A Giant Telescope Grows in Space

The James Webb Space Telescope has fired its thrusters and reached its orbital destination around a million miles (1.5 million kilometers) away from our planet, NASA said Monday, a key milestone on its mission to study cosmic history.

At around 2:00 pm Eastern Time (1900 GMT), the observatory fired its thrusters for 5 minutes in order to reach the so-called second Lagrange point, or L2, where it will have access to nearly half the sky at any given moment.

"Webb, welcome home!" said NASA Administrator Bill Nelson in a statement.

"We're one step closer to uncovering the mysteries of the Universe. And I can't wait to see Webb's first new views of the Universe this summer!"

In this region of space, it will stay in line with the Earth as it moves around the Sun, allowing Webb's sunshield to protect its sensitive equipment from heat and light.

For the giant parasol to offer effective protection, it needs the Sun, Earth, and Moon to all be in the same direction, with the cold side operating at - 370 degrees Fahrenheit (-225 Celsius).

The thruster firing, kwown as an orbital burn, was the third such maneuver since Webb was launched on an Ariane 5 rocket on December 25.

The plan was intentional, because if Webb had gotten too much thrust from the rocket, it wouldn't be able to turn around to fly back to Earth, as that would expose its optics to the Sun, overheating and destroying them.

It was therefore decided to slightly underburn the rocket firing and use the telescope's own thrusters to make up the difference.

Webb, which is expected to cost NASA nearly US$10 billion, is one of the most expensive scientific platforms ever built, comparable to the Large Hadron Collider at CERN, and its predecessor telescope, Hubble.