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Astronomers Discovered Nearest Bright Hypervelocity Star

Astronomers from China and the United States have discovered a hypervelocity star (HVS), which is regarded as the nearest bright HVS and one of the three most massive HVSs known to us at present.

LAMOST-HVS1

This is an artist’s impression of the hypervelocity star LAMOST-HVS1 speeding away from the visible part of Milky Way Galaxy. Image credit: Ben Bromley / University of Utah.

HVSs were thought to be remaining pairs of binary stars that used to orbit each other. When they got too close to the supermassive black hole at the galaxy’s center, the intense gravity from it caught one star so it started to closely orbit the hole and then slingshot the other star on a trajectory going beyond the galaxy.

According to Dr Zheng Zheng from the University of Utah and the lead author of the study published in the Astrophysical Journal Letters, the better understanding of the hypervelocity star could be much helpful to know more about our Galaxy, as well as especially its center and the dark matter halo in particular. Although it is impossible to see the dark matter halo, its gravity does act on the star. With knowledge of the star’s trajectory and velocity, it would be clear that they were affected by gravity from different parts of our Galaxy.

When Dr Zheng’s team was engaged in other research into stars with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), they happened to discover this new hypervelocity star, so they named it as LAMOST-HVS1.

The speed of LAMOST-HVS1 was nearly three times faster than ordinary star, which went around at the pace of 500,000-mph through space. That was 1.4 million mph relative to our Solar System and about 1.1 million mph relative to the speed of the center of the Milky Way Galaxy.

Even if it was regarded as the closest HVS, it was still 42,400 light years away from Earth and 62,000 light years from the center of our Galaxy.

LAMOST-HVS1 was four times hotter and almost 3,400 times brighter than the Sun, if seen from the same distance. However, in comparison of the Sun, it was a just a kid born 32 million years ago, considering its speed and position.

With the apparent magnitude of about 13, LAMOST-HVS1’s mass was 9 times bigger than the Sun, but 630 times fainter than stars that people could see with their naked eyes.

Journal reference: Zheng Zheng et al. 2014. The First Hypervelocity Star from the LAMOST Survey.ApJ 785, L23; doi: 10.1088/2041-8205/785/2/L23

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