As I’ve written about before, the existence of dark matter is well supported by observational evidence. There isn’t much debate in the astronomical community on the existence of dark matter and the fact that it makes up a large part of the mass of galaxies. We’d still like to have a direct observation of dark matter to be certain sure, but there is general consensus on dark matter.
Countless Worlds
One of the biggest advances of astronomy in the past decade has been the discovery of planets orbiting other stars, known as exoplanets. But just how many exoplanets have been discovered? According to the Extrasolar Planet Encyclopedia, a semi-official catalog based in Europe, there were as of the end of September last year 990 confirmed exoplanets and 2,321 candidate exoplanets. The discrepancy between these numbers has to do with the limitations of the observational data we currently have.
Modified Dark Matter
Dark matter is an aspect of the universe we still don’t fully understand. We have lots of evidence pointing to its existence (as I outlined in a series of posts a while back), and the best evidence we have points toward a specific type of matter known as cold dark matter (CDM). One big downside is that we have yet to find any direct detection of dark matter particles. In fact, many of the likely candidates for dark matter have been all but eliminated. Another is that cold dark matter doesn’t agree with our observations of dwarf galaxies. Now a new paper presents a solution to the second problem that might even help with the first.
Mix It Up
When we look at a cluster of stars, we find that they are chemically similar. That is, the ratio of different elements (or metals in astronomy lingo) in various stars are basically the same. This is pretty much what we expect, since these stars all formed in the same stellar nursery, and haven’t drifted apart from each other. Just as human siblings share similarities due to their common genetic origins, sibling stars share chemical similarities due to their common origin. But what about stars with a common origin that scatter across the galaxy? Do they have a common chemical fingerprint?
A Difficulty with Dwarfs
Most of the predictions of cold dark matter agree very well with observation, which is why it is a dominant part of modern cosmology. But there are aspects of the dark matter model that don’t agree well with observation. Take, for example, the clustering of dwarf galaxies around the Milky Way and Andromeda galaxies.
Animal Magnetism
One of the challenges to understanding black holes is that when things get close to a black hole, things get complicated. We actually have a good description of black holes by themselves, but the description of the heated material near a black hole is complex. To understand the behavior of this material you need to account for not only the gravitational attraction of the black hole, but also things such as magnetic fields. To model active black holes, you need sophisticated computer simulations, and those simulations rely on certain assumptions about how black holes interact.
Moving Heaven and Earth
We know that our solar system formed during the Sun’s youth, when it still had a protoplanetary disk. Such a disk contains gas and dust left over from the star’s formation, and over time the planets coalesced from that material. We can see such protoplanetary disks today around young stars, such as those forming in the Orion nebula.
Reboot
One of the challenges faced by astrophysicists is that you can’t repeat your experiments. With cosmology, that poses a particular challenge because we only have one observable universe. Not only can’t we repeat the experiment, we only have one experiment to observe. What we can do, however, is simulate the universe and see how it compares to the real one.
Second Look
One of the advantages of modern astronomy is that most observational data gets stored in a raw form. This is particularly true for the major space telescopes. Most of that raw data is also stored publicly, either a certain time period or even as the data is gathered. This means that long after an observation is made, people can go through the data to analyze it in new ways. As a case in point, a team recently gathered old data from the Hubble Space Telescope, and processed it using new methods.