Julius Caesar and Leap Days
28.02.2000

Even as leap days go, today is a remarkable one. In 46 BC, Julius Caesar, pictured above in a self-decreed minted coin, created a calendar system that added one leap day every four years.

A Twisted Meteor Train
1.02.2005

Did this meteor leave a twisting path? Evidently. Meteor trains that twist noticeably are rare - and even more rarely photographed - but have been noted before. The underlying reason for unusual meteors trains is that many meteors are markedly non-spherical in shape and non-uniform in composition.

Four Faces of Mars
5.07.1999

As Mars rotates, most of its surface becomes visible. During Earth's recent pass between Mars and the Sun, the Hubble Space Telescope was able to capture the most detailed time-lapse pictures ever from the Earth. Dark and light sand and gravel create an unusual blotted appearance for the red planet.

The Faces of Mars
5.05.2010

Enthusiastic astro-artists ranging from expert to beginner, the youngest age 10, all contributed their work to this entertaining panel featuring different faces of Mars. Their sketches are all based on telescopic views of the Red Planet from earlier this year, near its 2010 opposition.

Ganymede s Shadow
24.03.2017

Approaching opposition early next month, Jupiter is offering some of its best telescopic views from planet Earth. On March 17, this impressively sharp image of the solar system's ruling gas giant was taken from a remote observatory in Chile.

Galileo, Cassini, and the Great Red Spot
2.08.1996

Imagine a hurricane that lasted for 300 years! Jupiter's Great Red Spot indeed seems to be a giant hurricane-like storm system rotating with the Jovian clouds. Observed in 1655 by Italian-French astronomer Jean-Dominique Cassini it is seen here over 300 years later - still going strong - in a mosaic of recent Galileo spacecraft images.

Earthset from the Lunar Reconnaissance Orbiter
3.01.2016

On the Moon, the Earth never rises -- or sets. If you were to sit on the surface of the Moon, you would see the Earth just hang in the sky. This is because the Moon always keeps the same side toward the Earth.

A Total Solar Eclipse of Saros 145
10.08.2017

A darkened sky holds bright planet Venus, the New Moon in silhouette, and the shimmering corona of the Sun in this image of a total solar eclipse. A composite of simultaneous telephoto and wide angle frames it was taken in the path of totality 18 years ago, August 11, 1999, near Kastamonu, Turkey.

APOD: 2024 May 28 Б Solar X Flare as Famous Active Region Returns
27.05.2024

It's back. The famous active region on the Sun that created auroras visible around the Earth earlier this month has survived its rotation around the far side of the Sun -- and returned. Yesterday...

APOD: 2025 January 26 Б The Many Tails of Comet G3 ATLAS
25.01.2025

Why does this comet have so many tails? C/2024 G3 (ATLAS) has developed several long and intricate tails visible from Earth's southern hemisphere over the past two weeks. Many observers reported seeing the impressive comet without any optical aid above the western horizon just after sunset.