科学美国人60秒:Primordial Galaxy Shows How to Make a Big One

How did big galaxies get so big? A rare glimpse at a primordial galaxy undergoing a growth spurt may provide some answers.

The galaxy Himiko is named for a Japanese queen of the third century AD. Researchers peered into the galaxy using both the Hubble Space Telescope and the newly inaugurated ALMA telescope array in Chile. The galaxy is so distant that astronomers see it as it appeared just 800 million years after the big bang, when the universe was only about six percent of its present age.

At that early epoch, Himiko was already making new stars at a vigorous clip of about 100 per Earth year. The burst of star formation may be powered by a merger of three smaller galaxies—the detailed new observations show that Himiko is not one homogenous blob but three separate luminous clumps. The research has been submitted to the Astrophysical Journal. [Masami Ouchi et al., An Intensely Star-Forming Galaxy at z~7 with Low Dust and Metal Content Revealed by Deep ALMA and HST Observations]

The researchers say that their observations offer the first clear glimpse at how the most massive galaxies took shape, way back when the earliest stars and galaxies were lighting up the universe. And that should prove to be a very big deal.

—John Matson