Share

ESA’s Gaia Satellite Spots Six Hypervelocity Stars

With a assistance of an synthetic neural network, ESA’s Gaia satellite speckled 6 hypervelocity stars — stars whose quickness in a rest support of a Milky Way Galaxy exceeds a Galaxy’s internal shun velocity.

Artist’s sense of dual hypervelocity stars speeding from a core of a Milky Way to a outskirts. Image credit: ESA / CC BY-SA 3.0 IGO.

Artist’s sense of dual hypervelocity stars speeding from a core of a Milky Way to a outskirts. Image credit: ESA / CC BY-SA 3.0 IGO.

The Milky Way contains some-more than a hundred billion stars, all kept together by gravity.

Most are located in a flattened structure — a Galactic front — with a gush during a center, while a remaining stars are distributed in a wider round halo.

Stars are not quiescent in a Galaxy though pierce around a core with a accumulation of velocities depending on their plcae — for example, a Sun orbits during about 220 km/s, while a normal in a halo is of about 150 km/s.

Occasionally, a few stars surpass these already utterly considerable velocities.

Some are accelerated by a tighten stellar confront or a supernova blast of a stellar companion, ensuing in exile stars with speeds adult to a few hundred km/s above a average.

A new category of high-speed stars — hypervelocity stars — was detected in 2005 by astronomer Dr. Warren Brown of a Harvard-Smithsonian Center for Astrophysics.

Swooping by a Galaxy during several hundred of km/s, these are a outcome of past interactions with a supermassive black hole that resides during a core of a Milky Way and, with a mass of 4 million solar masses, governs a orbits of stars in a vicinity.

So far, usually 20 hypervelocity stars have been spotted.

“These stars are intensely critical to examine a altogether structure of a Milky Way,” pronounced Leiden University astronomer Dr. Elena Maria Rossi.

“These are stars that have trafficked good distances by a Galaxy though can be traced behind to a core — an area so unenlightened and vaporous by interstellar gas and dirt that it is routinely really formidable to observe — so they produce essential information about a gravitational margin of a Milky Way from a core to a outskirts.”

Dr. Rossi and her colleagues practical a new information mining algorithm formed on appurtenance training techniques, an synthetic neural network, to a Tycho-Gaia astrometric resolution (TGAS) catalogue.

They found a sum of 6 hypervelocity stars: TYC 2298-66-1, TYC 8422-875-1, TYC 2456-2178-1, TYC 2348-333-1, TYC 49-1326-1, and TYC 5890-971-1. All have low masses, identical to a mass of a Sun.

“We found that 6 stars can be traced behind to a Galactic center, all with velocities above 360 km/s,” pronounced Tommaso Marchetti, a PhD tyro during Leiden University.

One of a 6 stars, TYC 2298-66-1, seems to be speeding so fast, during 530 km/s, that it is no longer firm by a sobriety of a Milky Way and will eventually leave.

The other 5 stars are rather slower (360-450 km/s) and are still firm to a Galaxy.

These somewhat slower stars are maybe even some-more fascinating, as astronomers are fervent to learn what slowed them down — a invisible dim matter that is suspicion to emanate a Milky Way competence also have played a role.

“This outcome showcases a good intensity of Gaia opening adult new avenues to examine a structure and dynamics of a Galaxy,” pronounced Dr. Anthony Brown, also from Leiden University.

The investigate is published in a Monthly Notices of a Royal Astronomical Society (arXiv.org preprint).

_____

T. Marchetti et al. 2017. An synthetic neural network to learn hypervelocity stars: possibilities in Gaia DR1/TGAS. Mon Not R Astron Soc 470 (2): 1388-1403; doi: 10.1093/mnras/stx1304