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NASA is about to launch the most powerful space telescope ever

MARY LOUISE KELLY, HOST:

Next week on Christmas Eve, NASA is planning to launch the most powerful space telescope ever, the James Webb Space Telescope. Some of the astronomers who are the most excited want to study primordial stars and galaxies that existed at the dawn of the universe. NPR's Nell Greenfieldboyce reports that this telescope should reveal how the early universe revved up nearly 14 billion years ago.

NELL GREENFIELDBOYCE, BYLINE: The universe contains hundreds of billions, maybe even trillions, of galaxies. Marusa Bradac is an astronomer at the University of California, Davis. She says we citizens of the Milky Way galaxy can look up in the sky and see our neighbor, the Andromeda galaxy.

MARUSA BRADAC: You can even see it with the naked eye, which is kind of cool. And so when you look at that galaxy, you see it as it was 2.2 million years ago.

GREENFIELDBOYCE: You see it as it was back then because it took 2.2 million years for the light from that galaxy to travel all the way here through space. So even though you're looking at the Andromeda galaxy now, you're really seeing a snapshot of what it looked like in the past, when the light began its journey. That's why Bradac says astronomers are a lot like historians, looking through old records.

BRADAC: And the further way you can see, the further into history you can go, and more accurate is your understanding of how we - how our world came about.

GREENFIELDBOYCE: She and her colleagues want to see galaxies that are really, really far away - so far away that the light has been traveling for almost the whole history of the universe - so that they can see what the universe looked like right after it was born.

BRADAC: We are trying to build up the story of how the first galaxies ever emerged and how those evolved into galaxies we see today and we live in today.

GREENFIELDBOYCE: That story is about to be transformed by NASA's James Webb Space Telescope. This $10 billion instrument has been in the works for decades. It's designed to capture infrared light from amazingly old, faint galaxies. The telescope also has instruments that will let researchers probe the galaxy's chemical makeup. All of that will give astronomers a deeper look at the newborn universe than they've been able to get with the iconic Hubble Space Telescope.

And to be clear, Hubble has looked really far back. Charlotte Mason is an astronomer at the University of Copenhagen. She says the farthest, oldest galaxy that Hubble has seen is called GN-z11. To the untrained eye, it looks like a red blob. But for astronomers...

CHARLOTTE MASON: It's basically like looking back in time about 13.3, 13.4 billion years ago.

GREENFIELDBOYCE: That's just a few hundred million years after the Big Bang that got the universe started. She says Hubble's instruments can't reveal much about this galaxy, except that it's surprisingly bright.

MASON: Which means it's, you know, potentially more massive or is forming stars much more quickly than most theoretical models would predict. So even that by itself is actually pretty interesting.

GREENFIELDBOYCE: And that's just one galaxy. Mason says the James Webb Space Telescope is about to bust this time period wide open, with more information about galaxies this old and even older.

MASON: There is kind of this holy grail of, can you find the very first galaxy or the very first stars?

GREENFIELDBOYCE: By that, she means stars that formed just from the elements created in the Big Bang - hydrogen and helium. These first stars were super important for making the universe we know and love today.

MASON: They set the stage for all of the subsequent galaxy and star formation. It really fundamentally changed their surroundings.

GREENFIELDBOYCE: She says the odds of glimpsing those first stars are small. They're so rare. But there is a chance.

MASON: And actually, there's maybe more of a chance that we might see one of those stars explode.

GREENFIELDBOYCE: Those explosions would have spewed out other chemical elements created in the stars - you know, the kind of basic elements like carbon that make up the periodic table and, of course, us. Nell Greenfieldboyce, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.