When Will NASA's Groundbreaking James Webb Space Telescope Launch and How Big Is It?

The James Webb telescope is the largest and most powerful space observatory ever built, promising to revolutionize our understanding of the universe. But when is the observatory launching and how big is it?

The James Webb Space Telescope (JWST) is designed to observe the cosmos primarily in infrared light, unlike the Hubble Space Telescope which focuses on shorter visible and ultraviolet light wavelengths.

While JWST isn't truly replacing Hubble because the two telescopes focus on different parts of the electromagnetic spectrum, Webb is considered to be the successor to the pioneering observatory.

Jointly developed by NASA, the European Space Agency and the Canadian Space Agency, JWST is comprised of two main segments—a sunshield and its primary mirror. The five-layer sunshield measures 69.5 feet by 46.5 feet—comparable to the size of a tennis court.

This sunshield helps to keep the telescope cool, which is particularly important for infrared observatories. If the telescope is not sufficiently cool, it will not be able to properly observe astronomical objects in the infrared spectrum.

On top of JWST's sunshield lies a large mirror comprised of 18 gold-plated hexagonal segments that the telescope will use to observe the cosmos. This mirror measures 21.3 feet across, enabling the telescope to see objects that are much fainter than Hubble.

In fact, Webb is so sensitive that it could theoretically detect the heat signature of a bumblebee at the distance of the moon, according to NASA.

JWST was originally planned to be launched in 2007, but a major redesign, escalating costs and other delays pushed this back to around 2018. The project was then hit by further delays and the launch was moved to 2021.

The latest targeted launch of the $10 billion telescope is now Christmas Day, according to NASA and Arianespace—the French company that manufactures the Ariane 5 rocket, which will carry JWST into space.

The launch window on December 25 is open between 7:20 a.m. and 7:52 a.m. ET, or 12:20 p.m. and 12:52 p.m. UTC. The Ariane 5 rocket will lift off from Europe's Spaceport in French Guiana—an overseas department of France located on the northeast coast of South America.

If the weather on Christmas Day is not suitable, or other technical issues arise, lift off may have to be delayed again.

The launch had been due to go ahead on December 24, but dangerously high winds in the region forced it to be postponed an extra day. Previously, JWST had been scheduled to launch on December 22 but a "communication issue" between the observatory and the launch vehicle system forced a two-day delay.

"Every time we explore space, we find the unexpected. Hubble Space Telescope and the Spitzer Space Telescopes have pushed our characterization and knowledge of the galaxy and, in some cases, from the known to the unknown," Harold Connolly Jr. with Rowan University in New Jersey, who is involved in NASA's OSIRIS-Rex asteroid sample return mission, told Newsweek.

"We expect nothing less than this same heritage with the James Webb Space Telescope. James Webb will help us to understand what the universe was like a few hundred million years after its birth, and that will provide science with new insight into the its formation. How cool is that!"

The James Webb Space Telescope
An artist's conception of the James Webb Space Telescope in space. NASA GSFC/CIL/Adriana Manrique Gutierrez