The paper doesn’t calculate the radius of the star’s Roche limit, instead opting to calculate the orbital period of the Roche limit. I’ve never done a Roche limit calculation for stars, but I have for planets/moons, and I’m not seeing anything that suggests it’s different than for planets. So, I think I did this correctly (excepting typos):

The star’s Roche limit is about 1.5 million km from its centre (~1 million km above its surface), and the planet’s orbit is about 2 million km from the star’s centre. Assuming a circular orbit, which should be the case at these distances, the orbit has a circumference of about 12.7 million km, and the planet is whipping around at a speed of about 2.3 million km/h, or 0.2% the speed of light.

So much math here that my head is already overheating. I need to find the time to learn all this math. Kudos to you internet stranger on your examplary calculations.

The numbers are big, so it can be intimidating, but the math isn’t too bad. It’s a little bit of multiplication and division. The most daunting bit is a cube-root, which you can find on most scientific calculators these days.

It’s hunting down the numbers you need to use that’s the trick, and making sure they’re all in the right units.

The equation for the Roche limit is the most complex math, but that’s just something you look up:

Roche Limit = 2.44 x {the radius of the star} x cube-root(( {the mass of the planet} / {the radius of the planet}^3 ) / ( {the mass of the star} / {the radius of the star}^3 ))

All of the things in the braces are also just values you look up.

The article mentions the star being a dwarf. Are dwarf stars older and in a degrading state. Would the star have had less gravitational force when younger.

How would a plant form that close if the gravitational pull from the star was this strong.