James Webb Space Telescope snags its 1st direct photo of an alien world

[Admin]

The James Webb Space Telescope took its first direct image of a planet orbiting a distant star, proving its potential to revolutionize exoplanet research.

James Webb Space Telescope snags its 1st direct photo of an alien world : Read more

 

[rod]

"Second, HIP 65426 b is also extremely massive — 12 times the size of Jupiter, the solar system's largest planet."

JWST observations revised this mass lower, now considered to be 7.1 Mjup size. [2208.14990] The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems I: High Contrast Imaging of the Exoplanet HIP 65426 b from 2-16 $μ$m (arxiv.org)

"Independent of the choice of forward model atmosphere we measure an empirical bolometric luminosity that is tightly constrained between log(Lbol/L⊙)=-4.35 to -4.21, which in turn provides a robust mass constraint of 7.1±1.1 MJup. In totality, these observations confirm that JWST presents a powerful and exciting opportunity to characterise the population of exoplanets amenable to direct imaging in greater detail."

The exoplanet site has updated properties, The Extrasolar Planet Encyclopaedia — HIP 65426 b (exoplanet.eu)

 

[rod]

My note. In the paper cited, problems with the size of the exoplanet imaged is discussed near the end of the paper. “• Atmospheric Model Fitting: Using a BT-SETTL atmospheric forward model we are able to fit all data, in addition to the majority of ground-based observations to within 2σ. This agreement provides precise constraints on the Teff = 1667+25 −24 K, log(g) = 4.07+0.19 −0.19 dex, R = 0.92+0.04 −0.04 RJup, and log(Lbol/L)=−4.23+0.02 −0.02. Compared to a fit excluding the JWST data, this corresponds to a factor of ∼3 improvement in the precision of the radius and bolometric luminosity. Despite the excellent model agreement, both the temperature and unphysically small radius are in disagreement with the values obtained from the evolutionary models, further emphasising a long standing tension for this class of objects.”

My note. HIP 65426 b is 7.1 Mjup and radius 0.92 Rjup. Apparently, measurements for giant exoplanets like this conflict with various stellar evolution models in use for the giant exoplanets. Using properties updated now http://exoplanet.eu/catalog/hip_65426_b/, with e = 0, I calculate P = 2.1135E+05 days or 5.7865E+02 years. In 1 Gyr this exoplanet could complete 1.7282E+06 revolutions but the host star is listed some 15-20 Myr. Explaining the origin of giant exoplanets imaged in wide orbits is difficult.

At the exoplanet.eu site I find 87 giant planets listed in wide orbits ranging 50 to 9900 au from the parent star. They range in mass from 0.208 Mjup to 66 Mjup.