A Year of Resolving Backgrounds
29.12.2000

No matter which direction you look, no matter what type of light you see, the sky glows - but why? The sources of many of these background radiations have remained long-standing puzzles, but this millennial year brought some partial resolutions.

The Compton Observatory Turns Five
13.04.1996

Earlier this April, NASA's Compton Gamma Ray Observatory, completed its fifth successful year in orbit, exploring the gamma ray sky. Pictured is astronaut Jay Apt perched in the shuttle payload bay below the massive observatory. Compton is the largest civilian instrument ever flown - the whole observatory is roughly the size of a school bus.

NGC 3621: Far Beyond the Local Group
23.02.2017

Far beyond the local group of galaxies lies NGC 3621, some 22 million light-years away. Found in the multi-headed southern constellation Hydra, the winding spiral arms of this gorgeous island universe are loaded with luminous blue star clusters, pinkish starforming regions, and dark dust lanes.

The Planet, the White Dwarf, and the Neutron Star
18.07.2003

A planet, a white dwarf, and a neutron star orbit each other in the giant globular star cluster M4, some 5,600 light-years away. The most visible member of the trio is the white...

The Hercules Cluster of Galaxies
6.11.2020

These are galaxies of the Hercules Cluster, an archipelago of island universes a mere 500 million light-years away. Also known as Abell 2151, this cluster is loaded with gas and dust rich, star-forming spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars.

BATSE GRB Final Sky Map
28.06.2000

What causes the most powerful explosions in the universe? The BATSE modules that flew on the Compton Gamma Ray Observatory allowed more insight into enigmatic gamma-ray burst (GRB) explosions than ever before. From 1991-2000, BATSE detected 2704 GRBs, much more than ever previously recorded.

Tychos Supernova Remnant in Xray
12.01.2019

What star created this huge puffball? What's pictured is the hot expanding nebula of Tycho's supernova remnant, the result of a stellar explosion first recorded over 400 years ago by the famous astronomer Tycho Brahe. The featured image is a composite of three X-ray colors taken by the orbiting Chandra X-ray Observatory.

Albert Einstein s Miraculous Year
22.04.2005

In 1905 Albert Einstein had a miraculous year. One hundred years ago, he wrote four papers which revolutionized our understanding of the Universe. The papers outlined; the idea that light could behave...

The Hercules Cluster of Galaxies
25.06.2014

These are galaxies of the Hercules Cluster, an archipelago of island universes a mere 500 million light-years away. Also known as Abell 2151, this cluster is loaded with gas and dust rich, star-forming spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars.

APOD: 2025 October 3 Б Pandora's Cluster of Galaxies
2.10.2025

This deep field mosaicked image presents a stunning view of galaxy cluster Abell 2744 recorded by the James Webb Space Telescope's NIRCam. Also dubbed Pandora's Cluster, Abell 2744 itself appears to be a ponderous merger of three different massive galaxy clusters. It lies some 3.5 billion light-years away, toward the constellation Sculptor.