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Astronomers Measure Mass of Milky Way Galaxy

The Milky Way, the galaxy which contains Earth's solar system, is home to up to 400 billion stars and an estimated 100 billion planets.

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Milky way galaxy, scientists
The measurement includes all the stars and planets, dust and gas, as well as the four-million-solar-mass supermassive black hole at the center. Pixabay

Using data from NASA’s Hubble Space Telescope and the European Space Agency’s Gaia satellite, astronomers have come up with one of the most accurate measurements of mass of the Milky Way galaxy.

While previous research dating back several decades provided estimates for our galaxy’s mass, ranging between 500 billion to three trillion solar masses, according to the latest measurements, Milky Way weighs about 1.5 trillion solar masses (one solar mass is the mass of our Sun).

The measurement includes all the stars and planets, dust and gas, as well as the four-million-solar-mass supermassive black hole at the center.

“We want to know the mass of the Milky Way more accurately so that we can put it into a cosmological context and compare it to simulations of galaxies in the evolving universe,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

milky way galaxy, scientists
The more massive a galaxy, the faster its globular clusters move under the pull of gravity, according to a forthcoming paper in The Astrophysical Journal. Pixabay

To weigh the galaxy, the team augmented Gaia measurements for 34 globular clusters out to 65,000 light-years, with Hubble measurements of 12 clusters out to 130,000 light-years that were obtained from images taken over a 10-year period.

They also measured the three-dimensional movement of globular star clusters – isolated spherical islands each containing hundreds of thousands of stars each that orbit the center of our galaxy.

The more massive a galaxy, the faster its globular clusters move under the pull of gravity, according to a forthcoming paper in The Astrophysical Journal.

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The new mass estimate puts our galaxy on the beefier side, compared to other galaxies in the universe. The lightest galaxies are around a billion solar masses, while the heaviest are 30 trillion, or 30,000 times more massive.

The Milky Way, the galaxy which contains Earth’s solar system, is home to up to 400 billion stars and an estimated 100 billion planets. (IANS)

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Study Reveals Shape and Structure of The Milky Way Galaxy

So our Milky Way's twists are rare but not unique, they said

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Earth is part of the Milky way galaxy. Wikimedia

The Milky Way’s disk of stars is not stable or flat but instead becomes increasingly “warped” and twisted far away from the galaxy’s centre, according to astronomers.

“We usually think of spiral galaxies as being quite flat, like Andromeda which you can easily see through a telescope,” said Professor Richard de Grijs from Macquarie University in Australia.

To understand, the team used 1,339 “standard” stars, each up to 100,000 brighter than our sun, to map the real shape of our home galaxy.

The new 3D map of our galaxy showed that the warped Milky Way disc also contains young stars and confirmed that the warped spiral pattern is caused by torque from the spinning of the Milky Way’s massive inner disc of stars, accordoing to the study published in the Nature Astronomy journal.

From a great distance, our galaxy would look like a thin disk of stars that orbit once every few hundred million years around its central region, where hundreds of billions of stars, together with a huge mass of dark matter, provide the gravitational “glue” to hold it all together.

Representational Image of Milky Way.
Image Source: Wikimedia Commons.

But the pull of gravity becomes weaker far away from the Milky Way’s inner regions. In the galaxy’s far outer disk, the hydrogen atoms making up most of the Milky Way’s gas disk are no longer confined to a thin plane, but they give the disk an S-like warped appearance.”It is notoriously difficult to determine distances from the Sun to parts of the Milky Way’s outer gas disc without having a clear idea of what that disc actually looks like,” said Xiaodian Chen from the Chinese Academy of Sciences in Beijing.

“This research provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk,” added Licai Deng, also from the Chinese Academy of Sciences.

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Astronomers have observed a dozen other galaxies which showed similar progressively twisted spiral patterns in their outer regions.

So our Milky Way’s twists are rare but not unique, they said.  (IANS)