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Tuesday, 24 July, 2001, 14:55 GMT 15:55 UK
Stellar winds shake distant star
AFGL 2591/Gemini observatory
AFGL 2591 may be only a million years old
By BBC News Online science editor Dr David Whitehouse

A dramatic image taken in the infrared region of the spectrum is casting new light on the early stages of the formation of giant stars.

Captured by the Gemini North telescope on Hawaii's Mauna Kea, the picture reveals remarkable details in a vast cloud of gas and dust ejected from a young star named AFGL 2591.

Astronomers say this expulsion is a common feature in the formation of stars similar in size to the Sun, but it is far less common in their more massive counterparts.

"Gemini's unparalleled sensitivity and resolution in the infrared allows us to move beyond simply detecting such structures to being able to study them in great detail," says Gemini scientist Colin Aspin.

"Almost everything in this set of infrared images would be invisible with an optical telescope, since it is occurring within a dense molecular cloud of gas and dust," he adds.

AFGL 2591 is more than 3,000 light-years from Earth, in the constellation of Cygnus. Over the last few thousand years, it has created a vast expanding nebula more than 500 times the size of our Solar System. Its main star is at least 10 times the size of the Sun, over 20,000 times as bright, but perhaps only one million years old.

Vast and expanding

The wispy white and blue structures seen in the gas cloud next to the young star are from a huge outflow of gas and dust. Gemini scientists believe that the outflow is likely to be occurring symmetrically around the star - a second giant-sized expanding nebula to the left of the star is hidden from view by a dense and extensive disk of material encircling AFGL 2591.

"We strongly suspect the outflow occurs on both sides of the star in a bipolar structure, because we detect faint traces of gas at that location which indicate interactions between the outflowing gas and the material forming the parent molecular cloud," says Aspin.

"A unique feature of this object is a series of four distinct rings of nebulosity.

"These rings suggest that the expulsion of the material is not constant with time, but rather has occurred several times over the lifetime of the object," he adds.

"Studying the structure and velocity of these rings, and their relation to the infalling material, will allow us to better understand why such features are created and what functions they serve."

See also:

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