Lightning on Earth
Nobody knows what causes lightning. It is known that charges slowly separate in some clouds causing rapid electrical discharges (lightning), but how electrical charges get separated in clouds remains a topic of much research. Nevertheless, ...
M57: The Ring Nebula
cept for the rings of Saturn, The Ring Nebula (M57) is probably the most famous celestial band. This planetary nebula's simple, graceful appearance is thought to be due to perspective -- our view from planet Earth looking straight into what is ...
Star Trails In Southern Skies
As the Earth spins on its axis, the stars seem to rotate around us. This motion produces the beautiful concentric arcs traced out by the stars in this time exposure of the southern hemisphere night sky. In the foreground is the dome of the ...
Crater On Ice
Impact craters are common on Earth's moon but on Jupiter's large ice moon Europa, they are very rare. Over time, both bodies have been subjected to an intense pounding by the solar system's formative debris, but geological activity on Europa's ...
LP 944-20: A Failed Star Flares
The tiny spot circled on the right actually represents a big astronomical discovery -- the first detected flare from a failed star. Failed stars, termed brown dwarfs in astronomers' parlance, are too low in mass to ignite nuclear hydrogen burning ...
A Giant Starspot on HD 12545
What could cause a star to have such a large spot? Our Sun itself frequently has sunspots, relatively cool dark magnetic depressions that move across its surface. HD 12545, however, exhibits the largest starspots yet observed. Doppler imaging ...
The Crab Nebula in Blue and White
The Crab Nebula is a complex shell of expanding gas. The Crab Nebula formed from a star that was seen to explode in a supernova about 1000 years ago. This two color composite image taken with the WIYN 3.5-meter telescope shows in great detail ...
Comet LINEAR Extends
Comet LINEAR's tail appears to be extending. Many sky watchers are closely following Comet C/1999 S4 LINEAR and wondering if it will develop an impressive tail or become visible to the naked eye later this month. So far, the unpredictable comet ...
The Hubble Deep Field
Galaxies like colorful pieces of candy fill the Hubble Deep Field - one of humanity's most distant optical views of the Universe. The dimmest, some as faint as 30th magnitude (about four billion times fainter than stars visible to the unaided ...
The United States At Night
This is what the United States of America looks like at night! Can you find your favorite US city in this image? Surprisingly, city lights make this task quite possible. The above picture is actually a composite of over 200 images made by ...
