Comet Holmes Coma Expands
30.10.2007

Go outside tonight and see Comet Holmes. No binoculars or telescopes are needed -- just curiosity and a sky map. Last week, Comet 17P/Holmes underwent an unusual outburst that vaulted it unexpectedly from obscurity into one of the brightest comets in recent years.

M57: The Ring Nebula
15.11.2009

It looks like a ring on the sky. Hundreds of years ago astronomers noticed a nebula with a most unusual shape. Now known as M57 or NGC 6720, the gas cloud became popularly known as the Ring Nebula.

Iridescent Clouds from the Top of the World Highway
8.02.2011

Why would a cloud appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size.

The Unexpected Tails of Asteroid P5
12.11.2013

What is happening to asteroid P/2013 P5? No one is sure. For reasons unknown, the asteroid is now sporting not one but six discernible tails. The above images were taken two months ago by the orbiting Hubble Space Telescope and show the rapidly changing dust streams.

Comet McNaught Over New Zealand
19.10.2014

Comet McNaught was perhaps the most photogenic comet of modern times -- from Earth. After making quite a show in the northern hemisphere in early January of 2007, the comet moved south and developed a long and unusual dust tail that dazzled southern hemisphere observers.

A Mercury Transit Sequence
10.11.2019

Tomorrow -- Monday -- Mercury will cross the face of the Sun, as seen from Earth. Called a transit, the last time this happened was in 2016. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun.

APOD: 2024 July 7 Б Iridescent Clouds over Sweden
7.07.2024

Why are these clouds multi-colored? A relatively rare phenomenon in clouds known as iridescence can bring up unusual colors vividly -- or even a whole spectrum of colors simultaneously. These polar stratospheric clouds also, known as nacreous and mother-of-pearl clouds, are formed of small water droplets of nearly uniform size.

Burning Tree Sprite
2.08.2001

This dramatic, garishly colored image was captured with a low-light level camera on 2001 June 7. It shows what appears to be a "burning tree" above the National Cheng Kung University campus in Tainan City, Taiwan ... but the burning tree is actually a fleeting red sprite 300 kilometers away.

Saturns Moon Dione from Cassini
1.12.2004

What causes the bright streaks on Dione? Recent and likely future images of this unusual moon by the robot Cassini spacecraft now orbiting Saturn might help us find out. The above image was taken at the end of October from a distance of about one million kilometers.

Phoebe: Comet Moon of Saturn
12.02.2006

Was Saturn's moon Phoebe once a comet? Images from the robotic Cassini spacecraft taken two years ago when entering the neighborhood of Saturn indicate that Phoebe may have originated in the outer Solar System.