The Millennium that Defines Universe
31.12.1999

Welcome to the millennial year at the threshold of millennium three. During millennium two, humanity continually redefined its concept of "Universe": first as spheres centered on the Earth, in mid-millennium as the Solar System, a few centuries ago as the Galaxy, and within the last century as the matter emanating from the Big Bang.

Pwyll: Icy Crater of Europa
17.04.1997

The impact crater Pwyll (a name from Celtic Mythology) is thought to represent one of the youngest features on the surface of Jupiter's moon Europa. A combination of color and high resolution black...

The Belt of Venus over Elwood Beach
9.08.2005

Although you've surely seen it, you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly off-color, slightly pink.

Sagittarius Star Cloud
20.05.2001

Stars come in all different colors. The color of a star indicates its surface temperature, an important property used to assign each star a spectral type. Most stars in the above Sagittarius Star Cloud are orange or red and relatively faint, as our Sun would appear.

Landsat 7 Views Planet Earth
14.05.1999

Launched last month, NASA's Landsat 7 spacecraft now orbits planet Earth. Looking down from an altitude of 700 km, Landsat 7 can map the planet's surface in visible and infrared bands and resolve features 30 meters across or smaller.

Iridescent Cloud Edge Over Colorado
28.10.2014

Sometimes your eclipse viewing goes bad in an interesting way. While watching and photographing last Thursday's partial solar eclipse, a popular astronomy blogger suffered through long periods of clouds blocking the Sun. Unexpectedly, however, a nearby cloud began to show a rare effect: iridescence.

Moonbow and Rainbows Over Patagonia
10.08.2009

Have you ever seen a moonbow? Just as rainbows are lit by the Sun, moonbows are lit by the Moon. Since the Sun is so much brighter than the Moon, sunlit rainbows are much brighter and more commonly seen than moonbows.

Space Station over Lunar Terminator
26.04.2015

What's that in front of the Moon? It's the International Space Station. Using precise timing, the Earth-orbiting space platform was photographed in front of a partially lit Moon last year. The featured image was taken from Madrid, Spain with an exposure time of only 1/1000 of a second.

M57: The Ring Nebula
5.06.2013

Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to our own perspective, though. The recent mapping...

Uranus' Ring System
30.04.1996

The rings of Uranus are thin, narrow, and dark compared to other planetary ring systems. Brightened artificially by computer, the ring particles reflect as little light as charcoal, although they are really made of ice chucks darkened by rock.