The Universe in Hot Gas
20.08.2002

Where is most of the normal matter in the Universe? Recent observations from the Chandra X-ray Observatory confirm that it is in hot gas filaments strewn throughout the universe. "Normal matter" refers to known elements and familiar fundamental particles.

NGC 7331 and Beyond
17.12.2014

Big, beautiful spiral galaxy NGC 7331 is often touted as an analog to our own Milky Way. About 50 million light-years distant in the northern constellation Pegasus, NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog.

Three Tails of Comet NEOWISE
8.03.2021

What created the unusual red tail in Comet NEOWISE? Sodium. A spectacular sight back in the summer of 2020, Comet NEOWISE, at times, displayed something more than just a surprisingly striated white dust tail and a pleasingly patchy blue ion tail.

Explosions from White Dwarf Star RS Oph
22.08.2021

Spectacular explosions keep occurring in the binary star system named RS Ophiuchi. Every 20 years or so, the red giant star dumps enough hydrogen gas onto its companion white dwarf star to set off a brilliant thermonuclear explosion on the white dwarf's surface.

Pandora's Cluster of Galaxies
8.06.2024

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.

A Tale of Two Nebulae
16.05.2003

This colorful telescopic view towards the northern constellation Lyra reveals dim outer regions around M57, popularly known as the Ring Nebula. While modern astronomers still refer to M57 as a planetary nebula, at one light-year across M57 is not a planet but the gaseous shroud of a dying sun-like star.

APOD: 2023 March 21 Б Dark Nebulae and Star Formation in Taurus
21.03.2023

Can dust be beautiful? Yes, and it can also be useful. The Taurus molecular cloud has several bright stars, but it is the dark dust that really draws attention. The pervasive dust has waves...

A 2001 Leonids Meteor Shower Fireball
19.11.2001

The 2001 Leonids Meteor Shower gave quite a show to many parts of the world yesterday during the early morning hours. Many sleepy observers venturing into their own backyards were treated to several bright meteors per minute streaking across the sky.

Enhanced Color Caloris
4.03.2015

The sprawling Caloris basin on Mercury is one of the solar system's largest impact basins, created during the early history of the solar system by the impact of a large asteroid-sized body.

APOD: 2025 August 14 Б M13: The Great Globular Cluster in Hercules
14.08.2025

In 1716, English astronomer Edmond Halley noted, "This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent." Of course...