| Extrasolarplanet: | yes |
| HIP 65426 b / Najsakopajk | |
| Discovered: | 6 July 2017 |
| Discoverer: | SPHERE consortium[1] |
| Discovery Method: | Direct imaging |
| Alt Names: | Najsakopajk |
| Semimajor: | au |
| Inclination: | deg |
| Mean Radius: | Atmospheric model: RJ Evolutionary model: RJ |
| Mass: | MJ |
| Surface Grav: | dex |
| Single Temperature: | Atmospheric model: K 1560 K Evolutionary model: K |
HIP 65426 b, formally named Najsakopajk, is a super-Jupiter exoplanet orbiting the star HIP 65426. It was discovered on 6 July 2017 by the SPHERE consortium using the Spectro-Polarimetric High-Contrast Exoplanet Research (SPHERE) instrument belonging to the European Southern Observatory (ESO). It is 385 light-years from Earth. It is the first planet discovered by ESO's SPHERE instrument.[2]
In August 2022, this planet and its host star were included among 20 systems to be named by the third NameExoWorlds project.[3] 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".
The exoplanet HIP 65426 b orbits its host star HIP 65426, an A2V star with apparent magnitude 7.01 and a mass of .[4] This planetary system is located in the constellation Centaurus. The planet is around 14 million years old. However, it is not associated with a debris disk, despite its young age, causing it to not fit current models for planetary formation.[5] It is around 92 AU from its parent star, with a possible dusty atmosphere.[6] It was discovered as part of the SHINE program, which aimed to find planetary systems around 600 new stars.
In September 2022, HIP 65426 b became the first exoplanet directly observed by the James Webb Space Telescope.[7]
The spectrum taken in 2020 has indicated that HIP 65426 b is carbon-poor and oxygen-rich compared to Solar System gas giants.
Spectral analysis of data from the James Webb Space Telescope revealed strong evidence of silicate clouds containing enstatite with no evidence of a dusty atmosphere.[8]
In August 2022, a pre-print of the James Webb Space Telescope (JWST) observations was published. The JWST direct imaging observations between 2-16 μm of HIP 65426 b tightly constrained its bolometric luminosity to
log(Lbol/Lsun)=-4.23\plusmn0.02
HIP 65426 b is the first exoplanet to be imaged by JWST and the first exoplanet to be detected beyond 5 μm. The observations[9] demonstrate that the James Webb Space Telescope will exceed its nominal predicted performance by a factor of 10 and that it will be able to image 0.3 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 be able to push the limit to a 5 planet at 0.5 to 2.5 au.