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Cosmic Crash with Dwarf Galaxy Reshaped Milky Way: Study

This spacecraft has been mapping the stellar content of our galaxy, recording the journeys of stars as they travel through the Milky Way

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Cosmic Crash with Dwarf Galaxy Reshaped Milky Way: Study. (IANS)

A dramatic head-on collision with a dwarf galaxy, dubbed the “Gaia Sausage” galaxy, about 10 billion years ago reshaped the structure of our galaxy, the Milky Way, fashioning both its inner bulge and its outer halo, new research suggests.

The dwarf did not survive the impact. It quickly fell apart, and the wreckage is now all around us, according to the findings.

“The collision ripped the dwarf to shreds, leaving its stars moving in very radial orbits” that are long and narrow like needles, said Vasily Belokurov of the University of Cambridge and the Center for Computational Astrophysics at the Flatiron Institute in New York City.

The stars’ paths take them “very close to the centre of our galaxy. This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed.”

The results detailed in a series of new papers in the journals the Monthly Notices of the Royal Astronomical Society, The Astrophysical Journal Letters and arXiv.org outline the salient features of this extraordinary event.

Several of the papers were led by Cambridge graduate student GyuChul Myeong. He and colleagues used data from the European Space Agency’s Gaia satellite.

Cosmic rays
Representational image. Pixabay

This spacecraft has been mapping the stellar content of our galaxy, recording the journeys of stars as they travel through the Milky Way.

Thanks to Gaia, astronomers now know the positions and trajectories of our celestial neighbours with unprecedented accuracy.

The paths of the stars from the galactic merger earned them the moniker the “Gaia Sausage,” explained Wyn Evans of Cambridge.

“We plotted the velocities of the stars, and the sausage shape just jumped out at us. As the smaller galaxy broke up, its stars were thrown onto very radial orbits. These Sausage stars are what’s left of the last major merger of the Milky Way,” Evans said.

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The new research also identified at least eight large, spherical clumps of stars called globular clusters that were brought into the Milky Way by the Sausage galaxy.

Small galaxies generally do not have globular clusters of their own, so the Sausage galaxy must have been big enough to host a collection of clusters.

“While there have been many dwarf satellites falling onto the Milky Way over its life, this was the largest of them all,” said Sergey Koposov of Carnegie Mellon University in Pittsburgh, Pennsylvania, US. (IANS)

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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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Map, Milky Way, Galaxy
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.

Map, Milky Way, Galaxy
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)