James Webb Space Telescope takes ‘historic’ exoplanet picture

For the first time, astronomers have used Nasa’s James Webb Space Telescope to take a direct image of a planet outside our solar system, in what has been described as a “historic moment for astronomy”. 

The exoplanet chosen was HIP 65426 b, which is about six to 12 times the mass of Jupiter and between 15 to 20 million years old - a young age compared to the 4.5-billion-year-old Planet Earth. Since the planet is a gas giant, similar to Jupiter, it would never be habitable by living organisms.

The image, as seen through four different light filters, shows how Webb’s powerful infrared gaze can easily capture worlds beyond our solar system. 

“This is a transformative moment, not only for Webb but also for astronomy generally,” said Sasha Hinkley, associate professor of physics and astronomy at the University of Exeter. “James Webb is going to open the door to a whole new class of planets that have been completely out of reach to us and by observing them at a broad range of wavelengths we can study their compositions in a much more in-depth way.

Taking direct images of exoplanets is challenging because stars are so much brighter than planets. The HIP 65426 b planet is more than 10,000 times fainter than its host star in the near-infrared and a few thousand times fainter in the mid-infrared.

HIP 65426 b was first discovered in 2017 by astronomers using the SPHERE instrument on the European Southern Observatory’s Very Large Telescope. Due to Webb’s longer infrared wavelengths, its images have revealed new details that ground-based telescopes would not be able to detect because of the intrinsic infrared glow of Earth’s atmosphere.

“Obtaining this image felt like digging for space treasure,” said Aarynn Carter, a postdoctoral researcher at the University of California, Santa Cruz, who led the analysis of the images. “At first, all I could see was light from the star, but with careful image processing I was able to remove that light and uncover the planet.”

Webb’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) are both equipped with coronagraphs, which are sets of tiny masks that block out starlight, enabling Webb to take direct images of certain exoplanets like this one. 

While this is not the first direct image of an exoplanet taken from space – the Hubble Space Telescope has previously captured direct exoplanet images – they are the first images of an exoplanet using infrared light, which gives a far more precise indication of a planet’s mass and temperature and will allow astronomers to detect the planet's weather. 

“I think what’s most exciting is that we’ve only just begun,” Carter said. “There are many more images of exoplanets to come that will shape our overall understanding of their physics, chemistry and formation. We may even discover previously unknown planets, too.”

JWST is the largest and most powerful space science telescope ever launched, designed to give scientists a more detailed look at the start of the universe, the birth of stars and possibly the origins of life.

After 14 years of delays, the telescope was launched on an Ariane 5 rocket on Christmas Day 2021 from Europe’s Spaceport in French Guiana. Following the launch, JWST underwent an agonising months-long process of slowly unfurling its tennis court-sized sunshield as Nasa engineers anxiously watched on to see whether it had been damaged during the launch process.

JWST’s light-gathering ability is more than twice that of Hubble and its size is bigger than two double-decker buses. In the eight months it has been in space, the device has already allowed scientists to take unprecedented images, such as those of Jupiter's storms and what has been considered as the "deepest view of the universe" to date.  

In the future, the James Webb Space Telescope is expected to make detailed observations of more Earth-like distant planets, including those with potentially habitable conditions.