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2013: The Year of the Comet
This is an exciting year for the best and brightest of comets, with two recently discovered comets expected to be bright enough that Northern Hemisphere observers can view them with the naked eye. The first should be visible by March, and November should bring the second spectacle.
Comets PanSTARRS (C/2011 L4) and ISON (C/2012 S1) are generating lots of buzz in the astronomy community, but there are few places for consistent information and analysis on the paths and visibility of the comets. This page will be frequently updated with the most up-to-date information on both of these impressive celestial sights.
Comet PanSTARRS (C/2011 L4)
This information was last updated on Mar. 13.
Image courtesy of Sky & Telescope Magazine; Sky Publishing 2013
March 11: Comet PanSTARRS passed its perihelion with the sun on March 10, and all signs now point to a strong showing for observers in the Northern Hemisphere. The comet has brightened faster than expected, and will now peak at magnitude +1. As the comet leaves the sun's glare in the early evening, it should become progressively easier to see. The best dates to see the comet are March 12 to March 16, when the comet's brightness and distance from the sun will combine to provide excellent views. The comet should have a small dust tail visible, pointing directly away from the sun. To the unaided eye, the comet should be apparent starting about 20 minutes after sunset, but with binoculars, the comet should be even more impressive. The sky map to the right shows the position of the comet relative to the sun and the horizon over the next two weeks.
Comet PanSTARRS is currently exhibiting a beautiful fan-shaped dust tail that is visible to Southern Hemisphere observers through binoculars or a small telescope. As PanSTARRS moves closer to Earth and the sun, the tail will grow in size and in visual prominence. The tail itself is about one degree long – the span of a finger held at an arm's length against the sky – but will likely grow to five or 10 degrees by the middle of March. While the brightness estimate of magnitude +3 seems to be holding steady, there is some indication that the comet may brighten a bit more before perihelion on March 10. If it does, PanSTARRS will be even more prominent in the twilight for observers in the Northern Hemisphere during mid-March.
Comet PanSTARRS was discovered in June 2011 by the Panoramic Survery Telescope and Rapid Response System array of cameras and telescopes atop Mount Haleakala in Hawaii. The comet was first sighted at an impressive distance of nearly 700 million miles and a magnitude of +19, nearly 160,000 times fainter than the dimmest stars visible to the unaided eye. Since then, astronomers have tried to pinpoint what the expected brightness of the comet will be as it makes its closest approaches to the sun and Earth in March.
As of Feb. 20, the best estimate for the maxiumum brightness of Comet PanSTARRS is magnitude +3 (the larger the number, the fainter the object will look). Although this is well within the range of visibility for the unaided eye, it would not be terribly prominent in the glow of early twilight. It is important to note, however, that predicting comet brightnesses is a very difficult task more than two weeks or so before the comet's closest approach to the sun, or perihelion. Some estimates still show PanSTARRS brightening to a magnitude of 0 or -1. Such brightness would make PanSTARRS equivalent in magnitude to Comet Hale-Bopp in 1997.
The comet will be closest to Earth on March 5, passing at a distance of just under 100 million miles. The comet will then swing in for its closest approach to the sun, a distance of about 28 million miles, on March 10. As the comet emerges from the overwhelming glare of the sun, the best visibility should occur between March 12 and 17, when the comet will be due west and a fist's-width distance above the horizon about 30 minutes after sunset. If the close approach to the sun causes an increase in brightness, a tail should become visible to the unaided eye as the sky progressively grows darker.
Comet ISON (C/2012 S1)
As impressive as Comet PanSTARRS may end up being, the real showpiece comet of 2013 is likely to be Comet ISON. This comet was discovered in September 2012 by two astronomers utilizing a telescope built as a part of the International Scientific Optical Network (ISON). Once the orbital characteristics of the comet were confirmed, it was found that Comet ISON is part of a distinct group of comets known as "sungrazers," so named because their perihelions take them dangerously close to the sun. On Nov. 28, the comet will pass just 680,000 miles above the sun's surface.
Such a close approach will likely make the comet one of the brightest visible to observers in many decades. As of Feb. 11, the best estimate for the maximum brightness of Comet ISON is magnitude -13 – brighter than the full moon! Such brightness would not last very long, however, and would likely only reach such visibility several days before and after perihelion. Even so, the comet will likely be visible in the daytime for observers that properly shield the sun and know the comet's position relative to the star.
The comet will pass closest to Earth on Dec. 26 at a distance of more than 39 million miles. Around this time, Comet ISON will be well-placed for observation in the Northern Hemisphere. Even four weeks after perihelion, Comet ISON is predicted to continue to shine at magnitude 3 or brighter, which would still allow for easy observing. In fact, the comet may be visible to the unaided eye as early as November and as late as mid-January 2014.
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