Our galaxy is 50% more massive than previously thought

Artist's conception of what the Milky Way looks like from above the galactic plane. Click to enlarge and see labels.

Artist's conception of what the Milky Way looks like from above the galactic plane. Click to enlarge and see labels.

Our galaxy, the Milky Way, appears to be about 50% more massive than we previously thought.  A team of scientists lead by Mark Reid of the Harvard-Smithsonian Center for Astrophysics have conducted a detailed 3-D survey of our galaxy and determined that it’s diameter is about 15% greater than previously believed and it is spinning more rapidly than had been thought.  The greater rotational speed indicates the presence of more mass, most of which is probably dark matter.

It is much harder to measure our own galaxy than those which are a million light years away because we’re embedded within it and can’t see the whole thing.

The Andromeda Galaxy, the most distant object you can see with your naked eye, will crash into our galaxy in about 2-3 billion years.

The Andromeda Galaxy, the most distant object you can see with your naked eye, will crash into our galaxy in about 2-3 billion years.

The new findings, which were presented today at the American Astronomical Society’s convention in Long Beach, California, mean that the Milky Way is about the same size as, not smaller than, our nearest large neighbor: the Andromeda Galaxy.  Andromeda, a.k.a. M31, may be larger in volume than our home galaxy, but appears to only be about the same mass, likely due to differing amounts of dark matter between the two bodies.

The new mass data has another implication for Milky Way-Andromeda relations: the anticipated collision between the two galaxies may now happen sooner than previously thought.  But don’t worry, it’s still 2-3 billion years in the future.  The Sun won’t go nova for about 5-6 billion years, so it will still be around, as will the Earth. However, the expansion of the Sun will make it impossible for liquid water to exist on the Earth’s surface in only one billion years.

The Mice Galaxies (so-called because of their appearance) are colliding and will likely form one larger galaxy, in many millions of years.

The Mice Galaxies (so-called because of their appearance) are colliding and will likely form one larger galaxy, in many millions of years.

Galaxies collide are hardly unique occurrences in the universe.  When they do happen, the stars themselves don’t collide, they’re too far apart for that to be likely; however, a star or star system might be ejected from it’s galaxy or, less likely, the orbits of planets within a star system might be disrupted.  In any event, the gravity of the two galaxies will rip them apart until, millions of years later, they may form a new, bigger galaxy.  It is thought that the Andromeda-Milky War collision will form a large elliptical galaxy, which some have preemptively dubbed Milkomeda.

While you’re waiting for the collision, note that 2009 is the International Year of Astronomy.  Learn more about our endlessly fascinating universe by checking out some of the above links, or research any astronomical topics which are of interest to you.  It’s your universe—learn about it!

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