HIP 65426 b
First exoplanet directly imaged by the James Webb Space Telescope.
Last updated
HIP 65426 b, also called Najsakopajk, orbits the star Matza (HIP 65426), an A-type main-sequence star with an apparent magnitude of 7.01, a mass and radius not specified here, and an effective temperature of 8840 K. Located 385 light-years away in Centaurus, the planet is about 14 million years old—far younger than the 4.5-billion-year-old Solar System—yet lacks a debris disk, which contradicts current planetary formation models. It sits roughly 92 AU from its star and may have a dusty atmosphere, though later observations contradicted that. Discovered on 6 July 2017 by the SPHERE consortium using ESO’s SPHERE instrument, it was the first confirmed planet found by that instrument, as part of the SHINE program surveying 600 stars.
Nomenclature
In August 2022, the planet and its star were among 20 systems selected for the third NameExoWorlds project; the approved names, proposed by a Mexican team, were announced in June 2023. Najsakopajk comes from a Zoque word for "Mother Earth," and Matza means "star." In September 2022, HIP 65426 b became the first exoplanet directly imaged by the James Webb Space Telescope (JWST). A 2020 spectrum showed the planet is carbon-poor and oxygen-rich compared to Solar System gas giants. JWST observations, published as a preprint in August 2022, covered 2–16 μm and tightly constrained the planet’s bolometric luminosity, yielding a robust mass estimate.
James Webb Space Telescope observations
Evolutionary models suggest a radius 45% larger than Jupiter’s and an effective temperature of 1283 K, though atmospheric models give lower radii and higher temperatures that are unreliable. The JWST data also constrained the semi-major axis and inclination but did not significantly improve the orbit, leaving eccentricity unconstrained. JWST detected the planet at wavelengths beyond 5 μm for the first time, and the observations showed the telescope will exceed its nominal predicted performance by a factor of 10, potentially imaging 0.3 Jupiter-mass planets at 100 AU for main-sequence stars, Neptune- and Uranus-mass objects at 100–200 AU for M-dwarfs, and Saturn-mass objects at 10 AU for M-dwarfs, and possibly a 5 Earth-mass planet at 0.5 to 2.5 AU around α Cen A. Spectral analysis of JWST data revealed strong evidence of silicate clouds containing enstatite, with no evidence of a dusty atmosphere.
Lore & Background
HIP 65426 b was discovered as part of the SHINE program, which aimed to find planetary systems around 600 new stars. The planet is around 14 million years old, much younger than the Solar System, yet it is not associated with a debris disk, causing it to not fit current models for planetary formation.
It orbits its host star at roughly 92 AU, with a possible dusty atmosphere. In August 2022, the planet and its host star were included among 20 systems to be named by the third NameExoWorlds project; the approved names, proposed by a team from Mexico, were announced in June 2023. HIP 65426 b is named Najsakopajk, and its host star is named Matza, after Zoque words for 'Mother Earth' and 'star'.
Reader's Guide
HIP 65426 b holds significance as the first exoplanet confirmed by the SPHERE instrument and the first exoplanet directly imaged by the James Webb Space Telescope (JWST). JWST observations between 2–16 μm tightly constrained its bolometric luminosity, providing a robust mass constraint, and evolutionary models suggest a radius 45% larger than Jupiter and an effective temperature of 1283 K. The planet was also the first to be detected in wavelengths beyond 5 μm. These observations demonstrated that JWST will exceed its nominal predicted performance by a factor of 10, enabling it to image 0.3 Jupiter-mass planets at 100 AU for main-sequence stars, Neptune- and Uranus-mass objects at 100–200 AU for M-dwarfs, and Saturn-mass objects at 10 AU for M-dwarfs.
For α Cen A, JWST might push the limit to a 5 Earth-mass planet at 0.5 to 2.5 AU. The planet's spectrum from 2020 indicated it is carbon-poor and oxygen-rich compared to Solar System gas giants, while JWST spectral analysis revealed strong evidence of silicate clouds containing enstatite with no evidence of a dusty atmosphere. The new JWST astrometry did not significantly improve the orbit of the planet, and the eccentricity remains unconstrained.
Frequently Asked Questions
How was HIP 65426 b discovered?
The planet was identified on 6 July 2017 through direct imaging, meaning it was captured as a resolved point of light separated from its host star rather than inferred from gravitational wobbles. It later earned the distinction of becoming the first exoplanet directly imaged by the James Webb Space Telescope.
Where does HIP 65426 b orbit?
The planet circles its parent star Matza at a distance of approximately 92 astronomical units, placing it well beyond the region where Solar System giants reside. Its host star sits in the constellation Centaurus, about 385 light-years from Earth.
More in Exoplanets Found by Imaging and Microlensing
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: HIP 65426 b (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced