Hubble reaches new milestone in mystery of universe's expansion rate: 'The gold standard of telescopes and cosmic mile markers'

Completing a nearly 30-year marathon, NASA's Hubble Space Telescope has calibrated more than 40 "milepost markers" of space and time to help scientists precisely measure the expansion rate of the universe -- a quest with a plot twist.

Edwin P. Hubble and Georges Lemaitre, two astronomers working in the 1920s, were the ones who first started looking into the expansion rate of the universe. The term "dark energy," which refers to an unexplained factor that is responsible for speeding the expansion of the cosmos, was first coined in 1998. Data from Hubble, which includes a variety of cosmic objects functioning as distance markers, hints that something peculiar is taking place, and this may include new physical laws.

Adam Riess, who was awarded the Nobel Prize by the Space Telescope Science Institute and the Johns Hopkins University, is the leader of a scientific partnership that goes by the name SH0ES and investigates the rate at which the universe is expanding. He claims that the Hubble Space Telescope was conceived to provide the most accurate measurement possible of the rate at which the universe is expanding. In their most recent article, which was recently published in The Astrophysical Journal and will be included in a special emphasis issue, the team reports on the most comprehensive update to the Hubble constant to date, which includes over 1,000 Hubble orbits.

"You are getting the most precise measure of the expansion rate for the universe from the gold standard of telescopes and cosmic mile markers," Riess said.

The Hubble constant, which was named after Edwin Hubble, is an important measure of the expansion rate of the cosmos. It is significant for determining the age of the universe as well as verifying our understanding of it. In 1990, the Hubble Space Telescope was put into orbit around the Earth with the intention of resolving Cepheids, which are periodic stars, in order to improve the accuracy of the Hubble constant. Two separate groups had achieved an accuracy of 10% for the constant by the beginning of the new millennium. In 2005 and 2009, the Hubble Space Telescope was outfitted with powerful new cameras, which sparked a fresh wave of study that helped refine the value to an accuracy of one percent. The SH0ES team, which consists of members Wenlong Yuan, Lucas Macri, Stefano Casertano, and Dan Scolnic, has used Hubble to measure 42 of the supernova markers. Their calculations have produced a value of 73 plus or minus 1 kilometers per second per megaparsec, which is comparable to the findings of other teams.

However, the expansion rate of the universe was predicted to be slower than what is actually seen. The Standard Cosmological Model and the Planck mission of the European Space Agency both predicted a lower value for the expansion rate of the universe, which was 67.5 plus or minus 0.5 kilometers per second per megaparsec. This value was lower than the estimate provided by the SH0ES team. In spite of the vast number of samples used, the discrepancy's root cause has not been identified, leading researchers to hypothesize that strange physical principles may be at play here.