These stars may have been born only 250 million years after the Big Bang

A measly 250 million years after the Big Bang, in a galaxy far, far away, what may be some of the first stars in the universe began to twinkle. If today’s 13.8-billion-year-old universe is in middle age, it would have been just starting to crawl when these stars were born.

Researchers used instruments at the Atacama Large Millimeter/submillimeter Array observatory in Chile to observe light emitted in a galaxy called MACS1149-JD1, one of the farthest light sources visible from Earth. The emissions are a clue to the galaxy’s redshift — a stretching of the wavelength of light that signifies the speed at which an object is moving away from an observer. Scientists can use redshift to estimate how far away (and by extension, how old) a celestial object is.

The galaxy’s redshift suggests that the starlight was emitted when the universe was about 550 million years old, researchers report May 17 in Nature. But many of those stars were already about 300 million years old, further calculations indicate. That finding suggests that the stars would have blinked into existence some 250 million years after the universe’s birth, says study coauthor Takuya Hashimoto, an astronomer at Osaka Sangyo University in Japan.

That’s earlier than the 550 million years ago suggested in a previous estimate that also measured starlight from the early universe (SN Online: 2/9/2015). But it’s in the same ballpark as observations reported in March (SN: 3/31/18, p. 6), which suggest star formation began around 180 million years after the Big Bang. That conclusion, however, was drawn from radio signals rather than direct observations of starlight. “If [those] results were true, our results would independently support their claims that star formation activity had already initiated at a very early stage of the universe,” Hashimoto says.