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Explanation: 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 gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.
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NASA Web Site Statements, Warnings, and Disclaimers
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: gravitational lens - Einstein cross - quasar
Publications with words: gravitational lens - Einstein cross - quasar
See also:
- APOD: 2026 January 4 Á The Einstein Cross Gravitational Lens
- APOD: 2025 April 21 Á Galaxy Lenses Galaxy from Webb
- Galaxy Cluster Abell 370 and Beyond
- Webb's First Deep Field
- APOD: 2023 January 18 Á MACS0647: Gravitational Lensing of the Early Universe by Webb
- Webb s First Deep Field
- A Molten Galaxy Einstein Ring Galaxy