I have a lab where given the mass of a star being $1.23$ times the math of our sun, some planets wobble of central start is $273$ days, and the velocity of 79 m/s. I found that the mass of the planet is $5.3\times 10^{27}$ kg and is approximately $.82$ AU away from its star. Here is a screen shot of my excel file:

enter image description here

Now I am asked would we expect this planet to be hotter or colder than earth?

I believe this question is rather silly since we have no idea the composition of the planet or other related factors to make any conclusion. From what I found is based on the mass and radius it is probably a water world, and since it is pretty close to its star I would say that it is probably hotter than earth.

Anyways, any suggestions or thoughts on this matter would be appreciated.

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    $\begingroup$ Your data would be more useful in text form rather than in an image. Also what is the Wobble? Variation of the star? $\endgroup$ – James K Feb 14 '18 at 7:56
  • $\begingroup$ You also need the age of the star. It's brightness increases over time. $\endgroup$ – userLTK Feb 14 '18 at 12:37

Yes, it is absolutely silly to predict an atmospheric/surface temperature without knowing it's composition or density. And we don't understand the formation process of atmospheres well enough to exclude any type of atmospheres around different stars.

There is however one more or less objective quantity that you can calculate: The equilibrium temperature. That is the temperature that the planet would have without an atmosphere.

This is essentially given by the planetary distance (which you have) and the stellar irradiation (which you have still to find), and the planetary albedo (a free parameter between 0 and 1).


There are lots of unknowns however, you have a star that is more massive than the sun. More massive stars (on the main sequence) are brighter than smaller ones. So the star is brighter than the sun.

You also have a planet that is closer to the star than the Earth is to the sun. Both these effects would suggest that the planet would be warmer than the Earth.

Indeed rough estimates suggest that this planet could have gone the way of Venus, and suffered a run-away greenhouse effect. The planet is considerably more massive than Earth. It would likely have a thick atmosphere that could contain lots of CO2.


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