Worst video ever
Cool subject, poor video
Boffins in California report that they have managed to track the course of an unusually resilient comet as it crashed deep into the Sun before finally being crisped. "We believe this is the first time a comet has been tracked in 3-D space this low down in the solar corona," says Claire Raftery, a post-doctoral researcher …
The sun may be hot, but the only way that the comet 'sees' that is by absorbing radiation from the sun (no conduction / convection in space!). I would think that apart from the comets own reflectivity, the material that gets vaporised off the surface of the comet could also shield it from some of the radiation. The comet will only heat up at a rate depending on it's temperature, the quantity of water boiled off and the radiation actually absorbed.
As for the other message about mainly water or not, I though that the tail is normally formed from bits left behind after the water boils off ejecting parts. The length of the tail in this case may be due to the volume of water boiled off before meating it's maker (or a decendant of it!)
You can use any prefix you want (gotta love the metric system) but if you like megametres you don't have to go into space to use them. New York is about 5.5Mm from London.
You probably do need to be in space to use gigametres though - the Earth is approx 157Gm from the Sun.
You have to look a lot further afield to use petametres, examtres, zettametres and yottameteres. I had to go to Wikipedia in fact :D
"(100,000 degrees C is ) Shirley no more than 10 or 20 thousand kelvin, or thereabounts?"
Nope, 100,000 celcius = 100,000 - 273.15 kelvin, or 99,726.85 degrees kelvin.
So, ot all intents and purposes, still 100,000 with reasonable rounding.
Although Wikipedia lists the surface temperature as 5,778 degrees Kelvin. So, who's right, Wikipedia or El Reg?
It was talking about the chromosphere, which IIRC peaks out at around 20,000 kelvin, but is more nominally in the 5,000 K to 6,000 K range. (Source: dimly remembered astronomy course taken at Foothill Junior College when I was in 9th grade roughly 35 years ago ... I believe the data came from Skylab's Solar work, but I could be wrong, and I can't be arsed to look it up.)
The sun doesn't actually have a surface, it's just a big ball of gas that gets gradually thinner the further you get from it's center. What you see as the 'surface' is the point where the gas is dense enough to go from transparent to opaque. And yes, this point is cooler than the rest of the atmosphere above it. Why this is the case is still poorly understood.
Not too surprising really, considering comets are rocks with a little ice, not dirty snowballs.
Comet = A rock with an elliptical solar orbit.
Asteroid = A rock with a circular solar orbit.
Same stuff, different orbit.
The tail of a comet is an electrical phenomenon. As it moves nearer to the sun the comet changes its state of charge which takes ionized particles of rock dust with the shed electrons. Sort of like electrical discharge machining (Or a big fluorescent light without the glass tube).
Hear me now, believe me later... One of these days astronomers are going to have to admit they're wrong and come to grips with the data they've already collected. The 'dirty snowball' theory gets less rational with every probe we send. It's getting laughable now.
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