Variations in the brightness of light seen from around a stellar-mass black hole in the binary system MAXI J1820+070 were caused by a huge warp in its accretion disk, according to a paper to be published in the Monthly Notices of the Royal Astronomical Society. The discovery was made from an extensive and detailed light-curve obtained over almost a year by amateur astronomers who are part of the AAVSO (American Association of Variable Star Observers). An...