Aug
06
2006

Triangulum galaxy (M33)
Triangulum galaxy (M33)Courtesy NASA

Universe may be 15.8 billion years old

The Hubble constant, formulated by Edwin Hubble in 1929, has remained fairly constant since the 1950's. Kris Stanek, associate professor of astronomy at Ohio State, and his coauthors are publishing a paper that may change the accepted value of the Hubble constant and also the accepted size and age of the universe.

They studied two of the brightest stars in M33, which are part of a binary system, meaning that the stars orbit each other. As seen from Earth, one star eclipses the other every five days.

They measured the mass of the stars, which told them how bright those stars would appear if they were nearby. But the stars actually appear dimmer because they are far away. The difference between the intrinsic brightness and the apparent brightness told them how far away the stars were -- in a single calculation.

To their surprise, the distance was 15 percent farther than they expected: about 3 million light-years away, instead of 2.6 million light-years as determined by the Hubble constant.

Astronomers crunch numbers, universe gets bigger

This new method took 10 years to develop. To make such a drastic change to the accepted view of the universe will require additional experimentation.

"Our margin of error is now 6 percent, which is actually pretty good," Stanek said. Next, they may do the same calculation for another star system in M33, to reduce their error further, or they may look at the nearby Andromeda galaxy. The kind of binary systems they are looking for are relatively rare, he said, and getting all the necessary measurements to repeat the calculation would probably take at least another two years.

Soure article: Ohio State University Research Archive

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