The speed of the black hole jet of M87 has been measured

A team of astronomers has studied in greater detail the jet of materials and gas that escapes from the black hole at the center of the galaxy Messier 87, or M87, the black hole that was so prominent last year when astronomers published the first ever image of such an object.

This supermassive black hole, with a mass of 6.5 billion times that of the Sun, is located 500 million light-years away from Earth and is characterized by a very powerful jet of particles that come out at very high energy and very high speed as they “bounce” before being sucked into the event horizon of the black hole itself. Researchers have studied this jet at various wavelengths of light, including X-rays, also using the Chandra Space Telescope.

The results confirm that these jets coming out of supermassive black holes can reach speeds close to that of light. This is the first time that the speed of an object emerging from a black hole is recorded using X-ray data, as explained by Ralph Kraft of the Center of Astrophysics | Harvard & Smithsonian (CfA) in Cambridge. In fact, to make precise measurements of the speed of these jets, you need sharp X-ray vision, something that probably, at the moment, only the Chandra telescope can allow.

These jets, also called “relativistic jets”, are made of materials that initially form part of the swirling growth disk that rotates around the black hole at the center of the galaxy. Part of this material falls inside the black hole while another part is redirected at very high speed, in the form of narrow beams with real jets, along the magnetic field paths of the black hole itself.

In calculating the speed of the black hole’s object at the center of the galaxy M87, the researchers obtained the first example of a phenomenon called “superluminal movement” which, only apparently, sees sections of this jet move at speeds greater than the speed of light. This is just an optical effect that happens when these jets, travelling at very high speeds close to those of light, point in our direction.

The jet seems to travel towards us almost as fast as the light it generates and this generates the illusion, even measurable, that the jet’s motion is faster than light itself.

Researchers have measured an apparent speed of 6.3 times that of light for the “node” of the nearest black hole jet (a “node” is a kind of brighter lump that forms along the jet due to the irregularity of its fall).