Scientists are beginning to learn more about why stars tend to group themselves in pairs, which are called binary systems, or in clusters like a huge family, and their findings are actually the exact opposite of what was believed.
While researchers earlier thought that older stars stayed close to the center of a cluster, two studies have shown that the most aged stars are actually at the fringes of a group, National Geographic reported.
In one recent study, a Penn State University team examined data gathered by NASA's Chandra X-ray Observatory and infrared telescopes to estimate the ages of stars in two clusters, NGC 2024, located in the center of the Flame Nebula, and the Orion Nebula Cluster.
Before such studies, scientists believed that star clusters formed when gas and dust clouds condensed and material in the center of the giant cloud became solid enough to create a star. But because the oldest stars are found on the edges, they now say the earlier theory can't be right.
"Our findings are counterintuitive," lead researcher Konstantin Getman of Penn State University said in a NASA news release. "It means we need to think harder and come up with more ideas of how stars like our sun are formed."
The researchers looked at the stars' brightness in x-rays to find their masses, then determined how bright they were with infrared light. Their surprising findings showed that stars in the center of NGC 2024 were estimated to be 200,000 years old, compared with 1.5 million years for the stars at the edge of the cluster.
The same was true for the Orion Nebula, which had stars estimated to be 2 million years old at the cluster's fringes, while center stars were aged around 1.2 million years.
"A key conclusion from our study is we can reject the basic model where clusters form from the inside out," co-author Eric Feigelson, also of Penn State, said in the news release. "So we need to consider more complex models that are now emerging from star formation studies."
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