The Oldest Galaxies in the Universe
Peering through a wrinkle in spacetime, astronomers have just seen the first galaxies.
More than 12 billion years ago, a sea of stars fell into orbit around a baby black hole, and became a galaxy, one of the first.
The formation of this galaxy, and others like it, was a momentous event in cosmic evolution. This galaxy and its brethren helped to clear hydrogen gas left over from the Big Bang, making our universe transparent to light.
In the cores of its long-dead stars, atoms fused and popped out photons, which journeyed through the newly cleared universe, for nearly all of time—until they landed on a telescope’s sensor, which converted them into a small speck of light in the image at the top of this page.
As this light made its way to us from across the cosmos, it passed through fields of galaxies, some of which were snowballing in slow motion, into monstrosities like the Milky Way. As these galaxies grew, whole generations of their stars burned bright, died out, and exploded, seeding surrounding gas clouds with the materials to make new suns and planets.
Human beings have taken materials from one such planet, and shaped them into the Hubble Space Telescope, an orbiting camera that can, among other things, take snapshots of the deep cosmos.
In 2013, astronomers pointed the Hubble at an enormous galaxy cluster, hundreds of millions of light years distant. Dense with hundreds of galaxies, this cluster is massive enough to distort surrounding space, so that light flowing from behind it is magnified. This effect is called “gravitational lensing,” and it’s a windfall for astronomers, who often express astonishment at the fact that nature has placed looking glasses throughout the universe.
Through this particular looking glass, a team of stargazers led by Hakim Atek was able to see back to the first generation of galaxies, which were long theorized, but too faint to be spied by telescopes, until now.
“Hubble remains unrivaled in its ability to observe the most distant galaxies,” Mathilde Jauzac told NASA, late last week, when these findings were released.
Unrivaled until 2018, when the James Webb Space Telescope launches, with equipment that packs 100 times Hubble's seeing power. Some have already described Hubble’s lensing observations as “previews” of the universe the Webb will reveal.
That’s cause for excitement, but it will be bittersweet to see the Hubble eclipsed after such distinguished service. In April, astronomers marked the telescope’s 25th year in orbit. During that time, revolutions in imaging technology have repeatedly rendered previous years’ smartphones and SLRs obsolete. And yet, more than a quarter century on, trusty old Hubble continues to deliver wonders.
May its latest not be its last.