Where is Comet ISON now?

Elizabeth BarberThe Christian Science Monitor

Comet ISON is being watched.

As part of the Comet ISON Observing Campaign, astronomers fixed NASA's Spitzer Space Telescope on Comet ISON for 24 hours on June 13th. The results now show carbon dioxide emissions from the comet, which is expected to make a much anticipated journey within several thousand miles of the sun to become – maybe – one of the world's most famous comets.

Scientists believe that about 2.2 million pounds of the gas per day is fizzling off the "soda-pop comet,” drawing behind the comet a tail about 186,400 miles long. The stream is also made of the some 120 million pounds of dust that the comet loses each day.

That tail is expected to get even longer and brighter – if the comet survives long enough for that to happen.

ISON, a "sungrazer” comet, is expected to pass within 750,000 miles of the sun on November 28, 2013. There, it could disintegrate in the sun’s broil and radiation, as do so many comets that dare to come too close.

But if ISON does not burn up, it is expected to be the “comet of the century,” both for its fantastic tail that will be visible to the naked eye in the January skies – a prime shooting “star” on which to make a wish for 2014 – and its value to astronomers observing its behavior.

ISON still has millions of miles to go before it reaches the sun: the observations on the comet’s CO2 levels were made when ISON was about 312 million miles from the sun, about 3.35 times farther out than Earth.

Comet ISON – or C/2012 S1 – is less than 3 miles in diameter and has a mass of somewhere between 7 billion and 7 trillion pounds. Scientists will have a better understanding of comet’s size and composition later this month or in August, when the comet begins to warm up around Mars’ orbit.