Photo by: NASA/Hubble


Why Astronomers Care About Super-Old Galaxies?

A long time ago, our universe was dark.

It was just 380,000 years after the big bang. Up until that age, our entire observable cosmos was less than a millionth of its present size. All the material in the universe was compressed into that tiny volume, forcing it to heat up and become a plasma. But as the universe expanded and cooled, eventually the plasma changed into a neutral gas as the first atoms formed.

September 08, 2022

And at that moment, over 13 billion years ago, the lights went out. Radiation released during the phase transition process quickly cooled and dimmed below the visible range of wavelengths. But although the universe was dark, it was not without movement. Through the ensuing hundreds of millions of years, clumps of matter began to collect, forming ever more prominent and ever denser structures.

And in one hidden corner of the universe, a clump of gas reached the critical temperatures and pressures to ignite nuclear fusion. In that instant, the first star ever began to shine.

It was soon joined by billions more, and as time went on those stars began to collect into the first galaxies. Those galaxies, like our own Milky Way, persist to the present day, where astronomers can study them, and we can gaze upon them in awe and wonder.

And yet, even though we know there was a time before stars and galaxies, and we know that stars and galaxies inhabit the present-day universe, we have no direct observational evidence of the ignition of the first generation. The light from that distant epoch is simply too dim to see.

But that’s where James Webb comes in. That observatory is tuned to detect infrared radiation. The light released from the first galaxies was once as bright and intense as from our own, but over the billions of years, it has dimmed and stretched into the infrared. James Webb is a hunter of those early firstborn galaxies.

Photo by: NASA Goddard

NASA Goddard

Hence all the excitement as already, barely a month into its first science observation campaign, the James Webb is smashing record after record, finding the youngest known galaxies ever observed.

Those galaxies are like precious baby pictures from a forgotten childhood. We do not currently know how the first stars and galaxies formed; we do not know how quickly or slowly the process unfolded, and what violence or exotic forces accompanied those births. We remain ignorant as to how our own Milky Way came to be so long ago.

The birth of the first stars and galaxies – known poetically to astronomers as the Cosmic Dawn – remains the last major frontier in observational cosmology. And James Webb is leading us into the light.

Dive Deeper into Galaxies

Journey Through the Cosmos in an All-New Season of How the Universe Works

The new season premieres March 24 on Science Channel and streams on discovery+.

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

Next Up

What We’ve Already Learned From James Webb? (Hint: it’s a lot)

That was worth the wait. Just a quick handful of months since its historic launch on Christmas Day, the James Webb Space Telescope has flown to its observing position, unfolded its delicate instruments and ultra-sized mirror, and run through a suite of checks and alignments and calibrations. The team at NASA behind the telescopes released their first batch of images from the science runs, and besides being gorgeous, they're powerful.

How Astronomers Use a Trick of Gravity to See the Most Distant Objects in the Universe

Let’s say you’re an astronomer (work with me here) and you want to take a picture of something incredibly, deeply far away. You know, the typical business of astronomy.

How Exoplanets Became the Next Big Thing in Astronomy

To date, we know of over 5,000 planets outside the solar system. And astronomers suspect that there may be *checks notes* around a trillion more in our galaxy alone. The search for exoplanets is one of the hottest topics in astronomy, with expensive telescopes and giant collaborations all searching for the holy grail of the 21st century: an Earth 2.0, a habitable world like our own.

A Guide to this August’s Best Astronomy Attractions

Learn more about the exciting things happening in the night sky this month! From the rings of Saturn to the most popular meteor shower of the year, August 2022 has us stargazing all month.

Got You! Astronomers Find an Especially Sneaky Black Hole

Black holes are tricky creatures. Since ancient times the practice of astronomy has been to point our eyes and instruments at all the glowing things in the skies above us. But black holes are defined by the fact that nothing, not even light, can escape their gravitational clutches. So how you do see something that is completely, totally black?

This Year, James Webb will Take a Close Look at a Lava World

The James Webb Space Telescope is gearing up to be an exoplanet extraordinaire. Among many other missions and targets, astronomers plan to use the observatory, now in its final stages of preparations to study…well, a world where it might rain lava.

The Perseid Meteor Shower Reaches its Peak

Stargazers rejoice! The annual Perseid meteor shower is upon us. Here's what you need to know...(updated August 11, 2022)

Jupiter Makes Its Closest Approach to Earth in Nearly 60 Years

The last time Jupiter appeared this large and bright in the sky was in October 1963.

6 Months in Space Permanently Ages Bones by 10 Years

Astronauts on long-term space missions can experience bone loss equivalent to two decades of aging. New research suggests more weight-bearing exercises in space could help offset that decline.

South Korea Joins Space Race by Sending its First Spacecraft to the Moon

South Korea is launching its first lunar probe to the moon on August 4th. The Korea Pathfinder Lunar Orbiter (KPLO) or Danuri, developed by the Korea Aerospace Research Institute (KARI) is being launched to study moon carters, magnetic fields, and surface weathering.

Related To: