Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2006 May 24
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A Five Quasar Gravitational Lens
Credit: K. Sharon (Tel Aviv U.) and E. Ofek (Caltech), ESA, NASA

Explanation: What's happening near the centre of this cluster of galaxies? At first glance, it appears that several strangely elongated galaxies and fully five bright quasars exist there. In reality, an entire cluster of galaxies is acting as a gigantic gravitational lens that distorts and multiply-images bright objects that occur far in the distance. The five bright white points near the cluster centre are actually images of a single distant quasar. This Hubble Space Telescope image is so detailed that even the host galaxy surrounding the quasar is visible. Close inspection of the above image will reveal that the arced galaxies at 2 and 4 o'clock are actually gravitationally lensed images of the same galaxy. A third image of that galaxy can be found at about 10 o'clock from the cluster centre. Serendipitously, numerous strange and distant galaxies dot the above image like colourful jewels. The cluster of galaxy that acts as the huge gravitational lens is catalogued as SDSS J1004+4112 and lies about 7 billion light years distant toward the constellation of Leo Minor.

Tomorrow's picture: Trifid of the north

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