Astronomy Picture Of the Day (APOD)Ancient Craters of Southern Rhea
Saturn's ragged moon Rhea has one of the oldest surfaces known. Estimated as changing little in the past billion years, Rhea shows craters so old they no longer appear round their edges have become compromised by more recent cratering.
The M81 Galaxy Group Through the Integrated Flux Nebula
Large galaxies and faint nebula highlight this deep image of the M81 Group of galaxies. First and foremost in the above wide-angle 12-hour exposure is the grand design spiral galaxy M81, the largest galaxy visible in the image.
Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.
Stars and Mars
Wandering through the evening sky, on May 4th planet Mars stood in line with Castor and Pollux, the two bright stars of the constellation Gemini. In this time exposure of the celestial alignment, Mars...
Moon Meets Mercury
On Tuesday, May 6, while standing on planet Earth and sweeping your binoculars along the western horizon just after sunset, you might have encountered this arresting skyscape. The view features a slender crescent Moon and bright planet Mercury separated on the sky by only about 2 degrees.
The Dark Tower in Scorpius
In silhouette against a crowded star field toward the constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, clumps of dust and molecular gas collapsing...
The Gegenschein Over Chile
Is the night sky darkest in the direction opposite the Sun? No. In fact, a rarely discernable faint glow known as the gegenschein (German for "counter glow") can be seen 180 degrees around from the Sun in an extremely dark sky. The gegenschein is sunlight back-scattered off small interplanetary dust particles.
Galaxies Collide in NGC 3256
Galaxies don't normally look like this. NGC 3256 actually shows a current picture of two galaxies that are slowly colliding. Quite possibly, in hundreds of millions of years, only one galaxy will remain.
A Persistent Electrical Storm on Saturn
How do large storms evolve on Saturn? On Earth, a hurricane can persist for weeks, while the Great Red Spot on Jupiter has been in existence for over 150 years. On Saturn, a storm system has now set a new endurance record, now being discernable for greater than three months.
An Antarctic Total Solar Eclipse
The Sun, the Moon, Antarctica, and two photographers all lined up in 2003 Antarctica during an unusual total eclipse of the Sun. Even given the extreme location, a group of enthusiastic eclipse chasers ventured near the bottom of the world to experience the surreal momentary disappearance of the Sun behind the Moon.