A new Hubble Space Telescope image provides a glimpse into a previously unseen region of starbirth nestled inside a nearby galaxy.
Intense radiation from the ultra-bright newborn stars has blown out a glowing, spherical bubble in a nebula. Researchers say the image is helping them understand the interplay of gas and radiation in a star-forming region, where massive stars sculpt their environment by generating powerful cosmic winds.
Although most of the stars in the universe were born several billions of years ago, star formation continues today. This new Hubble image shows a very compact star-forming region -- the N83B nebula -- in a small part of a galaxy called the Large Magellanic Cloud. This galaxy is relatively nearby -- 165,000 light-years from our own Milky Way -- and can easily be seen from the Southern Hemisphere with the naked eye.
Researchers say the stars are young, massive and ultra-bright. They are seen in the new image just as they are born and emerge from the shelter of their prenatal molecular cloud.
Their high mass means that the young stars evolve rapidly. Because of this, it is difficult for astronomers to catch such events. Furthermore, the stars spend a good fraction of their youth hidden from view, shrouded by large quantities of dust in the cloud from which they form. The only chance is to observe them just as they start to emerge from their cocoon.
Astronomers from France, the United States and Germany who studied the nebula said several individual stars are responsible for lighting it up. The star at the center of the nebula, just below the brightest region, is some 30 times more massive and almost 200,000 times brighter than our Sun, the researchers said.
The intense light and powerful stellar "winds" from this ultra-bright star have cleared away the surrounding gas to form a large cavity. The bubble is approximately 25 light-years in diameter. Astronomers estimate that the spherical void in N83B must have been carved out of the nebula very recently -- in astronomical terms -- maybe as little as 30,000 years ago.
The hottest star in N83B is 45 times more massive than the Sun and is embedded in the brightest region in the nebula. This bright region, just above the center, is only about 2 light-years across. The region's small size and its intense glow are telltale signs of a very young, massive star.
A bright arc structure just can be seen just below the luminous star. This impressive ridge may have been created in the glowing gas by the hot star's powerful wind.
Measurements of the age of this star and neighboring stars in the nebula show that they are younger than the nebula's central star. Their formation may have been triggered by the violent wind from the central star. This possible chain-reaction of stellar births seems to be common in the universe, researchers said.
To the right of the glowing N83B is a much larger diffuse nebula, known as DEM22d, which is partly obscured by an extended lane of dust and gas.
The colors in the image have meaning. Red indicates ionized hydrogen in one electric state; green, ionized oxygen; blue, ionized hydrogen in another electric state. The blue corresponds to the warmest regions, the red to the coldest. The full image represents an area that is 55 by 108 light-years.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The results will be described in an upcoming issue of Astronomy & Astrophysics Journal.
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