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Hubble To Use the Moon To View Transit of Venus

Posted by Soulskill on from the oh-yeah-it-was-easy-i-just-used-the-moon dept.

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."

37 comments

  1. No business by girlintraining · · Score: 3, Informative

    The reason for the "no business" part is pretty simple: Hubble's optics would burn out if exposed to direct sunlight.

    --
    #fuckbeta #iamslashdot #dicemustdie
    1. Re:No business by siddesu · · Score: 2

      Actually, the optics may survive, but the sensors will not.

    2. Re:No business by Anonymous Coward · · Score: 2, Interesting

      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 telescopes. Most of the others were pointing down at the earth and were classified) had systems to prevent the lid from slamming, simple things like magnetic brakes (again, according MBM fo reading the book..).

      In the first few weeks or days the Hubble was in space, they had a heck of a time establishing controlled 'flight.' Then, it drifted and aimed toward the sun. The lid slammed shut. The vibrations further moved the craft, and it took days or weeks (see MBM) to reestablish control.

      I suggest you don't believe me. Find the book, and then find critics of the book. More fun than /.

    3. Re:No business by siddesu · · Score: 1

      Given how they botched the testing of the primary mirror, I would not put it past them. But we were discussing the hypothetical situation in which sunlight actually enters the telescope.

  2. couldn't they just do this with earth based? by DJRumpy · · Score: 1

    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?

    1. Re:couldn't they just do this with earth based? by rewt66 · · Score: 3, 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...

    2. Re:couldn't they just do this with earth based? by Genda · · Score: 1

      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 doing the serious analysis of atmospheres of exoplanets are space telescopes. Because one of the most important things we're looking for is water and we have a hard time seeing that correctly in an atmosphere full of water.

    3. Re:couldn't they just do this with earth based? by xevioso · · Score: 1

      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?

    4. Re:couldn't they just do this with earth based? by Anonymous Coward · · Score: 0

      Actually, you can use a ground based telescope for that observation, and you can do some interesting science.
      But we have three advantages using Hubble:
      1 - In space, you can observe the UV (absorbed by the Earth's atmosphere). And it is one of the promising light for the science objective (http://arxiv.org/abs/1112.0572)
      2 - There is no red-blueshift for Venus at the opposition, so the Earth's absorption lines will blend some of Venus lines
      3 - Some exoplanets observations are already made with Hubble, it is very interesting to compare!

    5. Re:couldn't they just do this with earth based? by Henriok · · Score: 1

      Hubble's sensors are made to detect faint stuff that Earth based telecopes just can't detect. Hubble's sensors will fry immediately.

      --

      - Henrik

      - when the Shadows descend -
    6. Re:couldn't they just do this with earth based? by CycleMan · · Score: 2

      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.

    7. Re:couldn't they just do this with earth based? by Chris+Burke · · Score: 2

      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.

      --

      The enemies of Democracy are
    8. Re:couldn't they just do this with earth based? by similar_name · · Score: 1

      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?

    9. Re:couldn't they just do this with earth based? by Anonymous Coward · · Score: 1

      Idiot. I know you were being sarcastic, but try to make it clearer. To those who missed the caustic sarcasm, NEVER NEVER NEVER look at the sun through a telescope or binoculars. You *will* be blinded.

    10. Re:couldn't they just do this with earth based? by Neil+Boekend · · Score: 2

      Haven't tested looking through it, but holding a white sheet of paper in the focal point was quite "enlightening". We used a 15 cm telescope. You can write with the scorchmarks on the paper with it. Just move fast enough because if you don't you'll set the paper on fire.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    11. Re:couldn't they just do this with earth based? by Anonymous Coward · · Score: 0

      Correction: try looking at the sun through a telescope that has an 8 foot diameter.
      http://www.youtube.com/watch?v=YoMjBkKOkPc

    12. Re:couldn't they just do this with earth based? by Shag · · Score: 1

      You can use earth-based telescopes with a similar sort of trick to study Earth's atmosphere, of course. At work 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.

