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NASA's Hubble Space Telescope has taken some of the clearest shots yet of Comet ISON on April 10 when the comet was at a distance of 386 million miles from the Sun (394 million miles from Earth).

Comet ISON is believed to light up the sky later this year as it nears the sun. Astronomers say it will be as bright as the Moon in the sky. The comet was discovered by Russian astronomers Vitali Nevski and Artyom Novichonok in September 2012.

With the Hubble data, astronomers have calculated that the comet measures anything from 3 to 4 miles wide. However, the gas and dust filled coma surrounding the ISON's nucleus stretches out approximately 3.100 miles in diameter, that is, wider than the Australian continent. Currently, the dust trail is 57,000 miles long. However, its size will increase as it goes nearer to the sun. Release of frozen cases will attribute to the further increase in size.

Astronomers are using these images to measure the activity level of this comet and constrain the size of the nucleus, in order to predict the comet's activity when it skims 700,000 miles above the Sun's roiling surface on November 28. It is expected to look as bright as the moon from Earth.

Scientists believe that this is ISON's first trip into the inner solar system, coming from the far outer reaches of the solar system, from a frozen reservoir of billions of hibernating comets.  

ISON stands for International Scientific Optical Network, which is a group of observatories in ten countries who have organized to detect, monitor, and track objects in space. 

Correction: A previous version of this article incorrectly said comet ISON measures 4 meters wide in the title, instead of 4 miles.