A New Look at the Map of the Milky Way

When Pluto was demoted from planet to dwarf planet, there was a massive outcry of support. However, the latest interstellar demotion is unlikely to gather the same amount of support, despite being exponentially larger in its fall from grace.

According to Astronomer Robert Benjamin of the University of Wisconsin in Whitewater, US, two of the Milky Way’s spiral arms may not be spiral arms at all, but just concentrations of gas, perhaps inhabited by a small amount of young stars.

Benjamin arrived at this conclusion after the two arms failed to appear in a sensitive survey conducted by the Spitzer Space Telescope. Spitzer is one of the first telescopes that is uniquely able to conduct such a survey of our galaxy, thanks to its infrared vision being able to pierce through the dust that obscures many stars at certain optical wavelengths of light.

The Milky Way was originally made up of four arms, intertwining to make the spiral galaxy that we inhabit. The four arms, Scutum-Centaurus, Perseus, Sagittarius and Norma may very well soon be narrowed down to the just the former two, with and Sagittarius and Norma being deleted.

“These major arms [Scutum-Centaurus and Perseus] could be the things that would really stand out if you were looking at the Milky Way galaxy from Andromeda,” Benjamin says.

Benjamin does admit that "Trying to create a picture of the Milky Way is about 40% hard science and 60% imagination.” But Thomas Dame of the Harvard-Smithsonian Center for Astrophysics in Cambridge, though not a member of Benjamin’s team, is intrigued by the idea of a major-minor arm theory. "I think it could be right, but I think we have a lot of work to do to shore this up," he said in an interview with New Scientist.

The four arms are not the only arms of our galaxy, but are, or were, the largest. The Milky Way has a variety of other smaller, partial arms. Our own Sun is located in one such called the Orion Spur, which is located somewhere between Sagittarius and Perseus.

Posted by Josh Hill.