Hi, I'm a biology student...with barrrrely any physics knowledge. However I have to write a report on this article, A Jupiter-mass companion to a solar-type star. and in it, the author finds the upper limit to the mass of the planet, but i read that using the radial velocity method only the lower limit can be found. can anybody please explain this? also in the equation M2sini=mass of planet, what is M2? thanks so much!