The Sky This Week: The James Webb Space Telescope


A historic mission launched early on December 25, giving astronomers around the world a Christmas present prepared for 25 years.

The first plans to develop a large space telescope to replace the Hubble Space Telescope began in 1996. It was originally called the Next Generation Space Telescope (NGST), but was later named after James Webb, the administrator of NASA from 1961 to 1968. Webb was instrumental in the success of the Apollo programs that took men to the moon.

Arianespace’s Ariane 5 rocket is seen in this false-color infrared exhibit as it launches with NASA’s James Webb Space Telescope on board on Saturday, December 25, 2021, from the ELA-3 launch pad at the European Spaceport at the Guyana Space Center in Kourou, France Guyana. The James Webb Space Telescope (sometimes referred to as JWST or Webb) is a large infrared telescope with a 21.3-foot (6.5-meter) primary mirror. The observatory will study every phase of cosmic history, from the interior of our solar system to the most distant observable galaxies in the early universe. Photo credit: (NASA / Bill Ingalls)

When development of this telescope began, scientists quickly realized that very little of the technology they wanted to use still existed. Webb was scheduled to study the cosmos in the infrared range of light, a range not visible to the human eye. This is a different set of light than Hubble is able to see, and will make it easier for Webb to see through thick clouds of dust and gas and to study older galaxies and stars. This requires the telescope to operate in extremely cold temperatures to minimize noise, and that was a big problem that scientists had to overcome. How do you keep a huge telescope cold enough in space?

Technicians inspecting the JWST mirror.
Technicians inspecting the JWST mirror. Source: NASA

Size-wise, the JWST is significantly larger than Hubble. The mirror alone is almost 3 times the size with a diameter of about 21 feet compared to Hubble’s 8. The telescope as a whole is simply gigantic. At 69.5 feet by 46.5 feet, the sunshade is about the size of a tennis court. The problem, as you can imagine, is figuring out a way to throw an object the size of a tennis court into space? This was another huge problem that had to be overcome. How do you launch such a large satellite into space, let alone a high-precision instrument such as a telescope that has to operate in extremely cold temperatures?

The JWST folded and ready to go.
The JWST folded and ready to go. Source: NASA

Many technologies have been developed to keep it cold, from cryocoolers to lightweight mirrors, this telescope is nothing less than an engineering masterpiece. And to top it off, the whole thing had to fold up to fit into a modern rocket: the Arianne 5. He put this rocket into orbit on December 25 and successfully started the journey to his last home: point L2 . What is that? Well, point L2 is the Lagrange-2 point, a point in space near Earth where the gravitational pull between the Earth and the Sun equilibrates, resulting in a net gravitational pull of zero. Webb will “orbit” around this point as part of his scientific mission. This allows him to observe at all times, a huge difference from Hubble which orbits the Earth and can only see its target part of the time. A video of this orbit is below.

Other fun facts:

  • The mirror is made of gold only 700 atoms thick!
  • The telescope will operate at a temperature of approximately -370F
  • The lens hood gives the telescope an SPF of 1,000,000. Much better than lotion you can find in the store.
  • The telescope is sensitive enough to detect a bumblebee at the moon’s distance from us.
  • The wavelengths in which he will study will allow him to see farther in time than any telescope before.
  • More than 40,000,000 man-hours have gone into the development and production of the telescope. That’s the equivalent of 50 lives of 90 years.
  • Webb will observe the universe from a point about 1 million kilometers from Earth!

It is an exciting time for astronomers, even if it is a difficult time. The next 6 months will feature many milestones as the telescope reaches its final vantage point and begins the long process of deployment to its maximum size. Once that happens, however, we’re sure to see some incredible footage of this epitome of engineering achievement.

Have a good week and, as always, look at the sky!

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