I know it's been online for a while here, but below is a description of the September 17th radio show, which in addition to covering the latest Astronomy news, I discuss the recent results on galaxy formation. On this program, I talked about:
- News: Conductivity probe on Phoenix Mars Lander returns some interesting results regarding humidity on Mars (link) as well as photographs several dust devils (link); NASA selects MAVEN project as its next spacecraft to Mars, designed to study Mars's atmosphere; NASA's Ares I rocket passes preliminary design review and one of its many motors passes its first round of testing, photos here; NASA developing nuclear fission power source to use on the Moon's surface - is NOT similar to an atomic weapon or a nuclear power plant, but convert the heat released during the radioactive decay of an atom to power (link 1,link 2); NASA getting ready to launch Lunar Reconnaisance Orbiter to scout future landing sites for manned missions (link); European researchers developing a way to imprint Asimov's Laws of Robotics on future robots (link); space shuttle Endeavor to move to launch pad in case it needs to rescue space shuttle Atlantis; European Space Agency to launch GOCE satellite to map out the gravitational field of the Earth (link); University of Kent joins new generations radio telescope LOFAR (link); results suggest that gamma-ray burst GRB080319B, originally discovered by the Swift satellite and was so bright in the optical that it was observable with the naked eye, believed to a stream of high-energy particles traveling almost at the speed of light directed towards the Earth (link); NASA awards education research grants to minority universities (link); ESA hosts contests for name of its next mission to the International Space Station.
- Wednesday Morning Astronomer (an Astronomer's take on the science content in Gregg Easterbrook's Tuesday Morning Quarterback) - Congratulations are definitely due to Hanny van Arkel, the Dutch school teacher who discovered a new class of astronomical object while taking part in the Galaxy Zoo project. And yes, astronomy will be helped immensely when new telescopes such as the Large Synoptic Survey Telescope come online which make their data available to everyone every night. However, it is extremely unfair to say the "telescope views of deep space are monopolized by the guild structure of professional astronomy" since a huge amount of data and the software required to analyze them are already available for free, online, for anyone to look at. This is true for any US government funded observatory - such as Hubble, Chandra, Very Large Array, and literally countless others.
- Calendar of upcoming science/astronomy events in the greater Poughkeepsie/New York City area.
- Galaxy Formation: The current belief is that galaxies were formed by the merger of smaller galaxies who were formed by the gravitational attraction of stars and, more importantly, the massive amount of dark halo around them, to each other. By measuring how the properties of galaxies change over time, for example: does the average size of a galaxy get bigger?, how often do we observe galaxies merging?, it is possible to determine if this picture is correct. Hubble Space Telescope observations have recently found nine galaxies in the early universe (about 3 billion years after the Big Bang) which are smaller than the Milky Way, but carry the same number of stars - likely to be the building blocks for galaxies similar to the most massive galaxies we observe today (link). A Galaxy cluster in a very early stage of formation has also been observed about 3 billion years after the Big Bang, which several galaxy mergers going on in this cluster (link). A survey of galaxy clusters at different ages of the universe have found that the brightest galaxy in each cluster has increased in mass by 50% over the last few billion years, evidence that galaxies are merging together during this period (link). A deep infrared image have identified galaxies with masses about 10x that of the Milky Way only 4 billion years after the Big Bang - not much time for smaller galaxies to have merged together to form a galaxy this massive (link), and these galaxies appear to already be full of very old stars - like giant elliptical galaxies observed today (link). Galaxy groups and clusters are believed to be formed by the gravitational attraction of galaxies and their more massive dark matter "halos" to each other. Galaxy clusters are normally filled with gas that is expelled by their galaxies, probably during mergers, that is heated to X-ray emitting temperatures by the total gravitational potential of the galaxy cluster. Recently, similar X-ray emission has been detected not from a galaxy cluster but a single galaxy, NGC 1132, suggesting that this source was only a galaxy cluster but they all merged together to one galaxy. An important prediction / test for this model for galaxy formation is the mass of the most massive galaxy cluster, for which a new record setter has been discovered. And, as alluded too before, an important consideration is that when galaxies merge, it just isn't the stars and gas in these galaxies merging but the surrounding dark matter - which is where most of the mass is - as well. Gas interacts with gas differently that dark matter interacts with dark matter: gas collides with gas, while dark matter will pass through dark matter and only interact gravitationally. Therefore, when two galaxies or galaxy clusters merge, one should initially see an offset between the gas and the dark matter / mass distribution. This has been observed for one cluster before, the "Bullet" cluster, and has been recently seen in another one (link). Observations like these provide some of the best evidence for the existence of dark matter, which plays an extremely important role in our current model for the universe.
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