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Astronomers Find the Most Distant Star in the Milky Way Galaxy

Washington, D.C, Gatra.com – Astronomers have detected in a stellar halo that represents the outer limits of the Milky Way, a group of stars farther from Earth than is known within our own galaxy – almost halfway to a neighboring galaxy.

Reuters reported on Thursday (12/1) that researchers said these 208 stars inhabit the most distant reaches of the Milky Way’s halo, a spherical cloud of stars dominated by a mysterious, invisible substance called dark matter that makes it known only through its gravitational influence. The farthest is 1.08 million light years from Earth. One light year is the distance light travels in a year, 9.5 trillion km.

These stars can be seen using the Canada-France-Hawaii Telescope on Hawaii’s Mauna Kea mountain. It is part of a category of stars called RR Lyrae, which are relatively low in mass and usually have an abundance of elements heavier than hydrogen and helium. The most distant one appears to have a mass of about 70 percent that of the sun. No other Milky Way star measures further than this.

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The stars that inhabit the fringes of the galactic halo, which can be seen as ‘orphaned’ stars, may have originated in smaller galaxies that later collided with the larger Milky Way.

“Our interpretation of the origin of these distant stars is that they were most likely born in the halos of dwarf galaxies, and star clusters that were later merged – or rather, cannibalized – by the Milky Way,” said Yuting Feng, a doctor of astronomy.

He’s a student at the University of California, Santa Cruz, who led the study, and is presenting this week at the American Astronomical Society meeting in Seattle.

“The parent galaxy has been destroyed and digested gravitationally, but these stars are left at great distances as debris from the merger event,” Feng added.

The Milky Way has grown over time through these disasters.

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“Bigger galaxies grow by ‘eating’ smaller galaxies – by eating their own kind,” said study co-author Raja Guha Thakurta, chair of astronomy and astrophysics at UC Santa Cruz.

Containing both an inner and outer layers, the Milky Way’s halo is much larger than the main disk of the galaxy and the central bulge is full of stars. The galaxy, with a supermassive black hole at its center some 26,000 light years from Earth, contains an estimated 100 billion–400 billion stars including the sun, which reside in one of the four main spiral arms that make up the Milky Way’s disk. The halo contains about 5 percent of the galaxy’s stars.

Dark matter, which dominates the halo, makes up most of the mass of the universe and is thought to be responsible for its basic structure. With its gravity influencing visible matter to gather and form stars and galaxies.

The far outer edge of the halo is a poorly understood region of the galaxy. These newly identified stars are almost half as far from the neighboring galaxy, Andromeda in the Milky Way.

“We can see that the fringes of Andromeda’s halo and the Milky Way’s halo are really extended – and almost ‘back to back’,” Feng said.

The search for extraterrestrial life focuses on rocky planets similar to Earth, which orbit in the so-called “habitable zone” around stars. More than 5,000 planets outside the solar system, which are called exoplanets, have been discovered.

“We don’t know for sure, but each of these outer halo stars most likely has planets orbiting them like the sun and stars, like other suns in the Milky Way,” said Guha Thakurta.


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