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Credit & Copyright: Geraint Lewis and Michael Irwin, William Hershel Telescope
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.
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: microlensing - Einstein cross
Publications with words: microlensing - Einstein cross
See also: