Gliese 710.

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A view of a small part of the sky as if you were staring at a star (centre) approaching nearly head on, and then as it passes by and away again. The motion can be likened to what an observer standing beside a road would see looking at an approaching car, and then swinging around to continue to follow it as it moves away. As a result, the objects in the background – in this case distant stars – become blurred as you move quickly to maintain a visual on the passing object. The focus of this animation is the star known as Gliese 710. It will have a close encounter with our Sun in 1.3 million years, passing within the Oort Cloud reservoir of comets in the outskirts of our Solar System. The star is predicted to pass within about 2.3 trillion kilometres, the equivalent of about 16 000 Earth–Sun distances. The star’s motion is set against a background of other moving stars and the visualisation covers, very quickly, the timeframe from about 1.1–1.5 million years in the future. The size of

NGC 6791: An Old, Large Open Cluster

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NGC 6791 is one of the oldest and largest open clusters of stars known. But how did it get so dirty? Open star clusters usually contain a few hundred stars each less than a billion years old.

Open star cluster NGC 6791, however, contains thousands of stars recently measured to be about 8 billion years old. What's really confusing, though, is that the stars of NGC 6791 are relatively dirty - the minuscule amounts of heavy elements (generically called metals) are high relative to most other star clusters.

Older stars are supposed to be metal poor, since metals have only been slowly accumulating in our Milky Way Galaxy.

This enigma makes NGC 6791, pictured above, one of the most studied open clusters and a possible example of how stars might evolve in the centers of galaxies.

NGC 6791: An Old, Large Open Cluster
Barbara J. Mochejska (CAMK) et al., 2.1-m Telescope, KPNO, NOAO, NSF

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