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Space telescopes · Webb

Where is the James Webb Space Telescope right now?

The James Webb Space Telescope: its sunshield and its mirror, drawn from its model in Exo-View

The James Webb Space Telescope is about 1.5 million km from the Earth, four times as far as the Moon, on the side away from the Sun. It circles a point called L2 where the gravity of the Sun and the Earth together hold it in line with them. Exo-View shows where it is today and lets you fly to it.

Fly to the Webb telescopeVisit Hubble
Distance
About 1.5 million km from Earth: a signal takes 5 seconds
Place
In a halo orbit round L2, the Sun–Earth point on the far side from the Sun
Mirror
6.5 m across, 18 gold-coated beryllium segments
Sunshield
Five layers, about the size of a tennis court
Sees
Infrared light, from orange light to the mid-infrared
Temperature
About −233 °C on the cold side
Launched
25 December 2021, on an Ariane 5; first images in July 2022

Why so far away?

Webb sees heat, and anything warm near it would blind it, so it has to be far from the Earth, Moon and Sun. At L2 all three are in the same direction, behind a sunshield that keeps its mirror and instruments at about −233 °C. The point is not steady, so Webb loops round it, in an orbit of about six months, and uses a little fuel to stay there. It has enough for over twenty years.

What it sees

The light of the first stars and galaxies has been stretched by the expansion of the universe from visible light to infrared, which is why Webb was built to see in infrared. It has found galaxies as they were less than 400 million years after the Big Bang, read the air of planets round other stars, and looked inside the dust of nurseries like the Pillars of Creation. Hubble, which sees mainly visible light, is the other half of the pair.

In Exo-View

The key below switches the Spacecraft layer on and flies to Webb, a model with its shield between it and the Sun. Its place is taken from NASA's Horizons system, and like all positions on the site it is approximate. Its plate gives its distance from the Sun and the Earth and its speed.

Fly to the Webb telescopeVisit Hubble

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