313 Years Since Discovery Of Comet Known To Have Made The Closest Pass To Earth, D/1770 L1, In 1770.
.by Anura Guruge
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>> — June 10, 2013.
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Yes, Comet ISON, C/2012 S1, is still on the way, but still a long ways out (as I pointed out 10 days ago). I am banking on it and have my hopes high. A blazing comet in the sky, à la Hale-Bopp [C/1995 O1] in 1997, is always inspirational and so uplifting. Just getting a glimpse of C/2011 L4 (Pan-STARRS), through binoculars, as it sped away from us, in April was a thrill.
If ISON survives perihelion it will flyby Earth on Boxing Day, i.e., Thursday, December 26, 2013, 39.9 million miles away from us. Contrary to the deluded this is by no stretch of the imagination a close call. That is quite a separation. Mars, every once in awhile, comes closer to Earth than that.
But, on July 1, 1770, when D/1770 L1 (sometimes referred to Lexell’s comet, though he was not the discoverer) passed within 0.0151 AU, i.e., 1.4 million miles of the Earth. This per the International Astronomical Union (IAU), the ultimate authority on such matters, is the closest documented cometary encounter.
So D/1770 L1 was nearly 29 times closer — and even it did no harm, because even 1.4 million miles is a ‘safe’ separation.
On February 4, 2011, the tiny asteroid 2011 CQ1 which came within 3,400 miles of Earth – just hours after it had been espied by the Catalina Sky Survey on February 4, 2011.
D/1770 L1 was discovered on June 14, 1770 by Charles Messier [1730 to 1817], a French astronomer of note, who had already discovered five earlier comets, and would go onto discover seven more. So this ‘near-Earth’ comet was only spotted two weeks prior to its ‘fairly close’ flyby.
The identification with ‘Lexell’ has to do with a bestriding polymath of the time, Swedish-born Russian Anders Johan Lexell [1740 to 1784] who using a new groundbreaking technique quickly calculated the orbital parameters of the new comet based on Messier’s observational data. It perihelioned on August 14, 1770 at 0.7 AU. It has since been lost as denoted by the ‘D/’.
We Saw C/2011 L4 (Pan-STARRS) Tonight From Alton, New Hampshire, Through Binoculars, Thanks To Heads Up From Dave Eagle.
.by Anura Guruge
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Dave Eagle, in an e-mail this morning, gave me a heads up that C/2011 L4 (Pan-STARRS) is still visible (though I am not sure whether it is still naked eye). Per Dave, and he would know, it will be close to ‘M31‘ — i.e., Andromeda.
It was more of less where I told you to look this morning. I used those same instructions, which were: For us in New England, that would be low in the Northwest sky around 8 pm. I think trees will be the problem for us. From what I can see from my trusty Sky Charts our best bet would be to start with The Pleiades (the easy to spot ‘Seven Sisters’/Subaru cluster). They (i.e., The Pleiades) should be close to West around 8 pm. Then start scanning North from there. With luck you should be able to spot the ‘W’, the upside down crown, of Cassiopeia. M31, and hence the comet, should be below Cassiopeia.
Beautiful night for admiring the firmament. Not a cloud in the sky. The cold air making everything bright and crisp. We started off on a cleared, abandoned housing estate site close by but it didn’t have enough elevation. So headed up Prospect Mountain Road to the very top. Got to see two delightful porcupines frolicking on the road. Yes, we stopped and watched. Then we turned into Ridge Road at the end of Prospect and parked right at the zenith, off the road. Now we were above the tree line. We used Google Sky Map on a Google Nexus 7 Android 7″ pad to fine tune our direction. Great App. Very easy to use. bang, Right there. Deanna could hold it up and match Cassiopeia with what is in the sky. That helps.
I started scanning with a pair of old, very old, Carl Zeiss, 10x50W binoculars. Took me a while. But then I saw it and I said: ‘WOW’! No escaping it. When you see it you know that that is different. It was rewarding. I saw Hale-Bopp, C/1995 O1, most nights for nearly a month in 1997. That made an indelible impression. I also saw Kohoutek, C/1973 E1, faintly, in 1974, after spending days clambering up hillocks in The Mumbles, near Swansea, Wales, with like minded fellow students from the University, spread over 4 months. That was dedication. C/2011 L4 was better.
Deanna thinks it is the first comet she has seen. She is not sure whether she saw Hale-Bopp. She was thrilled. She too went: ‘Wow’. It was, of course, a first for Devanee. Teischan wasn’t interested.
So this was a nice, welcome warm-up for C/2012 S1 (ISON) later this year. That should, with luck, be more spectacular.