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Milky Way is much more massive than previously thought



New scientific findings are much more fascinating when they turn generally accepted facts on their heads.

Until recently, it was assumed that our neighbor galaxy Andromeda is much larger than the Milky Way – more than twice the size of our home galaxy. Later investigations showed that Andromeda and the Milky Way were actually about the same size. Now, new research has emerged showing that the Milky Way is much larger than previously thought and indeed the tip of Andromeda.

According to a report by the European Space Agency (ESA), scientists have calculated the mass of our galaxy with new precision.

By combining data from the ESA's Gaia spacecraft and data from the Hubble Space Telescope ̵

1; jointly operated by ESA and NASA – astronomers were able to determine that the Milky Way's mass is 1.5 trillion solar masses. By contrast, the mass of Andromeda is about 800 billion solar masses according to current estimates.

Read more: Harvard scientists want to limit how much sunlight reaches the Earth's surface to curb global warming.

The reason for the inaccuracy of the previous calculations lies in the "dark matter". a theoretical kind of matter that could make up a considerable amount of all matter in the universe.

Dark matter can not be detected or measured in a typical way.

"This leads to the current insecurity in the mass of the Milky Way," Laura Watkins of the European Southern Observatory said in the new report, "You can not measure exactly what you can not see."

To gauge the mass of dark matter in the Milky Way, astronomers have measured the velocity of globular clusters – dense star clusters orbiting the spiral disk of the galaxy.

"The more massive a galaxy is, the faster its clusters move under the gravitational pull of gravity," said astrophysicist N. Wyn Evans of the University of Cambridge.

The Hubble Space Telescope, orbiting Earth shortly after NASA's astronauts, served as the observatory in May 2009.
NASA / ESA

far greater than what the visible matter in the galaxy suggests. Thus, the scientists concluded from this anomaly that dark matter was responsible for the additional gravity.

Using Gaia – a space probe to create a precise 3D map of the Milky Way – scientists were able to evaluate three-dimensional measurements of cluster velocities for the first time.

"Most previous measurements found the speed at which a cluster approaches or deviates from Earth, that is, the velocity along our line of sight," said Wyn Evans. "However, we were also able to measure the sideways movement of the clusters, from which the total velocity and thus the galactic mass can be calculated."

Read More: NASA has analyzed a photograph taken by the Hubble telescope so we can hear the sound of space.

Observations by Hubble allowed distant globular clusters – some up to 130,000 light-years from Earth – to be added to the study.

"We were lucky enough to have such a great combination of data," said Roeland P. van der Marel of NASA's Hubble Institute. "By combining Gaia's measurements of 34 spherical clusters with measurements of 12 more distant Hubble clusters, we could determine the mass of the Milky Way in a way that would not be possible without these two space telescopes."

With a mass of 1.5 billion solar masses, the Milky Way could even be the largest galaxy nearby.

The Andromeda Galaxy.
Adam Jesionkiewicz / Business Insider Polska

This also implies that a possible future collision and merging of the two galaxies would look very different from what the researchers had previously presented. Previously thought Andromeda would devour the Milky Way, but according to recent findings, the opposite could be the case.


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