The 2004 transit of Venus, image credit: Jay M. Pasachoff, David Butts, Joseph Gangestad, and Owen Westbrook

At the always-interesting blog Breaking Orbit, National Geographic space editor Victoria Jaggard has an interview with Jay Pasachoff, Field Memorial Professor of Astronomy, on next year’s big astronomical event — the last transit of Venus until 2117:

Why study Venus transits?
In the original studies, Edmond Halley [of Halley’s comet fame] figured out a way of calculating how far the sun is away from Earth, and therefore how big the solar system is, by studying a transit of Venus. Measuring the size of the solar system used to be the most important activity in astronomy in the 18th and 19th centuries, so hundreds of expeditions went all over the world to make observations of Venus transits.

Now we know the distance to the sun through other methods, so that’s no longer an important reason to study transits. But there are some contemporary uses … including calibrating the spacecraft that are observing the sun, because here’s a perfectly black disk outside Earth’s atmosphere silhouetted against the sun.

Also, before Venus goes into the sun, you can see its atmosphere. On my most recent scientific article, now in press in the Astronomical Journal, we brought in a scientist from France who is studying Venus’s atmosphere using the European spacecraft Venus Express to interpret Venus’s atmosphere and how what we saw corresponded to the circulation of Venus’s atmosphere at different latitudes, for example.

[Editor’s note: Capt. James Cook was funded by England’s Royal Society to sail to Tahiti and observe a Venus transit in 1769, collecting valuable data for astronomers back home, who were not in the viewing path. The 2012 transit will also be visible in the South Pacific, and travel agencies are already pitching trips to Tahiti’s black-sand beaches to “follow in Cook’s footsteps” during the celestial event … I think a field trip is in order!]

This could potentially set up a tough choice for astro-geeks: go to Tahiti with Jaggard, or chase Pasachoff to Hawaii:

We plan to observe from the solar observatory at Haleakala on Maui at 10,000 feet [3,054 meters] and also from the Sacramento Peak observatory in New Mexico at an altitude of 9,000 feet [2,743 meters]. I myself plan to be in Hawaii… [J]ust this morning I was talking with a colleague about getting some old telescopes from the 18th and 19th centuries and looking through them, so we’re planning on having a few of those set up outside the big telescope dome on Haleakala.

The Astronomical Journal article referenced by Pasachoff is entitled High Resolution Satellite Imagery of the 2004 Transit of Venus and Asymmetries in the Cytherean Atmosphere. According to its abstract, ”the paper presents the only space-borne observations of the 8 June 2004 transit of Venus.”

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