NASA's Deep Impact space probe has captured video of a comet which could outshine the moon when it passes through the inner solar system this autumn.
The three-kilometre-wide comet was discovered by two Russian astronomers last September.
NASA astronomers have plotted its orbit, and say its likely the object has never visited the inner solar system before.
That means it's more likely that the comet's surface will produce a bright 'tail' of gas and dust in the radiation from the sun.
"If it lives up to expectations, this comet may be one of the brightest in history," Raminder Singh Samra of the H R MacMillan Space Centre in Canada said when the comet was first seen.
The images were taken by the spacecraft's Medium-Resolution Imager over a 36-hour period on Jan. 17 and 18, 2013, from a distance of 493 million miles.
Many scientists anticipate a bright future for comet ISON; the spaceborne conglomeration of dust and ice may put on quite a show as it passes through the inner solar system this fall.
"This is the fourth comet on which we have performed science observations and the farthest point from Earth from which we've tried to transmit data on a comet," said Tim Larson, project manager for the Deep Impact spacecraft at NASA's Jet Propulsion Laboratory.
"The distance limits our bandwidth, so it's a little like communicating through a modem after being used to DSL. But we're going to coordinate our science collection and playback so we maximize our return on this potentially spectacular comet."
Long-period comets like ISON are thought to arrive from the solar system's Oort cloud, a giant spherical cloud of icy bodies surrounding our solar system so far away its outer edge is about a third of the way to the nearest star (other than our sun).
Every once in a while, one of these loose conglomerations of ice, rock, dust and organic compounds is disturbed out of its established orbit in the Oort cloud by a passing star or the combined gravitational effects of the stars in the Milky Way galaxy.
With these gravitational nudges, so begins a comet's eons-long, arching plunge toward the inner solar system.
ISON was discovered on Sept. 21, 2012, by two Russian astronomers using the International Scientific Optical Network's 16-inch telescope near Kislovodsk.
NASA's Near-Earth Object Program Office, based at JPL, has plotted its orbit and determined that the comet is more than likely making it first-ever sweep through the inner solar system.
Having not come this way before means the comet's pristine surface has a higher probability of being laden with volatile material just spoiling for some of the sun's energy to heat it up and help it escape.
With the exodus of the clean ice could come a boatload of dust, held in check since the beginnings of our solar system. This released gas and dust is what is seen on Earth as comprising a comet's atmosphere or 'coma' and tail.
ISON will not be a threat to Earth - getting no closer to Earth than about 40 million miles on Dec. 26, 2013.
But stargazers will have an opportunity to view the comet's head and tail before and after its closest approach to the sun -- and it could be an unforgettable moment.