A new Technique Could use Quasars to Directly Measure the Expansion Rate of the Universe

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fred8615
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A new Technique Could use Quasars to Directly Measure the Expansion Rate of the Universe

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One of the biggest challenges to measuring the expansion of the universe is the fact that many of the methods we use are model-dependent. The most famous example is the use of distant supernovae, where we compare the standard brightness of a Type Ia supernova with their apparent brightness to find their distance. But knowing the standard brightness depends upon comparing them to the brightness of Cepheid variables which is in turn determined by measuring the distances of nearby stars via parallax. Every step of this cosmic distance ladder depends upon the step before it.

This doesn’t mean our distance measurements are necessarily wrong, but it makes them more vulnerable to systematic errors. In recent years it has become clear that our various measures of cosmic expansion don’t quite agree, so either a systematic error has crept into our data, or something is wrong with our cosmological model. One way out of this mess would be to find new ways of measuring cosmic expansion. Preferably methods that aren’t model dependent. We’ve made quite a bit of progress in this area. Methods using phenomena such as astronomical masers and gravitational waves have shown a lot of promise. And a recent study in Physical Review A introduces a method using quasars and gravitational lensing.

Quasars are incredibly bright and distant objects. They are powered by active supermassive black holes in young galaxies. The light we see from quasars has traveled for billions of years to reach us, and so it is redshifted by the expansion of the universe during that time. Rather than trying to measure the distance of these quasars, this new method looks at quasars that are gravitationally lensed by closer galaxies.

Read more: https://www.universetoday.com/150999/a- ... -universe/
Frederick J. Barnett
"Someone's got to take the responsibility if the job's going to get done!! Do you think that's easy?!" Gregory Peck - The Guns Of Navarone
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