Julius Caesar and Leap Days
28.02.2024

In 46 BC Julius Caesar reformed the calendar system. Based on advice by astronomer Sosigenes of Alexandria, the Julian calendar included one leap day every four years to account for the fact that an Earth year is slightly more than 365 days long.

Mauna Kea Shadow Play
29.02.2008

Just opposite the setting Sun, the already-eclipsed Moon rose over the Hawaiian Islands on February 20. A view near the 14,000 foot peak of volcanic Mauna Kea on the Big Island, a popular spot for astronomers, offered this remarkable play of shadows and sunlight.

Over the Top
19.06.2014

The central bulge of our Milky Way Galaxy rises above a sea of clouds in this ethereal scene. An echo of the Milky Way's dark dust lanes, the volcanic peak in foreground silhouette is on France's Réunion Island in the southern Indian Ocean.

A Full Sky Aurora Over Norway
31.12.2016

Higher than the highest building, higher than the highest mountain, higher than the highest airplane, lies the realm of the aurora. Auroras rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from energetic electrons and protons striking molecules in the Earth's atmosphere.

Eclipse under the ISS
26.06.2020

The dark shadow of the New Moon reached out and touched planet Earth on June 21. A high definition camera outside the International Space Station captured its passing in this snapshot from low Earth orbit near the border of Kazakhstan and China.

Long Shadows of the Montes Caucasus
18.12.2025

When the Moon is at its first quarter phase, the Sun rises along the Montes Caucasus as seen from the lunar surface. The lunar mountain range casts the magnificent, spire-like shadows in this telescopic view from planet Earth, looking along the lunar terminator or the boundary between lunar night and day.

Leonid Meteor Shower Next Week
7.11.1998

Early next week, a spectacular meteor storm is expected: the 1998 Leonids. It is widely thought that that the meteors from the Leonids meteor shower are just small pieces of Comet Temple-Tuttle falling to Earth.

Gravel Ejected from Asteroid Bennu
15.09.2020

Why does asteroid Bennu eject gravel into space? No one is sure. The discovery, occurring during several episodes by NASA's visiting ORISIS-REx spacecraft, was unexpected. Leading ejection hypotheses include impacts by Sun-orbiting meteoroids, sudden thermal fractures of internal structures, and the sudden release of a water vapor jet.

Big Mars from Hubble
27.08.2003

At about 10 am Universal Time today, Mars and Earth will pass closer than in nearly 60,000 years. Mars, noticeably red, will be the brightest object in the eastern sky just after sunset.

Comet C 2002 T7 (LINEAR)
22.04.2004

Discovered by the the Lincoln Near Earth Asteroid Research (LINEAR) project in October of 2002, comet C/2002 T7 is now visiting the inner solar system, making its closest approach (see animation by L. Koehn) to the Sun tomorrow, April 23rd.