Astronomy Colloquium

I will be talking about astrophysics distances in light-years as opposed to the standard parsecs, among other techniques to attempt to convert scientific presentations into formats the public more readily understands. The video describes the
following research: Clusters of galaxies are the largest
gravitationally-bound objects in the Universe, some measuring 6-9 million light-years (~2-3 Mpc and up) across. Hart's work asked whether their shapes (morphologies) change over time as the Universe ages. A sample of 165 galaxy clusters was observed, stretching over a range of distances from 1.25 billion light-years away at the closest to almost 8 billion light-years away at the farthest (i.e., 0.1 < z < 1.3 in a LCDM cosmology). A variety of measures were used to quantify the shapes of galaxy clusters by observing their X-ray light with the Chandra X-Ray Observatory (AXAF) -- and this was done at two different distances from clusters' centers, for comparison (300 kpc, 500 kpc). In almost all cases, clusters retain their morphology over
the history of the Universe was ruled out, which is in agreement with our current picture of large-scale structure formation.