Year of the Comet
Comet C/2011 L4 (PANSTARRS)

PANSTARRS information

Comet C/2012 S1 (ISON)

ISON information

Web Extras
Go deeper into the stories of Astronomy magazine. These online features bring you additional research, interviews, photos, and more our editors turned up while creating the stories for this issue.
September 2009
Earth
Ammonia, silicon, and hydrocarbons can theoretically support life.
By Daniel Pendick // Published: July 27, 2009
Alpha and Proxima Centauri
Associate Editor Daniel Pendick talks about Proxima Centauri.
Published: July 27, 2009
September 2009 WE Dupree
Learn more about the life and ideas of Andrea Dupree.
By Karri Ferron // Published: July 27, 2009
Merging galaxies simulation
A simulation shows how merging galaxies can fling stars to hypervelocities.
By Liz Kruesi // Published: July 27, 2009
Andromeda Galaxy (M31)
See all the entries of the 2009 Astroimaging Contest.
By Michael E. Bakich // Published: July 27, 2009
September 2009 WE Cepheus
The first known Cepheid variable star lies in the southeastern corner of Cepheus the King. Here's how to find it.
By Richard Talcott // Published: July 27, 2009
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