What would the Webb Telescope look like if you saw it in space? This European space mission found out

Clever calculations by two astronomers enabled Gaia to capture an image of Webb in space.

By Iain Todd

Published: Thursday, 08 August 2024 at 08:03 AM

Ever wanted to see what the James Webb Space Telescope would look like if another spacecraft saw it in space?

On 18 February 2022, the European Space Agency’s Gaia spacecraft captured an image of the Webb Telescope in space from a distance of 1 million kilometres.

Capturing the image wasn’t a complete coincidence; rather some pretty clever calculations made by two scientists working on the Gaia mission.

How Gaia captured its image of the Webb Telescope

A view of the James Webb Space Telescope and Gaia mission’s orbits. Gaia’s orbit is in yellow, while Webb’s orbit is in blue-white. Click to expand. Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO

The Gaia spacecraft is tasked with surveying over 1 billion stars to create a detailed 3D map of our Galaxy.

Gaia is also capturing detailed data on asteroids, including discovering asteroids with moons orbiting them.

It orbits at Lagrange point 2, some 1.5 million kilometres from Earth in the direction away from the Sun.

A ‘Lagrange point’ is a point in space where the gravitational tug of two large objects acts as a stabilising force, enabling a spacecraft to remain in position without expending too much fuel.

In the case of the Gaia spacecraft, the two bodies in question are Earth and the Sun.

Image of the James Webb Space Telescope in space (marked b the green arrow), as seen by ESA's Gaia mission. Webb's red colour is artificial, chosen for illustrative reasons. Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO
Image of the James Webb Space Telescope in space (marked b the green arrow), as seen by ESA’s Gaia mission. Webb’s red colour is artificial, chosen for illustrative reasons. Click to expand. Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO

The Webb Telescope is also located at Lagrange Point 2, and just before JWST’s arrival at ‘L2’, Gaia scientists Uli Bastian of Heidelberg University in Germany, and Francois Mignard of Nice Observatory in France, worked out that Webb would occasionally pass into Gaia’s view.

Once Webb was in position at L2, Bastian and Mignard calculated that 18 February 2022 would mark their first opportunity to capture an image of the Webb Telescope in space using the Gaia spacecraft.

Image of the James Webb Space Telescope in space, captured by ESA's Gaia mission. In the main image, Webb is the red dot (the red colour being an artificial enhancement). In the large inset, Webb is the largest white speck in the centre. Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO
Image of the James Webb Space Telescope in space, captured by ESA’s Gaia mission. In the main image, Webb is the red dot (the red colour being an artificial enhancement). In the large inset, Webb is the largest white speck in the centre. Click to expand. Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO

While Gaia isn’t designed to capture amazing images of space – instead focusing on studying the positions and motions of objects – it does have a ‘finder’ instrument, and this was used to capture raw data that was sent back to Earth.

That data was used to produce this image of the Webb Telescope in space.

In the image inset, which zooms in on Webb, the bigger white speck is Webb, while the other three specks are cosmic ray particles picked up by Gaia’s CCD camera.