JWST takes its first ever direct images of a distant world

Image : NASA/ESA/CSA, A Carter (UCSC), the ERS 1386 team, and A.Pagan (STScI)

NASA has just unveiled the first images of HIP 65426 b, an exoplanet located 350 light years from our solar system, taken by the James Webb Space Telescope. These images have been analysed by a consortium of about 100 researchers, including astrophysicists from the PSILab (STAR Institute/Faculty des Science) of the University of Liège, who are involved in the analysis and comparison of the data obtained by the JWST and ground-based telescopes.


or the first time, astronomers have used NASA's James Webb Space Telescope (JWST) to take a direct image of a planet outside our solar system. This was a technical challenge because the light from this star is about 10,000 times brighter than that from the planet and the researchers had to use advanced observation and image processing techniques. In particular, the use of coronagraphs, an optical system that makes it possible to mask the star in order to study its immediate environment, reproducing the phenomenon of an eclipse.

The images represent the first images of an exoplanet at mid-infrared wavelengths. Some of these new images are impossible to obtain with ground-based telescopes, due to the high thermal emission from the atmosphere and the instruments themselves. “The images, seen through four filters at different wavelengths, show how the powerful infrared gaze of the JWST can easily capture worlds beyond our Solar System," says Valentin Christiaens, F.R.S.-FNRS research fellow at PSILab, who is involved in the data analysis. “This paves the way for future observations that will reveal more information than ever about exoplanets.”

The images taken in different infrared colours have enabled direct characterisation of the exoplanet’s atmosphere by comparing the measurements with atmospheric models at wavelengths yet untested for models, and have also enabled a refined estimation of the planet's temperature and gravity. “This is a first achievement that paves the way for infrared imaging of smaller and older planets," says Olivier Absil, F.R.S.-FNRS Senior Research Fellow and Director of PSILab. “We are talking about planets similar to those in our solar system, which are less bright, but which emit their peak luminosity at these same infrared wavelengths.”

These results were obtained from the joint efforts of an international group of about 100 experts in the field of high contrast exoplanet imaging. At ULiège, PSILab researchers contributed to the software used for image processing, but also to the comparison of the new data with existing observations of the planet made from ground-based telescopes. We note that the measurements obtained with the JWST at the shortest wavelengths, where there is an overlap with existing data obtained with ground-based instruments, are different from the latter," explains Valentin Christiaens. Despite the use of advanced ground-based instrumentation - in particular the Very Large Telescope (VLT) in Chile - this difference suggests either that the measurements from the ground were biased - potentially due to more difficult observing conditions from the ground - or that the amount of light received from the planet varied intrinsically between the two observations. Another possibility is that it is the light from the star, used to calibrate the measurement for the planet, that has varied over time. Further observations will be needed to understand these measurement differences.

About HIP 6542b

Located about 350 light years from our solar system (Centaurus constellation), HIP 65426 b is a giant planet about 7 times more massive than Jupiter, but 'young' (only about 20 million years old, or more than 4 billion years younger than Jupiter). HIP 65426 b is a gas giant, which means that it has no rocky surface and could not be habitable.


This image shows the exoplanet HIP 65426 b in different bands of infrared light, as seen from the James Webb Space Telescope: purple shows the NIRCam instrument’s view at 3.00 micrometers, blue shows the NIRCam instrument’s view at 4.44 micrometers, yellow shows the MIRI instrument’s view at 11.4 micrometers, and red shows the MIRI instrument’s view at 15.5 micrometers. These images look different because of the ways the different Webb instruments capture light. A set of masks within each instrument, called coronagraph, blocks out the host star’s light so that the planet can be seen. The small white star in each image marks the location of the host star HIP 65426, which has been subtracted using the coronagraphs and image processing. The bar shapes in the NIRCam images are artifacts of the telescope’s optics, not objects in the scene. Image credit: NASA/ESA/CSA, A Carter (UCSC), the ERS 1386 team, and A. Pagan (STScI)


Valentin Christiaens

Olivier Absil


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