How we mapped the Milky Way
After a centuries-long mystery, scientists now understand our galaxy's spiral shape. But there's more to unravel.
By Liz Kruesi
Seeking ground truth on Mars
Under the watchful eye of five spacecraft, the Red Planet's surface reveals weather and climate patterns and the complex history of water and ice.
By Richard Talcott
Epsilon Aurigae: Astronomy's longest-running mystery show
A huge, unknown object is dimming this supergiant star's light, just as it did 27 years ago. New technology may soon tell us what it is.
By Robert Zimmerman
Take the Ghost Hunt challenge
This Halloween season, grab your telescope and scare up these spooky objects.
By Stephen James O'Meara
Explore 12 great lunar targets
Sharpen your observing skills on the Moon's craters, lava flows, and an elusive letter X.
By Michael E. Bakich
Astronomy, 2009, October