October 18 Astronomy Colloquia

On October 18, the astronomy department welcomed back Matthew Walker, a former graduate student at U of M.  He came back and gave a talk on dwarf galaxies (http://michastrostudent.blogspot.com/2012/10/dwarf-galaxies.html) and how they can be used to determine the composition of dark matter (http://michastrostudent.blogspot.com/2012/10/dark-matter.html).

He went into great detail about how dark matter effects dwarf galaxies.  According to his observations dwarf galaxies are composed of nearly 99% dark matter, while the other 1% is real matter that can produce radiation.  Stars are included in the 1% of real matter in the dwarf galaxies.

Walker also told us that last summer radiation was detected from the center of the Milky Way and that, that radiation is hypothesized to be dark matter. On June 15, 2012 Douglas P. Finkbeiner observed strong evidence for gamma-ray emission from the center of the Milky Way.

One of the most interesting things that Walker told us was that dark matter was probably neither cold nor hot.  Based on his calculations dark matter can not be cold and based on the calculations at the big bang it was very unlikely that dark matter is hot.  That leaves us with warm dark matter, but the problem is how do we determine what it is comprised of.  This question will remain a mystery for years to come, but hopefully someone figures it out soon because I really want to know what dark matter is!