Comet ISON could be the comet of the century when it appears bright in the sky late this Fall. A new series of photographs by the Gemini North Observatory in Hawaii shows the comet is already developing a bright coma surrounding the nucleus (the comet itself) and it is beginning to form a larger-than-predicted tail.
The Gemini North observatory snapped these photos, taken between February and May 2013. The comet was photographed in the far-red part of the visible spectrum to bring out the gas and dust surrounding the nucleus. During that time, the comet, formally known as C/2012 S1, closed from 455 million to 360 miles from the Sun. This is just inside the orbit of Jupiter.
Thought to measure between three and four miles across, this "dirty snowball" was first discovered by Russian astronomers in September 2012. Most comets start to form a tail when they reach about the same distance from the Sun as the asteroid belt that lays between Mars and Jupiter. It is at this point that comets receive enough heat form the Sun for water to start forming a gaseous tail. ISON's tail started to form at twice this distance. After this occurred, however, the comet stopped brightening as quickly as before, leading some astronomers to conclude the comet may not be as bright as some estimates would have it.
"The current decrease may be because this comet is coming close to the sun for the first time, and a volatile frosting of ice may be coming off revealing a less active layer beneath. It is just now getting close enough to the sun where water will erupt from the nucleus, revealing ISON's inner secrets," Karen Meech of the University of Hawaii said.
ISON will make its closest approach to the Sun on Nov. 28, passing just 800.000 miles from the star's surface on December 26. That passage may even tear the comet apart.
"Our team, as well as astronomers from around the world, will be anxiously observing the development of this comet into next year, especially if it gets torn asunder, and reveals its icy interior during its exceptionally close passage to the sun in late November," Meech said.
This will be ISON's first-ever trip through the Solar System, making it difficult to predict how bright the comet will be as it swings past the Sun. The best show of ISON from this planet will begin in mid-November and continue through the end of the year.