I’m here today to talk about what promises to be the brightest comet during the first half of 2013 and likely one of the brightest comets of the 21st century — so far. Comet PANSTARRS (C/2011 L4) will peak in March and remain bright well into April. If predictions hold, it should be an easy naked-eye object and will look great through binoculars for several weeks.
Astronomers discovered this comet June 6, 2011. As the fourth new comet detected during the first half of June that year, it received the designation “C/2011 L4.” And because researchers first spotted the object on images taken through the 1.8-meter Panoramic Survey Telescope and Rapid Response System on Haleakala in Hawaii, it received the instrument’s acronym, PANSTARRS, as a secondary name. Astronomers credit this scope with more than two dozen comet discoveries, so the “C/2011 L4” designation is more precise even though it’s much easier to say “PANSTARRS.”
The comet is making its first trip through the inner solar system. Its journey began eons ago when a star or interstellar cloud passed within a light-year or two of the Sun. This close encounter jostled the so-called Oort Cloud, a vast reservoir of icy objects that lies up to a light-year from the Sun and probably holds a trillion comets. PANSTARRS has been heading toward the Sun ever since.
For complete coverage of Comet PANSTARRS, visit www.astronomy.com/panstarrs.
Southern Hemisphere observers had the best comet views during February. But by early March, PANSTARRS veers sharply northward and gradually becomes visible in the evening sky for Northern Hemisphere observers. The earliest views should come around March 6 or 7, when it appears a degree above the western horizon 30 minutes after sunset. Each following day, the comet climbs a degree or two higher, which dramatically improves its visibility.
It comes closest to the Sun (a position called “perihelion”) the evening of March 9, when it lies just 28 million miles (45 million kilometers) from our star. It then appears 7° high in the west 30 minutes after sunset. If predictions hold true — never a sure thing when it comes to comets making their first trip through the inner solar system — the comet will be a superb object through binoculars and probably an impressive naked-eye sight. Astronomers expect it to reach magnitude 0 or 1 at perihelion, although no one would be too surprised if it ends up one or two magnitudes brighter or dimmer.
From perihelion to the end of March, the comet moves almost due north through Pisces
while its brightness drops by about a magnitude every five days. In the admittedly unlikely event that the tail of PANSTARRS stretches 10° or more March 13, it will pass behind a two-day-old crescent Moon. The comet should glow around 4th magnitude in early April, which would make the extended object visible only through binoculars or a telescope. It passes 2° west of the Andromeda Galaxy (M31) on the 3rd, then crosses into Cassiopeia
on the 9th. During the third week of April, the comet fades to 6th magnitude and is visible all night for those at mid-northern latitudes, where it appears highest before dawn.