Infrared image of circumstellar disk illuminates massive star formation process

November 20th, 2009 - 3:51 pm ICT by ANI  

Washington, November 20 (ANI): A team of astronomers has captured the first direct, well-resolved infrared images of a circumstellar disk around a young massive star called HD 200775, to illuminate a massive star formation process.

Their findings contribute to understanding the role of circumstellar disks in massive star formation in particular and to the birth of stars in general.

Massive stars are those with masses eight times greater than that of the Sun, and they are the most prominent objects in distant galaxies.

They illuminate a large area around them and form a nebula of ionized gas as they develop into mature stars.

At the end of their lives, they explode as supernovae and scatter many kinds of heavy elements like iron into interstellar space.

Scientists understand relatively well how stars with masses similar to our Sun’s are born.

In August 2006, June 2007, and July 2008, a team of astronomers used the Subaru Telescope, fitted with Cooled Mid-Infrared Camera and Spectrometer (COMICS), to make infrared observations of the young massive star HD 200775 in the constellation Cepheus.

HD 200775 is located 1400 light-years from Earth and is actually a close binary system that contains at least one massive star that is about 10 times the mass of the Sun.

A large cavity of molecular gas surrounds the star and extends east to west from the central stars.

Molecular gas is dense within the cavity wall, and HD 200775 illuminates the gas closest to the star, forming the reflection nebula NGC 7023.

The binary orbit extends in the north-south direction, indicating that the binary is almost seen in its orbital plane.

The infrared images captured by COMICS revealed an elliptical emission with the same direction as the binary orbit.

The research team found that the emission arises from a circumbinary disk (a disk that surrounds both stars of the binary system) around HD 200775, the orbital plane of which is similar to that of the binary.

The direction is consistent with the fact that an outflow generally occurs in a direction perpendicular to a disk.

The images are significant because they are the first clear and direct infrared images of a disk around a massive star.

The team examined the disk images in detail and found that the center of the disk emission shifted from the central stars.

This indicates that the disk is not flat but flared; the disk height increases as the disk radius increases. (ANI)

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