A new map of the Milky Way galaxy

Maps are magical things: they contain both knowledge and mystery.

Modern maps may not explicitly show monsters drawn on the unexplored parts of the map, but we're free to put them in ourselves.

And maps are often wrong.

The image on the left represents the latest and best map of what our own Galaxy looks like, and our place within it [credit: R. Hurt, Spitzer Science Center / JPL-Caltech / NASA].

We know quite a lot about our own Galaxy [e.g. see galaxymap.org, but be aware that galaxymap.org shows the images rotated by exactly 180 degrees compared to the new map], but every now and again something interesting and unexpected pops out to surprise us.

For example, we used to think the Milky Way was a four-armed Spiral galaxy with a few straggly sub-arms or spurs (e.g. see here). The main arms in the old picture were the Norma, Scutum-Centaurus, Sagittarius and Perseus arms. Our Sun currently resides in none of these arms but in the Orion spur.

Now new work using the Spitzer Space Telescope by Bob Benjamin and his collaborators (this is a press release) has shown that the Norma and Sagittarius arms do not deserve their status as major arms: instead the Milky Way is a two-armed grand-design spiral (as shown in the image above). Compare the new image (shown above) to a recent but older Milky Way map also from the Spitzer Science Center's web site.

Space.com also as the story.

[Update 06/06/2008: Fixed a typo, noted that the Sun's location in the Orion Spur is only its current location, and added a label]