Any comet you can see is a good one. Comet PANSTAARS is beginning its run for observers in the Southern Hemisphere, and will become visible to those in the Northern Hemisphere in the first few days of March. However, updated estimates published on January 17 suggest the peak brightness will be considerably less than was earlier predicted.
When a major comet strides onto the stage of a dark sky, a simple pair of binoculars becomes a gateway to the heavens. You find yourself not only gazing at the comet, but also tracking down objects near the comet's path. This year, we are fortunate enough to have two comets predicted to reach a brightness and size sufficient to be obvious to the unaided eye.
The biggest and brightest comet to appear this year is likely to be Comet ISON (so-named because it was discovered using a telescope of the International Scientific Optical Network – ISON), which will make its appearance in the middle of the year.
Rather than wait so long, however, we are lucky enough to have a harbinger in Comet PANSTAARS.
Comet PANSTAARS was discovered by the Panoramic Survey Telescope and Rapid Response System on June 6, 2011. At the time it would have required a 1.5 m (5 ft) diameter telescope to be able to see the new comet by eye. At discovery it was just over a billion kilometers distant from Earth – just a bit past Jupiter – and moving at about 15 km/s (~9 miles/s).
Comet PanSTARRS has a slightly hyperbolic orbit that suggests that it is fresh from the outer Oort Cloud, and is approaching the Sun for the first time. Astronomers believe the Oort Cloud, a spherical group of icy objects extending a light-year from the Sun, is the source of all long-period comets entering the inner Solar System. Such comets often appear bright early on, so that the predicted peak brightness is very bright, but they can disappoint after their thin coating of volatile materials evaporates ... or not. At times these are the most wonderful comets of all. Time will tell.
Comet PANSTAARS is currently predicted to reach its brightest on March 10, at which point it should be fairly easy to see worldwide right on the horizon about 45 minutes to an hour after sunset. However, given the erratic nature of Oort Cloud objects, it could become its brightest before or after that date.
Regardless of details, however, Comet PANSTAARS should be visible to the unaided eye, so let's talk about where to find it.
The map above shows the path of Comet PANSTAARS through the heavens. The position is correct for the indicated dates, but depending on your location and the date, the comet may be visible at dawn, at dusk, at both, or neither.
The most important variable for finding Comet PANSTAARS is your latitude. For example, a pair of binoculars will allow you to see the comet in the Southern Hemisphere, but in the Northern Hemisphere it will not be visible until early in March. The sky chart above and the table below will assist you in locating the comet:
As mentioned earlier, predicting comet brightness is difficult. However, on Feb 1 the comet should be visible in binoculars as a fuzzy spot. On Mar 10 it should be at its brightest, a naked-eye object which should show a tail, although you will see the tail best in binoculars. By May 1, the comet is likely to fade to the point where it will be difficult to see in binoculars.
At about 0 h UT on February 1, Comet PANSTAARS will pass closer than half a degree (the Moon's angular size) to the magnitude 3 double star Beta Sagittarii. This might help a southern viewer find the comet in binoculars.
From February 9-11, Comet PANSTAARS will be northeast of Alpha Indi, a magnitude 3 star which is the brightest is a dim region of the sky. The star and the comet will appear together in a binocular's field of view on those days.
At about 5 h UT on February 22, Comet PANSTAARS will pass closer than 15 minutes of arc (half the Moon's angular size) to Lambda Grus, a magnitude 4.5 star in the Southern Hemisphere sky. While neither star nor comet will be very conspicuous, the juxtaposition may aid in locating the comet.
At about 3h UT on March 6, Comet PANSTAARS will pass closer than 20 minutes of arc southwest of Galaxy MCG-03-01-015, a mag 10.4 galaxy measuring 11 x 4 minutes of arc. This should make a nice grouping for a moderate (4-8 in - 10-20 cm) amateur telescope.
From March 9-12, Comet PANSTAARS will be about seven degrees WSW of the red planet Mars. At about 0h UT on March 13, the comet passes about half a degree west of the planet Uranus, marking a good chance to see this dim planet. For much of the 13th, the Moon is about four degrees north of the comet. Fortunately the light from this thin crescent Moon will not obscure the tail of the comet.
During the first few days of April, Comet PANSTAARS is about three degrees east of M31, the Great Nebula of Andromeda. The pairing should be impressive in a pair of binoculars. After this, the comet will be heading into Cassopeia, but will be fading steadily. At the start of May it may be a difficult binocular object.
Despite the current projections, Comet PANSTAARS could still become a so-called Great Comet – defined loosely as one which can be seen in the sky even if you don't know it is there. After all, in 2007 Comet Holmes brightened from magnitude 17 to magnitude 2.8 (over half a million times brighter) in only 42 hours! May we be as lucky with PANSTAARS.
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