The fact that the Milky Way is much smaller than the Andromeda Galaxy, which is our nearest neighboring galaxy has been a known fact for a long time. Well, it seems that our galaxy is actually 50% larger than it was believed in the past, and more than likely has four arms, not two.

Scientists succeeded in mapping the Milky Way in a more detailed, three-dimensional way and found that it is 15% larger in breadth. Moreover, it is denser, with 50% more mass, which is like weight. This means that the two galaxies that are the largest members of the Local Group of galaxies might smash into each other earlier than astronomers had predicted.

Mark Reid of Harvard University and his colleagues based their findings on observations of nearly 20 regions of intense star formation across the galaxy, many of them traced by methanol masers, concentrations that act as amplifiers for radio waves. The new findings were presented at the American Astronomical Society's convention in Long Beach, California.

Reid and his colleagues used a large system of 10 radio telescope antennas to measure the brightest newborn stars in the galaxy at different times in Earth's orbit around the sun. Thus they also found that the Milk Way is currently rotating at a speed of 600,000 miles per hour, which is 100,000 miles per hour faster than estimates from the past. This math equates to a 50% mass increase over what was initially reported - another proof regarding the greater potential for collision with the Andromeda Galaxy. This number puts the Milky Way on par with its nearest neighbor, the Andromeda galaxy.