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Most Precise Map to Date of Milky Way Reveals Warped, Twisted Galaxy

The researchers on Thursday unveiled a three-dimensional map of the Milky Way — home to more than 100 billion stars

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The warped shape of the stellar disk of the Milky Way is seen over the Warsaw University Telescope at Las Campanas Observatory, Chile, in an artist's rendition, Aug. 1, 2019. (Jan Skowron/University of Warsaw). VOA

Astronomers have created the most precise map to date of the Milky Way by tracking thousands of big pulsating stars spread throughout the galaxy, demonstrating that its disk of myriad stars is not flat but dramatically warped and twisted in shape.

The researchers on Thursday unveiled a three-dimensional map of the Milky Way — home to more than 100 billion stars including our sun — providing a comprehensive chart of its structure: a stellar disk comprised of four major spiral arms and a bar-shaped core region.

“For the first time, our whole galaxy — from edge to edge of the disk — was mapped using real, precise distances,” said University of Warsaw astronomer Andrzej Udalski, co-author of the study published in the journal Science.

Until now, the understanding of the galaxy’s shape had been based upon indirect measurements of celestial landmarks within the Milky Way and inferences from structures observed in other galaxies populating the universe. The new map was formulated using precise measurements of the distance from the sun to 2,400 stars called “Cepheid variables” scattered throughout the galaxy.

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Astronomers have created the most precise map to date of the Milky Way by tracking thousands of big pulsating stars spread throughout the galaxy. Pixabay

“Cepheids are ideal to study the Milky Way for several reasons,” added University of Warsaw astronomer and study co-author Dorota Skowron. “Cepheid variables are bright supergiant stars and they are 100 to 10,000 times more luminous than the sun, so we can detect them on the outskirts of our galaxy. They are relatively young — younger than 400 million years — so we can find them near their birthplaces.”

The astronomers tracked the Cepheids using the Warsaw Telescope located in the Chilean Andes. These stars pulsate at regular intervals and can be seen through the galaxy’s immense clouds of interstellar dust that can make dimmer stellar bodies hard to spot.

The map showed that the galaxy’s disk, far from flat, is significantly warped and varies in thickness from place to place, with increasing thickness measured further from the galactic center. The disk boasts a diameter of about 140,00 light years. Each light year is about 6 trillion miles (9 trillion km).

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The Milky Way began to form relatively soon after the Big Bang explosion that marked the beginning of the universe some 13.8 billion years ago. The sun, located roughly 26,000 light years from the supermassive black hole residing at the center of the galaxy, formed about 4.5 billion years ago. (VOA)

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Scientists: Milky Way Merged with Another Smaller Galaxy Roughly 10 Billion Years Ago

The Milky Way, home to our sun and billions of other stars, merged with another smaller galaxy in a colossal cosmic collision roughly 10 billion years ago

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FILE - A view of the Milky Way from an area of Puyehue National Park near Osorno City, Chile, May 8, 2008. VOA

The Milky Way, home to our sun and billions of other stars, merged with another smaller galaxy in a colossal cosmic collision roughly 10 billion years ago, scientists said Monday, based on data from the Gaia space observatory.

The union of the Milky Way and the so-called dwarf galaxy Gaia-Enceladus increased our galaxy’s mass by about a quarter and triggered a period of accelerated star formation lasting about 2 to 4 billion years, the scientists said.

“Yes, indeed it was a pivotal moment,” said astronomer Carme Gallart of Instituto de Astrofisica de Canarias in Spain, lead author of the research published in the journal Nature Astronomy.

Galaxies of all types including the Milky Way began to form relatively soon after the Big Bang explosion that marked the beginning of the universe some 13.8 billion years ago, but were generally smaller than those seen today and were forming stars at a rapid rate. Subsequent galactic mergers were instrumental in configuring galaxies existing now.

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The merger of the Milky Way and the dwarf galaxy Gaia-Enceladus roughly 10 billion years ago, left, and the current appearance of the Milky Way galaxy, right, are shown in this artist’s conception, July 22, 2019. VOA

High-precision measurements of the position, brightness and distance of around a million stars within 6,500 light years of the sun, obtained by the Gaia space telescope operated by the European Space Agency, helped pinpoint stars present before the merger and those that formed afterward.

Certain stars with higher content of elements other than hydrogen or helium arose in the Milky Way, they found, and others with lower such content originated in Gaia-Enceladus, owing to its smaller mass.

While the merger was dramatic and helped shape what the Milky Way has become, it was not a star-destroying calamity.

“This crash was big in cosmic terms, but if it was happening now, we could probably not even notice at a human or solar system level,” Gallart said.

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“The distances between stars in a galaxy are so huge — a galaxy is basically empty space — that the two galaxies intermix, change their global shape, more star formation may happen in one, and maybe the small one stops forming stars.

“But the individual stars in each galaxy don’t collide, don’t really notice the force of the event in a way that affects their individual evolution or the evolution of the planetary systems that may be attached to them,” Gallart said.

The Milky Way, spiral shaped with a central bar-like structure composed of stars, includes 100 to 400 billion stars, including the sun, which formed roughly 4.5 billion years ago, far after the merger. (VOA)