Anne’s Picture of the Day: Gas Cloud Hubble-V

read more at Anne’s Astronomy News http://annesastronomynews.com/

April 14, 2013

Hubble-V, a glowing gas cloud in Barnard’s Galaxy

Image Credit: C. R. O’Dell (Vanderbilt) et al., L. Bianchi (JHU) et al., Hubble Heritage Team (STScI/AURA), NASA and ESA

Hubble-V is a glowing gas cloud of about 200 light-years across within Barnard’s Galaxy (NGC 6822), which is located some 1.6 million light-years away in the constellation of Sagittarius.

This small, irregular host galaxy is one of the Milky Way’s closest neighbors and is considered prototypical of the earliest fragmentary galaxies that inhabited the early Universe. So, this intense star-forming region within it is giving astronomers more insight into the fierce birth of stars as it may have more commonly happened in the early Universe.

A faint tail of nebulosity trailing off the top of the image sits opposite a dense cluster of bright stars nestled in the bottom of the irregularly shaped nebula. This cluster consists of dozens of youthful 4-million-year-old, ultra-hot stars, each with a mass of some 20 solar masses and each glowing 100,000 times brighter than our Sun.

The hot, massive stars emit large amounts of radiation, which sculpted and illuminated the gas cloud in which the stars were born. The cloud is actually composed of several “bubbles” of gas blown by the hefty stars. The hot radiation also energizes the gas, making it glow.

These massive stars also lose a significant quantity of mass by stellar winds that travel at supersonic speeds of more than 10 million kilometers an hour. These winds, crashing in the surrounding gas cloud and compressing it, are triggering new star formation of lower-mass stars.

Massive stars are very important because – unlike most stars, including the Sun – these stars reach high enough temperatures in their interiors to transform through nuclear fusion great quantities of primordial elements, such as hydrogen and helium, into heavier elements. Therefore, they are responsible for producing all the existing oxygen, carbon, nitrogen, silicon, and calcium (very familiar, life-sustaining elements).

A very massive star completes its life cycle some 1000 times faster than a Sun-like star, in about 10 million years. When it reaches the end of its life, it releases most of its processed material back into space by exploding as a supernova or by forming a planetary nebula.

The image data were taken with Hubble’s Wide Field Planetary Camera 2 by C. Robert O’Dell of Vanderbilt University and collaborators, and Luciana Bianchi of Johns Hopkins University and Osservatorio Astronomico, Torinese, Italy, and collaborators. The color image was produced by The Hubble Heritage Team (STScI).

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