The orbiting Gaia space telescope is measuring the brightness, location, and movement of large chunks of our Milky Way galaxy, and this work makes it possible to see how some stars are simply passing in their very different orbits while others seem to originate from the same family of stars. 

Continuing the Sloan Digital Sky Survey’s tradition of announcing new stellar streams at AAS, researchers using Gaia announced that an object loved by many amateur astronomers, the Southern Beehive cluster or NGC 2516, is much bigger than what we see in our binoculars. The full system is at least 1600 light-years tip to tip, and at its distance, is able to sweep across 40 full moon-widths of the sky. Research co-author Gaspar Bakos explains: I have seen the Southern Beehive many times through a pair of binoculars under the dark skies of Chile. The cluster nicely fits the view of the binoculars, because its apparent size in the sky is something like the tip of my thumb at arm’s length. It is curious to know … that the cluster actually spans an area as big as my entire palm held toward the sky.

The lead author of this study, Luke Bouma, points out that: The broader implication is that there are bound to be other enormous open clusters like this. The visible part of the cluster, where we can easily see the stars close together, may be only a small part of a much, much larger stream.

Stars that all belong to the same cluster also have the same age and the same chemical composition. The more stars we know belong to one system, the more opportunities we have to see how solar systems can form when the chemistry is held constant. 

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Princeton press release