What is our galaxys halo made of, and how was it formed?
What is the halo around the Milky Way made of? And why is it there? How did it get there? The halo is a (nearly) spherical region surrounding the galaxy (like the diffuse light around the heads of saints, not like the yellow rings around angels’ heads in cartoons), made up mostly of dark matter. Dark matter is called dark because it does not radiate brightly enough to be observed. Because its radiation is not observed, the dark matter is studied through its gravitational interaction with light passing by, an effect known as “gravitational lensing”. This suggets the dark matter is made up of “MACHO’s” (MAssive Compact Halo Objects) and “WIMP’s” (don’t blame me, I didn’t name them–Weakly Interacting Massive Particles). MACHO’s are familiar matter, like dead stars and eggbeaters, and possibly some particles that have not been detected yet. WIMP’s are purely theoretical particles and are like neutrinos in that they rarely interact, but unlike neutrinos they can be extremely heavy. The mak
