Andromeda galaxy turns out to be smaller than expected

A new paper published in the Monthly Notices of the Royal Astronomical Society claims that the Andromeda galaxy is two to three times smaller than previously thought.

Our own Milky Way was seen as a smaller brother compared to Andromeda but new research learns both galaxies are actually close to the same size. The paper estimates Andromeda has a mass of about 800 billion times the mass of the sun.

It has long been thought that Andromeda was two to three times the size of the Milky Way and that Earth’s galaxy would eventually be engulfed during a gravitational close encounter in 5 billion years or so.

But Prajwal Kafle, an astrophysicist at The University of Western Australia, says the unavoidable encounter will be more a merger of equals. He based his conclusion on observations of fast-moving stars in the Andromeda galaxy that allowed him to calculate the velocity needed to escape the galaxy’s gravitational environment.

More details at Astronomy Now.