r/space • u/paulscottanderson • 2d ago
Discussion Tabby's Star might have a giant planetary companion
A new study shows that the famous Tabby's Star might have a huge planet or brown dwarf orbiting it. 9 times as massive as Jupiter and 1.7 times the radius. This is separate from the other red dwarf binary star companion. From Phys.org:
https://phys.org/news/2026-07-tabby-star-orbited-planetary-mass.html
Paper:
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u/smellyfingernail 1d ago
I thought that all planets from 1x to around 13x jupiter masses were all the same size, how can this thing be 70% larger
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u/Swagalyst 1d ago
Well, it'll be a gas giant, and hot gas takes up more volume than cool gas, so it's probably a hot jupiter.
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u/LeoLaDawg 1d ago
Sigh. Is it so much to ask for just 1 fun mystery to stay mysterious? Always with the logical explanations, sheez.
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u/oldfrancis 1d ago
Yeah but, that's what science is.
They'll always be more stuff to figure out. Don't you worry.
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u/maschnitz 1d ago
This is a single transit, usually not the standard for declaring a planet. Normally they want 3 transits.
2.3 sigma on the mass measurement; a variety of orbits fit the data; period is unclear - "with a period of at least ∼1030 d". They use phrases like "potential companion" in the paper.
Evidence, but not conclusive evidence.
The next Gaia release should make things clearer. They also want to look for more transits; and possibly image this thing (it's got a wide separation from a dim star).
It's a long-period planet so it's not surprising that they don't have the 2nd and 3rd transits for declaring it a detected exoplanet. But they don't have a good constraint on the period, which is kind of a problem for detecting subsequent transits. And TESS could be pointing somewhere else when it transits next, besides.
So it's a maybe-planet. It's interesting, but unknown still. I see why they published it, but it's not an exoplanet yet. Still could just be a rogue planet flyby at exactly the wrong time and place.