James Webb Space Telescope's first 'alien world' discovery unlocks new era of planet-hunting

Telescope used trick mimicking solar eclipse to uncover a new planet, a method that could change how scientists find distant worlds

The image of the exoplanet named TWA 7b, a planet outside of the solar system, captured by the James Webb Space Telescope. Photo: JWST / European Space Agency

Scientists have unveiled groundbreaking direct images of a planet outside of our own solar system, taken by the James Webb Space Telescope.

It is the first exoplanet discovered by the telescope, proving it can detect lighter and more elusive worlds orbiting distant stars.

The planet, named TWA 7b, is situated near a young star about 34 lightyears away, in the constellation Hydra.

It is the lightest exoplanet ever seen through direct imaging, with a mass similar to Saturn and about one-third that of Jupiter, as scientists are now able to study smaller, cooler planets that are more difficult to detect.

The findings were published in the Nature science journal on Wednesday.

Dr Anne-Marie Lagrange, a researcher with the French National Centre for Scientific Research (CNRS), led the study by an international team.

“Our observations reveal a strong candidate for a planet shaping the structure of the TWA 7 debris disc, and its position is exactly where we expected to find a planet of this mass,” she said.

How the planet was found

While thousands of exoplanets have been found over the past three decades, most have been detected through indirect methods. These included measuring the dimming of a star as a planet passes in front of it or by watching for tiny movements in a star caused by the gravitational pull of an orbiting planet.

Only some have ever been directly imaged, and those have typically been enormous gas giants.

TWA 7b was spotted using a powerful coronagraph installed on Webb’s Mid-Infrared Instrument (Miri), a telescope attachment developed the CNRS and the French Alternative Energies and Atomic Energy Commission.

The coronagraph acted like a solar eclipse, blocking out the light of a star so that the much fainter objects orbiting nearby could be seen.

This technique helped astronomers spot a faint source of light hidden inside one of the thin dust rings surrounding the star TWA 7.

After ruling out objects such as background galaxies or image glitches, scientists realised the signal was coming from a planet, one that had never been seen before.

Computer simulations showed that the planet was placed exactly where there is a strange gap in the star’s narrow dust ring, which meant strong evidence that its gravity is shaping the ring’s structure.

Building on past space telescope discoveries

Since the telescope’s science operations started in 2022, it has helped scientists make several discoveries. These included helping to confirm the chemical composition of atmospheres of other planets and extreme weather patterns on gas giants.

JWST’s predecessor, the Hubble Space Telescope, also made valuable discoveries in the early era of direct imaging.

It captured the first visible-light image of an exoplanetary system in 2008, however, it lacked the sensitivity to see planets smaller than Jupiter.

Now, the James Webb Space Telescope is now offering more advanced techniques.

“This observatory enables us to capture images of planets with masses similar to those in the solar system, which represents an exciting step forward in our understanding of planetary systems, including our own,” said Mathilde Malin, co-author of the study.

What comes next

The team behind the discovery thinks Webb could soon be able to spot planets with just 10 per cent the mass of Jupiter, getting close to the size of Neptune and “super-Earths”, planets outside the solar system that are larger than Earth but smaller than icy planets like Neptune and Uranus.

TWA 7 b also gives scientists a roadmap for how future space and ground-based telescopes that might detect even smaller, more Earth-like planets.