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Some have known as NASA’s James Webb Area Telescope the “telescope that ate astronomy.” It’s the strongest house telescope ever constructed and a posh piece of mechanical origami that has pushed the boundaries of human engineering. On Dec. 18, 2021, after years of delays and billions of {dollars} in price overruns, the telescope is scheduled to launch into orbit and usher within the subsequent period of astronomy.
I’m an astronomer with a specialty in observational cosmology—I’ve been finding out distant galaxies for 30 years. Among the greatest unanswered questions concerning the universe relate to its early years simply after the Large Bang. When did the primary stars and galaxies type? Which got here first, and why? I’m extremely excited that astronomers might quickly uncover the story of how galaxies began as a result of James Webb was constructed particularly to reply these very questions.
The universe went via a time period referred to as the Darkish Ages earlier than stars or galaxies emitted any mild. Picture Credit score: Area Telescope Institute
The ‘Darkish Ages’ of the Universe
Glorious proof exhibits that the universe began with an occasion known as the Large Bang 13.8 billion years in the past, which left it in an ultra-hot, ultra-dense state. The universe instantly started increasing after the Large Bang, cooling because it did so. One second after the Large Bang, the universe was 100 trillion miles throughout with a median temperature of an unbelievable 18 billion levels Fahrenheit (10 billion levels Celsius). Round 400,000 years after the Large Bang, the universe was 10 million light-years throughout and the temperature had cooled to five,500 levels Fahrenheit (3,000 levels Celsius). If anybody had been there to see it at this level, the universe would have been glowing uninteresting pink like an enormous warmth lamp.
All through this time, house was full of a clean soup of excessive vitality particles, radiation, hydrogen, and helium. There was no construction. Because the increasing universe turned greater and colder, the soup thinned out and all the things pale to black. This was the beginning of what astronomers name the Darkish Ages of the universe.
The soup of the Darkish Ages was not completely uniform and on account of gravity, tiny areas of gasoline started to clump collectively and develop into extra dense. The sleek universe turned lumpy and these small clumps of denser gasoline have been seeds for the eventual formation of stars, galaxies, and all the things else within the universe.
Though there was nothing to see, the Darkish Ages have been an essential section within the evolution of the universe.
Gentle from the early universe is within the infrared wavelength—that means longer than pink mild—when it reaches Earth. Picture Credit score: Inductiveload/NASA through Wikimedia Commons, CC BY-SA
In search of the First mild
The Darkish Ages ended when gravity shaped the primary stars and galaxies that finally started to emit the primary mild. Though astronomers don’t know when first mild occurred, the very best guess is that it was a number of hundred million years after the Large Bang. Astronomers additionally don’t know whether or not stars or galaxies shaped first.
Present theories based mostly on how gravity kinds construction in a universe dominated by darkish matter counsel that small objects—like stars and star clusters—probably shaped first after which later grew into dwarf galaxies after which bigger galaxies just like the Milky Manner. These first stars within the universe have been excessive objects in comparison with stars of as we speak. They have been 1,000,000 instances brighter however they lived very brief lives. They burned scorching and shiny and after they died, they left behind black holes as much as 100 instances the Solar’s mass, which could have acted because the seeds for galaxy formation.
Astronomers would love to check this fascinating and essential period of the universe, however detecting first mild is extremely difficult. In contrast as we speak’s huge, shiny galaxies, the primary objects have been very small and as a result of fixed enlargement of the universe, they’re now tens of billions of light-years away from Earth. Additionally, the earliest stars have been surrounded by gasoline left over from their formation and this gasoline acted like fog that absorbed many of the mild. It took a number of hundred million years for radiation to blast away the fog. This early mild could be very faint by the point it will get to Earth.
However this isn’t the one problem.
Because the universe expands, it constantly stretches the wavelength of sunshine touring via it. That is known as redshift as a result of it shifts mild of shorter wavelengths—like blue or white mild—to longer wavelengths like pink or infrared mild. Although not an ideal analogy, it’s just like how when a automobile drives previous you, the pitch of any sounds it’s making drops noticeably.
By the point mild emitted by an early star or galaxy 13 billion years in the past reaches any telescope on Earth, it has been stretched by an element of 10 by the enlargement of the universe. It arrives as infrared mild, that means it has a wavelength longer than that of pink mild. To see first mild, it’s a must to be searching for infrared mild.
Telescope as a Time Machine
Enter the James Webb Area Telescope.
Telescopes are like time machines. If an object is 10,000 light-years away, which means the sunshine takes 10,000 years to succeed in Earth. So the additional out in house astronomers look, the additional again in time we’re trying.
The James Webb Area Telescope was particularly designed to detect the oldest galaxies within the universe. Picture Credit score: NASA/JPL-Caltech, CC BY-SA
Engineers optimized James Webb for particularly detecting the faint infrared mild of the earliest stars or galaxies. In comparison with the Hubble Area Telescope, James Webb has a 15 instances wider subject of view on its digicam, collects six instances extra mild, and its sensors are tuned to be most delicate to infrared mild.
The technique shall be to stare deeply at one patch of sky for a very long time, amassing as a lot mild and knowledge from probably the most distant and oldest galaxies as potential. With this information, it might be potential to reply when and the way the Darkish Ages ended, however there are a lot of different essential discoveries to be made. For instance, unraveling this story might also assist clarify the character of darkish matter, the mysterious type of matter that makes up about 80 p.c of the mass of the universe.
James Webb is probably the most technically tough mission NASA has ever tried. However I feel the scientific questions it might assist reply shall be value each ounce of effort. I and different astronomers are ready excitedly for the info to begin coming again someday in 2022.
This text is republished from The Dialog underneath a Artistic Commons license. Learn the unique article.
Picture Credit score: Hubble Deep Subject / NASA
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