At the turn of the 21st century, the Anglo-Australian Observatory made a large survey of galaxies in our universe, known as the 2-degree-field galaxy redshift survey (2dFGRS). It measured the spectra and redshifts of more than 230,000 galaxies. The main goal of the survey was to determine the distribution of galaxies within a radius of about 4 billion light years. A statistical analysis of this distribution could then be used to put constraints on things like dark matter and neutrino mass (which I’ll talk about another day).
Galaxy Rangers
In an earlier post I wrote about one of the mysteries of dark matter. While dark matter matches most observations very well, it doesn’t do well in the area of dwarf galaxies. In particular, computer simulations predict that there should be many more dwarf galaxies than we observe. This has been taken to mean that either the simulations are somehow flawed, or dark matter isn’t the complete solution we’ve thought. But now new research has found that dark matter simulations might be right after all.
Not So Random
Gamma ray bursts (GRBs) are brief, intense bursts of gamma rays. They were first detected in the 1960s as part of a project to observe nuclear weapons tests (http://goo.gl/U9Qbu3). Since then we’ve been able to observe lots of gamma ray bursts, as they occur at a rate of about once a day. We aren’t entirely sure what causes them. One idea is that they occur when a hypergiant star collapses into a black hole. If that were the case, then we would likely see bursts come from random directions (if they originate from outside our galaxy) or along the galactic plane (if they originate in our own galaxy). But now a new study has shown that neither is the case.
Missing Mass Mystery
This year data from the Planck satellite released the most precise observations of the cosmic microwave background. The results tell us that about 68.3% of the universe is dark energy, 26.8% is dark matter, and 4.9% is baryonic matter. Baryonic matter is the regular matter that makes up stars and planets and me and you. It is called baryonic because protons and neutrons which form the nuclei of atoms are known as baryons. (There are other, more exotic, baryonic particles, but protons and neutrons are the most common) So all the atoms and molecules we are familiar with are baryonic matter.
Two of a Kind
A new paper in Nature has announced the discovery of a close binary of supermassive black holes. Known as J1502SE and J1502SW, the two black holes are estimated to have a mass of about 100 million solar masses each, and they are separated by only 450 light years. This means they orbit each other once every 4 million years. For …
Closer Than They Appear
Yesterday I talked about apparent sizes, and how Pluto can appear larger than a distant galaxy, even though the galaxy is much farther away. It turns out, however, that on really cosmic scales apparent size is only part of the story. That’s because the universe is expanding.
Under Pressure
If you’ve ever been in a traffic jam you’ve noticed that while you slowly make your way through it the overall traffic pattern remains the same. Usually when you’re caught in a traffic jam you eventually find the source (construction, minor accident, etc.) but sometimes you enter a traffic jam and go slowly through it without ever seeing a cause. At some time earlier something started it, but now there is just the traffic. The jam itself is now the cause of the jam.
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.
Light of Dead Stars
Science news has been a buzz about a whole posse of new black holes discovered in the constellation of Andromeda. The reason for this is not that these have suddenly been discovered, but rather that a new paper on results from Chandra is being published in the Astrophysical Journal last year, and the press releases have been published.