The Universe Is Expanding Faster Than Expected

“The Gaia parallaxes are by far the most accurate and precise distance determinations ever,” said Jo Bovy, an astrophysicist at the University of Toronto.Best of all for cosmologists, Gaia’s new catalogue includes the special stars whose distances serve as yardsticks for measuring all farther cosmological distances. Lindegren and colleagues managed to remove much of the telescope’s wobble from the newly released parallax data, while also devising a formula that researchers can use to correct the final parallax measurements depending on a star’s position, color and brightness.With the new data in hand, Riess, Freedman and Madore and their teams have been able to recalculate the universe’s expansion rate. “If you change the precision of the first step, then the precision of everything else changes.”Riess’s team has used Gaia’s new parallaxes of 75 Cepheids—pulsating stars that are their preferred standard candles—to recalibrate their measurement of the cosmic expansion rate.Freedman and Madore, Riess’s chief rivals at the top of the distance ladder game, have argued in recent years that Cepheids foster possible missteps on higher rungs of the ladder. So rather than lean too heavily on them, their team is combining measurements based on multiple kinds of standard-candle stars from the Gaia data set, including Cepheids, RR Lyrae stars, tip-of-the-red-giant-branch stars and so-called carbon stars.“Gaia’s [new data release] is providing us with a secure foundation,” said Madore. When used with various methods of plotting and dissecting the measurements, data points representing Cepheids and other special stars fall neatly along straight lines, with very little of the “scatter” that would indicate random error.“It’s telling us we’re really looking at the real stuff,” Madore said.Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.📩 Want the latest on tech, science, and more?