A research team of astronomers led by Hada (SOKENDAI/NAOJ) reported the location of the supermassive black hole in M87 with a pinpoint accuracy. The 43GHz radio data approached the central engine of the M87's jet, the site of material falling onto the black hole, within 0.02 lightyears.

Supermassive black holes containing hundreds of millions times more mass than the Sun are known to reside in the cores of galaxies. On the route of falling into these monsters, the material forms circular disk orbiting the black hole. Powerful jets of ultra-relativistic particles, powered by the gravitational energy of black holes, are expelled from this “black hole + circular disk” system at tremendous speeds. Supercharged gas speeding out from around black holes, and a pair of beams of particles, jets, is propelled outward along the poles of the disk.

A leading scenario says the jet materials are lifted up from the disk by tightly-twisted magnetic field close to the black hole. The lifted materials are accelerated to ultra-high energy via the shock or other particle acceleration mechanism at a little downstream of jets. However, the observational test of such a theoretical model was difficult because the true location of black hole was hardly explored by previous observations.

Using a continental-wide Very Large Baseline Array (VLBA) as the one of the most powerful radio cameras, the researchers peered through the upper stream of the jet and the heart of M87 pulsing as their central super massive black hole. M87 is the largest galaxy in the Virgo Cluster of galaxies and one of the closest examples of the powerful radio jets. With the VLBA's super eye, the researchers pinpoint the exact origin of the jet where the black hole resides in M87. The determination of the location of the black hole provides important new information about the mysterious about workings of the powerful "engines" in the centers of innumerable galaxies throughout the Universe.

They revealed that the intensity peak of the 43GHz image locates the immediate vicinity of the black hole. The “event horizon” (from which matter cannot escape) of M87's black hole is roughly twice the size of our Solar System. The new measurement indicates that the core in the 43 GHz image locates an area no larger than 7 times the size of the event horizon.

“The supersharp radio eye of the VLBA allowed us to see deeper into the jet. We found the radio 43GHz core is very near the black hole itself, just 0.02 light year upstream.”, the team leader HADA said. “Pinning down this location provides important clues for understanding how such highly energetic jet is produced. Moreover, we will soon be able to obtain a direct image of the accretion flow and the jet production site on a scale of the event horizon for M87.”

The results presented here were published in Nature, “An origin of the radio jet in M87 at the location of the central black hole” (Hada, K. et al., 2011).

Paper information

• Title: An origin of the radio jet in M87 at the location of the central black hole
• Author: Kazuhiro Hada, Akihiro Doi, Motoki Kino, Hiroshi Nagai, Yoshiaki Hagiwara & Noriyuki Kawaguchi
• Journal: Nature (Doi:10.1038/nature10387, published online 07 September 2011)