Astronomy Picture of the Day

Explanation: The famous "Einstein Cross" is a case where a single object is seen four times. Here a very distant QSO happened to be placed right behind a massive galaxy. The gravitational effect of the galaxy on the distant QSO was similar to the lens effect of a drinking glass on a distant street light - it created multiple images. But stars in the foreground galaxy have been found to act as gravitational lenses here too! These stars make the images change brightness relative to each other. These brightness changes are visible on these two photographs of the Einstein Cross, taken about 3 years apart.

For more information about this picture see the home page of the IAU Symposium 173 Astrophysical Applications of Gravitational Lensing in Melbourne, Australia 9-14 July, 1995.

January February March April May June July August September October November December

<  July 1995   > Mo Tu We Th Fr Sa Su 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.

Publications with keywords: microlensing - Einstein cross
Publications with words: microlensing - Einstein cross
See also:

• BLG 109: A Distant Version of our own Solar System
• A Network of Microlensing Caustics
• Sparkling Star May Indicate Galactic Composition
• Unusual Flashes Toward Globular Cluster M22
• Microlensing of the Einstein Cross
• The Einstein Cross Gravitational Lens