June 6, 2020

AstroEvent: Scouting out a Dusk Comet.

Discovery image of 2012 F1 (LINEAR)

(Credit: the Remanzacco Observatory).

2012 S1 (ISON)2011 L4 PanSTARRS… 2013 is already ramping up to be a great year for astronomy, with the promise of no less than two bright comets. This year came in with the surprise survival of Comet C/2011 W3 Lovejoy past the Sun and saw two decent binocular comets in Garradd C/2009 P1 and a surprise outburst recently of Comet 168P/Hergenrother last month. These icy visitors are fickle beasts, and any comet that rises above +10 magnitude officially piques our interest.

Such might be the case with Comet C/2011 F1 LINEAR this month. Starting November in Ophiuchus (the infamous 13th zodiac sign of non-news fame), C/2011 F1 will cross the border into Scorpius on November and pass just 3’ arc minutes past the +5.4 magnitude star 16 Scorpii on November 4th. This will make a fine guidepost for the comet before it begins to plunge into the dusk. Look low to the west, about 15 degrees above the horizon 30 minutes after sunset. The farther south in latitude you are, the better chances you’ll have of recovering comet C/2011 F1 LINEAR. The +3 magnitude star Zeta Ophiuchi (Han) will make the best overall guide to find the field and getting oriented to it at dusk.

The path of Comet C/2011 F1 LINEAR for the first half of November. (Created by the Author in Starry Night).

From there, Comet C/2011 F1 LINEAR will continue moving about half an angular degree of arc per day across Scorpius & back into Ophiuchus. Another interesting pass will be near the +8.9 magnitude star cluster M107 on November 15th. This conjunction will be within 30’ arc minutes, after which the comet is lost in the solar glare as it passes to the opposite side of the Sun. The Comet will reach solar conjunction on December 16th, &  Southern hemisphere observers may just be able to recover Comet C/2011 F1 LINEAR early in 2013.

Binoculars are your friend in attempting to recover this 9-11 magnitude comet. Start by sweeping and familiarizing yourself with the field; if you can spy M107 at magnitude +8.9, there’s a good chance that you can recover the comet. If you can aim and center 16 Scorpii with a telescope, use the lowest power available for a wide field of view. A clear horizon with minimal turbulence and light pollution also goes a long way in this comet-hunting endeavor.

Discovered on March 21st, 2011 as part of the ongoing Lincoln Laboratory Near-Earth Asteroid Research project, (LINEAR) automated survey based near Socorro, New Mexico, Comet C/2011 (LINEAR) is expected to reach perihelion on January 28th 2013. At +18.3 magnitude at the time of discovery in the constellation Ursa Major, the comet has an orbital inclination of 56.6 degrees. The “C” in the designation indicates that Comet C/2011 is a non-periodic comet and the “F1” denotes the discovery month; “F” being the last half of the month of March. (Hey, we just learned that one, too!)

Do attempt to track down this binocular comet as the Moon is waning and out of the dusk sky for the first week of November. And speaking of which, next week is the beginning of the 2nd eclipse season of the year, and we’ll have all of juicy bits of how to observe the Total Solar Eclipse of November 13-14th from Down Under!


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