PG 1115: A Ghost of Lensing Past
1.11.1998

In this tangle of quasars and galaxies lies a clue to the expansion rate of the universe. A diffuse glow evident in the picture on the left reveals a normal elliptical galaxy. Directly behind this galaxy lies a normal quasar.

APM 08279+5255: The Brightest Object Yet Known
18.08.1998

It shines with the brightness of 100 billion Suns. Is it a mirage? The recently discovered quasar labeled APM 08279+5255 has set a new record as being the brightest continuously emitting object yet known.

A Quasar Portrait Gallery
8.03.2002

Quasars (QUASi-stellAR objects) lie near the edge of the observable Universe. Discovered in 1963, astronomers were astounded that such objects could be visible across billions of light-years, as this implies they must emit prodigious amounts of energy. Where does the energy come from?

The Galaxy and the Quasar
7.10.2002

Is the galaxy in the center connected to the quasar on the upper right? Disagreements about systems like this have raged for decades and have been used to challenge the foundations of modern cosmology.

A Quasar-Galaxy Collision?
21.10.1995

In 1963 astronomers were astounded to discover that certain faint, star-like objects have very large redshifts. The large redshifts imply that these objects, now known as quasars (QUASi-stellAR objects), lie near the edge of the observable Universe.

BLG 109: A Distant Version of our own Solar System
17.02.2008

How common are planetary systems like our own? Perhaps quite common, as the first system of planets like our own Solar System has been discovered using a newly adapted technique that, so far, has probed only six planetary systems.

Unusual Flashes Toward Globular Cluster M22
3.07.2001

What is causing the unusual flashes behind globular cluster M22? This teaming ball of stars is the brightest globular cluster visible in Earth's northern hemisphere. M22, shown in full in the inset, spans about 50 light years away and lies 8500 light-years toward the constellation of Sagittarius.

High Redshift Quasars
10.12.1998

Each red speck indicated above is a powerful quasar estimated to be over 100 times brighter than a galaxy. Yet in these Sloan Digital Sky Survey discovery images the quasars appear faint because they are extremely distant.

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.

The Lyman Alpha Forest
23.02.1998

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.