Incredible Images of the Sun 239
shelterit writes "A new swedish telescope facility in La Palma uses a new technology to remove the blurriness of the atmosphere to snap new and astonishingly sharp images of the sun. Want to have a closer look at the surface of it? Reminds me of paintings I did as a kid."
Also on MSNBC (Score:5, Informative)
Re:Hmm (Score:5, Informative)
Buried in the site (Score:5, Informative)
Bloody slashdotting (Score:2, Informative)
another link (Score:5, Informative)
This article [space.com] has the links.You can also zoom in and use the viewer.
mirror! (Score:5, Informative)
Re:GIFs??? (Score:5, Informative)
Re:Where is the 1600x1200 version? (Score:3, Informative)
whoops
extra link. (Score:4, Informative)
Re:GIFs??? (Score:3, Informative)
Re:Hubble? (Score:5, Informative)
Re:Also on MSNBC One Question from article. (Score:2, Informative)
The highest resolution solar image ever shows part of the largest sunspot in Active Region 10030. The central region is dark because the strong magnetic fields there stop upwelling hot gas from the solar interior.
Ok, so that's SUPPOSED to explain why it's dark.. by I thought fire gave off light. While I can see a strong magnetic field blocking gas, shouldn't the surrounding gas give off enough light to see in the hole itself?
Or is the hole just THAT BIG? (But light from the sun gets to us, you'd think it could light a hole from all sides..)
Re:Also on MSNBC One Question from article. (Score:4, Informative)
The real reason they are "dark" is that they are cooler than the gas aronud them. Not that they are cold of course. From one of my astro textbooks:
Temperature of sunspot: 3900K
Temperature of surrounding photosphere: 5780K
Resulting in approximately 1/5 the flux (bolometric flux goes as T^4).
Doug
Re:Cooling question (Score:2, Informative)
Oddly enough, the CCD's generally are not cooled at all. The amount of light falling on the detector is actually not that great. Remember that each pixel corresponds to less than 0.1 x 0.1 arcsec, which means it covers about one-billionth of the solar surface (and hence the flux is one billion times less than integrated sunlight). Then you start taking very small slices in wavelength (0.01 nm or less, compared to the 100's of nanometers over the sun's emission peak in the visible wavelengths). Toss in a polarizer too (though they didn't use one in these observations), and next thing you know, you are running out of photons! That's why we need a big (by solar telescope standards) 4-meter telescope like the ATST ( http://atst.nso.edu [nso.edu]).
The exposure times in observations like these are also very short, on the order of 20 milliseconds or less, so there is no time for the dark current to build up during a long exposure (this is why nighttime CCD's, with exposures of minutes or hours, are often cooled). For some applications, even simple video rate CCD's can be used (the problem often being the small number of pixels).
As you might surmise, even if the detector isn't getting hit with that many photons, a lot of extra light is going through the telescope. Getting rid of waste heat IS a problem, and, as is the case with the Swedish Tower, often the main body of the telescope (entrance aperture -> main mirror -> instrument feed) is kept in a vacuum to reduce currents from heated air in the optical path. However, the Swedish Tower appears to be at the limit for the size of the entrance window (must be of optical quality and with minimal stress) that can be used (the entrance window is the size of the main lens on the Yerkes telescope [uchicago.edu] - the world's biggest refractor). That is why bigger telescopes like the GREGOR (1.5 m) and ATST (4 m) will be open, like nighttime telescopes, and will have to use different methods of thermal control. We can't go bigger than four meters now because of the limits of our thermal control capabilities.
do it yourself (Score:4, Informative)
I actually do this sometimes for a whole class of students, and for that I need a big, bright image they can all see, so I use the full aperture of my 8-inch scope. You just have to be careful to limit how long you have it pointed at the sun, because the heat can destroy your eyepiece (melts the glue).
Pictures in the flames (Score:4, Informative)
It's a phenomenon known as pareidolia [skepdic.com], and is quite a fascinating subject in its own right. Briefly, the human mind tends to seek patterns that it recognizes. When faced with a chaotic input, the mind creates patterns where none exist. Carl Sagan argues that faces in particular are hardwired into our recognition centres.
Incidentally, I can't see the face you're talking about there. (I'm probably not tired enough, as I find I'm very prone to seeing faces everywhere after an all-nighter.)
I did find a yin/yang symbol, though...
'Dark' Current explanation (Score:2, Informative)
Any matter will radiate energy according to its temperature - you've heard of this as Black Body Radiation.
Now in remote sensing you are often working in the IR region, because
a) this is where the 'windows' in the atmospheres absorption curve are
b) comparision of two bands give us intresting information - eg NVDI tells us the approximate vegitation cover from a simple comparisson of 2 channels.
In this case the detector must be cooler then the thing it is observing, otherwise your detector will respond to radiation emitted by itself and the equipment around it.
In the case of astronomical CCDs a similar effect is at work. CCDs work by creating small pockets in silicon that work very much like capacitors. The energy of photons (light particles) striking the material causes charge to build up in these pockets.
When enough charge has built up you can then 'read' the charge level in a similar way you can read memory (though clearly with more than a binary state) and infer the brightness of each pixel from the charge level.
This is fine for Video/Digital Photography use as a short exposure gets plenty of photons and you have an image.
In astronomy however you take exposure on a timescale of hours, sometimes your image maybe formed from a handful of photons. The problem here is that thermal processes in the CCD material itself can also deposit charge in the pockets by causing small stray currents and from phonon interaction in the silicon lattice itself.
If you cool the CCD in a dewar of liquid nitrogen, you limit these thermal issues, and have long exposures. The cost comes from building electronics that can survive the thermal shock of going from 25 Centigrade to -197 Centigrade in 10 minutes or so, and also having very very high quality CCDs to start with.
Been there, done that to extend the life of the 16inch telescope at my old Uni.
BTW - its not just an astronomy issue, consumers are starting to see it in digital cameras, especially SLR replacements. Take a look at a long exposure and you will see speccles - this is in part due to dark current, and in part due to increasing the gain of the CCD to try and limit the exposure length and therefore dark current issues - a tricky balance to get right, and some are better than others.
Re:GIFs quite common in sat imaging (Score:1, Informative)