The immensity of the universe; new measurement (The nature of a \'Creator\')

by David Turell , Wednesday, January 30, 2019, 20:53 (2122 days ago) @ David Turell

Gravitational waves also can possibly be used to define Hubble's constant:

https://www.scientificamerican.com/article/the-universes-fate-rests-on-the-hubble-const...

"A burst of gravitational waves from the merger of two black holes is one piece of the new method for calculating the Hubble constant. Not unlike standard candles, binary black hole systems oscillate. As they spiral into each other, the frequency of the gravitational waves they spew out changes at a rate correlated to the system’s size. From this, astronomers derive the waves’ intrinsic amplitude. And by comparing that with their apparent amplitude (similar to a comparison of the actual brightness of a Cepheid with its apparent brightness), they compute how far away the system is. Astronomers call these “standard sirens.” The measured the distance to this particular collision as some 540 megaparsecs, or about 1.8 billion light-years, from Earth.

"An associated redshift, such as that of the sirens’ host galaxy, provides the second piece of the new method. The researchers used redshift data from the Dark Energy Survey, which just finished mapping a portion of the southern sky more broadly and deeply than any previous survey. The redshift data combined with the distance measurement provided researchers with their new figure for the constant.

"Antonella Palmese, a research associate at Fermilab and co-author of the study, says the method holds promise in part because black hole mergers are relatively plentiful. Although it is still a proof of concept, she says that as more gravitational events from LIGO/VIRGO become available, the statistics will improve. University of Oxford astronomer Elisa Chisari, who was not involved in the study, agrees. “The level of constraints that they obtained on the Hubble rate is not competitive at the moment compared to other measurements,” she says. “But as LIGO builds up its catalogue of gravitational wave events in the coming years, then by combining multiple events, this will really become a competitive method.”

Comment: It would be nice to have agreeing methods. We will better understand the future of the universe