Column By Jim Kidd, Amateur Astronomer and Network Administrator of Jones Media Inc.
Comet ISON could be visible in the Greene County skies this month. The comet has surprised astronomers by unexpectedly becoming brighter in the past couple days.
Astronomers now say that Comet C/2012 S1 (ISON’s more scientific name) is visible with a dark sky and binoculars. They say it might even be visible with the naked eye for a couple of weeks.
Here in East Tennessee to catch a glimpse of the comet, budding astronomers may look to the southeast sky during pre-dawn hours, between the planet Mercury and the constellations Big Dipper and Virgo.
The comet will be very close to the star Spica in the constellation Virgo on Nov. 17 and 18.
When it was first discovered in 2012, Comet ISON was called the “Comet of the Century,” due to its expected incredible brightness.
Some astronomers were even expecting the comet to be as bright as a full moon. Unfortunately, comets are notoriously unpredictable.
Measurements in the past couple months have downgraded the high expectations to almost disappointment … until recently.
ISON has just passed the orbit of Venus on its travels through our solar system.
When it whips around the Sun on about Nov. 28, ISON will come within 800,000 miles of our Sun’s surface, which is a very close pass in astronomical measurements.
This close pass has three possible outcomes, according to astronomers: ISON will disintegrate before reaching the Sun, will melt and disintegrate during its voyage around the Sun, or will survive its close pass for another bright trip past Earth.
Luckily for us Earth-bound viewers, we will probably get a nice nighttime show, if it either disintegrates before reaching the Sun or it survives its trip around the Sun.
The apparent magnitude (or brightness) of celestial objects is measured on a logarithmic scale.
As of Nov. 14, the comet’s brightness was measured at an apparent magnitude of +6.8.
A +6 magnitude is the limit of naked-eye visibility in dark rural environments, while a +3 or +4 is needed for viewing in brighter city environments.
For further perspective, the dimmest objects viewable by the Hubble Space Telescope have an apparent magnitude of +32, a full moon measures -13 magnitude, and the Sun comes in at -27.
For up-to-date news on Comet ISON, visit http://www.isoncampaign.org/blog. The website is a service of NASA.