The Hubble Space Telescope of NASA has captured two complete sets of massive stars to be merged. The star clusters are in the Large Magellanic Cloud , a small satellite galaxy of our Milky Way about 170,000 light years away.
What at first was thought to be one group, in the center of the massive star-forming region of the Tarantula Nebula , have proved to be two clusters that differ by about a million years old.
The whole complex of the Tarantula Nebula has been an active star-forming region for 25 million years, and currently unknown how much longer this region can continue creating new stars. Scientists looked in the runaway stars , which have been expelled from the stellar nurseries where they formed. “It is assumed that stars form in clusters, but there are many young stars that are out of the Tarantula Nebula, which could not have formed where they are, but were expelled at very high speed of the nebula,” says Elena Sabbi , Space Telescope Science Institute in Baltimore.
The researcher noticed something unusual in the group when looking at the distribution of low-mass stars detected by Hubble. It was spherical, as expected, but had characteristics somewhat similar to the shape of two colliding galaxies , which have elongated shapes by the tidal force of gravity. Evidence of the impending merger is an elongated structure of groups and different ages of both groups.
According to some models, the giant clouds of gas out of which are formed star clusters may fragment into smaller pieces. Once these small pieces originate stars, they can interact and unite to become a larger system. This interaction is what Sabbi and his team think is happening in the Tarantula Nebula. There is also an unusually large number of stars around the nebula fast. Astronomers believe these runaway stars were ejected from the nucleus of the nebula, as a result of the dynamic interactions between them.These interactions are very common during a process called core collapse, in which the most massive stars sink to the center of a group interacting with stars of lower mass. When many massive stars have reached the nucleus, the nucleus becomes unstable and these massive stars begin to eject each other from the pool.
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The large cluster R136 in the center of the nebula is too young to have already experienced a core collapse. However, as in the smaller systems this process is much faster, the large number of runaway stars have been found in the region can be better explained if a small group has been merged into R136.
Further studies will look at the area in more detail and greater scale to see if any group is in contact with those observed. The future large telescope of NASA, James Webb , with infrared sensitivity will allow astronomers to look deep into the regions of the Tarantula Nebula is obscured in visible light photographs. In these areas, and weak cooler stars are hidden from view within clusters of dust.This discovery could help scientists understand the details of the formation of star clusters in the early universe.