Why did it take so long to share the first images of Webb?
Heading into space on Christmas Day last year was just the first step for the James Webb Space Telescope.
The spacecraft has been orbiting the second Lagrange point, or L2, about a million miles from Earth since Jan. 24. At L2, the gravitational forces of the Sun and Earth keep Webb’s motion around the Sun in sync with that of the Earth.
Before it got there, the parts of the telescope had to be carefully unfolded: the sunshade that keeps the instruments cool so they could accurately capture weak infrared light, the 18 gold-plated hexagonal pieces of the mirror.
For astronomers, engineers and officials watching on Earth, the deployment has been a tense time. There were 344 one-time failures, which means that if one of the actions hadn’t worked, the telescope would have ended up as useless space junk. They all worked.
The telescope’s four science instruments also had to be turned on. In the months following the telescope’s arrival at L2, its operators painstakingly aligned the 18 mirrors. In April, the mid-infrared instrument, or MIRI, which requires the coldest temperatures, was cooled to minus 447 degrees Fahrenheit, and scientists were able to begin a final round of checks. Once these and other steps were taken, the science could begin.
How does the Webb compare to the Hubble Telescope?
The Webb telescope’s main mirror is 6.5 meters in diameter, compared to Hubble’s 2.4 meters, giving Webb about seven times more light-gathering capacity and therefore the ability to see farther into the Earth. space and therefore deeper into the past.
Another crucial difference is that Webb is equipped with cameras and other instruments that are sensitive to infrared radiation, or “heat.” The expansion of the universe causes light that would normally be in visible wavelengths to shift to longer infrared wavelengths that are normally invisible to the human eye.