The James Webb telescope has been making history since 2022, when the first images taken by the telescope were released. This week, the equipment reached another important milestone: for the first time, the JWST has directly photographed an exoplanet, without it having been first recorded by ground-based telescopes.
The planet is a cold super-Jupiter with a temperature of around 0 degrees Celsius and a wide orbit comparable to that of Neptune around the Sun. The record was made by the team at the Max Planck Institute in Germany.
This measurement was made possible by JWST’s unprecedented thermal infrared imaging capabilities. It exemplifies the potential for finding many more planets similar to Jupiter in mass, temperature and orbit. Studying them will improve our understanding of how gas giants form and evolve over time.
Team of astronomers at the institute’s website
“We were excited when we realized we had imaged this new planet,” said Elisabeth Matthews, a researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. She is the lead author of the underlying research paper published in the journal Nature. “To our surprise, the bright spot that appeared in our MIRI images did not match the position we expected for the planet,” Matthews said. “Previous studies correctly identified a planet in this system, but underestimated the mass and orbital separation of this super-Jupiter gas giant.”
The image summarizes the JWST/MIRI observations that led to the rediscovery of Eps Ind Ab (Image: Max Planck Institute)
MIRI stands for the Mid-Infrared Instrument. The mechanism resembles a selector wheel, with which astronomers choose between short, medium and long wavelengths when making their observations. MIRI requires the coldest temperatures of all Webb’s instruments to operate accurately.
The planet orbits the main component of the nearby triple star system Epsilon Indi. The new JWST data are consistent with a super-Jupiter with a mass six times that of Jupiter in the Solar System.
Only a few cool gas giant planets orbiting solar-age stars are known to date, and all of them have been inferred indirectly from radial velocity measurements. “However, such planets are difficult to find using classical detection methods. Planets far from their host stars are typically very cold, unlike hot Jupiters that circle their stars at separations of only a few stellar radii,” the statement reads.
Read more:
“Wide orbits are highly unlikely to be aligned along the line of sight to produce a transit signal. Furthermore, measuring their signals with the radial velocity method is challenging when only a small section of the orbit can be monitored,” he adds.
Due to the difficulty, the team decided to take a picture of the planet using a direct imaging method. Because the exoplanet’s host stars are so bright, they outshine any other nearby objects. Ordinary cameras would be overwhelmed by the blinding starlight.
But this is not the case with James Webb’s MIRI, since the equipment has a coronagraph, which blocks the light by covering the star. “MIRI was the perfect choice because it observes in the thermal or mid-infrared, where cold objects shine brightly,” explains the Institute.
