Most precise measurement of Orion Nebula’s star forming region made

November 14th, 2007 - 1:52 am ICT by admin  
Scientists said the measurement to the heavily studied Orion Nebula has changed their understanding of the characteristics of the young stars in the region.

“This measurement is four times more precise than previous distance estimates. Because our measurement reduces the distance to this region, it tells us that the stars there are less bright than thought before, and changes the estimates of their ages,” said Geoff Bower, an astronomer at the University of California at Berkeley.

The scientists determined the distance to a star called GMR A, one of a cluster of stars in the Orion Nebula by measuring the slight shift in the star’s apparent position in the sky caused by the Earth’s motion around the Sun.

Observing the star when the Earth is on opposite sides of its annual orbit allowed the astronomers to measure the angle of this small shift, thus providing a direct trigonometric calculation of its distance.

“By using this technique, called parallax, we get a direct measurement that does not depend on various assumptions that are required to use less-direct methods,” said Bower.

“Only a telescope with the remarkable ability to see fine detail that is provided by the VLBA is capable of the measurement we made,” he added.

“Knowing the accurate distance to this region is vitally important to properly understanding the general characteristics of the star-formation processes there,” said co-researcher Karin Sandstrom.

The scientists said the new distance to the region, determined with the VLBA, was 1270 light-years, compared with the best previous measurement of 1565 light-years.

They said the old measurement had an uncertainty of about 17 percent, while the new VLBA measurement had an uncertainty of only six percent.

They said since the newly-measured distance to the region was 20 percent closer than the earlier measurement, the stars in the region were intrinisically fainter by a factor of 1.5.

They said this had a major impact on scientists’ understanding of their ages.

“These stars are nearly twice as old as previously thought,” said Bower.

“Getting a more-accurate distance is going to pay off in many ways by improving our understanding of what is one of the most frequently-studied star-forming regions in the Universe,” added co-researcher JEG Peek.

“By using the same technique on other stars in the region, it would be possible to build up a three-dimensional picture of the area,” he said.

The study appears in the October 10 issue of the Astrophysical Journal. (ANI)

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