A Group Of Stars Rotating At High Speed Spotted In The Milky Way

A group of stars in the Milky Way is moving faster than most other stars. They were spotted by a team of European astronomers.

The descriptions of the finding were published on arXiv.org on Nov. 2, 2016. The discovery could provide key information about stellar dynamics.

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Jason Hunt from the University College London, U.K., and who led the discovery told the Phys.Org that they wanted to examine the speed with which the stars rotate around the Galaxy. With this, they need velocity in three directions. He added that they have never could explore local galactic dynamics in such detail because very few stars have had reliable distance estimates.

Hunt explained that the first data that was released provides the distance estimates for around 2 million stars in the solar neighborhood. Meanwhile, the next data release will have more than 1 billion. He further explained that this is a substantial improvement on the previous mission, Hipparcos, which specified measurements for about 150,000 stars.

Hipparcos was a satellite of the European Space Agency, which was launched in 1989 and became operational till 1993. It aimed to provide accurate measurements of the positions of celestial objects on the sky known as astrometry. This also determined the motion of stars.

In the discovery, the astronomers found that the group of stars is rotating faster than the Sun by about 20 km s̵¹. They also discovered that it is rotating significantly faster than the mean rotation of stars.

The team said that this may be caused by one or two major spiral arms of the Milky way known as the Perseus Arm. Thus, the stars that are behind the spiral arm and at the pericenter of their orbits experience an extended period of acceleration from the gravitational potential of the Perseus Arm.

Hunt explained that the extended period of acceleration causes them to move significantly faster than the other stars. They also know that this will either occur at one point along the spiral arm if the arm moves as a wave with a constant pattern speed through the disc, or it will happen along the arm is the spiral arm moves with the same velocity as the stars that is predicted by computational models based on the gravitational interaction of stars known as N-body simulations.