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ESO 47/08 - Associated Images

12 December 2008
For Immediate Release

Astronomers Dissect a Supermassive Black Hole with Natural Magnifying Glasses

The Einstein Cross and the galaxy that causes this 'cosmic mirage', as seen with the FORS instrument on ESO's Very Large Telescope. This cross-shaped configuration consists of four images of a single very distant source. The multiple images are a result of gravitational lensing by a foreground galaxy, an effect that was predicted by Albert Einstein as a consequence of his theory of general relativity. The light source in the Einstein Cross is a quasar approximately ten billion light-years away, whereas the foreground lensing galaxy is ten times closer. The light from the quasar is bent in its path and magnified by the gravitational field of the lensing galaxy.
Credit: ESO/F. Courbin et al.

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Close-up of the Einstein Cross, as observed with the SINFONI instrument on ESO's Very Large Telescope. SINFONI makes use of the adaptive optics technique and so, allows astronomers to overcome the blurring effect of the atmosphere, thereby providing very sharp images. The central blob is the nucleus of the lensing galaxy, surrounded by the four mirage images of the distant quasar.
Credit: ESO/F. Courbin et al.

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This animation shows the principle of macro- and microlensing. In "macrolensing", a galaxy plays the role of a cosmic magnifying glass or a natural telescope, an effect that was predicted by Albert Einstein as a consequence of his theory of general relativity. The light from a distant quasar is bent in its path and magnified by the gravitational field of the lensing galaxy. This proves very useful in astronomy as it allows us to observe distant objects that would otherwise be too faint to explore using currently available telescopes. In addition to macrolensing by the galaxy, stars in the lensing galaxy act as secondary lenses to produce an additional magnification. This secondary magnification is based on the same principle as macrolensing, but on a smaller scale, and since stars are much smaller than galaxies, is known as "microlensing". As the stars are moving in the lensing galaxy, the microlensing magnification also changes with time. From Earth, the brightness of the quasar images (four in the case of the Einstein Cross) flickers around a mean value, due to microlensing.
Credit: ESO

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