2011 at 7:35 am
Dunno if that will make a list of best astronomy pictures, but it could easily make it onto the all-time great space exploration pictures. Right up there with Buzz Aldrin on the moon and the Apollo 8 earthrise, in my not-so humble opinion.
July 22nd, 2011 at 7:36 am
It is certainly a remarkable photo.
Clear skies, Alan
July 22nd, 2011 at 7:43 am
Meh, I’d prefer a video of it
July 22nd, 2011 at 7:54 am
Not only a spectacular picture of the shuttle reentry put an optical illusion as a bonus.
I first saw the portion of the ISS at the upper right as a tree which really makes the picture surreal.
July 22nd, 2011 at 8:07 am
“To follow knowledge like a falling star,
beyond the utmost bound of human thought.”
Tennyson (as closely as I can remember him).
July 22nd, 2011 at 8:09 am
When I first looked at the picture I saw it the correct way, but now, having read Alan and Daniel’s posts, I see it wrong half the time. Funny the way the mind works.
July 22nd, 2011 at 8:30 am
Conscious of a similar illusion with lunar craters, I tried seeing it another way when I first looked – and failed. It was only after Daniel’s post that I was able to switch it around.
Indeed – funny how the mind works. But the world would be less interesting without illusions.
Clear skies, Alan
July 22nd, 2011 at 8:55 am
I saw one cross over the Gulf of Mexico at sunrise after going over Vera Cruse. Something to see and comprehend there were people riding that fireball
July 22nd, 2011 at 9:06 am
“You win again, gravity!” — Zapp Branigan
July 22nd, 2011 at 9:12 am
What are the glowing patches on the Earth at the top right of the image ?
July 22nd, 2011 at 9:15 am
looking at it backwards – that would be one steep descent.
July 22nd, 2011 at 9:16 am
VERY cool. I had actually heard them say that they had seen the plasma trail from the ISS while I was watching the reentry yesterday, and I was hoping they took a photograph. Now it turns out they have!
July 22nd, 2011 at 9:16 am
I remember actually getting to watch the trail one time – I live in Louisiana, so it was still fairly high – but it was … beyond words. It wasn’t just a glow – there was more to it. I know I’ve never seen a meteor look like it did, though I’ve never seen a really bright meteor. Amazing, really. There was a quality to the fire that was unlike any I’ve ever seen. You could easily tell it wasn’t reflected sunlight from the Sun, just below the horizon.
That, and watching a launch from Daytona Beach, and then having the sound wash over me 5 minutes later, are scenes I’ll never forget.
Requiescat in Pace Semper, Endeavor, Discovery, and Atlantis. Perhaps one day, we will get our act together, and lift you back to the Deep Black, where you belong.
July 22nd, 2011 at 9:19 am
Does this mean that Atlantis began reentry over the horizon w.r.t the space station, and during reentry the shuttle slowed down and the space station caught up a little and could then seen it?
July 22nd, 2011 at 9:20 am
I thought I read you couldn’t see the stars in space because of the brightness of the Sun and/or Earth. This shows them clearly. Remarkable.
July 22nd, 2011 at 9:22 am
A pretty amazing image! Thanks for the explanations!
July 22nd, 2011 at 9:41 am
What’s all that mess at the top-right? Looks like a blast remnant.
July 22nd, 2011 at 9:43 am
Hmm.. Looking at it, I think you saw the trail in the right orientation, but perhaps were mistaken about what was happening. First of all, you need to keep in mind that the space station, itself, is moving, and you are really seeing the exposure of point source glow on the heat shield of the shuttle over time, and not an instantaneous picture of a trail.
Think about the process that goes on: First, the shuttle, in an orbit similar to that of the ISS executes a de-orbit burn. That burn establishes an elliptical orbit where the high point is near the ISS’s orbit and the low point is deep enough in the Earth’s atmosphere that the shuttle will slow down too much to come back up in this new orbit. It does this by slowing down in it’s orbit at the high point, so it starts to fall behind the ISS. As it descends, it should start to catch back up to the ISS, but depending on this new orbit, it may well be behind the ISS, still, as it enters the atmosphere. So, my guess is, at the shuttle reenters, it will be closer to the Earth and trailing the ISS. At some point, around this time, the camera that took this picture opens the shutter or begins collecting light, depending on the type of camera.
