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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."

9 of 37 comments (clear)

  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.

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    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 /.

  2. 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...

  3. 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.

  4. 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.

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  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

  6. 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.

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    Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
  7. 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.