PSR J0337+1715 is a millisecond pulsar discovered in a Green Bank Telescope drift-scan survey from 2007. It is spinning nearly 366 times per second, 4200 light years away in the constellation Taurus. It is the first pulsar found in a stellar triple system. It is co-orbiting very closely with another star, a 0.2 solar-mass white dwarf, with a period of 1.6 days. There is a second white dwarf further out (within one astronomical unit) which is orbiting both the pulsar and the inner white dwarf, and has an orbit with a period of 327 days and a mass of 0.4 solar masses.^[1][2] The fact that the pulsar is part of a triple system provides an opportunity to test the nature of gravity and the strong equivalence principle, with a sensitivity several orders of magnitude greater than before.^[3][4][5]

Results were published in 2018 showing that if there is any departure from the equivalence principle it is no more than three parts per million^[2][6][7] at 95% confidence level, improved to two parts per million in 2020.^[8]

In 2022 evidence for a small planet on a wide orbit was found.^[9]