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It's SOHOt
July 8, 2011 10:42 PM   Subscribe

On July 5th the SOlar and Heliospheric Observatory (SOHO) captured video of a comet, known as a sungrazer, in route to collide with our star. SOHO is equipped with an occluding coronograph that blocks direct sunlight and reveals the corona, but also prevents direct study of the terminal impact of sungrazers. But on July 6th, with the help of the Solar Dynamics Observatory (SDO), astronomers were able to observe the comet (slyt) streaking in front of the surface of the sun for the first time in history. It likely disintegrated before impact due to extreme heat and radiation.
posted by troll (18 comments total) 8 users marked this as a favorite

posted by hank at 10:54 PM on July 8, 2011

Amazing. Our Sun is pretty neat. I can't believe something as Neat as the Sun revolves around our Earth, much less the entire Rad universe!

(Take that, Copernicus!)
posted by glaucon at 11:10 PM on July 8, 2011

There isn't anything to impact. The sun has no surface.
posted by Chocolate Pickle at 11:46 PM on July 8, 2011

I was trying to figure out how quickly the comet was moving in that last link, thinking, "Holy sh*t, that's FAST", but after some quick back-of-the-envelope guesstimation, I was coming up with something around 200,000 miles per second, which is flatly impossible. (speed of light is 186,262 miles per second, and you can never, ever see anything moving faster. Space and time will bend in any way required to prevent that kind of measurement.)

So I was digging around, trying to figure out what the heck was wrong, and it turns out the link is very time-compressed. The real event took about twenty minutes. The video is kinda cheating, but if they didn't speed it up that much, it would be very hard to see. Even accelerating twenty minutes to maybe 1.25 seconds, it's still pretty subtle and easy to miss.

So, net takeaway: the last link is the easiest to see what was going on, but it didn't really happen that fast. Nothing could.

Which also leads to a way of actually understanding just how slow light actually is. If something were transiting the sun very closely, the absolute fastest it could cross the whole disk at the widest point would be roughly four and a half seconds. Nothing can ever go faster than that.
posted by Malor at 12:02 AM on July 9, 2011 [5 favorites]

That SOHO clip was awesome - the CME it looked like the sun was blowing a smoke ring and trying to aim for the comet.

So was a coincidence, or is there a physics explanation for the location (i.e. the comet was influencing the sun corona somehow (I'm guessing corona - I don't know the proper terms))... Like - you'd think it wouldn't have much an effect on the sun, but... maybe it does?

Anybody know?
posted by symbioid at 12:15 AM on July 9, 2011

Chocolate Pickle wrote: There isn't anything to impact. The sun has no surface.

It is true that the sun has no definitive surface boundary. The material gets progressively denser towards the center. The photosphere is "the region from which externally received light originates" and is a "reference to the fact that it is a spheric surface perceived to emit light." It is commonly known as the "surface" of the sun, and is where the comet would cease to be visible upon immersion - otherwise known as an "impact."

Take your uncharity elsewhere.
posted by troll at 12:24 AM on July 9, 2011 [1 favorite]

Also, the "astronomers" link in the OP leads to Bad Astronomy, where Phil Plat states "...that comet really was just above the Sun’s surface, and most likely impacted the Sun or disintegrated from the heat."

If an astronomer is entitled to a colloquial, if technically incorrect, use of the terms "Sun's surface" and "impact," then so am I. Maybe you should read the links before you post.
posted by troll at 12:42 AM on July 9, 2011

Amazing phenomena. Good thing the Sun has a nice solid spin on it and all that gravity is holding it together. It would be horrible if big flaming pieces of it started shooting out into the solar system and setting planets on fire and whatnot.

It would really mess up the Summer. Everyone would have to move into caves deep inside the Earth for protection from all the flying molten pieces of Sun flying about.
posted by Skygazer at 2:27 AM on July 9, 2011 [2 favorites]

I think it was a Larry Niven story talking about the sun winking out of existence; even if the whole thing just went blip it would take a few seconds for the light to fade away because the sun is just That Big.
posted by seanmpuckett at 5:47 AM on July 9, 2011

Well, just like a transit of the Sun would take 4.5 seconds, if the entire thing went out 'at the same instant' (which is actually a concept that doesn't really exist in any kind of absolute sense, very noticeably so at astronomic distances), the center would stop glowing for an Earthly observer about 4.5 seconds before the edges would. You'd see darkness expand outward from the center.
posted by Malor at 6:38 AM on July 9, 2011

But we could come out of the caves at night.
posted by hal9k at 6:39 AM on July 9, 2011 [2 favorites]

Oops, I didn't think that through; halve that. You're seeing only halfway to the other side of the sun, so it would be about 2.25 seconds from the center ceasing until the edges ceased to glow.

(and that's presuming a magical on-off switch that instantly stopped all photon emission from the surface, which is way past silly.)
posted by Malor at 6:41 AM on July 9, 2011

Twin Comets Impact Sun
June 3, 1998

image of a comet impacting the sun. March 12, 2010 "the researchers believe that the comet contained heavier elements that do not evaporate as easily.... the comet was able to penetrate so deeply into the sun's chromosphere, not only surviving the extreme temperatures but the strong solar winds as well, before finally evaporating."
posted by hank at 10:29 AM on July 9, 2011

I love it just as much when these unimaginably energetic events are so subtle and boring to watch.
posted by cmoj at 10:42 AM on July 9, 2011 [1 favorite]

Malor: "(and that's presuming a magical on-off switch that instantly stopped all photon emission from the surface, which is way past silly.)"

So you think, my friend, so you think.

Stop by my place for a while, I will show you this little mechanism I've been building for the past decade in my closet. It's a beautiful piece of equipment. AND IT WILL DESTROY THAT INFERNAL SUN ONCE AND FOR ALL!!!! BWAHAHAHAHA.
posted by symbioid at 11:33 AM on July 9, 2011 [1 favorite]

Seems a little silly to come over. I should be able to see it fine from here, no? :)
posted by Malor at 12:11 PM on July 9, 2011 [2 favorites]

Hank, your second link is broken. Here is the correct address.
posted by troll at 12:56 PM on July 9, 2011

Death plunge of a dirty snowball
July 28, 2011 11:31
"Note to comets: stay away from the Sun." (SLYT)
posted by IvoShandor
posted by troll at 12:00 PM on July 28, 2011

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