Sunday, November 24, 2013

Countdown to the Sun For Comet ISON

Hey Space Placers!

Comet ISON, the pristine comet from the vast reservoir of comets called the Oort Cloud, is headed for a close encounter with the Sun on November 28, Thanksgiving Day, at 2 p.m. EST. Each passing hour brings the comet inexorably closer to the Sun due to the pull of the Sun’s gravity. The ultimate fate of the comet may well be determined by its solar rendezvous but as the well known phrase of cometary studies says, “Comets are like cats; no one knows what they will do”.

At its closest approach to the Sun Comet ISON will pass only 730,000 miles from our star and will be traveling at 864,000 miles per hour. The comet will be subjected to heating at 5,000 degrees F and gravitational forces that could tear the comet apart. No one knows what Comet ISON’s fate will be but astronomers around the world will be watching and waiting to find out.

Comet ISON was discovered last year and because it was so far away when sighted, media speculation flourished as to it becoming the “Comet of the Century”, “bright as the Full Moon” and “visible in daylight”. As time progressed the comet did not live up to brightness predictions and the real possibility of a cometary dud for the viewing public arose.

Comet ISON has come to life in the past week and brightened to naked eye visibility although it has been necessary to know precisely where to look. I tried to look for the comet while crossing the Atlantic Ocean aboard ship but could not see it. 

The comet’s tail, caused by the sublimation of gases and dust from the comet’s solid nucleus due to solar heating has become quite a sight in photographs. The tail has lengthened considerably in the sky and developed complex structure.

Comet ISON is diving in to the glare of the rising Sun and will probably be no longer visible after the 25th or 26th to ground based observers. The good news is that a fleet of solar spacecraft will be watching Comet ISON as it approaches and recedes from the Sun so the world will have an almost “live as it happens” view.

What makes Comet ISON of extreme interest to the astronomical community is the fact that it has never been to the inner solar system before and that it will pass so close to the Sun. Both of these factors combine to provide an opportunity to observe and learn about a comet that is an unaltered left over from the formation of our solar system 4.5 billion years ago. The close solar encounter will provide information on the comet’s structure and composition which will complement the myriad of observations already made as well as those yet to come. 

Observations of Comet ISON have been conducted with ground and space-based assets since its discovery. Even spacecraft at Mars observed the comet when it passed by the Red Planet in October. Hubble Space Telescope (HST) has been providing observations to show that the comet has not fragmented as some scientists had predicted would happen before Comet ISON passed by the Sun. Comet ISON is already being observed by NASA’s STEREO solar spacecraft with two others, Solar Dynamics Observatory (SDO) and Solar Heliospheric Observatory (SOHO) waiting for the comet to enter their fields of view. A Japanese spacecraft will give us our best view when Comet ISON passes closest to the Sun.

No one knows what will happen to Comet ISON when it encounters the Sun up close and personal. We do know however that our knowledge of comets will be greatly enhanced by all of the data accumulated on Comet ISON. If the comet becomes a viewing spectacle or suffers a destructive end, you will read about it here.

Sky Guy Headed Home In the Atlantic

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