Hubble Spies Star Clusters on a Collision Course
Posted on August 16, 2012
Astronomers using data from NASA's Hubble Space Telescope have caught two clusters full of massive stars that may be in the early stages of merging. The clusters are 170,000 light-years away in the Large Magellanic Cloud, a small satellite galaxy to our Milky Way. The clusters lie in the gigantic 30 Doradus nebula. The Hubble observations, made with the Wide Field Camera 3, were taken Oct. 20-27, 2009. The blue color is light from the hottest and most massive stars. The green color is from the glow of oxygen and the red from fluorescing hydrogen.
What at first was thought to be only one cluster in the core of the massive star-forming region 30 Doradus (also known as the Tarantula Nebula) has been found to be a composite of two clusters that differ in age by about one million years. The entire 30 Doradus complex has been an active star-forming region for 25 million years. Astronomers say it is currently unknown how much longer the region can continue creating new stars.
Lead scientist Elena Sabbi of the Space Telescope Science Institute in Baltimore, Md., and her team began looking at the area while searching for runaway stars. She says, "Stars are supposed to form in clusters, but there are many young stars outside 30 Doradus that could not have formed where they are; they may have been ejected at very high velocity from 30 Doradus itself."
During her research, she noticed something unusual about the cluster when looking at the distribution of the low-mass stars detected by Hubble. It is not spherical, as was expected, but has features somewhat similar to the shape of two merging galaxies where their shapes are elongated by the tidal pull of gravity. Hubble's circumstantial evidence for the impending merger comes from seeing an elongated structure in one of the clusters, and from measuring a different age between the two clusters. According to some models, the giant gas clouds out of which star clusters form may fragment into smaller pieces. Once these small pieces precipitate stars, they might then interact and merge to become a bigger system. This interaction is what Sabbi and her team think is happening in 30 Doradus.
You can find larger versions of the above image here on HubbleSite.org.
Photo: NASA, ESA, R. O'Connell (University of Virginia), and the Wide Field Camera 3 Science Oversight Committee