NASA’s Hubble Space Telescope in conjunction with the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile have found half a dozen “dead” galaxies that seemingly ran out of the cold hydrogen gas needed to make stars far sooner than expected. The technique used to find these anomalies is arguably just as fascinating as what was found.
As NASA recounts, when the universe was roughly three billion years old, it was in its prime formation phase. Yet oddly enough, the six distant, massive galaxies recently discovered were no longer making stars as they’d depleted all of their cold hydrogen gas, a key fuel source.
Roughly 11 billion years later in the present day, it is believed that these galaxies have swelled in size but are still “dead” as it relates to new star formation. So, what went wrong?
Kate Whitaker, assistant professor of astronomy at the University of Massachusetts, Amherst, and lead author on the research, believes there could be multiple explanations. Perhaps a supermassive black hole in the center of the galaxy heated up all of the gas in the region. If that’s the case, the gas would still be there, it’d just be hot. Or maybe, the galaxy simply used up all of its supply and there’s none left.
“These are some of the open questions that we’ll continue to explore with new observations down the road.” Whitaker added.
To peer that far back into history, researchers utilized a technique called gravitational lensing. In space, the gravity of massive galaxy clusters in the foreground stretch and amplify the light of background galaxies. This acts as a natural magnifying glass, allowing astronomers to study details in galaxies that would otherwise be impossible to see with our current technology.
“I like to think about it like doing science of the 2030s or 40s – with powerful next-generation space telescopes – but today instead by combining the capabilities of Hubble and ALMA, which are boosted by strong lensing,” Whitaker said.