the world through quasar-lensed glasses

Quasars, or quasi-stellar radio sources, are the brightest known objects in the universe. The brightest known quasar has an absolute magnitude of -32.2 when it was discovered in 1998. However more recent data from Keck and Hubble show that the quasar APM 08279+5255 is gravitationally lensed, making it appear 10 times brighter than it actually is.

But what exactly are quasars? It is thought that they are a type of early, active galaxy, surrounding a super massive black hole. Their extreme brightness is due to the accretion disk of black holes that they surround, which can convert a whopping 10% of matter into energy. By comparison, proton-proton fusion converts about 0.7% of matter into energy. Because of their massive consumption (to sustain a luminosity of 10^40 watts would requite a consumption of about ten suns a year), quasars are thought to have been much more common in the early universe. The oldest/farthest detected quasar has a redshift of 7.085, meaning it was formed about 700 million years after the Big Bang. It is thought that after a quasar "burns out", it settles and forms a regular galaxy. Some astronomers even think that most galaxies once hosted quasars, even our own Milky Way.

Their extreme luminosity and distance of quasars makes it very hard to study their host galaxies. Of course, there are ways to get around that. Quasars cause gravitational lensing on their host galaxies, and that can be used to detect their mass.

http://www.nasa.gov/mission_pages/hubble/science/quasar-lens.html#

Einstein's General Theory of Relativity predicted gravitational lensing, and was observationally confirmed in 1979 by the first images of a double quasar. Lensing can cause double, triple or even quadruple images of the same quasar.


picture of the Einstein Cross

A team of astronomers using the Hubble telescope will be putting together a directory of "quasar-lenses" to compare masses of galaxies with quasars to those without.