Posted by pat
on April 12, 2012
One of the biggest stories in Cosmology over the last two decades has to be the discovery of the accelerating expansion of the universe. It left most scientists gob-smacked but has received no serious criticism since the evidence, mostly taken from type 1-A supernovas, continues to pile up. If the red shift of the 1-A flashes were the only evidence there might be other explanations for the data. Shouldn’t there be some other independent way to verify the expansion data, something that helps validate the explanation?
I love watching for these weird effects and anomalies because, once in a great while they pan out to be the real deal and lead to new science. Enter an international team of researchers led by Masamune Oguri at Kavli IPMU and Naohisa Inada at Nara National College of Technology who have conducted a unique survey of gravitational lensing effects. They calculate the probability of lensing at various times in the past to produce a model. But when the model is fit to the survey data it produces an acceleration very much consistent with the type 1-A red shift measurements. Woohoo, one more vote for Einstein’s Cosmological Constant.
Posted by pat
on March 05, 2009
A recent analysis of galaxy clusters has given us some very nice images so I couldn’t resist posting them. The first shows a cluster and a computer analysis of the affect of gravitational lensing. You will notice in the image to the right that, if you scrape off all the spikes, there is a gradual bulge. Scraping off all the spikes amounts to removing all of the visible objects (seen as bright galaxies). The underlying bulge can be explained by the presence of large amounts of something that we can’t see—dark matter.
Gravitational Lensing of Galaxy Clusters
The second photo comes from another cluster. The left image is in visible light, the right in x-rays. The x-rays show a very hot gas halo around the cluster. This hot gas would have escaped into the void if not for a gravitational affect beyond what can be explained by the object in the visible light image.
X-Ray producing hot gas in the grip of dark matter.
This is nothing ground breaking but gives us a clearer picture of the shape of dark matter. One more thing interesting in this arxiv paper is a discussion of dark matter stars as a candidate for dark matter. How’s that for a recursive argument?
Update: A new study of several globular galaxies shows indirectly the effects of dark matter. The galaxies pictured were observed in the middle of a cluster where other galaxies were being ripped apart by tidal forces. These remained undisturbed in the center of the gravity maelstrom hinting at a halo of dark matter which must be sheilding them.