Scienceology: All we care about this week is the transit of Venus! edition.
Post by Christie Taylor on 6/4/2012 12:30pm
Tuesday evening, you’ll be able to watch something you’ll never see again in your lifetime. All potential political jokes aside, I’m serious. This is legitimately exciting: the planet Venus will cross the path between the earth and sun, and make the itty-bittiest, most adorable of shadows on the disk of the sun. And it won’t happen again for more than one hundred years.
This is what scientists call a transit: it’s like an eclipse, but because Venus can’t possibly block enough of the sun to noticeably affect its light, you won’t even see it unless you look for it. Carefully. Like, with eclipse glasses or a solar filter on your camera/telescope.
It won’t look like much: just a black speck slowly crossing the sun, barely visible to the unmagnified eye. But hundreds of years ago, this tiny event led astronomers to an important insight: the transit could tell us the actual distances between objects in the solar system, when before all scientists knew were the relative distances. By placing two observers to view and time the transit from different latitudes, astronomers could use parallax, which is the way objects move against a background depending on where you view them from (you can do this by winking your eyes one at a time). Since each observer sees a different path of transit, they’ll each see a different duration as well. From duration, the angle between the observers can be found, and from there you can use trigonometry to calculate distances to Venus the sun.
Measurements of the 1761 and 1769 transits were an early example of scientific collaboration, with observers stationed worldwide to ensure the most precise possible measurement. Using this method, astronomers narrowed down their estimation of the astronomical unit (AU) to approximately 149 million km following the 1882 transit. (After that, spacecraft and radar made parallax a moot methodology).
The 1761 transit also gave Russian astronomer Mikhail Lomonosov an early insight into the existence of an atmosphere of Venus. This year, astronomers will be watching the Venus transit not for insights into Venus so much as into exoplanets: measuring how the sun dips in brightness and other aspects of the transit will help them understand what to look for when searching for planetary transits in other solar systems, and how to interpret what they find.
The transits only occur every hundred years or so, in pairs with eight years between them. The last one was in 2004 (some photos here). The next one will be in 2117. For the record, that’s rarer than every kind of eclipse and Halley’s Comet.
So far, the forecast for Tuesday night is looking good for getting a glimpse in Madison, though storms could still get in the way. But you’ll have a good chunk of time for viewing: The transit starts at approximately 5 p.m., and lasts until 11, meaning Madison viewers will get to watch until the sun sets at 8:33 p.m.
If you’re an ordinary citizen with no other access to telescopes with the appropriate filters, there are still several options for viewing the once-or-twice-in-a-lifetime event. All of them are free, but solar glasses might set you back between $1 and $2.
* The UW-Madison Space Place is hosting a telescope viewing at its South Park Street headquarters at 5 p.m. until sunset. In case of clouds, they’ll stream a live video in their lecture hall. Eclipse viewing glasses also will be available for sale.
* The Madison Metropolitan School District Planetarium is hosting a telescope viewing outside Keva Sports Center in Middleton, from 4:45 p.m. until sunset. The event is weather dependent. Eclipse viewing glasses will be available for sale, while supplies last.
* Washburn Observatory on the UW-Madison campus will also have a telescope viewing from 4:45 to 8:15 p.m.. Members of the public are invited, and solar viewing glasses will be available for sale.
* For viewings in other parts of Wisconsin, check out this list by Wisconsin Astronomy. (h/t CapTimes)
And if you want to get portent-y about the fact that all of this is happening on the very same day as Wisconsin’s historic recall election, where four state senators and one state governor might all get the boot, check out this clip from MSNBC’s Rachel Maddow, who spends a few minutes connecting the transit to the recalls. She actually doesn’t say anything about astrological omens (thank goodness), but rather links the knowledge scientists gained from such a relatively tiny event to the potential implications the senate recalls, which could flip the balance of power in one house of the state Legislature and, in so doing, stall any further legislation next session, could have for national politics in the decades to come. Also omenous? The transit's evening time slot is actually about perfect for anyone who needs something to get their mind off the election before polls close at 8, and the returns begin trickling in.
Christie Taylor (@ctaylsaurus) covers science, environment, and, depending on the season, state politics for dane101. She verbs a lot of nouns, including rollerskates, radio, and Kurt Vonnegut. A Madison native, she's not sure she'll ever quite manage to leave Wisconsin, and that's just fine by her. Contact her at email@example.com.