(I know it’s a weird headline, but try coming up with something short that explains this!)
If you live in southwest Georgia or northeast Florida, on Tuesday evening April 17th at 8:56 p.m. local time, you might see the star Iota Cancri blink out as an asteroid named Xanthe passes in front of it.
This type of event is called an occultation. The asteroid’s orbit takes it right in front of a star, and the star appears to wink out or drop in brightness. Because asteroids are small, a specific occultation can only be seen along a narrow corridor, which is why those parts of Georgia and Florida get to see this. This particular one should be really nifty, too, since Iota Cancri is a visible star, shining at magnitude 4.2 (meaning it’s easily visible from dark skies, though people near bigger towns might need binoculars to see it).
These are more than just curiosities, too. By getting careful timings of the occultation from observers at different locations, the shape of the asteroid can be determined! Imagine the asteroid is a perfect sphere. The path of the occultation would be easy to predict, and people north and south of that line would see the asteroid "miss" the star.
Now imagine a small hill on the asteroid. An observer on Earth slightly farther north might still see the occultation! So very precise timing and location measurements can provide a pretty good projection of the asteroid’s shape. To learn how to get timings, read what they have about it at the International Occultation Timing Association’s site. And get out there and observe!
April 16th, 2007 at 11:57 am
Cool, I just happen to be in Jacksonville, FL
April 16th, 2007 at 1:57 pm
BA didn’t mention that the occultation method can be used to find asteroid satellites! If you see the star disappearing twice, you may have found a moon orbiting Xanthe…
April 16th, 2007 at 2:31 pm
I’m in Tallahassee. I wonder how far I would have to go out of my way. I found this map of the path of occultation for the Jacksonville area.
April 16th, 2007 at 3:14 pm
I see that Chieflad, home of the Chiefland Astronomy Village (http://www.chiefland.org/) is just inside the one sigma line.
Rob
April 16th, 2007 at 4:15 pm
Darn! I’m too far south to see it! I’m in southeast FL.
I’m not sure I’d even know where to look for Iota Cancri, or if it even is visible in my light polluted area.
Well, good luck to those that CAN see it!
April 16th, 2007 at 4:28 pm
Well, im in Europe and for a couple of days now we could see a nice, bright Venus just to the side of the Pleiads
April 16th, 2007 at 5:53 pm
[...] my RSS feed. Thanks for visiting!One of my favorite sites on the web, Bad Astronomy, has news of an interesting event happening tomorrow night in Georgia and Florida… If you live in southwest Georgia or northeast Florida, on Tuesday [...]
April 16th, 2007 at 6:45 pm
Or you could reveal a secondary star around Iota. I co-discovered a star around 89 Leo that way about 35 years ago. (It was a lunar occulatation though. A cheap and common spectacle compared to an asteroid occultation.)
April 16th, 2007 at 6:46 pm
Oops. Sorry. It was 87 Leo.
April 17th, 2007 at 5:55 am
Even with this bright star this one is a bit tough since it happens in late twilight so little or no setup time before the event. Worth a try tho …
The UF Rosemary Hill Observatory is just a bit south of the southern limit (in the 1 sigma zone).
April 17th, 2007 at 5:57 am
Tim G. : You may be in lick … see
http://www.floridastars.org/IOTACAN/IotaCancri.Path.800.gif
April 17th, 2007 at 9:27 am
Since I didn’t see it mentioned above: As an added bonus, Iota Cancri also happens to be a really beautiful double star, with a very marked color difference between the widely separated components.
We always show it to our undergrads at campus observatory (when Albireo isn’t up) to demonstrate stellar colors and their correspondence to temperature.
April 17th, 2007 at 11:33 am
Those at the University of Florida and Florida state should be able to get the best view with a short drive. I’m too far away in South Florida.
I think it would be interesting to see a video of the occultation, if someone could capture that.
April 18th, 2007 at 8:02 am
At least some of the UF astronomers and Alachua Astronomy Club observers were sucessful and I know of at least one video sucess. I will try to post a link when it becomes available.
April 19th, 2007 at 2:04 am
whoops … video here
http://www.youtube.com/watch?v=iiC28i3v44U
April 19th, 2007 at 4:29 am
Tuesday night, 2007 April 17 (EDT), Iota Cancri A dimmed out as expected when asteroid 411 Xanthe passed over this fourth magnitude, colorful double star.
Despite potential clouds and haze that would have ruined seeing this exciting event, most people who tried to time the occultation had remarkable success.
This event was even more dramatic since this yellowish star winked out but left its fainter bluish companion behind!
Preliminary results suggest the actual path may have been about 20 km farther north than expected. For example, observers in Valdosta, GA were not expected to see the event but saw an approximate 6 sec duration. And, an AAC observer in Gainesville, FL who should have seen the occultation, did not. Observers near the center line path close to Live Oak, FL saw an approximate 8 sec duration, as was expected.
The occultation also occurred earlier than predicted. (My own observations had the occultation about 15 seconds early.)
Data provided by the many observers including members of the Alachua Astronomy Club, Inc. (AAC), Universities of Florida and Valdosta, and many others, should ultimately allow one to determine the shape of this main belt asteroid, its diameter, and the star’s angular diameter.
More info about this occultation and preliminary results are on an AAC Web page:
http://www.floridastars.org/occult.iotacan.2007-04.html
April 20th, 2007 at 6:05 pm
Wouldn’t “Florida, Georgia to see asteroid block star” have been a less grammatically ambiguous headline?
June 13th, 2007 at 12:25 am
If anyone has location of stars over florida e-mail me at the above address please…….. Thanks