Hubble Finds Infant Stars in Neighboring Galaxy

An American Astronomical Society Meeting Release

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January 12, 2005: Astronomers using NASA's Hubble Space Telescope have uncovered for the first time a population of embryonic stars in the Small Magellanic Cloud, a companion galaxy of our Milky Way. Hubble's exquisite sharpness plucked out an underlying population of embryonic stars embedded in the nebula NGC 346 that are still forming from gravitationally collapsing gas clouds. They have not yet ignited their hydrogen fuel to sustain nuclear fusion. The smallest of these infant stars is only half the mass of our Sun.

Q & A: Understanding the Discovery

1. 1. What is the Small Magellanic Cloud?




The Small Magellanic Cloud and its bigger brother, the Large Magellanic Cloud, are actually small irregular galaxies orbiting our own larger Milky Way. They are members of the Local Group, a collection of more than 30 galaxies to which our Milky Way belongs. Almost unknown to casual observers in the Northern Hemisphere, the Magellanic Clouds are seen in the southern sky. The Small Magellanic Cloud is about 210,000 light-years away and contains many hot, young stars, indicating that the galaxy has undergone a recent period of star formation. The Portuguese explorer Ferdinand Magellan reported seeing the Magellanic Clouds from the South Pacific during the early 1500s.

2. 2. What triggered the recent star formation in the Small Magellanic Cloud?




Astronomers are not sure. There are not many places in the Small Magellanic Cloud with very recent star formation. The Hubble observations are part of a bigger project whose goal is to determine what triggered the more recent star formation. Astronomers hope that a more detailed analysis of the puzzling distribution of the infant stars will provide some hints.

One possibility is that the galaxy's next-door neighbor, the Large Magellanic Cloud, could, in part, be responsible for instigating the star birth. Dwarf galaxies like the Small Magellanic Cloud, however, all show regions of similarly recent star formation activity, even when there is no interacting companion. A detailed study of the galaxy will hopefully provide crucial information to understand why.