The Grandfather of Galaxies

Somewhere out —about 13.2 billion light-years away— the Hubble Space Telescope has recently discovered a magnificent red, amorphous mass. It's a galaxy —or it was— but it is not beautiful, it is magnificently old.

The newly discovered star block — a hundred times smaller than our Milky Way — was formed just 480 million years after the 13.7 billion-year-old universe was born, making it the oldest galaxy. As such, it provides astronomers with a look at the universe in a phase when small galaxies were being formed out of hot gas, only to disappear —leaving the skies free for the immense and mature galaxies that would come along later.

Its size, shape and the era in which it formed all suggest that it began its life as a mass of gas trapped in a pocket of dark matter. In those early days, stars took about 10 times as long to form as they did in later epochs. They were typically part of the blue star class — extremely hot stars, heavy on helium, oxygen and nitrogen. Blue stars last only a few million years before ending their lives in massive explosions.

Soon, stabler stars began to form in much larger galaxies as the universe rapidly cooled. Between 480 million and 700 million years after the Big Bang — when UDFj-39546284 was still in the skies — star formation accelerated. It was then when spiral galaxies and the other glorious formations that define the modern universe appeared.

It is not certain what forces drove those changes. The Hubble Space Telescope has a lot more work to do before more answers are revealed — and a lot more images of thousands of other galaxies to analyze.

By Jeffrey Kluger, TIME Magazine. Picture by NASA.