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by adolph 1015 days ago
That is if density remains constant. If the planet were 8x mass but with same radius, gravity would be 8 g, or 8 × 9.795 m/s^s.

  Earth mass:
  5.97×10^24 kg, 6378.137 km yields 9.795 m/s^2

  8x mass:
  (8×5.97)×10^24 kg, 6378.137 km yields 78.36 m/s^2
All calculations: https://www.wolframalpha.com/input?i=surface+gravity+calcula...
2 comments
pdonis 1015 days ago
> That is if density remains constant.

No, the calculation I made did not assume constant density. I just used the direct Newtonian formula for surface gravity and plugged in the known mass and radius of the planet. (You could also use that known mass and radius to calculate the average density. But you don't need to do that to calculate the surface gravity.)

> If the planet were 8x mass but with same radius

But we know it isn't. We know the planet's radius is 2.6 times the Earth's radius. That's stated in the article.

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mr_toad 1015 days ago
> If the planet were 8x mass but with same radius

That’s not possible for normal stable matter. The Earth’s density is about 5g per cubic centimetre. Iron is 7.8g per cubic centimetre. Osmium is the densest stable element at 22.6g per cubic centimetre.

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