What is the mass of the M87 black hole in billions of solar masses?

The mass of the M87 black hole is approximately 6.5 billion solar masses.

M87*, the supermassive black hole at the center of the giant elliptical galaxy Messier 87, became famous when the Event Horizon Telescope released the first image of a black-hole shadow in April 2019. The EHT collaboration measured its mass as approximately 6.5 billion times the mass of the Sun, with statistical and systematic uncertainties.

Astronomers had estimated M87*'s mass for decades by studying how stars and ionized gas move near the galaxy's center. Earlier measurements varied considerably, including estimates around 3.5 billion, 6.6 billion, and more than 7 billion solar masses. The EHT result made 6.5 billion the widely recognized headline figure.

The black hole's enormous mass corresponds to a Schwarzschild radius of roughly 120 astronomical units, or about 18 billion kilometers, if it were treated as non-rotating. Its surrounding accretion flow powers a relativistic jet that extends thousands of light-years from M87's nucleus. The dark region in the famous image is the black-hole shadow, which is larger than the event horizon itself.