Transit of Venus today!

UPDATE:  This other NASA site shows you what it will look like from your location, and also provides a live feed.

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Today you’ll get the rare chance to see a transit of Venus across the Sun. You’ll probably be dead by the time the next one occurs. A piece at the Guardian will answer all your questions, including these:

What is the transit of Venus?

A rare astronomical event that happens when Venus travels across the face of the sun and appears as a small black dot on its surface.

Here’s what it looks like (WARNING: DO NOT LOOK DIRECTLY AT THE SUN WITHOUT EYE PROTECTION!):

An astronomer points to Venus on a projection from the solar telescope at the Astrophysical Institute of Potsdam in Germany on 8 June 2004 – the century’s penultimate transit of Venus. Photograph: Sven Kaestner/AP

When does it happen?

Transits occur in pairs eight years apart. There are two in December that repeat every 121.5 years, and two in June that repeat every 105.5 years.

The last transit of Venus of the 21st century occurs on Tuesday and Wednesday (5 and 6 June 2012) depending on where you are viewing from. The transit starts at 11.04pm BST (6.04pm ET) on Tuesday, when it will be visible from the US. The final hour of the transit will be visible from the UK just before 5am BST on Wednesday (12am ET US), clear skies permitting. The transit will not happen again until December 2117.

How long does the transit last?

Venus takes nearly seven hours to cross the face of the sun, but the event is divided into four “contacts” that mark different phases of the transit. Venus makes first contact when it encroaches onto the disc of the sun. Twenty minutes later, on second contact, the planet will be fully silhouetted. On third contact, at 5.37am BST (12.37am ET), Venus will begin to leave the sun, and the transit will be over on fourth contact at 5.55am BST (12.55am ET).

NASA will host a live streaming of the transit (from Hawaii) that you can see here; it starts at 5:45 p.m. EST in the US or 11:45 p.m. London time.  The site links to other live webcams in Europe and America, which of course operate at different times.

Besides being a rare spectacle, the transit was used in what may have been the first international scientific collaboration: 200 astronomers observing the transit in 1769 and using trigonometry (see the method here) to calculate, from the transit time, the size of the solar system. Another article in the Guardian describes the endeavor (do read it: it’s informative and has some quite dramatic incidents):

The major British expedition for the 1769 transit was Captain Cook’s voyage to Tahiti. Following success with the measurements on the island, Cook sailed on. Cook’s return to England in 1771 allowed the final calculation of the sun’s distance to be made. The combined results from all the various missions were within about 4% of the modern accepted value of 93m miles (150m kilometres). At the next pair of transits, in 1874 and 1882, the accuracy was improved to 1%.

Only since the Second World War have radar experiments with radio telescopes bettered those results. Yet the 18th century transits will always stand out. They represent the first time in history that the distances to the Sun and planets were measured, and the first global scientific collaboration.

h/t: Martim

24 Comments

  1. Griff
    Posted June 5, 2012 at 10:30 am | Permalink

    In theory, we’re supposed to catch the end of it towards sunrise in the UK.

    But as it’s been raining all day and the sky is overcast with dense cloud, I won’t be getting up for it 🙁

  2. Posted June 5, 2012 at 10:41 am | Permalink

    I’m going to the natural history museum in NY later today to watch the broadcast from Hawaii!

    • Posted June 5, 2012 at 6:57 pm | Permalink

      UPDATE: I got to see Neil deGrasse Tyson! And then on the subway ride home, I sat across from Kevin Bacon and his wife! All in all a good day.

      • John Scanlon, FCD
        Posted June 6, 2012 at 10:25 am | Permalink

        What was your angular separation from KB?

        Use radians if you prefer.

  3. Posted June 5, 2012 at 10:53 am | Permalink

    DO NOT LOOK DIRECTLY AT THE SUN WITHOUT EYE PROTECTION!

    Don’t worry. I’ll go watch it at night.

  4. daveau
    Posted June 5, 2012 at 10:54 am | Permalink

    Those eclipse glasses from last month will sure come in handy. $1.50 well spent.

    • Griff
      Posted June 5, 2012 at 11:15 am | Permalink

      Will the 3D glasses I got for watching Prometheus 3d work?

      • daveau
        Posted June 5, 2012 at 11:30 am | Permalink

        I’m not a scientist*, but I don’t see why not…

        *I sure as hell hope that qualifies as a disclaimer.

        • Griff
          Posted June 5, 2012 at 11:33 am | Permalink

          Cool. Transit in 3D!! I’m sure the permanent eye damage will be worthwhile 🙂

      • Gregory Kusnick
        Posted June 5, 2012 at 2:22 pm | Permalink

        You won’t see the transit in 3D, if that’s what you mean.