Initially, the shuttle is still traveling rather quickly, and it holds it’s position relative to the ISS. So it spends more time at the initial point in the exposure, and that initial point is where it’s brightest. As the atmosphere slows it down, it moves back (relatively speaking) along that “trail”, and as it picks up speed backwards, along the “trail” it spends less time in any given point in the “trail”, and so that point in the “trail” is less exposed and less bright. Of course, the shuttle isn’t moving backwards, at all. But the camera taking this picture is moving forward quite quickly, so as the shuttle loses speed, it appears (from the camera’s point of view) to be moving backwards along the “trail”. and again, the “trail” isn’t really a trail so much as the sum of all the glowing from reentry that the camera sees over a long exposure.
So I think your initial impression of the shape you see was correct. It’s oriented like the trail of a missile launched so that it almost chases the ISS. But, while it’s natural for us to assume were seeing a trail standing in the air, that’s really not what we’re seeing, here. This is a long exposure of the reentry glow from the point of view of an camera that’s pulling away from the shuttle.
I hope this helps.
Adrian
July 22nd, 2011 at 10:05 am
9. AK
The air stays hot because it’s absorbing the kinetic energy of the Shuttle. As the Shuttle slows, that energy(by virtue of velocity) is converted to heat.
Gary 7
July 22nd, 2011 at 10:06 am
I don’t know if it’s really an astronomy picture, but it definitely on my list of top 10 space program pictures.
July 22nd, 2011 at 10:27 am
@27 That’s the ISS.
Amazing picture… A nice one to end it all.
July 22nd, 2011 at 10:42 am
[...] Astronomer Phil Plait explains the fiery streak we’re seeing here: Since the stars aren’t trailed, this must be a fairly [...]
July 22nd, 2011 at 11:39 am
Hey, maybe someone can explain, why can’t the orbiter slow down ~in space~ so as to lessen the effect of the compression as it passes through the atmosphere? Is it merely a matter of fuel, or would the effect of gravity on the vehicle still cause compression of that intensity at lower velocities?
July 22nd, 2011 at 11:41 am
Actually looking again at the photo, it seems that is exactly what happens in the deorbit burn, slow down, drop thru atmosphere… yikes.
July 22nd, 2011 at 11:50 am
M Burke: Remember how orbital mechanics work – the Shuttle was always ‘falling’ towards the Earth (or at least experiencing acceleration in the direction of the middle of the planet) at roughly 9.8 m/s^2 (gravity is basically just as strong up there as it is down here).
It’s just that, as it was falling, it was also moving ‘forward’ at roughly 8 km/s. So it keeps falling and keeps missing the Earth, all the way around the planet, over and over again.
Simply trying to slow down is what causes you to re-enter – you keep falling at the same rate and now you don’t have enough speed to ‘miss’ the Earth anymore. Eventually you interface with the atmosphere and use that interaction to slow to more Earth-like speeds.
To slow down without falling to Earth would take a huge amount of energy because you have to counteract gravity while slowing down. Overcoming the force of gravity is why you need to strap yourself to a giant explosive device to even get up there !
edit – fixed something that said ‘speed’ that should have said ‘rate’. language + physics = confusion.
July 22nd, 2011 at 11:51 am
@28 AdrianG:
Well, except that whatever the mechanics of de-orbiting Atlantis, it was considerably ahead of the ISS. The Astronomy Picture of the Day for July 21 shows this:
http://apod.nasa.gov/apod/ap110721.html
Assuming that the estimated separation of two minute was correct, this would mean that Atlantis was 575 miles ahead of the ISS along their common orbital path at the time the picture linked above was taken.
July 22nd, 2011 at 12:26 pm
The explanation that compression causes the heating is flawed.
When you compress air in a cylinder, like a bicycle pump or the cylinders in a diesel engine, then if we neglect transfer of heat to/from the walls then the process is isentropic: the entropy of the gas remains the same. Ideally, all the energy of compression can be recovered if the gas is allowed to reexpand.
This is NOT true of the fluid flow around a supersonic body. The passage of gas through a shock is an irreversible process. Entropy is generated.
What is happening is that the density and velocity of the gas change over a distance of about one mean free path of the gas molecules. The incoming air, in effect, collides violently with air that has been slowed down, and slows down itself.
