原文:In the intro to Murder Drones, we see that the Moon of Copper-9 has rings. This already means its Moon must be many times larger than Earth, as Earth cannot sustain rings for very long (on a cosmic scale).
Using angular sizing, we can tell that the Moon has an angular distance of 10.79 degrees. Assuming that the distance between Copper-9 and its moon is the same as the distance between Earth and its Moon, we can determine that Copper-9's Moon has a diameter of 72600 kilometers.
Now, let's get into Roche and his funny stuff about planets and gravity and whatnot. For this, we will be assuming the mean density of Copper-9's Moon is the same as our Moon, and that the mean density of Copper-9 is the same as Earth's. This is a rather large assumption, but considering the fact that Copper-9 shares many similarities to Earth, most notably being able to harbor life (at least before the first core explosion), it's not too big of an assumption.
With those assumptions all said and done, let's get into the MATH. The Moon's radius is 36300000 meters, making its volume 2.00359e23 m3. With the assumption that its density is similar to our Moon's, its mass would be 6.7e26 kg. We can now use an equation for finding the mass of Copper-9, with Roche limit. The equation we'll use is d=Rm(2*(MM/Mm))^(1/3) (found here 一个网址 where d is the distance between the bodies, Rm is the radius of the satellite (in this case Copper-9's Moon), MM is the mass of the main body (Copper-9), and Mm is the mass of the satellite (Copper-9's Moon). With our values, the equation looks like this: 384400=36300(2*(x/6.7e26))^(1/3), where x is MM. This results in x being equivalent to 3.97809e29 kg. Using the density of the Earth, Copper-9 should have a volume of 7.20799e25 m3, making its radius 258172000 meters, and its diameter 516344000 meters.

You may notice that its radius is quite large, nearly as large as the distance between Earth and the Moon In the intro to Murder Drones, we see that the Moon o

省流:比木星大，体积 7.20799e25 m3，半径为 258172000 米，直径为 516344000 米

感觉是不是有点贷款

地球的密度，五十一万公里的直径（相当于3.5倍的木星直径）计算又是基于带星环的卫星和铜9距离差不多地月距离这个条件，所以这么近的距离，那星环为啥还能留在卫星上？

@亚里亚德 @亚伯拉罕-伯特利

这个不好说，求解器还能手搓黑洞呢，不到一厘米的黑洞都有10的十几次方kg的重量，求解器凭空变出来还能消掉，这种番没必要那么讲科学