Pulsars orbiting the Milky Way's black hole could sharpen its mass measurement a thousandfold.

Measuring gravity near a giant black hole is very difficult. Researchers want to study Sagittarius A*, the supermassive black hole at the center of our galaxy, by tracking pulsarspulsarsA pulsar is a rapidly spinning dead star that emits regular radio pulses, like a lighthouse beam.. Pulsars are dense, rotating stars that flash light like cosmic clocks. The researchers created a new timing method. It calculates the exact travel time of light using the physics of relativity, which describes how extreme gravity bends space and slows time. They tested this method by simulating arrival times for hypothetical pulsars on tight orbits near the black hole. They found that future telescopes could track these signals to measure the black hole's mass at least three orders of magnitude better than today's best star and event-horizon observations.

Why it matters

A supermassive black hole sits at the center of our galaxy, and its mass is not known as precisely as astronomers would like. Pulsars orbiting it could improve the measurement by at least three orders of magnitude — a thousandfold — compared with current observations. That would give the sharpest possible picture of the black hole's properties.

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