Sirius: The Brightest Star in the Night
2.09.1996

Sirius is the brightest star in the night sky. Intrinsically, Sirius is over 20 times brighter than our Sun and over twice as massive. As Sirius is 8.7 light years distant, it is not the closest star system -- the Alpha Centauri system holds this distinction.

Retrograde Mars
11.05.2008

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.

Six Planets from Yosemite
14.06.2018

The five naked-eye planets, Mercury, Venus, Mars, Jupiter and Saturn, have been seen since ancient times to wander the night skies of planet Earth. So it could be remarkable that on this night, standing at the side of a clear, calm lake, six planets can be seen with the unaided eye. Have a look.

Black Hole Candidate Cygnus X 1
11.08.2008

Is that a black hole? Quite possibly. The Cygnus X-1 binary star system contains one of the best candidates for a black hole. The system was discovered because it is one of the brightest...

The North Pole of Venus
14.05.2003

If you could look down on the North Pole of Venus what would you see? The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar.

Juno Rockets Toward Jupiter
9.08.2011

Next stop: Jupiter. Last week included one of the few times in history that humanity launched something completely off the Earth, moving away so fast that it will never return. Well, almost -- Juno...

Golden Gate Sunset: Green Flash
2.12.2015

The setting is San Francisco Bay, the time is sunset, and the bridge is the Golden Gate. What you are about to see is an unexpected double sunset ending with a rare green flash.

Epsilon Tauri: Star with Planet
26.01.2024

Epsilon Tauri lies 146 light-years away. A K-type red giant star, epsilon Tau is cooler than the Sun, but with about 13 times the solar radius it has nearly 100 times the solar luminosity.

APOD: 2026 May 5 Б Orion over Mount Teide
5.05.2026

Orion is rarely seen like this. To achieve this majestic vista, you need a camera capable of taking such long duration exposures that faint features in the night sky become revealed. Iconic nebulas that appear include the Orion Nebula, the Flame Nebula, and Barnard's Loop.

The Brightest Star Yet Known
8.10.1997

Star light, star bright, a new brightest star has been discovered in the night. This new brightest star is so far away and so obscured by dust, however, that it took the Hubble Space Telescope to confirm it.