Finetuning the Hubble Constant

credit: Dark Energy Survey

Astronomers think the universe might be expanding faster than expected.

If true, it could reveal an extra wrinkle in our understanding of the universe, says Nobel Laureate Adam Riess of the Space Telescope Science Institute and Johns Hopkins University. That wrinkle might point toward new particles or suggest that the strength of dark energy, the mysterious force accelerating the expansion of the universe, actually changes over time.

The result appears in a study published in The Astrophysical Journal this July, in which Riess’s team measured the current expansion rate of the universe, also known as the Hubble constant, better than ever before.

In theory, determining this expansion is relatively simple, as long as you know the distance to a galaxy and the rate at which it is moving away from us. But distance measurements are tricky in practice and require using objects of known brightness, so-called standard candles, to gauge their distances.

The use of Type Ia supernovae—exploding stars that shine with the same intrinsic luminosity—as standard candles led to the discovery that the universe was accelerating in the first place and earned Riess, as well as Saul Perlmutter and Brian Schmidt, a Nobel Prize in 2011. … (Symmetry Magazine)

credit: Dark Energy Survey

credit: Dark Energy Survey

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