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File:Small magellanic cloud.jpg



Hubble astronomers have uncovered, for the first time, a population of infant stars in the Milky Way satellite galaxy, the Small Magellanic Cloud (SMC, visible to the naked eye in the southern constellation Tucana), located 210,000 light-years away.

Hubble's exquisite sharpness plucked out an underlying population of infant 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.

Although star birth is common within the disk of our galaxy, this smaller companion galaxy is more primeval in that it lacks a large percentage of the heavier elements that are forged in successive generations of stars through nuclear fusion.

Fragmentary galaxies like the SMC are considered primitive building blocks of larger galaxies. Most of these types of galaxies existed far away, when the universe was much younger. The SMC offers a unique nearby laboratory for understanding how stars arose in the early universe. Nestled among other starburst regions with the small galaxy, the nebula NGC 346 alone contains more than 2,500 infant stars.

The Hubble images, taken with the Advanced Camera for Surveys, identify three stellar populations in the SMC and in the region of the NGC 346 nebula — a total of 70,000 stars. The oldest population is 4.5 billion years, roughly the age of our Sun. The younger population arose only 5 million years ago (about the time Earth's first hominids began to walk on two feet). Lower-mass stars take longer to ignite and become full-fledged stars, so the protostellar population is 5 million years old. Curiously, the infant stars are strung along two intersecting lanes in the nebula, resembling a "T" pattern in the Hubble plot.

Français : Nébuleuse NGC 346 dans le petit nuage de Magellan
Date 12 January 2005
Source NASA
Author NASA, ESA and A. Nota (STScI/ESA)


Public domain This file is in the public domain because it was created by NASA and ESA. NASA Hubble material (and ESA Hubble material prior to 2009) is copyright-free and may be freely used as in the public domain without fee, on the condition that only NASA, STScI, and/or ESA is credited as the source of the material. This license does not apply if ESA material created after 2008 or source material from other organizations is in use.
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