The Decade that Defined Star System
29.12.1999

As the 1990s began, the only planetary star system known was our own Solar System. The first extra-solar star system was discovered orbiting a pulsar in 1991. Slight changes in the precise arrival times of the pulses from the central small dense neutron star gave evidence of orbiting planets.

Movie: A Green Flash Over Italy
29.01.2007

How could the Sun turn green? Difficult to observe, the momentary green flash above the rising or setting sun has been documented as a phenomenon caused by the atmospheric bending or refraction of sunlight.

Eclipsed Moon in the Morning
9.12.2011

Tomorrow, December 10, the Full Moon will slide through planet Earth's shadow in a total lunar eclipse. The entire eclipse sequence, including 51 minutes of totality, will be visible from Asia and Australia...

The Big Dipper
21.04.2013

Do you see it? This common question frequently precedes the rediscovery of one of the most commonly recognized configurations of stars on the northern sky: the Big Dipper. This grouping of stars is one of the few things that has likely been seen, and will be seen, by every generation.

Space Shuttle Rising
24.05.2015

What's that rising from the clouds? The space shuttle. Sometimes, if you looked out the window of an airplane at just the right place and time, you could have seen something very unusual -- a space shuttle launching to orbit.

Sunrise at Copernicus Crater
30.05.2019

A prominent impact site anchored in the lunar Oceanus Procellarum, Copernicus crater is at the center of this telescopic portrait in light and shadow. Caught in stacked and sharpened video frames recorded on April...

APOD: 2025 September 22 Б Equinox at Saturn
22.09.2025

On Saturn, the rings tell you the season. On Earth, today marks an equinox, the time when the Earth's equator tilts directly toward the Sun. Since Saturn's grand rings orbit along...

Triton: Neptune's Largest Moon
10.10.1996

Today marks the 150^th anniversary of the discovery of Triton. On October 10 1846, William Lassell was observing the newly discovered planet Neptune. He was attempting to confirm his observation, made just the previous week, that Neptune had a ring. But this time he discovered that Neptune had a satellite as well.

Bakasa Eclipse Sequence
6.07.2001

Starting at the upper left, this sequence of images follows the progress of the magnificent 21 June, 2001 solar eclipse in the clear skies over Bakasa, Zimbabwe. These pictures were recorded using a small reflecting telescope and digital camera with the approximate local time given above each frame.

Moon Occults Saturn
8.09.2001

On September 18, 1997, many stargazers in the U. S. were able to watch a lovely early morning lunar occultation as a bright Moon passed in front of Saturn. Using a 1.2 meter reflector, astronomer Kris Stanek had an excellent view of this dream-like event from the Whipple Observatory atop Arizona's Mount Hopkins.