New Comet Found

In this series of images, the comet C/2011 L4 (PANSTARRS) can be seen moving across the field of view. Credit: Institute of Astronomy, University of Hawaii

Astronomers at the University of Hawaii at Manoa have discovered a new comet that they expect will be visible to the naked eye in early 2013.

Originally found by the Pan-STARRS 1 telescope on Haleakala, Maui, on the night of June 5-6, it was confirmed to be a comet by UH astronomer Richard Wainscoat and graduate student Marco Micheli the following night using the Canada-France-Hawaii Telescope on Mauna Kea.

A preliminary orbit computed by the Minor Planet Center in Cambridge, Mass., shows that the comet will come within about 30 million miles (50 million km) of the Sun in early 2013, about the same distance as Mercury. The comet will pose no danger to Earth.

Wainscoat said, “The comet has an orbit that is close to parabolic, meaning that this may be the first time it will ever come close to the Sun, and that it may never return.”

The comet is now about 700 million miles (1.2 billion km) from the Sun, placing it beyond the orbit of Jupiter. It is currently too faint to be seen without a telescope with a sensitive electronic detector.The comet is expected to be brightest in February or March 2013, when it makes its closest approach to the Sun. At that time, the comet is expected to be visible low in the western sky after sunset, but the bright twilight sky may make it difficult to view.

Over the next few months, astronomers will continue to study the comet, which will allow better predictions of how bright it will eventually get. Wainscoat and UH astronomer Henry Hsieh cautioned that predicting the brightness of comets is notoriously difficult, with numerous past comets failing to reach their expected brightness. Making brightness predictions for new comets is difficult because astronomers do not know how much ice they contain. Because sublimation of ice (conversion from solid to gas) is the source of cometary activity and a major contributor to a comet’s overall eventual brightness, this means that more accurate brightness predictions will not be possible until the comet becomes more active as it approaches the Sun and astronomers get a better idea of how icy it is. Understanding the composition of comets is important in determining whether or not these objects could have played a role in the origin of life on Earth.

Still image identifying the comet C/2011 L4 (PANSTARRS). Credit: Institute of Astronomy, University of Hawaii

The comet is named C/2011 L4 (PANSTARRS). Comets are usually named after their discoverers, but in this case, because a large team, including observers, computer scientists, and astronomers, was involved, the comet is named after the telescope.

C/2011 L4 (PANSTARRS) most likely originated in the Oort cloud, a cloud of comet-like objects located in the distant outer solar system. It was probably gravitationally disturbed by a distant passing star, sending it on a long journey toward the Sun. Comets from the Oort cloud are of interest to astrobiologists who are studying the potential of such objects colliding with the Earth in the future.

Comets like C/2011 L4 (PANSTARRS) offer astronomers a rare opportunity to look at pristine material left over from the early formation of the Solar System. The comet was found while searching the sky for potentially hazardous asteroids — ones that may someday hit Earth.

Software engineer Larry Denneau, with help from Wainscoat and astronomers Robert Jedicke, Mikael Granvik and Tommy Grav, designed software that searches each image taken by the Pan-STARRS 1 telescope for moving objects. Denneau, Hsieh and UH astronomer Jan Kleyna also wrote other software that searches the moving objects for comets’ tell-tale fuzzy appearance.The comet was identified by this automated software. The Pan-STARRS 1 telescope has a 1.8-meter-diameter mirror and the largest digital camera in the world (1.4 billion pixels). Each imageis almost 3 gigabytes in size, and the camera takes an imageapproximately every 45 seconds. Each night, the telescope images morethan 1,000 square degrees of the night sky.