Astronomy Picture Of the Day (APOD)Sunspot Group AR 2192 Crackles
One of the largest sunspot groups in recent years is now crossing the Sun. Labelled Active Region 2192, it has already thrown a powerful solar flare and has the potential to produce more.
Mimas: Small Moon with a Big Crater
Whatever hit Mimas nearly destroyed it. What remains is one of the largest impact craters on one of Saturn's smallest moons. The crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel, spans about 130 kilometers and is pictured above.
Comet Siding Spring Passes Mars
Yesterday, a comet passed very close to Mars. In fact, Comet C/2013 A1 (Siding Spring) passed closer to the red planet than any comet has ever passed to Earth in recorded history. To take...
Comet McNaught Over New Zealand
Comet McNaught was perhaps the most photogenic comet of modern times -- from Earth. After making quite a show in the northern hemisphere in early January of 2007, the comet moved south and developed a long and unusual dust tail that dazzled southern hemisphere observers.
Melotte 15 in the Heart
Cosmic clouds form fantastic shapes in the central regions of emission nebula IC 1805. The clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster, Melotte 15.
Messier 6 and Comet Siding Spring
This looks like a near miss but the greenish coma and tail of Comet Siding Spring (C/2013 A1) are really 2,000 light-years or so away from the stars of open cluster Messier 6. They do appear close together though, along the same line-of-sight in this gorgeous October 9th skyscape toward the constellation Scorpius.
Rosetta s Selfie
This Rosetta spacecraft selfie was snapped on October 7th. At the time the spacecraft was about 472 million kilometers from planet Earth, but only 16 kilometers from the surface of comet 67P/Churyumov-Gerasimenko. Looming beyond...
Mysterious Changing feature on Titan
What is that changing object in a cold hydrocarbon sea of Titan? Radar images from the robotic Cassini spacecraft orbiting Saturn have been recording the surface of the cloud-engulfed moon Titan for years. When...
Auroral Corona over Norway
Higher than the highest mountain lies the realm of the aurora. Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from energetic electrons and protons striking atoms and molecules in the Earth's atmosphere.
Sprite Lightning in Slow Motion
What causes sprite lightning? Mysterious bursts of light in the sky that momentarily resemble gigantic jellyfish have been recorded for over 25 years, but their root cause remains unknown. Some thunderstorms have them -- most don't. Recently, however, high speed videos are better detailing how sprites actually develop.