This article was talking about the possible presence of a dwarf galaxy present in the Milky Way. It is a possible presence because said galaxy has not been observed but merely expected. This is based on the gravitational interactions with dust clouds around it that suggests it should exist. The theory from this particular professor is that this is a galaxy that is primarily dark matter. Chances are that the galaxy is not entirely dark matter but does contain some light emitting elements. I find it interesting that he claims the location of the galaxy and now waits for someone else to confirm his findings. Barring summary, what really got me thinking was the difference between a location in the Milky Way that contains dark matter vs one that contains a black hole. Further research leads me to the conclusion that because the black hole is massive enough that light cannot escape its field whereas the dark matter does not interact/emit light. This means that if there was a light source behind this area the light would pass through the dark matter galaxy but would be trapped by a black hole. The problem with this is that the galaxy is across the disc of the Milky Way from us. This means that there is a bunch of rubbage between here and there making it difficult to make such simple observations.
As a side note, I also linked my way to this article where they claim to find preliminary evidence for dark matter.
http://news.nationalgeographic.com/news/2009/12/091218-dark-matter-detected-mine-minnesota.html
It seems that they may not have their evidence but at the very least they may have the groundwork for building more sensitive equipment that they can use to make more decisive observations. Basically, the dark matter particles are massive but rarely interact with our typical matter. Rarely means they sometimes do. They did this deep in a mine to try to narrow down any background noise and chilled the liquid as far as they could. When a dark matter particle interacted with matter, some heat residue was left. These heat signatures were actually what they were looking for. The picture to the left is the device mentioned.-David Downing
Great article! Your're right, one of the differences between a dark matter galaxy and a black hole is the fact that light would just pass through the galaxy, since dark matter does not interact electromagnetically. Light also interacts with gravity, but a black hole is enormously more compact than a dark matter galaxy, and the gravitational field of the galaxy will interact much more weakly with light.
ReplyDeleteThe article about detecting possible dark matter candidates is also interesting; especially in how it illuminates the scientific method at this level. They detected a signal which is consistent with WIMPS (Weakly Interacting Massive Particles), but it is also possible that the signal arose by chance due to other factors. Therefore at this point we cannot say conclusively that this is a dark matter detection. In science, especially when studying a new phenomenon, one must repeat the experiment or observation many, many times for it to be statistically likely that the detection is positive.