Exploring the First Galaxies with the James Webb Space Telescope

Posted on Tue, March 13, 2018

Picture a sunrise: the light becomes bright very quickly as the Sun comes up over the horizon. Now, imagine that billions of years ago, and instead of just the Sun, it’s galaxies, bursting into light from what once was darkness. That brightening of the sky is what Garth Illingworth calls a “cosmic sunrise,” and it’s something he hopes to explore with the revolutionary new James Webb Space Telescope.

Illingworth, professor emeritus in the department of astronomy and astrophysics at the University of California Santa Cruz, describes this moment as “when the first galaxies turn on.” After the Big Bang, for hundreds of millions of years, there was “nothing going on in the universe,” he said. Then, it all changed.

“Suddenly one of these dark matter regions creates a star, and then those stars started forming into galaxies—coming together, merging together—when those first galaxies turn on and illuminate the universe,” Illingworth described.

Those early galaxies look different than our galaxy today. Illingworth said to think of our galaxy as a Frisbee: the stars are mostly in the Frisbee plane, circling around the center in an organized fashion. Early galaxies were messier, “blobby” in shape, with stars that moved in every direction—up, down, in, out, “all over the place,” he said.

Called the eXtreme Deep Field, or XDF, the photo was assembled by combining 10 years of NASA Hubble Space Telescope photographs taken of a patch of sky at the center of the original Hubble Ultra Deep Field.

Right now, we have a sense of what some of those early galaxies look like thanks to the Hubble Space Telescope. Particularly since the Hubble’s Infra-red Wide Field Camera 3 WFC3/IR became operational in 2009, Illingworth and other scientists have been able to look back at a galaxy just 400 million years after the Big Bang. The camera also helped expand the Hubble’s Deep Field images, the deepest pictures of the sky ever taken. Illingworth led the eXtreme Deep Field (XDF) data efforts in 2012, and these have helped to search out the youngest galaxies for closer scrutiny.

Webb, scheduled to launch in 2019, is poised to show us much more.

“At this point we have one galaxy at 400 million years and only nine at 450 million years,” Illingworth said. “We need more, many more, galaxies that span the crucial time of formation and build-up from about 300 million years to 800 million years after the Big Bang. Webb will deliver thousands of such very early galaxies (those before 600-700 million years after the Big Bang) over its life.”

The deployed primary mirror of the James Webb Space Telescope at NASA's Goddard Space Flight Center. 

Webb will not only give scientists a new, unprecedented view of the first galaxies, it will help us answer fundamental questions about what those galaxies were like: When did the first galaxies begin? What were the stars like as they grew? 

Illingworth’s work on the project began in 1987, when he was the Deputy Director of the Space Telescope Science Institute and Webb was still called the “Next Generation Space Telescope.” So, he’s looking forward to more decades of discovery once Webb launches.

“Given all this effort, I am both very interested in seeing [Webb] be a stunning success as well as using it,” Illingworth said.  

Garth Illingworth, professor emeritus in the department of astronomy and astrophysics at the University of California Santa Cruz, will be giving a lecture at the National Air and Space Museum in Washington, DC, on March 14 at 8 pm. Tickets for “The Earliest Galaxies: Exploring Cosmic Sunrise with Hubble, Spitzer, and JWST” are free, but are now in overflow seating. This event is part of the ongoing John N. Bahcall lecture series. Request tickets or learn how you can stream the lecture online.

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