The Webb Space Telescope is built using some of the most advanced scientific instruments ever sent out of Earth’s orbit. Astronomers believe the spacecraft will help them understand more about black holes, how stars are born and die and what lies in the atmospheres of planets orbiting other stars; Perhaps, it will give us a glimpse into an era close to the Big Bang.
Remember the speed of light? A steady pace of more than 186,000 miles per second, or roughly six trillion miles per year, through the vacuum of space.
This makes a light year – the distance light travels in one year – a handy measuring stick for cosmic distances.
It also explains why we look at the universe in the past.
If the star is 10 light years away, then its light took 10 years to reach us: we are observing the star as it was 10 years ago. (It takes sunlight eight minutes to reach us on Earth.)
For objects as far away as the Web can detect, these particles of light have traveled about 13 billion light-years, and have traveled through space for 13 billion years. The light in Webb’s “Deep Field” image released Monday is a snapshot of a part of the universe when it was less than a billion years old.
What can you learn more about the period closest to the Big Bang for astronomers?
When did the first stars light up? When did the first galaxies merge from the gas clouds? How different were the first stars and galaxies from those that populate the universe today?
Nobody really knows. It is a missing chapter in the history of the universe. We know that the universe began at the moment of the Big Bang. This explosion left a background whisper of microwave noise that was discovered in 1964, and has been studied in detail in the decades since. The universe cooled, matter began to clump and the first stars are believed to have formed about 100 million years after the Big Bang.
The early stars must have been different because the Big Bang produced only hydrogen and helium along with a small amount of lithium and beryllium. None of the heavier elements—carbon, silicon, iron, and the rest of the periodic table—were present. Some astrophysicists believe that many of the first stars, devoid of heavy elements, were massive, burned up bright and died young in supernova explosions to disperse material that could later form planets and, eventually, living beings like us.
Webb is the first telescope that may be able to identify and analyze those early stars.
Why do Webb tools help advance this work?
The two main differences between Webb and Hubble are the size of the mirror – larger mirrors collect more light – and the wavelengths of light they observe. Hubble focused on visible and ultraviolet wavelengths, and provided unparalleled new views of much of the universe.
But for the early universe, the infrared portion of the spectrum becomes key. This is due to the Doppler effect. When a police car is advancing quickly, the siren is louder when the car approaches and lowers when it drives away. The same thing happens with light. Objects speeding toward us appear bluer, and objects moving away become redder because the receding motion extends from the wavelengths of the light particle. For distant objects, such as stars and early galaxies, much of the light was converted all the way to infrared.
Infrared observations are essentially impossible from telescopes on Earth. The atmosphere blocks those wavelengths.
Infrared notes can also be easily distorted by thermal radiation. That’s why Webb was positioned a million miles from Earth and shaded by a massive sun shield. One of the instruments, the mid-infrared instrument, or MIRI, must be cooled to minus 447 degrees Fahrenheit to function properly.
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