July 12, 2022, 11:52 am ETNASA workers inspect the Webb telescope mirrors at the Goddard Space Flight Center in Greenbelt, Md., in 2016. Credit…Kevin Lamarque/Reuters The Webb Space Telescope was built with some of the most advanced scientific instruments ever sent beyond Earth orbit. Astronomers believe the spacecraft will help them understand more about black holes, how stars are born and die, and what’s in the atmospheres of planets orbiting other stars. perhaps, even give us a glimpse of an era close to the Big Bang.
Why does tracking further help scientists see billions of years into the past?
Remember the speed of light? A steady pace of more than 186,000 miles per second, or close to six trillion miles per year, through the void 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 looking out into the universe is looking into the past. If a star is 10 light-years away, that means its light took 10 years to reach us: We observe the star as it was 10 years ago. (Light from the sun takes eight minutes to reach us on Earth.) For the most distant objects Webb can detect, these light particles have traveled about 13 billion light-years, traveling 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 could learning more about the period closer to the Big Bang teach astronomers?
When did the first stars light up? When did the first galaxies merge from gas clouds? How different were the first stars and galaxies from those that fill the universe today? Nobody really knows. It is a missing chapter in the history of the universe. We know that the universe began in an instant from the Big Bang. This explosion left a microwave noise background that was discovered in 1964 and has been studied in detail in the decades since. The universe cooled, matter began to accumulate, and the first stars are thought to have formed about 100 million years after the Big Bang. The first stars must have been different because the Big Bang created only hydrogen and helium with some 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 heavier elements, were massive, burned bright, and died young in supernova explosions to scatter materials that could later form planets and, eventually, living creatures like us. Webb is the first telescope that could detect and analyze these first stars.
Why do Webb’s tools help advance this work?
The two main differences between Webb and Hubble are the size of their mirrors—larger mirrors gather more light—and the wavelengths of light they observe. Hubble focused on visible and ultraviolet wavelengths, offering unparalleled new views of much of the universe. But for the early universe, the infrared part of the spectrum becomes essential. This is due to the Doppler effect. When a police car speeds by, the siren pitch is higher when the car is approaching and lower when it is speeding away. Essentially the same thing happens with light. Objects speeding toward us appear bluer and those moving away appear redder because receding motion extends beyond the wavelengths of the light particle. For the most distant objects, such as early stars and galaxies, much of the light has been shifted into the infrared. Infrared observations are virtually impossible from telescopes on Earth. The atmosphere blocks these wavelengths. Infrared observations can also be easily distorted by heat radiation. This is why Webb was placed a million miles from Earth and shadowed by a huge solar shield. One of the instruments, the Mid-Infrared Instrument, or MIRI, must be cooled to minus 447 degrees Fahrenheit to function properly. See more
