 HIP 65426 b is on the lower left of the image, with the circle representing what Neptune's orbit would look like around the star HIP 65426, represented by a small cross. | |
| Discovery[1] | |
|---|---|
| Discovered by | SPHERE consortium[2] |
| Discovery date | 6 July 2017 |
| Direct imaging | |
| Designations | |
| Najsakopajk[3] | |
| Orbital characteristics | |
| 87+108 −31 AU[4] | |
| Inclination | 100°+15° −6°[4] |
| Physical characteristics | |
| 1.44±0.03 RJ[4] | |
| Mass | 7.1±1.2 MJ[4] |
| 3.93+0.07 −0.09dex[4] | |
| Temperature | 1,283+25 −31 K[4] |
HIP 65426 b, formally namedNajsakopajk,[3] is asuper-Jupiterexoplanet orbiting thestar HIP 65426. It was discovered on 6 July 2017 by the SPHERE consortium using theSpectro-Polarimetric High-Contrast Exoplanet Research (SPHERE) instrument belonging to theEuropean Southern Observatory (ESO),[5][6] being the first confirmed planet discovered by the SPHERE instrument.[7][a] It is 385light-years from Earth in theCentaurus constellation.[9]
HIP 65426 b is a designation inherited from the host star's name, HIP 65426, following theexoplanet naming convention, where exoplanets receive lowercase letters. The designation HIP 65426 has its origin on theHipparcos catalogue.[10]
In August 2022, this planet and its host star were included among 20 systems to be named by the thirdNameExoWorlds project.[11] The approved names, proposed by a team fromMexico, were announced in June 2023. HIP 65426 b is namedNajsakopajk and its host star is namedMatza, afterZoque words for "Mother Earth" and "star".[3]
The exoplanet HIP 65426 b orbits its host star HIP 65426, anA-type main-sequence star withapparent magnitude 7.01, with a mass of1.96±0.04 M☉, a radius of1.77±0.05 R☉ and aneffective temperature of 8,840 K (8,570 °C).[12] This planetary system is located in the constellationCentaurus. The planet is around 14 million years old, much younger than theSolar System which is 4.5 billion years old, but is not associated with a debris disk, despite its young age,[6][9] causing it to not fitcurrent models for planetary formation.[13] It is around 92AU from its parent star, with a possible dustyatmosphere.[14] It was discovered as part of the SHINE program, which aimed to findplanetary systems around 600 new stars.[1]
In September 2022, HIP 65426 b became the first exoplanet directly observed by theJames Webb Space Telescope.[15]
The spectrum taken in 2020 has indicated that HIP 65426 b is carbon-poor and oxygen-rich compared to Solar System gas giants.[16]
Spectral analysis of data from the James Webb Space Telescope revealed strong evidence of silicate clouds containingenstatite with no evidence of a dusty atmosphere.[17]
In August 2022, apre-print of theJames Webb Space Telescope (JWST) observations was published. The JWST direct imaging observations between 2-16 μm of HIP 65426 b tightly constrained itsbolometric luminosity to, which provides a robust mass constraint of7.1±1.2 MJ. Evolutionary models suggest a radius 45% larger than that of Jupiter and aneffective temperature of 1,283 K (1,010 °C). Atmospheric models suggest lower radii down to0.9 RJ and higher temperatures, but these results are unreliable. The team also constrained thesemi-major axis and theinclination of the planet, but the new JWST astrometry of the planet did not significantly improve the orbit of the planet, especially theeccentricity remains unconstrained.[4]
HIP 65426 b is the first exoplanet to be imaged by JWST and the first to be detected inwavelengths beyond 5 μm. The observations 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 0.3MJ planets at 100au formain-sequence stars,Neptune andUranus-mass objects at 100-200 au forM-dwarfs andSaturn-mass objects at 10 au for M-dwarfs. Forα Cen A JWST might be able to push the limit to a 5R🜨 planet at 0.5 to 2.5 au.[4]
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