M1: Filaments of the Crab Nebula
7.02.1997

The Crab Nebula is filled with mysterious filaments. The Crab Nebula is the result of a star that exploded in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers.

NGC 6826: The Blinking Eye
19.12.1997

The colorful planetary nebula phase of a sun-like star's life is brief. Almost in the "blink of an eye" - cosmically speaking - the star's outer layers are cast off, forming an expanding emission nebula. This nebula lasts perhaps 10 thousand years compared to a 10 billion year stellar life span.

The Mysterious Cone Nebula
25.12.2005

Sometimes the simplest shapes are the hardest to explain. For example, the origin of the mysterious cone-shaped region seen on the far left remains a mystery. The interstellar formation, dubbed the Cone Nebula, is located about 2700 light years away.

The Witch Head Nebula
29.08.1999

Double, double toil and trouble; Fire burn, and cauldron bubble ... Maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from Rigel.

Breaking Distant Light
4.01.2009

In the distant universe, time appears to run slow. Since time-dilated light appears shifted toward the red end of the spectrum (redshifted), astronomers are able to use cosmological time-slowing to help measure vast distances in the universe.

Anticrepuscular Rays Over Colorado
28.11.2010

What's happening over the horizon? Although the scene may appear somehow supernatural, nothing more unusual is occurring than a setting Sun and some well placed clouds. Pictured above are anticrepuscular rays. To understand them, start by picturing common crepuscular rays that are seen any time that sunlight pours though scattered clouds.

The Terraced Night
6.02.2014

Long after sunset on January 25 an unusually intense red airglow floods this south-looking skyscape. The scene was recorded with a long exposure using a digital camera over Yunnan Province in southwest China. At best faintly visible to the eye, the lingering airglow is due to chemiluminescence, the production of light through chemical excitation.

Shadow of a Martian Robot
28.03.2015

What if you saw your shadow on Mars and it wasn't human? Then you might be the Opportunity rover currently exploring Mars. Opportunity has been exploring the red planet since early 2004, finding evidence of ancient water, and sending breathtaking images across the inner Solar System.

Lenticular Clouds over Mount Etna
19.08.2019

What's happening above that volcano? Although Mount Etna is seen erupting, the clouds are not related to the eruption. They are lenticular clouds formed when moist air is forced upwards near a mountain or volcano.

APOD: 2023 December 4 Б Plane Crossing Crescent Moon
4.12.2023

No, the Moon is not a bow, and no, it did not shoot out a plane like an arrow. What is pictured is a chance superposition. The plane's contrail would normally appear white...