On Tuesday evening, April 8, you can experience one of the most beautiful events the sky can deliver. Head outside no later than an hour or so after sunset (around 8:30 P.M. local daylight time) and look to the west. Your eyes should land immediately on the slender crescent Moon, oriented with its cusps standing nearly straight up from the horizon. Point your binoculars at the Moon to reveal a stunning sight: the bright Pleiades star cluster (M45...

It seems to me that Saturn’s moon Rhea is a leading candidate for Rodney Dangerfield of the solar system. I tell you, it doesn’t get much respect. Even in the Saturn system, where Rhea is the second-largest moon, it ranks pretty low. You hear about Titan, with its thick atmosphere and methane lakes. Enceladus is known for its liquid-water geysers and Iapetus for its strange black and white hemispheres. Even tiny Mimas, with its cute “Death Star” crater...

On November 7, Japan’s SELENE spacecraft captured this high-definition image of Earth rising over the Moon’s north pole. JAXA/NHK If prime-time television, National Geographic specials, and sports programming don’t get you pumped for seeing TV at the highest-possible resolution, then what else is there? Television may not be the “vast wasteland” it once was claimed to be, but you could make a good case that seeing incredible detail in TV’s moving...

On January 14, NASA’s MESSENGER spacecraft flew past Mercury. MESSENGER — short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging — made the first close-up observations of the innermost planet in 33 years. This flyby marked the first of three encounters with the planet, providing gravity assists necessary to place the probe in orbit around Mercury in March 2011. January 25, 2008 As Mercury fades in the distance, MESSENGER continues...

On January 14, NASA’s MESSENGER spacecraft flew past Mercury. MESSENGER — short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging made the first close-up observations of the innermost planet in 33 years. This flyby marked the first of three encounters with the planet, providing gravity assists necessary to place the probe in orbit around Mercury in March 2011. January 16, 2008 The first close-up images of Mercury have made their way...

On January 14, NASA’s MESSENGER spacecraft flew past Mercury. MESSENGER — short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging — made the first close-up observations of the innermost planet in 33 years. This flyby marked the first of three encounters with the planet, providing gravity assists necessary to place the probe in orbit around Mercury in March 2011. January 15, 2008 It’s okay to exhale. Everyone involved with the MESSENGER...

On January 14, NASA’s MESSENGER spacecraft flies past Mercury. MESSENGER — short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging — will be making the first close-up observations of the innermost planet in 33 years. This flyby marks the first of three encounters with the planet, providing gravity assists necessary to place the probe in orbit around Mercury in March 2011. January 14, 2008 This afternoon, NASA’s MESSENGER spacecraft...

On January 14, NASA’s MESSENGER spacecraft will fly past Mercury. MESSENGER — short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging — will be making the first close-up observations of the innermost planet in 33 years. This flyby marks the first of three encounters with the planet, providing gravity assists necessary to place the probe in orbit around Mercury in March 2011. January 11, 2008 This morning, NASA’s MESSENGER spacecraft...

Sinuous valley networks like these imaged by Viking 1 led many planetary scientists to think Mars’ climate once was warm and wet, but some researchers aren’t so sure. NASA/JPL Today marked the 114th consecutive day in Orlando in which the temperature never dipped below 70°. I'm currently sweating in Orlando, attending the annual meeting of the American Astronomical Society's Division for Planetary Sciences (DPS). Florida's warm, humid...

If you've been watching the Moon after sunset this week, you may have noticed it lies lower in the sky than usual (at least if you live at mid-northern latitudes). It's not your imagination — the Moon is figuratively scraping the treetops this week. Although this is no great mystery, it never hurts to remind yourself about the Moon's monthly and yearly cycles. The Moon's maximum altitude from any given location depends on its declination...