July 22nd, 2011 at 12:36 pm
1.6 sec exposure at f/2.8 and ISO 10000 (according to EXIF)
July 22nd, 2011 at 12:40 pm
The more I look at this, the less consistent my explanation seems with the image. If we were watching a long exposure of the shuttle moving backwards with respect to the camera, the ground would move even further back. While the ground is more distant, I would still expect to see more movement than we see in the image. I think Phil’s right that this has to be a short exposure (or we’d see star trails), so I just don’t think there’s time for the effect I was describing.
Adrian
July 22nd, 2011 at 1:01 pm
@36 Arthur: That’s even more reason to doubt my explanation. Thanks for the correction.
July 22nd, 2011 at 1:11 pm
“If I could turn back time…”
July 22nd, 2011 at 1:17 pm
Clearly, this is actually the trail of ignited fuel being dumped from the Galileo shuttle craft so that the Enterprise can find them.
Really though, I love how real life turns out to be more awesome (in the true sense of the word) than fiction writers often imagine.
July 22nd, 2011 at 2:19 pm
What is the golden arc above (or part of?) the atmosphere?
July 22nd, 2011 at 3:14 pm
@1 This was visible and actually recorded from the ground. Check out this video:
http://www.youtube.com/watch?v=2XZgu7FStbw
July 22nd, 2011 at 3:37 pm
@ 43 sedwards
Actually BA explained the brownish arc in this previous post here:
http://blogs.discovermagazine.com/badastronomy/2011/07/18/southern-lights-greet-iss-and-atlantis/
There is a thin aerosol haze high in the atmosphere which is unnoticed when we are looking through it from the ground, but in night space photos looking towards the horizon of the Earth that haze is apparent because we are looking at it edgewise.
I assume that in similar space photos taken in daylight that this haze is too dim to be photographed.
July 22nd, 2011 at 5:14 pm
I live in Naples, FL. I was able to stay awake to view the landing, my first and obviously last. I watched the shuttle move from 12 o’clock high to the horizon and landing. One of the things I noticed most was the trail, at first I thought it was a contrail until I realized that without an engine, there would be no contrail. What I saw was this same plasma trail in this picture. Wow!
July 22nd, 2011 at 5:34 pm
That’s real purty!
July 22nd, 2011 at 8:27 pm
“Uh, did IQ’s suddenly drop while I was away?” In order to get out of orbit the shuttle fires it’s main engine. This perforce leads to a bright flare, and then that elevator ride down…
July 22nd, 2011 at 8:40 pm
Amazing. That reentry path looks pretty darn steep, though!!! Is that an effect caused by the velocity of the ISS?
When I first saw it, I thought it was a time-lapse of the de-orbit burn, or something.
@33MBurke: Yep, it’s all about fuel. If you could come to a full stop relative to the earth’s surface and fall straight down, there would be some heating from thunking straight down into the atmosphere, but not nearly as much as de-orbiting spacecraft experience (the G-forces might actually be higher, as you’d encounter thicker air much more quickly).
The shuttle uses about 1.5 million pounds of fuel (plus the solid rocket boosters) to reach orbital velocity. As it is, it barely squeaks by – the ISS is about the highest orbit the Shuttle can (could… sigh) achieve. So yeah, it’d be impossible to carry enough fuel to slow down by any significant amount – it just makes a lot more sense to let the atmosphere do most of the decelerating for ya.
Of course, that’s a whole lot of energy to dissipate. Energetically speaking, on reentry, it’s a lot like the orbiter is sitting right under the main engines of another shuttle at liftoff! All that energy from all that fuel is still there (as kinetic energy) until it’s turned into heat by reentry.
July 22nd, 2011 at 10:40 pm
Wow! [Jaw on floor.] That is one superluminous photo.
I saw the Shuttle – and then shortly afterwards the International Space Station – pass overhead at 6.30-40 pm local Adelaide time just under an hour before the Atlantis landed for the final time. It – and the ISS looked like aircraft, too far above to be more than points of light. Guess it was already in descent through our atmosphere when I saw it. Wonder if this was taken then or roundabouts then?
Y’know BA, there are so many great photos posted on this blog that some great ones seem to keep missing your ‘Top Ten’ yearly cut because of sheer numbers that I reckon you should make that a half-yearly or even monthly feature! I, for one, just love those posts.
