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Recent Podcast
Tour of NGC 2207
Tour of NGC 2207
When galaxies get together, there is also the chance of a spectacular light show. (2014-12-16)


Macs J0025.4-1222 in 60 Seconds Plus

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Narrator (Megan Watzke, CXC): Two galaxy clusters, each a quadrillion times the mass of the Sun, collided to form the system formally known as Macs J0025.4-1222. When these clusters merged at speeds of millions of miles per hour, the hot gas in each cluster collided and slowed down, but the dark matter in each system did not. Optical images from Hubble were used to infer the distribution of the total mass, which includes dark matter, using a technique known as gravitational lensing. This is seen as blue in the image. Chandra data enabled astronomers to accurately map the position of the ordinary matter, mostly in the form of hot gas, which glows brightly in X-rays and is colored pink in the composite. The separation between the pink and the blue provides direct evidence for the existence of dark matter.

In some ways, Macs J0025 can be thought of as a prequel to the famous system known as the Bullet Cluster. At a much larger distance of 5.7 billion light years, astronomers are witnessing this collision that occurred long before the Bullet Cluster. This finding is important because it independently verifies the results found for the Bullet Cluster in 2006, and shows once again that dark matter is real.

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