Object Analysis

OJ 287 is a BL Lacertae object located 3.5 billion light-years away in the constellation Cancer. It is a type of active galaxy known as a blazar. OJ 287 is famous because it contains one of the most massive black holes ever measured, with a mass of 18 billion solar masses.

The system is actually a binary black hole. The 18-billion-solar-mass giant is orbited by a "smaller" black hole of 150 million solar masses. Every 12 years, the smaller black hole punches through the massive accretion disk of the larger one, creating a predictable and spectacular flare of light.

Observations of these flares have allowed astronomers to test Einstein's general relativity with extreme precision. The orbital decay of the smaller black hole, caused by the emission of gravitational waves, matches Einstein's predictions perfectly. It is a unique laboratory for the study of the most extreme gravity in the universe.