Centaurus A
19.11.2015

What's the closest active galaxy to planet Earth? That would be Centaurus A, only 11 million light-years distant. Spanning over 60,000 light-years, the peculiar elliptical galaxy is also known as NGC 5128.

A Note on the Perseus Cluster
12.09.2003

A truly enormous collection of thousands of galaxies, the Perseus Cluster - like other large galaxy clusters - is filled with hot, x-ray emitting gas. The x-ray hot gas (not the individual galaxies) appears in the left panel above, a false color image from the Chandra Observatory.

Airglow, Gegenschein, and Milky Way
20.04.2013

As far as the eye could see, it was a dark night at Las Campanas Observatory in the southern Atacama desert of Chile. But near local midnight on April 11, this mosaic of 3 minute long exposures revealed a green, unusually intense, atmospheric airglow stretching over thin clouds.

X-Ray Earth
16.09.2000

Above is a picture of the Earth in x-rays, taken in March of 1996 from the orbiting Polar satellite. Most of the planet is dark with superposed continent and coordinate grids, while the bright x-ray emission near the north pole is shown in red. Why does the Earth have an x-ray glow?

In the Arms of M83
11.11.2011

Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. This cosmic close-up, a mosaic based on data from...

Jumbled Galaxy Centaurus A
30.06.2007

At the center of this sharp skyscape, Centaurus A seems to be a fantastic jumble of old yellow stars, young blue star clusters, and imposing dark dust lanes. Spanning over 60,000 light-years, the peculiar elliptical galaxy is apparently the result of a collision of two otherwise normal galaxies.

APOD: 2025 October 22 Б Comet Lemmon over the High Tatras
22.10.2025

Comet Lemmon putting on a show for cameras around the globe. Passing nearest to the Earth this week, the photogenic comet C/2025 A6 (Lemmon) is now extending two long tails : a blue ion tail and a white dust tail.

The Cocoon Nebula from CFHT
14.01.2008

What creates the colors of the Cocoon Nebula? The Cocoon Nebula, cataloged as IC 5146, is a strikingly beautiful nebula located about 4,000 light years away toward the constellation of the Swan (Cygnus). Inside the Cocoon Nebula is a newly developing open cluster of stars.

M83: The Thousand Ruby Galaxy
27.09.2008

Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name of the Southern Pinwheel.

M83: The Thousand Ruby Galaxy
8.10.2015

Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name, The Southern Pinwheel.