The 6.5-meter James Webb Space Telescope (JWST) launched In December 2021, organizes Early Release Science (ERS) programs designed to test JWST’s various observational capabilities and has a prospect to yield initial scientific findings.
One of the ERS programs has accepted a program pioneering JWST’s high-contrast imaging capabilities (PI: Sasha Hinkley from the University of Exeter in the UK).
Recently, NASA released images of an exoplanet obtained from this high-contrast ERS data. These images represent the first direct imaging result by JWST, as the earlier released “first-light” images on July 12 did not include direct imaging observations of exoplanets. Two researchers from the Astrobiology Center participated in this program.
The images captured the exoplanet “HIP 65426 b” within the wavelength range of 3 to 15 micrometers using JWST’s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). The background is a cropped image of the digital catalog of ground-based all-sky celestial objects at visible wavelengths. The light from the bright central star was removed using JWST’s high-contrast observation capability (coronagraph), enabling imaging of the planet near the star across all wavelengths. This marks the first time that exoplanets have been imaged using infrared wavelengths of 5 micrometers and above, demonstrating JWST in high-contrast observations of exoplanets. From this data, the planet’s mass is estimated to be about four times that of Jupiter, with a temperature of approximately 2000 degrees Celsius.
While the SEEDS (Strategic Explorations of Exoplanets and Disks with Subaru) project, which utilized the 8.2-meter Subaru Telescope, has also achieved direct imaging of exoplanets, observations are primarily limited to wavelengths below 2 micrometers due to significant influence from Earth’s atmosphere and telescope thermal emissions. However, for studying planetary atmospheres, observations across a wide wavelength range are crucial, making JWST’s capability in wavelengths longer than 3 micrometers particularly valuable.
In summary, JWST is expected to frontier new horizons in infrared high-contrast observations of exoplanets and brown dwarfs (objects slightly heavier than planets but unable to be stars) where ground-based telescopes face challenges.
Note 1: James Webb Space Telescope (JWST)
A space telescope with a diameter of 6.5 meters developed by NASA (National Aeronautics and Space Administration), ESA (European Space Agency), and CSA (Canadian Space Agency), launched on December 25, 2021. It is known as the successor to the Hubble Space Telescope and is equipped with observational instruments covering the near-infrared to mid-infrared range. Expectations are high for discoveries across various fields of astronomy.
Note 2: SEEDS Project
A project aiming at direct imaging of exoplanets and their parent circumstellar disks at the Subaru Telescope. Over five years starting in 2009, the project carried out observations on 120 nights and succeeded in multiple direct imaging of exoplanets. However, due to ground-based observations, the observations were primarily limited to wavelengths shorter than 2 micrometers even in the near-infrared range.
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