This planet doesn't have to be habitable/comfortable for humans, however it must be able to possess limited surface water, so that it is habitable for carbon based life, the planet should occupy an orbit between 0.38 AU and 0.5 AU, in order for tidal locking to occur very early in the planets history. What should the physical properties of the planet be? In terms of its mass and atmosphere.

Let's assume the central star has 96% of the sun's mass and 79% of its luminosity.


closed as too broad by Aify, Mołot, sphennings, James, MolbOrg May 17 '17 at 18:57

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  • $\begingroup$ Is the planet tidally locked with the star or with a satellite? Also I don't see what atmosphere has to do with this. $\endgroup$ – zzz May 17 '17 at 16:32
  • $\begingroup$ Those are some pretty specific numbers. $\endgroup$ – RonJohn May 17 '17 at 16:33
  • 1
    $\begingroup$ Without an atmosphere there would be no surface water at all @ Zxu. $\endgroup$ – Stephanie May 17 '17 at 16:58
  • $\begingroup$ So you want a star that's almost exactly as big as sun, is the same type as sun, and has arbitrary lower luminosity, or luminosity calculated to the 1 percentage point, and you know orbit's radius interval to the 1% of AU, you calculated that already somehow and still have problems with your planet? That seems a bit strange. $\endgroup$ – Mołot May 17 '17 at 17:00
  • $\begingroup$ Related (or even a duplicate): worldbuilding.stackexchange.com/q/79646/809 $\endgroup$ – Mołot May 17 '17 at 17:08

The amount of spin a planet starts with depends on how the momentum of the accretive material came together to create its angular momentum. Imagine a zone of the accretion disk of a star which comes together, like an ice skater pulling in his arms, thereby rotating much faster, and in the same direction as the disk. This can be increased or decreased by further off-center impacts of smaller bodies. Your planet may have had some major impacts early on at an angle that countered its rotation.

The spin slows gradually from tidal effects: motions and shifts in the planet from the variation of gravitational forces as it rotates in proximity to another celestial body. That energy comes from the rotation and reduces it. Clearly, the closer and more massive the other body, the greater the effect. Your planet may also be squishy or crumbly.

To truly lock, there must be some slight unevenness in the density or shape so that there is a tiny bit more pull at some points of rotation, so it should not be too spherical and should have lumps of differing density.


A G-Type is the same as our sun. With an orbit that close they gather much more energy from their star. They need something to protect the planet from the increased energy. A highly reflective atmosphere or magnetosphere could do this.

A highly dense and reflective atmosphere would allow heat transfer from day to night side of the surface along with reducing the energy input to a reasonable level.

I do not know what chemical makeup is required for this.

I do not know what kind of crazy weather the heat transfer would cause.


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