Geostationary Highway
20.02.2010

Put a satellite in a circular orbit about 42,000 kilometers from the center of the Earth (36,000 kilometers or so above the surface) and it will orbit once in 24 hours. Because that matches Earth's rotation period, it is known as a geosynchronous orbit.

The Moon During a Total Lunar Eclipse
25.05.2021

How does the Moon's appearance change during a total lunar eclipse? The featured time-lapse video was digitally processed to keep the Moon bright and centered during the 5-hour eclipse of 2018 January 31. At first the full moon is visible because only a full moon can undergo a lunar eclipse.

Spherical Planetary Nebula Abell 39
8.10.2012

Ghostly in appearance, Abell 39 is a remarkably simple, spherical nebula about five light-years across. Well within our own Milky Way galaxy, the cosmic sphere is roughly 7,000 light-years distant toward the constellation Hercules.

Distant Galaxies in Radio Vision
8.02.2001

Radio waves, like visible light, are electromagnetic radiation and radio telescopes can "see" -- their signals translated into radio images of the cosmos. While individually even the largest radio telescopes have very blurry vision compared to their optical counterparts, networks of radio telescopes can combine signals to produce sharper pictures.

The Antlia Cluster of Galaxies
18.10.2016

Galaxies dot the sky in this impressively wide and deep image of the Antlia Cluster. The third closest cluster of galaxies to Earth after Virgo and Fornax, the Antlia cluster is known for its compactness and its high fraction of elliptical galaxies over (spirals.

The Gegenschein Over Chile
2.12.2012

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.

A Meteor and the Gegenschein
12.05.2021

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.

The Gegenschein Over Chile
7.05.2008

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.

Deep Orion Over the Canary Islands
23.01.2012

Which attracts your eye more -- the sky or the ground? On the ground are rocky peaks in Teide National Park on Tenerife Island of the Spanish Canary Islands off the northwestern coast of Africa. The volcanic landscape features old island summits and is sometimes used as a testbed for instruments on future Martian rovers.

The Gegenschein Over Chile
14.01.2014

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.