Anne’s Picture of the Day: Star Cluster NGC 1850

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February 19, 2013

NGC 1850, an open star cluster in the LMC

Image Credit: FORS Team, 8.2-meter VLT Antu, ESO

NGC 1850 is an open star cluster located about 168,000 light-years away in the bar of the Large Magellanic Cloud, a satellite galaxy of our Milky Way galaxy, in the southern constellation of Dorado. After the 30 Doradus complex, NGC 1850 is the brightest star cluster in the Large Magellanic Cloud.

It is an unusual cluster of stars because its size and the distribution of its stars is like a globular cluster, but unlike the globular clusters which roam our own Milky Way Galaxy’s halo it is composed of young stars. It is representative of a special class of objects — young, globular-like star clusters — that have no known counterpart in our own galaxy.

NGC 1850 is also a double star cluster, that consists of a main globular-like cluster (known as NGC 1850A) in the center and a younger, smaller cluster (known as NGC 1850B), seen below and to the right of the main cluster. Stars in the large cluster are estimated to be 50 million years young, while the smaller cluster is composed of extremely hot, blue stars, with an age of about 4 million years and fainter, red T-Tauri stars. This wide variety of stars allows a thorough study of star formation processes.

T-Tauri stars are young, solar-class stars that are still forming, so young that they may have not started converting hydrogen to helium, which is how stars produce their energy. Instead they radiate energy released by their own gravitational contraction. By investigating these stars astronomers learn about the births and lives of low-mass stars. T-Tauri stars tend to occur in crowded environments, but are themselves faint, making them difficult to distinguish with ground-based telescopes.

NGC 1850 is surrounded by a glowing pattern of filamentary nebulosity that is thought to have been created during violent supernova explosions, indicating short-lived massive stars were also present in NGC 1850. The birth of new stars can be triggered by the enormous forces in the shock fronts where the supernova blast waves hit and compress the gas.

The red supernova remnant N57D is visible on the upper left.

This image is a colour composite of three individual exposures, taken with FORS1 at the VLT UT1 on 3 February 1999, obtained through 3 different filters.

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