Best of AOP - Galaxies

Einsteinʼs Cross

Here is an example of a chance alignment whose probability boggles the mind. However, in a Universe the size of our own even the seemingly impossible happens every so often. In the foreground is a small barred spiral galaxy- PGC 69457. Given a value of Hubble's constant of 75- this galaxy is roughly 500 million light years away. Think that is incredible? Look closely at the nucleus of this galaxy, it appears to have four parts! While questionably resolved in this amateur image, HST images of the same clearly show this strange feature. The four images are not of the nucleus of PGC 69457, instead they are images of a background quasar! (QSO2237+0305). This quasar (very luminous galaxy of the early Universe) is around 13 billion light years away! The mass of PGC 69457 changes the geometry (curvature) of space. As the light of the quasar passes near to the foreground galaxy, it acts like a lens and shows us multiple images of the background quasar. This is one of the best examples of the effect that Einstein postulated in the early 1900's (and much later detected in this example in 1989 (Huchra et al). More recently astronomers have discovered that the four images change in their relative brightness due to stars in the foreground galaxy. By measuring the difference of time of these variations astronomers can learn a lot about both objects.

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Last Updated: 19-Feb-2014

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About This Image

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Equipment

20in RC Optical Systems telescope Operating at f/8.1

Paramount ME Robotic Telescope Mount

SBIG ST10XME CCD camera with color filter wheel

LRGB color production was used to create this image.

Four iterations of L-R deconvolution (sharpening) algorithm using CCDsharp were applied to the luminance image.

Digital Development (DDP) via Maxim/DL was also used in order to display the very dim and very bright details of

the image simultaneously.

Luminance = 75 minutes binned 1x1

Red = 10 minutes binned 2x2

Green = 10 minutes binned 2x2

Blue = 10 minutes binned 2x2

Minimum credit line: Adam Block/NOAO/AURA/NSF