The James Webb Space Telescope: Ready for Launch!

Webb will observe a wide band of the infrared spectrum, including parts observed by the Hubble - which also observes in a bit of ultraviolet light as well as visible - and the recently retired Spitzer Space Telescope. Webb will even observe parts of the infrared spectrum not seen by either of these missions! Credits: NASA and J. Olmstead (STScI)

NASA’s James Webb Space Telescope is ready for lift-off! As of this writing (December 22), the much-anticipated next-generation space telescope is being carefully prepared for launch on December 25, 2021, and will begin its mission to investigate some of the deepest mysteries of our universe.
The development of the Webb began earlier than you might expect – the concept that would develop into Webb was proposed even before the launch of the Hubble in the late 1980s! Since then, its design underwent many refinements, and the telescope experienced a series of delays during construction and testing. While frustrating, the team needs to ensure that this extremely complex and advanced scientific instrument is successfully launched and deployed.  The Webb team can’t take any chances; unlike the Hubble, orbiting at an astronaut-serviceable 340 miles (347 km) above Earth, the Webb will orbit about one million miles away (or 1.6 million km), at Lagrange Point 2. Lagrange Points are special positions where the gravitational influence between two different bodies, like the Sun and Earth, “balance out,” allowing objects like space telescopes to be placed into stable long-term orbits, requiring only minor adjustments - saving Webb a good deal of fuel!

Since this position is also several times further than the Moon, Webb’s sunshield will safely cover the Moon, Earth, and Sun and block any potential interference from their own infrared radiation. Even the seemingly small amount of heat from the surfaces of the Earth and Moon would interfere with Webb’s extraordinarily sensitive infrared observations of our universe if left unblocked. More detailed information about Webb’s orbit can be found at, and a video showing its movement at
Infographic showing two key comparisons between the Hubble Space Telescope and the James Webb Space Telescope. It is titled HUBBLE & WEBB SPACE TELESCOPES, and a small note in the top left that says NOT TO SCALE.  A silhouette of a person stands between two mirror illustrations: a smaller circle a little larger than the person on the left, which is Hubble's mirror, labeled 2.4 meters or 8 feet, and Webb's much larger mirror dwarfing the person, measuring 6.5 meters or 21 feet. Hubble's orbit is shown as 340 miles above earth, while Webb is shown orbiting 1 million miles away, or 1,600,000 million kilometers. The Moon, Sun, and Earth are all shown behind Webb's sunshield. The Moon is also shown with its orbit listed as 240,000 miles or 363,000 kilometers - much less than Webb's orbit!

Webb will follow up on many of Hubble’s observations and continue its mission to study the most distant galaxies and stars it can - and as you can see in this comparison, its mirror and orbit are both huge in comparison, in order to continue these studies in an even deeper fashion! Credits: NASA, J. Olmsted (STScI)

Once in its final position, its sunshield and mirror fully deployed and instruments checked out, Webb will begin observing!  Webb’s 21-foot segmented mirror will be trained on targets as fine and varied as planets, moons, and distant objects in our outer Solar System, active centers of galaxies, and some of the most distant stars and galaxies in our universe: objects that may be some of the first luminous objects formed after the Big Bang! Webb will join with other observatories to study black holes - including the one lurking in the center of our galaxy, and will study solar systems around other stars, including planetary atmospheres, to investigate their potential for hosting life. 

Wondering how Webb’s infrared observations can reveal what visible light cannot? The “Universe in a Different Light” Night Sky Network activity can help - find it at .  Stay alert to the latest news from NASA and Webb team as it begins its mission by following #UnfoldTheUniverse on social media, and on the web at
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Additional Skywatching Resources

Plan your skywatching with help from our planner page, featuring daily stargazing tips courtesy EarthSky monthly sky maps, and videos from NASA/JPL. You can even find out how to spot the International Space Station! Both Astronomy and Sky and Telescope magazines offer regular stargazing guides to readers, both in print and online. Want to join a group of folks for a star party? Find clubs and astronomy events near you, and may you have clear skies!
Last Updated: December 22, 2021 with updated launch date.
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