The Sun fries a comet and we got to watch

By Phil Plait | January 19, 2012 4:11 pm

In July of last year, I wrote about a comet that passed extremely close to the Sun. Astronomers have now had a chance to pore over that data, and were able to determine some very cool stuff.

First, here’s the video of the comet’s fiery demise (watch it in HD to make it easier to spot the comet):

See it? It’s faint, but there. Actually, there are a lot of observations from multiple observatories and detectors, which allowed astronomers to find out quite a bit about this doomed chunk of ice and rock.

For one thing, it was screaming along at about 650 kilometers per second (400 miles/second) as it flamed out. To give you an idea of how flippin’ fast that is, it would’ve crossed the entire United States in about eight seconds.

Yeah, I know.

It also passed an incredible 100,000 km (62,000 miles) above the Sun’s surface. Have you ever stood outside on a hot day, and thought the Sun would cook you? Now imagine the Sun filling half the sky. That’s what that comet saw. No wonder it disintegrated.

As it approached the Sun, it was watched by NASA’s Solar Dynamics Observatory. In its final 20 minutes or so, the comet broke up into a dozen pieces ranging from 10 – 50 meters in size (and no doubt countless smaller ones too small to detect), with a tail of vaporized material streaming behind it that went for thousands of kilometers. For that size, it would’ve had a mass of hundreds of thousands of tons — about what a loaded oil tanker weighs on Earth!

We’ve learned a lot about how comets break up and disintegrate by observing this event, but it’s raised further questions: like, why did we see this at all? Comets are faint, and to be able to see it this way against the bright Sun is odd. It was definitely one of the brightest comets seen, but it’s interesting to me that it appears to glow in the ultraviolet, as it did in the above video. That means, at that wavelength, it was brighter than the Sun! It wasn’t like a meteor, burning up as it slammed through material, so some other process must have affected it. I suspect that the Sun’s strong magnetic field may have had something to do with it; in the far ultraviolet magnetism is a strong player. Gas under the influence of intense magnetic fields can store a lot of energy, which is why sunspots — themselves the product of magnetic squeezing — look bright in UV.

Perhaps as the comet broke up, the particles inside got excited by the magnetic fields of the Sun and glowed. I’m no expert, and I’m spitballing here. The thing is, no one is exactly sure. But that doesn’t mean we won’t find out. Nothing makes a scientist’s noggin itch as much as a mystery like this, something apparently misbehaving.

One of the single most important words in science is "yet". We don’t know yet. But we will. Someone’ll figure this out, and we’ll have one more victory in our quest to better understand the Universe.

Science! I love this stuff.

Credits: Credit: NASA/SDO; SOHO (ESA & NASA)


Related posts:

- NASA’S SDO captures final moments of a comet streaking across the Sun
- Amazing video of comet on a solar death dive
- Ten Things You Don’t Know About Comets
- The comet and the Coronal Mass Ejection

Comments (18)

  1. The first time I looked I got a video named “smiley face.avi”, but I got the right video the second time.

  2. Mike Saunders

    Yeah some smiley face.avi action over here too.

  3. Messier Tidy Upper

    Great video – but gee, you to be quick and look hard to catch it! 8)

    Good thing the arrow was there.

    It also passed an incredible 100,000 km (62,000 miles) above the Sun’s surface. Have you ever stood outside on a hot day, and thought the Sun would cook you?

    Stood? Hah! trying working outside in it! :-0

    That was I was doing just yesterday in 32 degree Celsius (89.6 Fahrenheit) heat & I’ve worked in far hotter too.

    Now imagine the Sun filling half the sky. That’s what that comet saw. No wonder it disintegrated.

    The thing that really amazes me is that Comet Lovejoy – and some other sungrazers actually
    manage to survive it! 8)

  4. Dragonchild

    It’s poetry in motion
    Sol neared her glowing face to me
    Deeper than any ocean
    Brighter than Moon at perigee
    But she blinded me with science
    (She blinded me with science!)
    Vaporized me astronomically

  5. Wzrd1

    Hmmm…
    “It also passed an incredible 100,000 km (62,000 miles) above the Sun’s surface. Have you ever stood outside on a hot day, and thought the Sun would cook you?”
    I’ve been outside when it was a bit over 50C, didn’t melt, but WANTED to. Fortunately, it was windy, as usual, so sweating kept me from evaporating (Persian Gulf region and I didn’t go outside without two water bottles in my pockets AND a camelback).

    Phil, the intense UV, thermal and even light would certainly start ionization of the comet. Add in ions from the sun itself at that range. Now, stir gently with super strong magnetic fields at fairly close range.
    I’m willing to bet that thing was glowing in bright in x-ray AND gamma too, by a little bit! Under those conditions, electrons get positively dizzy riding around magnetic fields!
    Middle aged Sol is NOT a gentleman when you get too close!
    Just think what we could learn if we could make a probe that could survive such proximity to the sun!

