Scientists have managed to calculate the mass of our galaxy more accurately than ever before, according to a report published by the European Space Agency.

Until relatively recently, it was thought that our neighboring galaxy, Andromeda, was far larger than the Milky Way.

But the Milky Way is, in fact, considerably larger than Andromeda.



New scientific findings are much more intriguing when they turn widely accepted facts on their heads.

Until recently, it was thought that our neighboring galaxy, Andromeda, was far larger than the Milky Way — more than twice the size of our home galaxy. Later research showed that Andromeda and the Milky Way were actually around the same size. But now new research has surfaced showing that the Milky Way is much larger than previously assumed, and in fact tops Andromeda.

According to a report published 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 space probe and data from the Hubble space telescope — which is jointly operated by the ESA and NASA — astronomers were able to determine that the mass of the Milky Way is 1.5 trillion solar masses. The mass of Andromeda, on the other hand, is roughly 800 billion solar masses, according to current estimates.

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The reason that previous calculations weren't quite accurate is due to "dark matter", a theoretical type of matter that could account for a sizeable quantity of all matter in the universe.

Dark matter can't be detected or measured in the typical ways.

"That's what leads to the present uncertainty in the Milky Way's mass," Laura Watkins of the European Southern Observatory explained in the new report, "you can't measure accurately what you can't see."

To estimate the mass of dark matter in the Milky Way, astronomers measured the velocity of globular clusters — dense star clusters that orbit the spiral disc of the galaxy.

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

The Hubble Space Telescope orbiting Earth shortly after NASA astronauts serviced the observatory in May 2009. NASA/ESA

The orbital velocity of the globular clusters around the Milky Way was far greater than what the visible matter in the galaxy would suggest. So the scientists were able to deduce from this anomaly that dark matter was responsible for the additional gravitation.

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

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

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Observations from Hubble allowed for distant globular clusters — some as far as 130 000 light-years from Earth — to be added to the study.

"We were lucky to have such a great combination of data," explained Roeland P. van der Marel of NASA's Hubble Institute. "By combining Gaia's measurements of 34 globular clusters with measurements of 12 more distant clusters from Hubble, we could pin down the Milky Way's mass in a way that would be impossible without these two space telescopes."

With a mass of 1.5 trillion solar masses, the Milky Way could even be the largest galaxy in the vicinity.

The Andromeda galaxy. Adam Jesionkiewicz / Business Insider Polska

This also means a potential future collision and fusion of the two galaxies would look quite different than what researchers had previously pictured. Until now, it was thought that Andromeda would devour the Milky Way but, according to these recent findings, the opposite may be true.