Talk:Epsilon Indi Ab

Image

A image of the planet is available at https://webbtelescope.org/contents/media/images/2024/127/01J01FZVQBX30APWZ3W2VSG1V0?news=true . Can someone include it in the article? Rps (talk) 15:42, 24 July 2024 (UTC)

 Done SevenSpheres (talk) 16:28, 24 July 2024 (UTC)

Thanks. I also included the image on the Epsilon Indi page. Rps (talk) 13:51, 25 July 2024 (UTC)

Isn't this the historical, very first direct photo of an exoplanet, rather than just occlusion of its star or deductions from trajectory anomalities? This photo is certainly not receiving the credit that it deserves! --2003:DA:CF25:5A03:E1FC:FB3C:BF59:5558 (talk) 15:09, 25 July 2024 (UTC)

No (see list of directly imaged exoplanets), but it's almost the first direct image of an exoplanet that was previously detected indirectly. Beta Pictoris c is the only similar case, but it wasn't imaged as clearly, and I don't think its image is under a free license suitable for use on Wikipedia. SevenSpheres (talk) 15:20, 25 July 2024 (UTC)

New Data

The team that analyzed the recent JWST image published an article (https://www.nature.com/articles/s41586-024-07837-8) which has new estimates for the planet's parameters: Mass: 6.31 MassJupiter (+0.60/-0.56) Semi-major axis: 28.4 AU (+10/-7.2) Orbit eccentricity: 𝑒 = 0.40 (+0.15/-01.8) Temperature: 275K "The data indicates that this is likely the only giant planet in the system and we therefore refer to it as “b”, despite it having significantly different orbital properties than the previously claimed planet “b”." Rps (talk) 14:23, 25 July 2024 (UTC)

The data has been updated now, but the new paper doesn't have a full orbital solution so orbital parameters from earlier work are retained in the infobox. I don't think this is correct due to the discrepancy between the old and new orbital solutions; it may be best to remove parameters from the infobox that aren't in the new paper. The orbital period can be calculated from the data in the new paper; I get ~174 years which is significantly longer than previous estimates. SevenSpheres (talk) 15:04, 25 July 2024 (UTC)

Nearer ~173 years if the substantial mass of the planet is included in the Kepler 3rd law calculation. But, it's an estimated value and so I suppose that tiny difference doesn't matter much. 82.43.224.143 (talk) 10:24, 27 July 2024 (UTC)

I don't get the equation ${\begin{smallmatrix}P={\sqrt {(A^{3})(1/M)}}\end{smallmatrix}}$ and I don't see how it works. Because that equation surely should be written much simpler as ${\begin{smallmatrix}P={\sqrt {A^{3}/M}}\end{smallmatrix}}$, but even then I still can't see how the equation can be used to calculate the orbital period, or anything else for that matter. What do A or P even stand for? Looking at Kepler's third law as defined in the wikipedia article - ${\begin{smallmatrix}{\frac {4\pi ^{2}}{T^{2}}}={\frac {GM}{a^{3}}}\end{smallmatrix}}$, where 'a' is distance or radius from the star in metres, 'T' is seconds, G is the Gravitational Constant and M is the mass of the star in kilograms, I can see how that can be rearranged to get ${\begin{smallmatrix}T={\sqrt[{}]{\frac {4\pi ^{2}a^{3}}{GM}}}\end{smallmatrix}}$ or ${\begin{smallmatrix}T=2\pi {\sqrt[{}]{\frac {a^{3}}{GM}}}\end{smallmatrix}}$ but I can't see how that is then rearranged to give ${\begin{smallmatrix}P={\sqrt {A^{3}/M}}\end{smallmatrix}}$. I found it simple to calculate the period for the planet as 173.6 years using the equations ${\begin{smallmatrix}T={\sqrt[{}]{\frac {4\pi ^{2}a^{3}}{GM}}}\end{smallmatrix}}$ and ${\begin{smallmatrix}T=2\pi {\sqrt[{}]{\frac {a^{3}}{GM}}}\end{smallmatrix}}$ but I just don't see how it is possible to calculate that exact figure with ${\begin{smallmatrix}P={\sqrt {A^{3}/M}}\end{smallmatrix}}$ alone. 82.43.224.143 (talk) 13:24, 28 July 2024 (UTC)

It's a simplified version of Kepler's third law using years, AU, and solar masses. Yes, that other version should probably be used instead. SevenSpheres (talk) 15:43, 28 July 2024 (UTC)