        Nor will they offer much protection against eye damage. Proper eclipse glasses are so dark you can’t see anything but the sun. If yours aren’t that dark, do not use them to look directly at the sun.

        Basically, anything short of welding goggles is a no-go.

        • daveau
          Posted June 5, 2012 at 2:31 pm | Permalink

          Yes. For all you kids out there, Griff & I were just joking around. A proper eclipse filter, or welding glasses with a value of 14 or higher are the appropriate eyewear. Also, don’t nail yourself to a cross to see if you will be resurrected in three days. Leave that to the professionals.

          • Griff
            Posted June 5, 2012 at 2:36 pm | Permalink

            You mean I don’t get to see Transit 3D?

            Awww.

            I tried nailing myself to a cross once. Could never get that last hand.

            • daveau
              Posted June 5, 2012 at 2:52 pm | Permalink

              A professional would know that you need to hire a bunch of Romans to do the nailing.

              Ben & I were set up next to Ikuo Nakamura at the Grand Canyon for the eclipse. He shot the whole thing in time-lapse 3D, but I’m sure it is not available yet. Here’s a sample of his work at Easter Island.

              He demo’d it for us on an iPhone with some viewer that you can get at WalMart for $10.

  5. Grania Spingies
    Posted June 5, 2012 at 11:23 am | Permalink

    DO NOT LOOK DIRECTLY AT THE SUN WITHOUT EYE PROTECTION!

    If I could actually see the sun I would worry about not looking at it 🙁

    I’m going to have to enjoy this via the interwebz.

    • Griff
      Posted June 5, 2012 at 11:29 am | Permalink

      why couldn’t it have happened a week ago?

      • Grania Spingies
        Posted June 5, 2012 at 12:52 pm | Permalink

        I suspect it’s a Cosmic Conspiracy.

  6. Posted June 5, 2012 at 11:49 am | Permalink

    If my calculations are right, the transit-in-progress will set behind the Phoenix downtown skyline when viewed from that butte behind Tempe Diablo Stadium. Late notice, I know, but anybody in the area who wants to join me is more than welcome to. I’ll be there in a few hours with the 400 and the solar filter.

    It’ll be a fun event to witness and there’ll probably be an interesting photo right as the Sun starts dipping behind the skyscrapers, but it won’t be anywhere near as special a photographic event as the Eclipse a couple weeks ago…and, yes, I do still have some more post-production work to do on that one…once I clear out my schedule….

    b&

    • daveau
      Posted June 5, 2012 at 12:48 pm | Permalink

      I’ll see a finished print by the end of the year, right? 😉

      If anyone is going, bring Ben some jerky. He loves jerky. I’ll pay you back.

  7. Ichthyic
    Posted June 5, 2012 at 1:57 pm | Permalink

    WARNING: DO NOT LOOK DIRECTLY AT THE SUN WITHOUT EYE PROTECTION!

    …unless you are xian, in which case your Jesus Glasses will protect you, so stare away!

  8. Hempenstein
    Posted June 5, 2012 at 2:01 pm | Permalink

    I’d love to try to watch live, but Pittsburgh is in full cloud cover so I’ll watch the replay. I have an HPLC run I need to get in, anyway.

  9. MadScientist
    Posted June 5, 2012 at 2:12 pm | Permalink

    Unless you’re in Hawaii or Alaska you won’t see much. I don’t think there are any solar observatories in Hawaii though. If only the full event were visible from Az – the Pierce-McMath telescope projects a beautiful HUGE image of the sun. I’m in the antipodes and it’s very hazy and likely to cloud over – otherwise it’s a great place for this event. There *was* a solar observatory near here 40+ years ago.

  10. corio37
    Posted June 5, 2012 at 4:06 pm | Permalink

    Never mind the transit of Venus — shouldn’t we do something about that giant blocking the Sun?

  11. Mark Joseph
    Posted June 5, 2012 at 10:54 pm | Permalink

    Only very slightly tangential to this thread, but you all may want to take a look at today’s comic at Zen Pencils: http://zenpencils.com/comic/52-phil-plait-welcome-to-science/
    It’s a quote from Phil Plait, and is quite wonderful.

  12. Suren Das
    Posted June 8, 2012 at 4:44 am | Permalink

    It’s unbelieavable but true that I have seen black spot on rising sun few days before 5th Jun 2012. While on morning walk, at about 5.35 to 5.40am I could saw infront of me a red rising sun with a vivid black spot,sky was clear,no appearance of cloud at all. Never thought of venus trnsition in coming days. On discussion of venus transition, I could recollect the picture in front of me but could not recollect the exact date. It’s seems to be ridiculous but I can say it has happend with me.


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