The Lyman Alpha Forest
26.01.2003

We live in a forest. Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects. These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.

The Lyman Alpha Forest
24.02.1998

We live in a forest. Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects. These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.

The Einstein Cross Gravitational Lens
2.01.2013

Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar.

Mystery Object Explained
28.09.1999

Explorers often discover the unexpected. Such was the case when the Second Palomar Observatory Sky Survey chanced upon the unusual object circled in the above photograph. The so-called mystery object appeared star-like but displayed colors unlike most stars or quasars.

The Einstein Cross Gravitational Lens
17.12.2017

Most galaxies have a single nucleus -- does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar.

The Lyman Alpha Forest
12.11.2000

We live in a forest. Strewn throughout the universe are "trees" of hydrogen gas that absorb light from distant objects. These gas clouds leave numerous absorption lines in a distant quasar's spectra, together called the Lyman-alpha forest.

APOD: 2023 July 5 Б A Map of the Observable Universe
5.07.2023

What if you could see out to the edge of the observable universe? You would see galaxies, galaxies, galaxies, and then, well, quasars, which are the bright centers of distant galaxies. To expand understanding...

A Network of Microlensing Caustics
15.12.2002

A virtual sky map like this would be of interest to astronomers studying gravitational microlensing. In microlensing, the gravity of stars near the line of sight can act to magnify the light of background objects such as distant stars, or quasars. Nowhere is this magnification greater than near a gravitational lensing caustic.

A Network of Microlensing Caustics
24.08.1999

A virtual sky map like this would be of interest to astronomers studying gravitational microlensing. In microlensing, the gravity of stars near the line of sight can act to magnify the light of background objects such as distant stars, or quasars. Nowhere is this magnification greater than near a gravitational lensing caustic.

A Radio Vista of Cygnus
18.02.2002

Shells of ancient supernovas, cocoons surrounding newborn stars, and specks from distant quasars highlight this tremendous vista toward the constellation of Cygnus. The representative color image covers about 10 degrees across on the sky but is only a small part of the Canadian Galactic Plane Survey in radio light.