      --
      Village idiot in some extremely smart villages.
    13. Re:couldn't they just do this with earth based? by Defenestrar · · Score: 1

      Only a little bit. The solar spectrum from earth and space are extremely well known. A space based look is definatly the most useful, but accounting for our own atmosphere isn't all that hard.

  3. Venus is too close by acariquara · · Score: 1, Troll

    If you moon me, I can see Uranus.

    --
    Dear aunt, let's set so double the killer delete select all
  4. Sun's too close, but not the moon? by Anonymous Coward · · Score: 0

    The summary says "the sun is too close for its optics", so instead they are going to point it at the moon instead. Makes perfect sense.

    (I assume astroengine meant the sun is too bright at this proximity for the hubble to point at directly).

    1. Re:Sun's too close, but not the moon? by siddesu · · Score: 1

      Also, it is a good way to test indirect measurement methods. Next up: spectroscopy of reflections from invisible planets far away.

    2. Re:Sun's too close, but not the moon? by RaceProUK · · Score: 1

      The intensity of light reflected from the Moon compared to the Sun is like a match compared to the largest nuke ever made. So the proximity isn't a question of focal lengths, but more a question of not melting Hubble's sensors.

      --
      No colour or religion ever stopped the bullet from a gun
    3. Re:Sun's too close, but not the moon? by AC-x · · Score: 1

      I think they meant "the sun is too close [a star] for its optics [to handle the light intensity]"

  5. Transit of Venus, eh? by Dusty101 · · Score: 3, 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

    1. Re:Transit of Venus, eh? by RenderSeven · · Score: 1

      Sure, but according to your link "He got back his seat in the academy, remarried, and lived apparently happily for another 21 years." I can think of quite a few people that would call that an enviable "win"!

    2. Re:Transit of Venus, eh? by camperdave · · Score: 1

      Go insane because you miss an eclipse? Guess I don't have what it takes to be an astronomer.

      --
      When our name is on the back of your car, we're behind you all the way!
  6. Science is awesome. by GeekDork · · Score: 1

    "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 ;-)

    --

    Fight hunger. Filet a politician and send him to a 3rd world country of your choice.

  7. Wait, what? by Robert+Zenz · · Score: 1

    Can somebody please assist me here: Sun is too close to Hubble, but Moon is fine?

    1. Re:Wait, what? by Anonymous Coward · · Score: 0

      Somehow you're missing the obvious - would you care to stare at the sun with a set of binoculars? How 'bout the moon? It's not the distance, but rather the fact that the sun is a massive nuclear furnace that would fry Hubble's sensors (if all the safeties were overridden and it was pointed in that direction), whereas the moon is, well, not so much. ;)

    2. Re:Wait, what? by Anonymous Coward · · Score: 0

      Somehow you're missing the obvious - would you care to stare at the sun with a set of binoculars?

      Do not stare at the sun with remaining eye!

    3. Re:Wait, what? by AC-x · · Score: 1

      I think they mean "the sun is too close [a star] for its optics [to handle the light intensity]"

    4. Re:Wait, what? by Robert+Zenz · · Score: 1

      That makes much more sense, thanks.

    5. Re:Wait, what? by Ripley · · Score: 1

      They tried it before. http://thedoghousediaries.com/974 It must be been before the camera was upgraded.

  8. Optics are at risk also by opentunings · · 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 cracking as a result.

    1. Re:Optics are at risk also by Anonymous Coward · · Score: 0

      Catadioptric telescopes are usually Schmidt(-Cassegrain) or Matsukov designs, with a corrector glass plate at the front, a primary mirror of approximately the same size at the back, and a small secondary mirror in the center of the corrector that bounces the light back through a hole in the center of the primary mirror to the eyepiece/camera/spectrometer/... You usually don't count glass in the eyepiece towards the "catadioptric" label, otherwise even a newtonian reflector would be a catadioptric. Hubble is basically a Ritchey-Chretien, where the secondary mirror is held in place by four metal vanes(?), which result in the "star shape" of bright objects.

      You can destroy basically anything near the focal point with even a moderately sized telescope.. The primary mirror will won't care about the sun, as it is probably >>95% reflective.