Hubble captures possible 'comet of the century'

NASA's iconic Hubble Space Telescope has captured the clearest view yet of Comet ISON, which experts believe could become one of the brightest comets ever seen when it lights up the sky later this year.

Comet ISON was discovered in September 2012 by Russian amateur astronomers Vitali Nevski and Artyom Novichonok.

The new photos were snapped on April 10, when the comet was slightly closer than Jupiter. At the time the icy wanderer was about 621 million kilometers from the Sun and 634 million km from the Earth.

The new images are already helping astronomers take a bead on the mysterious Comet ISON, which may shine as brightly as the full Moon when it makes its closest pass by the Sun in late November, SPACE.com reported.

Images show that ISON is already becoming quite active, though it is still pretty far from our star. The comet's dusty head, or coma, is about 5,000 km wide, and its tail is more than 92,000 km long, astronomers said.

It sports a dust-blasting jet that extends at least 3,700 km - no more than 4.8 to 6.5 km across.

Researchers said this small core makes the comet's behaviour on its trip around the Sun, which will bring ISON within nearly 1.2 million km of the solar surface, especially tough to predict.

ISON is apparently making its first trip through the inner solar system from the distant, icy Oort cloud.

Therefore, it is difficult to know if ISON will live up to its expectations or fizzle out like Comet Kahoutek - another possible "comet of the century" - did in 1973.

"As a first-time visitor to the inner solar system, Comet C/ISON provides astronomers a rare opportunity to study a fresh comet preserved since the formation of the solar system," Jian-Yang Li of the Planetary Science Institute in Arizona, who led the team that imaged the comet, said.

"The expected high brightness of the comet as it nears the Sun allows for many important measurements that are impossible for most other fresh comets," Li said.