Alfred_The_Sartan t1_ixwbl0l wrote on November 26, 2022 at 9:54 PM

Reply to comment by lacgibra in How would one calculate the gravity of a planet? by LoreCriticizer

Is there any reasonable way to use equations to measure the mass of a rogue planet? Like let’s say there’s a brown dwarf that got ejected from its system and is rolling through interstellar space without anything really being able to measurably affect it. Would we have any idea of the mass?

AstroBryGuy t1_ixxb99l wrote on November 27, 2022 at 2:41 AM

Sure, via gravitational micro lensing. When the rogue planet or brown dwarf (which is not a planet) passes directly in front of a distant star (as viewed from Earth), the gravity of the rogue planet/brown dwarf will bend the starlight, focusing it towards Earth, causing the distant star to briefly increase in brightness. The amount of brightening depends on the mass of the body.

https://roman.gsfc.nasa.gov/exoplanets_microlensing.html