17 December 2013

New massive star forming cluster discovered

Image Caption: This image from the Smithsonian's Submillimeter Array maps the projected density of molecular gas in the central 30 light years of W49A. Brighter colors mark denser regions. The brightest region at the image center is less than three light-years across, yet it contains about 50,000 suns' worth of molecular gas. Credit: Roberto Galván-Madrid (ESO), Hauyu Baobab Liu (ASIAA, Taiwan), Tzu-Cheng Peng (ESO)

Astronomers using the Smithsonian’s Submillimeter Array (SMA) have discovered a giant star-forming region. Known as W49A, the region is located 36,000 light-years away from Earth on the opposite side of the Milky Way. Astronomers say the star-forming region shines 100 times brighter than the Orion nebula.

In order to view W49A, astronomers had to aim SMA through dusty fog, after which the telescope helped reveal an active site of star formation that was being fed by streamers of infalling gas.

“We were amazed by all the features we saw in the SMA images,” said lead author Roberto Galván-Madrid, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA) and the European Southern Observatory (ESO).

W94A represents a nearby example of the sort of star formation seen in so-called starburst galaxies, where stars form 100 times faster than in our galaxy.

The heart of the star forming region holds a giant compact star cluster where about 100,000 stars already exist within a space of only about 10 light-years on a side. In comparison, fewer than 10 stars lie within 10 light-years of our Sun. The team said the giant star cluster located in W49A will be almost as crowded as a globular cluster.

The telescope used in the observation revealed an intricate network of filaments feeding gas into the center, like tributaries feeding water into large rivers on Earth. These filaments form three big streamers, which funnel star-building materials inward at speeds of about 4,500 miles per hour.

Scientists say W49A is denser than the average star cluster, which will help it survive even longer. Most star clusters in the galactic disk dissolve rapidly when stars migrate away from each other due to the influence of gravitational tides. However, because the cluster in W49A is so compact, the astronomers predict it will remain intact for billions of years.

SMA helped map the molecular gas within the star-forming region in great detail, showing how 30 light-years away from the center of W49A is several hundred times denser than the average molecular cloud in the Milky Way. According to the observations, the nebula contains about 1 million suns’ worth of gas, mostly made up of molecular hydrogen.

“We suspect that the organized architecture seen in W49A is rather common in massive stellar cluster-formation,” said Hauyu Baobab Liu of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan and co-author of the paper published in the Astrophysical Journal.

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