XMM Launched
21.12.1999

X-ray astronomy entered a golden age earlier this month with the successful launch of the X-ray Multi-Mirror (XMM) satellite. XMM's three huge telescope barrels each hold 58 concentric cylindrical mirrors, together totaling a surface area rivaling a tennis court.

Merging NGC 2623
19.10.2012

NGC 2623 is really two galaxies that are becoming one. Seen to be in the final stages of a titanic galaxy merger, the pair lies some 300 million light-years distant toward the constellation Cancer.

A Year of Resolving Backgrounds
30.12.2000

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 Giant Radio Lobes of Fornax A
28.06.2005

Together, the radio lobes span over one million light years -- what caused them? In the center is a large but peculiar elliptical galaxy dubbed NGC 1316. Detailed inspection of the NGC 1316 system indicates that it began absorbing a small neighboring galaxy about 100 million years ago.

Messier 106
19.03.2011

Close to the Great Bear (Ursa Major) and surrounded by the stars of the Hunting Dogs (Canes Venatici), this celestial wonder was discovered in 1781 by the metric French astronomer Pierre Mechain. Later, it was added to the catalog of his friend and colleague Charles Messier as M106.

APOD: 2023 January 23 Б The Colliding Spiral Galaxies of Arp 274
23.01.2023

Two galaxies are squaring off in Virgo and here are the latest pictures. When two galaxies collide, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small fraction of that space.

A Nearby Supernova in M51
19.07.2005

One of the nearest supernovas of recent years was discovered late last month in the bright nearby galaxy M51. It is visible on the right of the above before and after images of the picturesque spiral. Can you spot it?

APOD: 2025 June 24 Б In the Center of Spiral Galaxy M61
24.06.2025

Is there a spiral galaxy in the center of this spiral galaxy? Sort of. Image data from the Hubble Space Telescope, the European Southern Observatory, and smaller telescopes on planet Earth are combined in this detailed portrait of face-on spiral galaxy Messier 61 (M61) and its bright center.

NGC 253: Dusty Island Universe
26.07.2014

Shiny NGC 253 is one of the brightest spiral galaxies visible, and also one of the dustiest. Some call it the Silver Dollar Galaxy for its appearance in small telescopes, or just the Sculptor Galaxy for its location within the boundaries of the southern constellation Sculptor.

The Tulip and Cygnus X 1
16.02.2017

Framing a bright emission region, this telescopic view looks out along the plane of our Milky Way Galaxy toward the nebula rich constellation Cygnus the Swan. Popularly called the Tulip Nebula, the reddish glowing cloud of interstellar gas and dust is also found in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101.