Astronomers have found a galaxy with a heartbeat—and they’ve taken its pulse. They are the first to measure the effect that pulsating, older red stars have on the light of their surrounding galaxy.
“We tend to think of galaxies as steady beacons in the sky, but they are actually ’shimmering' due to all the giant, pulsating stars in them,” says Pieter van Dokkum, an astronomy professor at Yale University, and coauthor of the study in Nature.
Later in life, stars like our Sun undergo significant changes. They become very bright and swell up to an enormous size, swallowing any planets within a radius roughly equivalent to Earth’s distance from the Sun. Near the end of their lifetime, they begin to pulsate, increasing and decreasing their brightness every few hundred days. In our Milky Way galaxy, many stars are known to be in this phase.
Until now, no one had considered the effects of these stars on the light coming from more distant galaxies. In distant galaxies, the light of each pulsating star is mixed with the light of many more stars that do not vary in brightness.
“We realized that these stars are so bright and their pulsations so strong that they are difficult to hide,” says Charlie Conroy, an assistant professor at Harvard University, who led the research. “We decided to see if the pulsations of these stars could be detected even if we could not separate their light from the sea of unchanging stars that are their neighbors.”
