Jupiter and Io
28.11.2012

On December 3 (UT), Jupiter, the solar system's largest planet, will be at opposition, opposite the Sun in planet Earth's sky, shining brightly and rising as the Sun sets. That configuration results in Jupiter's almost annual closest approach to planet Earth.

Prometheus and the F Ring
8.01.2016

In Greek myth Prometheus was a Titan, known for bringing fire from Mount Olympus. But in modern times the name is given to is a small moon of Saturn, orbiting just inside Saturn's F ring.

Oceans Under Jupiters Callisto
31.07.2001

Why does Jupiter's moon Callisto alter the magnetic field of Jupiter in its vicinity? Callisto itself does not have a strong magnetic field. One possible answer is that Callisto harbors sub-surface oceans of electrically conducting salt-water. This hypothesis was bolstered recently by a new analysis of how Callisto creates and dissipates heat.

Saturn's Rings Seen Sideways
29.04.1996

Saturn's rings are actually very thin. This picture from the Hubble Space Telescope was taken on August 6, 1995 when the rings lined up sideways as seen from Earth. Saturn's largest moon Titan is seen on the left, and Titan's shadow can be seen on Saturn's cloud tops!

Lunar Dust and Duct Tape
17.04.2004

Why is the Moon dusty? On Earth, rocks are weathered by wind and water, creating soil and sand. On the Moon, the long history of micrometeorite bombardment has blasted away at the rocky surface creating a layer of powdery lunar soil or regolith. This lunar regolith could be a scientific and industrial bonanza.

The Double Haze above Titan
10.08.2004

Most moons have no haze layer at all - why does Titan have two? Images from the Cassini spacecraft that slipped into orbit around Saturn last month confirm that the Solar System's most mysterious moon is surrounded not only by a thick atmosphere but also by two distinct spheres of haze.

When Mars met Neptune
13.01.2017

On January 1, a Mars-assisted viewing opportunity allowed binocular-equipped skygazers to cross an ice giant off their life list. Remarkably, the line-of-sight to the bright Red Planet could guide you to within 0.02 degrees of a faint, pale Neptune in Earth's night skies.

A Shadow on the Rings of Saturn
21.07.2004

This picture of Saturn could not have been taken from Earth. No Earth based picture could possibly view the night side of Saturn and the corresponding shadow cast across Saturn's rings. Since Earth is much closer to the Sun than Saturn, only the day side of the planet is visible from the Earth.

Clouds, Plane, Sun, Eclipse
11.04.2005

How can part of the Sun just disappear? When that part is really hiding behind the Moon. Last Friday, the first partial solar eclipse of 2005 and the last total eclipse of the Sun until March 2006 was visible. During a solar eclipse, the Sun, Moon and Earth are aligned.

Aurora Through a Moonlit Sky
2.11.1999

A night sky can glow in fascinating ways. Through a clearing in the woods, the pictured sky above Alaska shines by reflected light from a nearby city, by the brightness of the Moon, and by aurora.