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Taking Stock of a Southern Starburst.

In an ongoing study of our galaxy's starburst regions, an international team of astronomers led by Bernhard Brandl (Cornell University) finds that these stellar nurseries spawn not only massive O- and B-type stars but also large numbers of stars less massive than our Sun. This graphically demonstrates that low-mass stars can survive in starbursts, where bigger stars emit copious ultraviolet radiation and high-speed particles. Using Antu, the first operating 8.2-meter element of the European Very Large Telescope (VLT), Brandl and his colleagues obtained deep near-infrared images of NGC 3603, a starburst region comprising a massive star cluster and associated nebulosity in the southern constellation Carina. Dozens of individual images were taken last April and combined to form this false-color composite, which spans 3.4 arcminutes, or 20 light-years at the cluster's distance (20,000 light-years). At near-infrared wavelengths many faint stars are seen that were obscured by cosmic dust in a recently published visible-light image taken with the Hubble Space Telescope (S&T: September 1999, page 50). Antu's light-gathering power is greater than the 2.4-meter Hubble's, and it observed NGC 3603 for a longer time. Moreover, low-mass stars, being generally reddish, are relatively bright at infrared wavelengths. A computer analysis quantified the brightnesses and colors of some 7,000 of NGC 3603's stars, enabling Brandl and his colleagues to estimate their ages and masses. Writing in the December 1, 1999, issue of Astronomy and Astrophysics, Brandl and his colleagues conclude that NGC 3603 contains thousands of subsolar stars as faint as 0.1 solar mass; most of these stars are 300,000 to 1 million years old. According to the authors, "Only [the VLT's] high angular resolution, image stability and overall sensitivity enabled us to study the subsolar stellar population in a starburst region on a star by star basis."

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Title Annotation:observations of subsolar stars
Publication:Sky & Telescope
Article Type:Brief Article
Date:Feb 1, 2000
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