Scientists observing two star clusters have uncovered new information on how stars are born. The observations used for the study were gathered using NASA's Chandra Observatory.
With the help of the Chandra Observatory, researchers were able to determine that previous theories on star formation and star clusters were incorrect. Previous theories proposed that stars where formed when clouds of space dust and gas condensed. This would have resulted in the formation of star clusters. These theories supposed that stars located in the middle of star clusters should be the oldest stars in the cluster. However, the recent observations using the Chandra Observatory indicate otherwise.
"Our findings are counterintuitive," said Penn State University researcher Konstantin Getman. "It means we need to think harder and come up with more ideas of how stars like our sun are formed."
Instead of finding older stars in the middle of the star clusters NGC 2024 and the Orion Nebula Cluster, the scientists found that the oldest stars in these clusters could be found in the outer regions of the gas clouds. The two clusters observed by the scientists contained newly formed stars that were very similar to the Sun.
"A key conclusion from our study is we can reject the basic model where clusters form from the inside out," said Penn State University researcher Eric Feigelson. "So we need to consider more complex models that are now emerging from star formation studies."
The researchers were able to determine that the oldest stars in the clusters were located in the outer regions by using a two-step methodology. The researchers analyzed data gathered by the Chandra Observatory on the brightness of the stars in the clusters. This was done by measuring the brightness of certain target stars in X-rays. Using this method, the scientists were able to determine the mass of the target stars. After determining the mass, the researchers then looked to infrared measurements of the light emitted by the stars. This was done using ground-based observatories combined with observations taken by the NASA operated Spitzer Space telescope.
After analyzing the data from various ground and space based telescopes, the researchers were able to compare the data with existing theoretical models of star formation. According to their findings, the stars located on the outer areas of the clusters were around 1.5 million years old. In comparison, the stars in the center were only around 200,000 years old.
"The next steps will be to see if we find this same age range in other young clusters," said Michael Kuhn, a graduate student at the Penn State University.
