A couple days ago the "Gl 486" paper dropped; h/t GalaxyMaps and of course Nyrath. We've met this before. As GalaxyMaps points out, this star was a 1919 Max Wolf discovery so really should be named Wolf 437.
The paper comes off a hunt for transiting exoplanets within triple-digit parallax == ten parsecs of us. Ignored are such exoplanets as don't transit, like Proxima's. The hope is to measure more of their atmospheres and radii so that Webb can look in on 'em - like 55 Cancri Ae and LHS 3844 b. The authors are aware of ten transits in total.
In the meantime these researchers figured they could constrain this particular system better. Wolf 437 at 8.1 pc is the third closest of all transits. The 55 Cancri system is two-digit parallax (barely) so - beyond that.
What we have here is a "warm" planet at 700 K if we assume zero albedo. That temperature is thereby a maximum - if there's no greenhouse. Per Mansfield, M., Kite, E. S., Hu, R., et al. ApJ 886 (2019) 141; 880 K means lavaworld, like Io I guess. Mind you, I did say it was a transit - unless we are very lucky, those are so close to their star they are tidally locked. As is the case here.
It is three times Earth's mass but 1.343 times the radius - so 4/5 the density. The paper did calculate the metallicity of the star, so they figure on a low-mass core. All surrounded by silicates, maybe hydrated. It could be that the circle of opacity means this (large) radius is only apparent, showing only an opaque atmosphere like Venus'.
The haze would be water or maybe sulfuric-acid droplets like Venus'. Much would depend on any magnetic field, which is not constrained in the study.
MANSFIELD 7/16: She's got dibs. The argument goes, I think, that Wolf 437 being closer and not saddled with a binary star suggests it'll be easier to study, such as nail down constraints (the Rosetta is noted). I'm sure 55 Cancri A will be forthcoming, but what is learnt at Wolf 437 will be applied to further systems later.
No comments:
Post a Comment