[jbotz]

Keep in mind that surface gravity depends very much on density. The earth is pretty dense, having a core of mostly iron. Even a rocky planet can be a lot less dense if it's iron-poor, and so could have a reasonable surface gravity (by our standards) even if several times the earth's mass.

[bmgxyz]

Indeed. I learned this the hard way when I made some claim to a political science roommate about the local acceleration due to gravity near one of the outer planets and was corrected and embarrassed. It's easy to forget that gravitation is the result of many tiny things all pulling on each other, not just a few big and small things.

I looked through the paper and didn't see anything about the radius of the planet candidate. I suppose it's quite difficult to determine it from so far away. Is a value known? If so, that would obviously give a good idea about the local g.

[Robotbeat]

The radius is often not known. Radius is found most easily with transiting exoplanets, which are easy to detect but also only visible if you're lined up along the plane of the exoplanet's orbit.

You can also possibly find it via imaging, but even then, since you can't directly resolve it better than a point light source, you're making assumptions about albedo that lead to a wide dispersion in possible radii. High resolution optical imaging would require a telescope roughly 1-2km in diameter. Pretty tough... and because of the glare of the star, would be nearly impossible to image with an interferometric (i.e. non-filled-aperture) telescope since the light gather power would be so low. However, astronomers are incredibly clever at pulling data out of tiny points of light, so there may be some way.

[bmgxyz]

Thanks for this, it's quite interesting.

I have a friend who used to work in a lab doing super-resolution microscopy (i.e. beating the diffraction limit by various means) for use with bio/medical applications. Some of the techniques he told me about have to do with more or less taking lots of data from many images and assembling it all into something meaningful. I suppose what you're describing as "pulling data out of tiny points of light" is kind of the same thing. It's just that the scale is different.

[cwmma]

fun fact, if you were to travel into the earths core, gravity would go up first before it started to go down as you got closer to the dense center of the earth