Hubble To Use the Moon To View Transit of Venus 37
astroengine writes "As we recently discussed, on June 5 or 6 this year — the exact time and date depends on where you are in the world — Venus will be visible as a small black circle crossing the disk of the sun. Usually, the Hubble Space Telescope would have no business observing this event — the sun is too close for its optics. But plans are afoot for Hubble to observe the reflected sunlight bouncing off the lunar surface during the transit. As the sunlight will pass through the Venusian atmosphere, the transit will provide invaluable spectroscopic data about Venus' atmospheric composition. This, in turn, will help astronomers in characterizing the atmospheres of planets orbiting other stars."
No business (Score:3, Informative)
The reason for the "no business" part is pretty simple: Hubble's optics would burn out if exposed to direct sunlight.
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Actually, according to (MBM) my bad memory from the book "Hubble Wars....", if it were to point at or near the sun, some sensors would detect that, and slam the front lid shut very very quickly. That safety system was one of the things they did right with the Hubble. I don't know if it can be overridden.
Now, the implementation of that safety system had something wrong. It literally slams shut. Other similar sized instruments (Hubble was about #19 or #24, according to MBM, in a series of large space tele
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Optics are at risk also (Score:2)
Both the optics and the sensors are at risk. The optics heat up with direct exposure to the Sun's rays. The heating can cause them to crack.
From Jamey L. Jenkins, "The Sun and How to Observe It":
"A catadioptic telescope should never be used for solar projection because of the risk of damaging the internal components of the telescope from the heat of the sun."
Catadioptric = optical system with both mirrors and lenses. Hubble has lots of mirrors, built to be lightweight, but probably more susceptible to cr
couldn't they just do this with earth based? (Score:2)
Someone help me out here, but couldn't they observe it directly with earth based telescopes without having to look at a reflected image? Wouldn't a direct observation (albeit through he earths atmosphere) be better in this case?
Re:couldn't they just do this with earth based? (Score:4, Informative)
Not really. They'd have earth's atmosphere to account for. Since what they're trying to look at is Venus' atmosphere changing the spectrum of sunlight, getting Earth's atmosphere into the act would complicate things quite a bit...
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Why use earth-based telescopes? Why not turn Hubble directly towards Venus as it does its transit? Is there just too much light for Hubble to get a good spectrographic reading by doing it directly?
if so, how will this help us when looking at exoplanet atmospheres, since we will be directly looking at their atmospheres as they have transits in front of bright stars as well?
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Why not turn Hubble directly towards Venus as it does its transit? Is there just too much light for Hubble to get a good spectrographic reading by doing it directly? if so, how will this help us when looking at exoplanet atmospheres, since we will be directly looking at their atmospheres as they have transits in front of bright stars as well?
There is way too much light to look directly at it, since the Hubble would have to be pointed at the sun to do this. Other stars and other planets are much further away, so their light will be dim enough to be safe to point at.
If you want to see the transit of Venus from Earth, you'll need to be wearing special solar glasses that blot out everything but the sun itself. Unless we put a big solar filter on the Hubble, we can't point it at the sun.
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Why not turn Hubble directly towards Venus as it does its transit? Is there just too much light for Hubble to get a good spectrographic reading by doing it directly?
Yes, because it's very hard to get good readings out of sensors fried to a crisp by the sun's light. As a rule (as in, the control software prohibits it) the Hubble is not allowed to get within 50 degrees of the sun.
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You can use earth-based telescopes with a similar sort of trick to study Earth's atmosphere, of course. At work [naoj.org] last December, we had astronomers using an 8-meter telescope to do high-res spectroscopy of the light reflected off the moon during a total lunar eclipse, since during totality that light has all passed through Earth's atmosphere.
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To a degree you answered your own question. Trying to look for spectrographic data about Venus' atmosphere, while looking through you own would be like trying to listen to a radio station transmitted from Venus while simultaneously listening to a station broadcasting here. The signal you're trying to find would be lost in the noise from the local signal. That said, it should be possible to subtract earth's atmosphere from the signal, but its just a lot easier and cleaner to use Hubble, and the telescopes do
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Someone help me out here, but couldn't they observe it directly with earth based telescopes without having to look at a reflected image? Wouldn't a direct observation (albeit through he earths atmosphere) be better in this case?
A direct observation will be different. It's not like using Hubble negates also using Earth bound telescopes. If it doesn't happen again for a while why not use Hubble in addition to earth bound telescopes?
Venus is too close (Score:2, Troll)
If you moon me, I can see Uranus.
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I think they meant "the sun is too close [a star] for its optics [to handle the light intensity]"
Transit of Venus, eh? (Score:4, Interesting)
As a a professional astronomer myself, I just hope they have more luck than this guy:
https://en.wikipedia.org/wiki/Guillaume_Le_Gentil [wikipedia.org]
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Science is awesome. (Score:2)
"We will just use the moon as a projection surface to gather spectroscopic data from a tiny speck moving across the sun. Because we can. We're that awesome."
Men and their toys ;-)
Wait, what? (Score:2)
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I think they mean "the sun is too close [a star] for its optics [to handle the light intensity]"
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They tried it before. http://thedoghousediaries.com/974 It must be been before the camera was upgraded.