Abell 1689 – a massive galaxy cluster 700 megaparsecs distant

abell1689
Image and full story credits are here and the image is now at APOD.

The astronomers used Hubble’s Advanced Camera for Surveys to peer deep inside the heart of Abell 1689, detecting the visible-light glow of 10,000 globular clusters, some as dim as 29th magnitude. Based on that number, Blakeslee’s team estimated that more than 160,000 globular clusters are huddled within a diameter of 2.4 million light-years. “Even though we are looking deep into the cluster, we’re only seeing the brightest globular clusters, and only near the center of Abell 1689 where Hubble was pointed,” he said. The brightness of most of the globular clusters is estimated to be 31st magnitude. This is out of reach for Hubble, but not for NASA’s James Webb Space Telescope, an infrared observatory scheduled to launch later this decade. By going fainter, Webb should be able to see many more of the globular clusters.

This great image of Abell 1689 is a fantastic demonstration of gravitational lensing and I urge readers to follow the link and find out more about how these new observations of extragalactic globular clusters can shed light on the dark matter problem.

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