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Scientists discover a Fossil Relic of early Milky Way harboring stars of hugely different ages

These similarities could make Terzan 5 a fossilised relic of galaxy formation, representing one of the earliest building blocks of the Milky Way

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Milky Way Galaxy. Image Source: Wikimedia Commons.

LONDON, Sept 08, 2016: An international team of researchers has found that a stellar system classified as a globular cluster for the 40-odd years since its detection actually has properties uncommon for a globular cluster that make it the ideal candidate for a living fossil from the early days of the Milky Way.

The cluster, known as Terzan 5 — 19,000 light-years from Earth- harbours stars of hugely different ages — an age-gap of roughly seven billion years and bridges the gap in understanding between our galaxy’s past and its present, the study said.

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“Such galactic fossils allow astronomers to reconstruct an important piece of the history of our Milky Way,” explained lead author of the study Francesco Ferraro from University of Bologna in Italy.

While the properties of Terzan 5 are uncommon for a globular cluster, they are very similar to the stellar population which can be found in the galactic bulge, the tightly packed central region of the Milky Way.

These similarities could make Terzan 5 a fossilised relic of galaxy formation, representing one of the earliest building blocks of the Milky Way.

“Terzan 5 could represent an intriguing link between the local and the distant Universe, a surviving witness of the Galactic bulge assembly process,” Ferraro said.

The team scoured data from the Advanced Camera for Surveys and the Wide Field Camera 3 on board Hubble, as well as from a suite of other ground-based telescopes.

They found compelling evidence that there are two distinct kinds of stars in Terzan 5 which not only differ in the elements they contain, but have an age-gap of roughly seven billion years.

The ages of the two populations indicate that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation.

“This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” co-author of the study Davide Massari from National Institute for Astrophysics (INAF) , Italy.

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Its unusual properties make Terzan 5 the ideal candidate for a living fossil from the early days of the Milky Way, said the study published in the Astrophysical Journal.

Somehow Terzan 5 has managed to survive being disrupted for billions of years, and has been preserved as a remnant of the distant past of the Milky Way.

The researchers believe that this discovery paves the way for a better and more complete understanding of galaxy assembly. (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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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)