Newly discovered sun-diving comet could be as bright as the moon
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A newly discovered comet more than three-kilometres wide is headed for the centre of our solar system, and could become one of the brightest objects ever seen in the night sky, Russian scientists announced last week.
Astronomer Raminder Singh Samra with Vancouver's H.R. MacMillan Space Centre said it's hard to tell whether the comet, which he described as a "loosely-held dirty snowball", will survive the sun's pressures long enough to be seen by the naked eye.
"Next fall it's coming toward the inner solar system, so it's going to pass by Mars, and shortly after that it's going to get really close to the sun, like two million kilometers from the sun," Samra said.
The sungrazing comet, dubbed C/2012 S1 (ISON), is currently passing Saturn. It is believed to have come from the Oort Cloud, a spherical cloud of comets astronomers believe surrounds the solar system.
If it does make it past the sun, it is estimated ISON will come within 60 million kilometres of Earth at its closest approach, posing no threat to humans, but potentially offering them thrills in the northern hemisphere.
"In terms of brightness, it could be similar brightness to the moon," Samra said.
"It's exciting because most of the comets that we see, they're regular visitors, like Halley's Comet every 76 years or so, but this one looks like it's new."
ISON's observed orbit, sky-watchers have pointed out, is strikingly similar to that of "The Great Comet of 1680", which threw out a long, brilliant tail after it moved away from the sun that could be seen even during the day.
If history repeats itself, this one's tail could stretch as wide as 70 degrees of arc in the sky, which is roughly equivalent to the width of seven fists held out at arm's length.
Comet ISON is expected to reach its closest point to the sun around Nov. 28, 2013.