Only a few times in the history of a species have it gained the know-how, the audacity and the tools to advance the interrogation of its origins. Astronomers say that humanity is at a point.
The first stars flickered on when the universe was 100 million years old, according to a story they have been telling themselves for the last few decades.
They burned hard and died quickly in the spectacular supernova explosions, which dispelled the gloomy fog of gas left over from the Big bang. All that we care about in the universe is the long, ongoing chain of evolution that has produced everything from galaxies and planets to microbes and us.
Is that story correct?
There are tools to address that question. The biggest, most powerful and most expensive telescope ever to be launched into space is sitting in a spaceport in French Guiana, wrapped like a butterfly in a chrysalis of technology, ambition, metal and wires. Its job is to look back in time at the first stars and the universe.
The chief scientist for the telescope said that they were looking for the first things to come out of the Big bang. He likes to ask: "How did we get here?"
The telescope will be loaded onto an Ariane 5 rocket and flown to a spot beyond the moon on the morning of December 24.
The chrysalis will unfold into a telescope in a series of movements more complicated than anything ever attempted in space, and it will not be helped by any astronauts or robot. Six months of high anxiety is what engineers and astronomer call it.
The first thing that will happen is that antennas will pop out and aim at Earth. The sunscreen is made of five thin sheets of plastic called Kapton, and it will open the scaffolding.
The 18 gold-plated beryllium octagons will form a mirror that is 21 feet across. The telescope will aim at eternity when it reaches its destination, a point called L2 floating on its sun shield.
Astronomers will spend six months tweaking, testing and calibrating their new eye.
The Canadian Space Agency and the European Space Agency collaborated with NASA to create the James Webb Space Telescope. Its official mission is to explore a realm of history that was not accessible to Hubble and every telescope before it.
Alan Dressler of the Carnegie observatory in Pasadena, Calif. said that we are all here because of the stars and galaxies.
Our eyes or the Hubble can see a different kind of light than the Webb can. Because of the expansion of the universe, the earliest stars and galaxies are moving so fast that their light is shifted to longer, redder wavelength, like the sirens from an ambulance.
By the time it reaches us today, the light from the infant galaxy 13 billion years ago has been stretched to invisible heat radiation.
The telescope needs to be very cold so that its own heat doesn't wash out the heat being detected. The telescope will be shade by the sun shield.
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An artist's rendering of a quasar, one of the phenomena the telescope will investigate.
Astronomers were arguing about what to do after the Hubble Space Telescope was launched. A Next Generation Space Telescope was proposed by Dr. Dressler as a way to see the first stars and galaxies in the universe. It would need to be at least 4 meters in diameter, and highly sensitive to radiation, and it would cost $1 billion.
Dan Goldin, the administrator of NASA, was worried that a 4-meter telescope would not be able to detect the first stars. He scolded Dr. Dressler and his committee for being too cautious in 1996. He said the new telescope would be 8 meters wide, a huge leap in power, cost and development time.
The crowd went crazy. Many of us knew from that day that this was a big problem. The more expensive it was, the more critical it was that it not fail, and that made it even more expensive.
The telescope couldn't fit on any existing rocket. The mirror would have to be foldable and assembled in space. NASA settled on a mirror that was almost three times the size of Hubble and seven times the light-gathering power. The challenges of developing and building remained.
The foldable mirror could be used to launch giant telescopes that are too big to fit on rockets. A National Academy of Sciences panel recommended last month that NASA build a giant space telescope to look for planets in the solar system. NASA and the astronomy community will have to take a long walk back to the drawing board if Webb fails.
Dr. Dressler said that NASA committed too early to a particular design. This discouraged creative solutions that might have delayed the start of construction but made the telescope better and more affordable and, in the end, faster to launch.
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The Ariane 5 rocket will take the telescope to space on December 24.
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The primary mirror of the telescope at the NASA's Goddard Space Flight Center in Maryland was installed in 2016
The setbacks mounted. It took 25 years for the telescope to be ready after it was projected to cost $5 billion. NASA's science budget was threatened by cost overruns and mistakes. Nature called it the telescope that ate astronomy. Congress considered canceling it completely a decade ago.
The telescope's name was a challenge. The instrument was named after Mr. Webb, who was a champion of space science and the agency's leader during the crucial days of the Apollo program. The astronomer was disappointed that it did not honor a scientist like the Hubble Telescope or the Einstein X-ray Observatory do. Some of them were critical of Mr. Webb, questioning his role in a purge of gay men and lesbians from the State Department during the Truman administration.
The telescope's initials stood for the "Just Wait Space Telescope." The delays were part of the process, Dr. Mather said, and that it was always harder to build a telescope than people think.
It was difficult to design the foldable mirror. During a rehearsal of the unfolding process, the sunscreen was torn and the project was set back again.
The telescope arrived in French Guiana in October of last year. The telescope had troubles that were not over. The whole instrument quivered as technicians prepared to attach it.
