Epimetheus and Janus: Interchangeable Moons of Saturn
1.11.2005

These two moons change places. Epimetheus and Janus, two small moons of Saturn, actually switch positions as they orbit their home planet. The orbital radii of the moons are strangely separated by less than the radii of the moons themselves: about 50 kilometers. One moon orbits Saturn well ahead of the other, at first.

Firefall by Moonlight
6.05.2022

On certain dates in February, an elusive firefall can be spotted at sunset in Yosemite National Park, when water flows, the weather cooperates and the direction to the setting Sun is just right. Often...

Cassini Approaches Saturn
9.12.2003

Cassini, a robot spacecraft launched in 1997 by NASA, is close enough now to resolve many rings and moons of its destination planet: Saturn. The spacecraft has now closed to within a single Earth-Sun separation from the ringed giant. Early last month, Cassini snapped the contrast-enhanced color composite pictured above.

Comet Lovejoy through Morby Castle Ruins
4.12.2013

This new comet is quite photogenic. Comet Lovejoy, discovered only three months ago, was imaged through ruins of ancient MЖrby Castle in Sweden last week sporting a green-glowing coma and tails trailing several degrees.

APOD: 2020 August 15 Б Mars at the Moons Edge
14.08.2020

Does the Moon ever block out Mars? Yes, the Moon occasionally moves in front of all of the Solar System's planets. Just this past Sunday, as visible from some locations in South America, a waning gibbous Moon eclipsed Mars.

Ski Enceladus
23.01.2002

A small inner moon of Saturn, Enceladus is only about 500 kilometers in diameter. But the cold, distant world does reflect over 90 percent of the sunlight it receives, giving its surface about the same reflectivity as new-fallen snow.

Simeis 147: Supernova Remnant
24.04.2016

It's easy to get lost following the intricate strands of the Spaghetti Nebula. A supernova remnant cataloged as Simeis 147 and Sh2-240, the glowing gas filaments cover nearly 3 degrees -- 6 full moons -- on the sky. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years.

Cassini Approaches Saturn
10.09.2017

What would it look like to approach Saturn in a spaceship? One doesn't have to just imagine -- the Cassini spacecraft did just this in 2004, recording thousands of images along the way, and hundreds of thousands more since entering orbit.

Lunation Matrix
30.09.2022

Observe the Moon every night and you'll see its visible sunlit portion gradually change. In phases progressing from New Moon to Full Moon to New Moon again, a lunar cycle or lunation is completed in about 29.5 days.

Cassini Approaches Saturn
18.04.2020

What would it look like to approach Saturn in a spaceship? One doesn't have to just imagine -- the Cassini spacecraft did just this in 2004, recording thousands of images along the way, and hundreds of thousands more since entering orbit.