It’s tough to be a comet.
You spend most of the time — billions of years, really — out in deep space where it’s cold and dark. Of course, since you’re mostly made of ice, that’s not so bad. After all, the Sun is hot, and if you venture too close…
Well, you know what happens then. And such was the fate of Comet SWAN, discovered just a few days ago as it plunged headlong into the seething fires of the Sun. And I have video!
That was made from images taken by NASA’s SOHO satellite. In fact, the comet is named SWAN because it was first seen in the SOHO SWAN camera, designed to look for ultraviolet light coming from hydrogen. Here’s the thing: no comet has ever been seen before in that camera, including the phenomenally bright comet Lovejoy from a few months ago. But Lovejoy got incredibly bright overall, while this new comet never did brighten much. Comet SWAN must have undergone some sort of outburst to make it so bright and then fade again; that’s happened before.
Here’s another shot of it from SOHO:
[Click to enhalleyenate.]
Comets like these are called Kreutz family Sun grazers, a collective group of comets on similar orbits that take them very close to the Sun’s surface. Some survive, like Lovejoy did, and some… don’t.
Image credit: NASA/SOHO. Music in the video was "Heavy Interlude" by Kevin MacLeod, used under Creative Commons license from incompetech.com.
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)
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Comet Lovejoy was only discovered in late November, but it’s had quite a ride. It was quickly determined to be a Sun-grazer, the kind of comet that plunges down very close to the Sun in its orbit. The date of this solar close encounter: yesterday!
That’s a shot of it using SOHO, a solar observatory orbiting the Sun. The Sun itself is blocked by a mask, and the white circle represents its outline. The comet is obvious enough! The line through the top of it is not real; that’s called blooming and it happens sometimes when a bright object is seen by a digital detector. The electrons in the chip overflow the pixels and leak into adjacent ones. The comet got very bright as it neared the Sun, almost as bright as Venus! This picture, taken on December 15th at 22:36 UT, was shortly before closest approach: a mere 180,000 km (110,000 miles) from the Sun’s searing surface.
Amazingly, after the comet screamed past the Sun, and to the surprise of many, it survived. A lot of comets don’t make it through such an event, but this one did. Here’s a video of the comet reappearing from behind the Sun, as seen by SDO; watch closely or you’ll miss it!
Nifty. But on the way down it had several interesting things happen to it. Read More
Back in the day, it used to be that most new comets and asteroids were discovered by astronomers diligently sitting at their eyepieces, spending one cold night after another patiently scanning the skies. The advent of robotic astronomy changed that, and now the vast majority of all celestial newcomers are found automatically.
But Australian "amateur" astronomer Terry Lovejoy changed that last week: not only did he discover a comet — which isn’t that unusual, though still cool — but it turns out to be a sungrazer, a comet that plunges deep down to the center of the solar system, practically skimming the Sun’s surface.
Here is Lovejoy’s discovery image:
This is a combination of three images; the comet moves between exposures a bit so he re-centered the comet in each shot and added them together. It’s the fuzzy blob in the middle of the frame. The comet’s official name is C/2011 W3 (Lovejoy), and on December 16th it will pass just about
880,000 km (500,000 miles) from the Sun’s surface — only a little bit more than than the radius of the Sun itself! 180,000 km (110,000 miles) — less than half the distance from the Earth to the Moon!* This may be a death dive, since many such comets don’t survive the intense heat of the Sun from that distance. Comets are composed of lots of rock held together by ice, so when the ice vaporizes, the comets disintegrates.
It’s not known how many comets orbit the Sun in our solar system, but the number may be in the trillions. They spend a long, long time in the deep reaches of the outer solar system, only occasionally plunging toward us. If they pass near a planet their orbit can be changed, and some wind up on paths that take them so close to the Sun they burn up. These are called sungrazers.
That is what NASA’s Solar Dynamic Observatory saw on the evening of July 5/6, 2011. This has been seen many times before, but this is the first time one has been seen streaking directly across the Sun’s face!
Here’s the video (I recommend watching it in HD — at least 720p –to make the comet easier to spot):
Did you see it? The whole event took about 20 minutes to unfold, and is seen here highly compressed in time. This is no perspective effect; that comet really was just above the Sun’s surface, and most likely impacted the Sun or disintegrated from the heat. Astronomers are even now going over the data from the event to see if they can determine the comet’s fate.
On the NASA Sun-Earth news site is more information, and a very cool video from SOHO showing the comet’s approach to the Sun.