Getting Closer 
A comet that’s caused a lot of excitement is racing toward a close encounter with the Sun on Thanksgiving Day. It’ll pass about three-quarters of a million miles above the Sun before whipping around and heading back toward deep space. That’s expected to make the comet easily visible to the unaided eye for a few weeks after the encounter.
Comet ISON was discovered just more than a year ago. It probably came from the farthest reaches of the solar system, and is making its first pass by the Sun.
As it nears the Sun, solar heat is vaporizing some of the ice at its surface, surrounding the comet itself with a big ball of gas and dust. Sunlight and the solar wind push some of this material away from ISON to form a tail.
Observations in recent weeks show that the comet is a little fainter than had been expected, but it’s still on track to be bright enough to see with the unaided eye.
It’s not there yet, though, and probably won’t be for another few weeks. In mid-November it’ll pass by Spica, the brightest star of Virgo, making it easier to spot — either with the eye alone, or with the help of binoculars.
The comet will get brighter as it approaches the Sun, but harder to see through the Sun’s glare. It’ll shine at its brightest as it passes the Sun. If it survives the encounter — and many comets don’t — it’ll become visible in the mornings in early December, with a beautiful tail stretching far across the sky.
Script by Damond Benningfield, Copyright 2013