A candidate giant planet imaged in the habitable zone of α Cen A

54 pinewurst 16 8/7/2025, 1:42:18 AM arxiv.org ↗

Comments (16)

Qem · 4h ago
> Based on the photometry and orbital properties, the planet candidate could have a temperature of 225 K, a radius of ≈1-1.1 RJup and a mass between 90-150 MEarth, consistent with RV limits.

Hope it has some interesting moons.

UI_at_80x24 · 4h ago
225K = -48C

So not exactly cozy. I'm not sure what the other measurements mean.

andrewflnr · 3h ago
What are the numbers for the temperature Earth would have without any greenhouse gases? The right atmosphere might make it work.
dvh · 1h ago
-19°C
jaredhallen · 4h ago
I don't either, but if its radius is the size of Jupiter, I imagine the gravity's a real buzz kill.
alanbernstein · 3h ago
For that range of mass values, the surface gravity would be relatively close to that of earth, even lower at 90x.
fc417fc802 · 1h ago
Is it Jupiter that's unusually dense or this planet that's unusually light? Related, any idea what the feasible range of densities is for a planet of a given size? I always assumed something as large as Jupiter would be impossible for a human to set foot on due to being crushed.

A ball of foamed rock the size of a planet is an amusing thought but I have to assume that's physically impossible.

ch4s3 · 4h ago
RJup is the radius of Jupiter. 1 MEarth is equal to one million times the mass of the Earth. I’m not sure about RV limits.
mkl · 3h ago
1 MEarth is 1 Earth mass. Even our sun is only a third of a million Earth masses. Jupiter is about 318 Earth masses.
samplatt · 2h ago
...so it's got a mass 3x that of our sun, but it's the size of Jupiter? And it's a planet? ...What? The star it orbits is about the same size as our sun, yet a planet orbits it with 3x the mass? I'm missing something massive here, or the summary is terrible.
Teever · 2h ago
The M in this context stands for "Mass" not "Mega."

If you take a look at the linked PDF you'll see that the "Earth" portion of that term is a subscript, so it reads "90-150 Earth masses."

JumpCrisscross · 4h ago
> not sure about RV limits

Radial velocity, how quickly a planet moves “back and forth towards an observer” as it revolved about its star [1]. Its amplitude suggests planetary mass, its spectral shape orbital eccentricity.

[1] https://arxiv.org/pdf/2308.00701

floxy · 4h ago
axblount · 1h ago
I was curious about the acceleration due to gravity at the surface:

    G * (120 Earth masses) / (radius of Jupiter ^ 2)
Comes out to 9.7 m/s. Not bad!
addaon · 56m ago
> gravity at the surface

Unfortunately that "surface" is gaseous…

microtherion · 5m ago
That's what I (as a layperson) would think. The size of Jupiter, with half to a third of the mass would make it even more gas gianty than Jupiter.

… or it has a massive shell that is hollow inside /s.

Do any of the other measurements suggest anything about the nature of the surface?