Peering deep into a distant galaxy, astronomers from the University of Wisconsin, Madison and the University of Colorado at Boulder have obtained a glimpse of what may be the youngest massive star clusters ever observed.
The discovery, announced at the 195th meeting of the American Astronomical Society Jan. 11 to Jan 15 in Atlanta, provides astronomers with a look inside stellar nurseries at massive clusters of stars in their infancy. Estimated to be only about 500,000 years old, the star clusters are in the very earliest stages of development, analogous to the first day of life of a human, the astronomers said.
"This is exciting because it may reveal the types of environments where globular clusters form," said Henry Kobulnicky, a UW-Madison astronomer and lead scientist on the project. "No one has ever seen a star cluster of any type, much less a possible globular cluster, at such a young age."
Kobulnicky聮s colleague in the discovery, Kelsey Johnson, is a doctoral student in CU-Boulder聮s astrophysical and planetary sciences department and a research assistant at JILA. JILA is a joint institute of CU-Boulder and the National Institute for Standards and Technology.
The discovery was made with the help of the Very Large Array, a huge, highly sensitive radio telescope located near Socorro, N.M. Using the VLA, Kobulnicky and Johnson were able to look deep into a galaxy known as Henize 2-10 and penetrate obscuring clouds of dust and ionized gas surrounding at least five clusters consisting of hundreds of young, massive stars.
Common in galaxies, star clusters are tightly packed groups of hundreds to thousands of stars that are much more luminous and massive than the sun, said Johnson. "Their ages are typically estimated to be several million years old," she said. "Globular clusters are similar, but far older -- 8 to 12 billion years -- and consist of stars more like the sun."
Free of the obscuring clouds of dust and gas found around stars in the earliest stages of their existence, most star clusters can be seen with conventional optical telescopes. Stars coming to life within cocoons of dust and gas, while hidden from view, can be detected by the radio waves that pass through the obscuring clouds, Kobulnicky said.
The Wisconsin-Colorado team observed five clusters of stars with an estimated 500 to 1,000 massive stars each in Henize 2-10, a galaxy located 32 million light years from Earth in the constellation Pyxis. Packed into relatively small areas of space, such dense clusters of massive stars are believed to evolve over billions of years into globular clusters like the ones orbiting the Milky Way.
Knowing about the first stages of their development is important because it will provide some insight into how such objects -- which appear to be common in all galaxies -- come into being, said Johnson.
The work was supported by NASA through grants to the University of Wisconsin, Madison and CU-Boulder. The VLA is operated by the National Radio Astronomy Observatory, an arm of the National Science Foundation.
A radio telescope image of an ancient star cluster is available at: .