The telescope had not been damaged and the launch date was pushed back four days. A broken data cable forced the adventure back another couple of days.
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The telescope's primary imager is the product of 20 years of effort by the University of Arizona.
When the universe was less than a trillionth of a second old, quantum fluctuations in the density of matter and energy gave rise to the first stars.
Scientists believe that the stars we see in the night sky were composed of only hydrogen and helium, which was created in the thermonuclear furnace of the Bigbang. Such stars might have grown to be hundreds of times larger than the sun and then exploded as supernovas. It seems that they don't exist in the present-day universe.
The early stars are too faint to be seen individually with the telescope. He said that they come in herds and that they explode when they explode.
The process of seeding the galaxy with heavier and more diverse elements like oxygen and iron is thought to have begun after the supernova explosions.
The University of Arizona'sMarcia Rieke said that the top item on the agenda would be to hunt for the first galaxies. Dr. Rieke has spent the last 20 years leading the development of a special camera that takes the light from the telescope mirror and converts it into a spectrum.
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Dr. Rieke is at the University of Arizona. The University of Arizona will conduct a survey of new galaxies after the new telescope is put in place.
The earliest and most distant known galaxy was discovered by the Hubble and is only 400 million years old. The telescope will be able to see back to 100 million years after the Big bang.
Dr. Rieke expects to find many more infant galaxies in that foggy realm. These are the building blocks of the clusters of galaxies that are visible today.
The galaxies acquire supermassive black holes at their centers with mass millions or billions larger than the sun. How does this happen, and which comes first: the black hole or the galaxy?
An astronomer at Yale, Priyamvada Natarajan, and her colleagues are hoping to find out the origin of black holes.
Did they come from the first stars collapsing? Was the black holes legacies of the Big bang?
A lot is on the line in terms of our understanding of black-hole growth, and in terms of careers for the younger members of our team and that of others working on this important open question, said Dr. Natarajan. It's assumed that all goes well, and the data is taken as expected.
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One of the targets of inquiry will be Alpha Centauri, a star only 4.5 light-years from Earth.
The search for and study of exoplanets, worlds that are outside the solar system, has become the fastest-growing area of astronomy. There are as many planets in the universe as there are stars.
Dr. Mather said that everything they have learned about exoplanets has been a surprise.
He said that the telescope would look at Alpha Centauri, a star that is only 4.5 light-years from Earth.
It turns out that the emission from the sun is ideal for studying exoplanets. The atmosphere of an exoplanet is backlit when it passes in front of a star. Sara Seager, a planetary expert at the Massachusetts Institute of Technology, said that Ozone and water are both of interest.
The list of 65 exoplanets that the astronomer with viewing time on the telescope have made is relatively nearby, circling small stars known as red dwarfs. An Earth 2.0 is a sunlike star and is a true analog to our planet. Finding one of those will require a bigger telescope. They could be wet.
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The first things to come out of the Big bang are what John Mather is looking for.
The planets in the Trappist-1 system are 40 light-years away and will be some of the most anticipated early observations. There are seven planets around a dim red-dwarf star. Water could be on the surface of the three Earth-size rocks.
Dr. Seager is part of a team that is studying one of the most promising exoplanets, Trappist-1e. Researchers will try to determine if the world has an atmosphere.
She said that nothing is scheduled yet, and that there are many steps needed before the telescope is operational. It's like waking someone up from a coma. You don't ask them to run a marathon right away. It is step-by-step testing.
When asked what he was looking forward to studying, Dr. Mather mentioned primordial galaxies, dark energy and black holes. He hopes for something that we don't expect.
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The galaxy is visible in the sky. The blue ribbons of young stars dangle from the galaxy's disk like tentacles. The hot tail of gas coming from the galaxy will be studied by the telescope.
Wendy could be excused for thinking that she is living in the same place again.
Thirty years ago, before the Hubble Space Telescope was launched, experts were arguing about how fast the universe was expanding. The Hubble constant has been called the most important number in the universe. The measurement of the cosmic expansion rate was disagreeing by a factor of two. Calculating the age or fate of the universe was not possible because of this.
The Hubble Telescope was supposed to resolve the problem, but Dr. Freedman ended up running a key project that settled on an answer. There is a new disagreement about the expansion rate. The Hubble constant is being remeasured by a new space telescope.
She said in an email that they have a chance to learn something about the early universe. We can now ask if there are cracks in the current standard model, because the issue has changed as we have gotten higher accuracy. Is there a new missing fundamental physics?
She said it is exciting. A new space telescope will allow us to resolve a controversy.
That will create new ones. Klaus Pontoppidan, an astronomer with the Space Telescope Science Institute, said at a recent news conference that the telescope was built to answer questions they didn't know they had.
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A guide to the craft.
The New York Times has an interactive section aboutexploring the solar system.
