07-25-2024, 08:50 AM
Today we have a news (LINK) about the direct imaging of Epsilon Indi A b by JWST, which returns a rather unexpected result.
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Epsilon Indi A b from Matthews et al. (2024)
Note: this orbital solution is only true if Epsilon Indi A b is dominates the perturbation of its star.
Semi-major axis: 28.4 +10 -7.2 AU
Eccentricity: 0.40 +0.15 -0.18
Mass: 6.31 +0.60 -0.56 Jupiter masses
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Based on radial velocity and astrometric data, Epsilon Indi A b was expected to be a planet with around 3 times Jupiter's mass which orbits in an eccentric orbit with semi-major axis ('average distance') of approximately 12 AU from the star. Its current description in EG reflects this, and the rest of the planetary system is essentially designed around it. With this new revision, we may need to look at what it implies about the stability of the system and, more importantly, the system's history, and whether it is still conducive for the current planet.
There are two known mechanisms that can send massive jovian planets into eccentric orbits, including planet-planet scattering and disk-planet interaction. Planet-planet scattering between such large jovians would likely cause chaos throughout the entire planetary system, and while disk-planet interaction may be less disruptive, I am not sure whether this is likely to produce the observed eccentricity, as the papers I have seen seem to imply rather mild eccentricities, and in one case, extreme eccentricity of 0.7-0.9, rather than 0.4.
====
Epsilon Indi A b from Matthews et al. (2024)
Note: this orbital solution is only true if Epsilon Indi A b is dominates the perturbation of its star.
Semi-major axis: 28.4 +10 -7.2 AU
Eccentricity: 0.40 +0.15 -0.18
Mass: 6.31 +0.60 -0.56 Jupiter masses
====
Based on radial velocity and astrometric data, Epsilon Indi A b was expected to be a planet with around 3 times Jupiter's mass which orbits in an eccentric orbit with semi-major axis ('average distance') of approximately 12 AU from the star. Its current description in EG reflects this, and the rest of the planetary system is essentially designed around it. With this new revision, we may need to look at what it implies about the stability of the system and, more importantly, the system's history, and whether it is still conducive for the current planet.
There are two known mechanisms that can send massive jovian planets into eccentric orbits, including planet-planet scattering and disk-planet interaction. Planet-planet scattering between such large jovians would likely cause chaos throughout the entire planetary system, and while disk-planet interaction may be less disruptive, I am not sure whether this is likely to produce the observed eccentricity, as the papers I have seen seem to imply rather mild eccentricities, and in one case, extreme eccentricity of 0.7-0.9, rather than 0.4.