Comet ISON approaches the Sun
Seen shining in the dawn sky
On 28 November 2013, about a week’s time from when I’m writing this, comet ISON will reach the closest point in its orbit to the Sun — known as the “perihelion”.
Comets originate from the very earliest days of the solar system, and their orbits arc out huge ovals in space. The time it takes them to travel their orbit defines how often we see them — the famous Halley’s comet takes about 75 years to return to us, making it the only comet that might appear twice in a person’s lifetime.
ISON is a newly-identified comet. It was first seen on 21 September 2012 by Belarusian and Russian astronomers, who calculated that its path would take it to just 1,165,000km above the solar surface on 28 November 2013.
When it does, we don’t exactly know what’s going to happen. The comet could break up entirely, disintegrating in a cloud of gas. It could break apart before it gets to perihelion, or just after. Or it could survive intact. What’s getting astronomers excited is the uncertainty.
Right now, with the countdown clock sitting at six days, the comet is easily visible in the dawn sky. Juan Carlos Casado photographed it falling over Gran Canaria (above, via Spaceweather.com) from the Teide Observatory on Tenerife in the Canary Islands. The bright light just below and to the left of it is the planet Mercury.
Over the coming days, ISON will disappear into the dawn and the job of tracking it will be left to Nasa’s various solar satellites. It’s about to enter the field of view of the STEREO-A heliospheric imager, and three more will join it in the next few days.
Karl Battams at the ISON Campaign wrote:
We have already obtained unprecedented scientific knowledge of this comet with data from ten different spacecraft to date, and a vast wealth of ground-based observations from professional and amateur astronomers. In this sense, cometary science has already won. It just remains to be seen how big that win will be