    I remember some Swedish solar photos that showed high resolution of sunspots, as in full frame shot at high resolution. Plus the usual convection cells.
    I could look at them and watch them all day long!
    Sol just has a positively magnetic personality! ;)

  6. Keith Hearn

    Phil,

    You said “Gas under the influence of intense magnetic fields can store a lot of energy”. I doubt what we were seeing was gas, it was probably plasma, which really does interesting things in intense magnetic fields. Glowing in UV is perfectly ordinary for stuff at that temperature, just basic blackbody radiation from a hot plasma.

  7. I actually saw the video somewhere else and came back here to ask a question that has always bothered me. What is the definition of the “surface” of the sun? The article I saw talked about the atmosphere of the sun and how far it was from the surface when it disintegrated. By one definition the Earth is inside the sun’s atmosphere. Is the surface that glob of heavier elements near the core? I’m assuming it isn’t.

    Now, same question, but with Jupiter.

  8. @ ^ Ibid : From what I understand, the photosphere layer (click on my name here for wiki-link) is conventionally defined as being the surface of the Sun & vice-versa. For Jupiter and the other gas giant planets the “surface” is generally defined as the cloudtops since there is no solid surface. I agree that this is rather problematic and arbitrary esp. for the latter but it’s what they tend to use.

    @ 5. Wzrd1 – January 19th, 2012 at 8:39 pm :

    I’ve been outside when it was a bit over 50C, didn’t melt, but WANTED to. Fortunately, it was windy, as usual, so sweating kept me from evaporating (Persian Gulf region and I didn’t go outside without two water bottles in my pockets AND a camelback).

    Yikes! :-o

    Okay, you win! ;-)

    The hottest conditions I’ve ever experienced are 45 Celsicus (113 Fahrenheit) days here in Adelaide, South Australia. I’ve been outside in that but not for long. Fifty C (122 F)? Ouch, that is hardcore.

    BTW. what’s a “camelback”?

    @4. Dragonchild : Are those lyrics to a song?- if so, please can you say who sung it and what the title is? If its something you’ve just come up with then, hey, I like it. :-)

  9. Navneeth

    For that size, it would’ve had a mass of hundreds of thousands of tons — about what a loaded oil tanker weighs on Earth!

    Why the comparison between mass and weight? A fully-loaded tanker will have the same mass anywhere! It have been simpler just to say, “about the same [mass] as a loaded oil tanker”, no?

  10. Nigel Depledge

    MTU (8) said:

    BTW. what’s a “camelback”?

    Flexible water pouch worn in a backpack, and connected to a drinking tube.

  11. JMW

    Now imagine the Sun filling half the sky. That’s what that comet saw.

    Well, not to pedantic, but…

    …I drew a circle that represented the sun, and then picked a point at 62,000 scale miles from its surface. Assuming I’ve done the math correctly, the sun would have spanned about 134 degrees from the comet’s point of view. Not quite half the sky, but then what’s 46 degrees when you’re that close to the surface of the sun?

  12. dcsohl

    Well, no… if you assume the surface of an object to be a smooth sphere then the only way for it to occupy 180 degrees is to actually be standing ON that object. When Phil says “half the sky”, as he does here and as he does in the “boiling planet” post, I’ve been assuming he meant 90 degrees. But you say 134, which doesn’t fit any definition of “half the sky”.

    Must be poetic license. Phil, I’m gonna need to see that license — when was the last time you had it renewed?

  13. Dragonchild

    @8. Messier Tidy Upper
    The lyrics are mine; I just parodied the first verse of Thomas Dolby’s “She Blinded Me with Science” from the point of view of the poor, doomed comet. If you haven’t heard it before I’m sure you can find it on YouTube — if SOPA/PIPA doesn’t shut it down!

    It came to mind because Phil wrote, “Science!” One of the ongoing effects in the song is the voice of late, great Magnus Pyke shouting that word.

  14. JohnDoe

    @Boingo: I never get the right video on the front page, but always to matching video if I open just a specific post.

  15. Messier Tidy Upper

    @13. Dragonchild : Cheers. Good work there. :-)

    @10. Nigel Depledge : Thanks for that explanation too. :-)

  16. Matt B.

    @ 11 & 12,

    The sky is a hemisphere, so for the sun to fill half of it (area-wise) it would have to appear 120 degrees wide. Therefore the distance of the comet from the center of the sun would be (2/√3) * R☉, and its distance from the surface of the sun would be (2/√3 - 1) * R☉ = 0.1547 * 696,342 km = 107,724 km.

    Ha! Phil was DEAD ON.

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