How Baby Stars Grow to Massive Proportions: Older Stars 'Nurture' Younger Ones

Some stars shouldn't exist--at least in theory. The massive giants that grow to ten times as large as the Sun tend to push away the gas that they feed on, which starves their own growth. So how do some stars get so big? New research may hold the answer.

A group of astronomers studying the phenomenon suggest that baby stars may turn into these giants if they happen to be born within a corral of older stars. If positioned favorably, these older stars could potentially feed the younger ones in their midst.

In order to confirm this theory, though, the researchers studied actual stars. They examined high-quality and high-resolution far-infrared images from the Herschel Space Observatory telescope. The telescope's two cameras are able to record light that's not visible to the naked eye, which allowed the researchers to examine the birth of very massive stars in nearby giant clouds of gas and dust in our own galaxy.  In particular, they looked at a giant cloud of gas called Westerhout 3 (W3), which is located about 6,500 light-years from Earth.

In order to better understand the star formation, the scientists tracked the regions of the gas cloud where stars are about to be born by mapping the density of dust and its temperature. Since stars are born in the denser parts of the clouds where gas gets compressed enough by gravity to trigger nuclear fusion, scientists are able to locate them using the instruments on the Herschel Space Observatory.

In the end, the researchers found that the densest region of the cloud was surrounded by a congregation of old, high-mass stars. This was no coincidence. Each generation of stars may have created the right conditions for another generation to grow, ultimately leading to the formation of the massive cluster. In other words, the older stars help give birth to larger, new stars by being in the same general area. Although the new star will automatically push away the gas that it feeds on, the old stars will keep "nudging" the gas back at it, which causes it to grow larger.

The findings finally give an explanation as to how and why some stars grow so large. In the future, the researchers plan to test their idea through computer modeling.

The results are published in The Astrophysical Journal.