(Hint, hint, please – pretty please!
)
July 23rd, 2011 at 12:49 am
AK (9) said:
This is a bit of a guess, but it seems to me that it doesn’t matter what the temperature of the gas is once it has been ionised. It’ll still be ionised until all the free electrons have recombined with atoms or cations. It doesn’t glow because it’s hot, it glows because it’s ionised, and it became ionised because it was heated to a high temperature.
July 23rd, 2011 at 1:01 am
M Burke (33) said:
Essentially, all our space vehicles use aerobraking to re-enter in order to save fuel.
In principle, one could build and launch a space vehicle that could slow itself to a mere few miles per hour relative to the ground before it re-entered, but it would need to carry such a hugeous quantity of fuel to do so that you’d probably end up with something the size of a Saturn V merely to launch a teacup into low-Earth orbit (LEO).
At lower velocities, the air would still be compressed on re-entry but less so. If you slowed down enough (as in my extreme example above), the air would be compressed too little to noticeably heat up. Conversely, the Apollo vehicles, on their return from the moon, compressed the air a lot more than does anything returning from LEO, and would have made a larger or brighter trail.
Of course, if you slowed your space vehicle enough to have a near-vertical descent, you would also need to thrust against the Earth’s gravity to prevent the vehicle from simply plummeting towards the Earth.
July 23rd, 2011 at 10:05 am
Embiggen…….?!…….EMBIGGEN?! Treat the language with more respect please, otherwise you risk ‘UGLYFYING ‘ it….
July 23rd, 2011 at 12:32 pm
It’s a perfectly cromulent word.
July 23rd, 2011 at 1:00 pm
[...] incredible picture of Atlantis’ re-entry taken from the space [...]
July 23rd, 2011 at 8:14 pm
@ 54 Paul D:
Win. The timing, the reference in context… Just, WIN.
July 23rd, 2011 at 9:15 pm
Reminds me of this :
http://blogs.discovermagazine.com/badastronomy/2010/02/22/pic-of-the-shuttle-reentry-from-space/
similar old image from here via Soichi Noguchi of the Endeavour orbiter’s landing on STS-130, Feb. 2010.
This image is, IMHON, the better of the two but both are pretty neat.
July 24th, 2011 at 3:14 am
Paul (37) said:
But note please that entropy increases in whatever system is used to apply the work to compress the gas in the cylinder.
Entropy increases, certainly, but this is not substantively different from the situation in which something (e.g. a person) compresses gas in a cylinder.
Or, in other words, the gas is compressed and then permitted to disperse, in a sort of wave.
July 24th, 2011 at 8:48 am
Pertaining to the visible piece of ISS in the photo:
What you are seeing is park of the Canadian built SPDM (Special-Purpose Dexterous Manipulator) or DEXTRE. Which you can read about on Wikipedia.
http://en.wikipedia.org/wiki/Dextre
It’s actually quite large. The third photo on Wikipedia shows it in the same location as it was during the Atlantis photo – berthed to the lower port side of the US Lab module.
- Ben H.
ISS Flight Controller
Mission Control, Houston, TX
July 24th, 2011 at 9:07 am
Found a recent APOD that demonstrates the size of SPDM:
http://apod.nasa.gov/apod/ap110718.html
July 24th, 2011 at 10:47 am
Entropy increases, certainly, but this is not substantively different from the situation in which something (e.g. a person) compresses gas in a cylinder.
Incorrect! Compression of a gas in a cylinder is, ideally, a completely reversible process. The entropy of the gas does not change.
But note please that entropy increases in whatever system is used to apply the work to compress the gas in the cylinder.
Work is being done by the piston. No entropy is flowing into the system. Whether entropy increases outside the cylinder is irrelevant.
July 24th, 2011 at 1:21 pm
[...] Astronáutica: La ISS y el Atlantis, capturados de día. El Atlantis ya está en casa. STS-135 Atlantis: resumen. Comienza la Era de las Soyuz . Lanzamiento del radiotelescopio espacial Spektr-R (Zenit-3F). Los otros transbordadores espaciales. The fiery descent of Atlantis… seen from space!. [...]
September 8th, 2011 at 2:01 pm
Missed opportunity for a headline: “Atlantis sinks again!”
September 26th, 2011 at 8:58 am
really amazing