Archive for the ‘Venus’ Category

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Transit of Venus resources

February 17, 2012

I mentioned a couple of posts ago that there will be a transit of Venus across the face of the sun on June 5/6, an event that comes along only twice per century. The last one was in 2004, and the next one will be in 2117. I’m starting to collect online resources that have to do with the transit, and I’ll probably set up a separate page on the sidebar to make them easier to find (hey, look, I did!). For now, though, here are the two best:

Transit of Venus .org is probably the most comprehensive online resource for the upcoming transit, with links to tons of other transit sites and resources.

Astronomers Without Borders have an excellent transit page and blog going here. Particularly useful is their Local transit times page, which will show you the timing and path of Venus in front of the sun depending on your location. Here’s a screenshot of the map I generated for Claremont, California:

Note that the transit will still be in progress when the sun sets at 8:00 PM, so I’ll see about 80% of the transit (assuming no clouds!) but not the whole thing. I’ll take what I can get!

Also at that site is a sweet set of instructions on how to build a “sun funnel” projection screen to show lots of people the sun at once with a single telescope. Here’s a pic borrowed from the site of the sun funnel in action:

I am SO building one of those!

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Coming in 2012–solar and lunar eclipses and a transit of Venus

February 11, 2012

There are some things coming up this May and June that you really do not want to miss, and happily all three will be visible from the western US:

  • a solar eclipse on May 20
  • a lunar eclipse on June 4
  • a transit of Venus on June 6

There is a ton of information on the eclipses at MrEclipse.com, which is one of the best online resources for all things eclipse-related.

The solar eclipse will be an annular eclipse, in which the moon will be near its apogee–far from Earth in its elliptical orbit–and thus will not cover the entire solar disk. So the sun’s corona will not be visible, but hey, it’s still a solar eclipse. Here’s the projected path across the western US, from the interactive Google map on this page:

To see why the eclipse path cuts off so abruptly over west Texas, see the animated eclipse map here. For those on the west coast, the eclipse will occur around 5:30 PM, Pacific Time.

The lunar eclipse on June 4 will only be a partial eclipse: only part of the moon will pass through Earth’s umbra, or deepest region of shadow. But it will be the deepest lunar eclipse this year; the lunar eclipse on November 28 will be penumbral, so the moon will not pass through the umbra at all. Follow the links for detailed charts with graphical depictions of the moon relative to the Earth’s umbra and penumbra.

I missed the last couple of lunar eclipses, one because of clouds and the other because I was sick as a dog. The last one I caught was in February 2008, about 5 months after I’d bought my first telescope, and it had a powerful effect of cementing my budding interest in astronomy (that’s my composite photo of it above). You can see my old eclipse write-ups here and here.

All right, eclipses are great, but they come around regularly, so if you miss one, you’ll get another chance. Not so with the final item on the list. Venus will transit the sun on June 6, and it’s the last time this particular event will happen for a very long time. Venus transits come in pairs separated by eight years, but the pairs come along less than once per century. The last pair happened in 1874 and 1882, the first transit in the current pair happened in 2004, and after this June there won’t be another transit until 2117.

The 2004 transit of Venus, from Wikipedia

Transits of Venus are cool for all kinds of reasons. They have played a large and somewhat tragicomic role in the development of astronomical science, especially as an international endeavor. People have traveled the globe, gone bankrupt, gone mad, gotten clouded out, and been erroneously declared dead trying to observe previous transits, and the scientific data from these efforts have generally not solved the problems they were gathered to answer. In particular, early efforts to calculate the size of the solar system by timing the transits were confounded by the black drop effect. But there have been spin-off benefits: Captain Cook’s first circumnavigation of the globe started as an expedition to observe the transit of 1769 from the South Pacific. Observations made from the American colonies were published in 1771 in the first volume of the Transactions of the American Philosophical Society.

And in the final analysis, there aren’t that many predictable astronomical phenomena that are only going to occur once in your lifetime. Like the return of Halley’s comet, a transit of Venus both fixes us in time and connects us to observers past and future. I’m bummed that I didn’t get into astronomy until four years after the 2004 transit. I don’t intend to miss this one as well.

I’ll have more info on all these things as the dates approach, just wanted to get the word out early. Also to remind myself to buy a solar filter for my scope!