For the next few weeks, astronomy buffs will have a chance to view a cosmic visitor that is not only making a once-in-a-lifetime swing through the Solar System but may also offer watchers a glimpse of color that's just right for the holiday season.
Comet Catalina is completing its pass around the Sun and is on its outbound course, leaving the Solar System. Originating from the Oort Cloud, the distant source of many comets that travel through the Solar System, Catalina is a one-time visitor that will eventually leave for interstellar space, according to Tim Collins, senior presenter at the Whitworth Ferguson Planetarium at Buffalo State College and community education instructor at the Williamsville Spacelab Planetarium.
"Viewers can see it in the predawn sky. It will slowly begin an upward track to the northeast as it heads out of the Solar System," Collins said. "For example, on December 7 it will be near Venus. The planet Venus is the brightest object in the (pre-sunrise) morning sky."
Collins says the comet is not expected to be bright enough to see without the aid of a telescope or binoculars. That may change, he adds, if the comet breaks up, the result of gravitational pull as it passed around the Sun. In the meantime, Catalina may also offer viewers a very rare treat: a greenish hue.
"The green coloration is due to some of the makeup of the comet," Collins explained. "It is made of diatomic carbon, which has a tendency to burn green. That's predominantly what's making this color and it's perfect for the holiday season."
Information including a chart by which to follow the comet's course can be found in this article by Sky and Telescope.