Chandra Catches Relativistic Jets from Stellar-Mass Black Hole

Astronomers using NASA’s Chandra X-ray Observatory have observed a pair of relativistic jets blasting away from a black hole in the binary system MAXI J1820+070.

In this illustration, MAXI J1820+070 pulls material off a neighboring star and into an accretion disk; above the disk is a region of subatomic particles called the corona. Image credit: Aurore Simonnet / NASA’s Goddard Space Flight Center.

MAXI J1820+070, also known as ASASSN-18ey, is a binary system located about 10,000 light-years away in the constellation of Ophiuchus.

This artist’s impression illustrates how high-speed jets from supermassive black holes would look. Image credit: NASA / ESA / Hubble / L. Calçada, ESO.

The black hole has a mass about 8 times that of our Sun. Its companion star has about half the mass of the Sun.

The black hole’s strong gravity pulls material away from the companion star into an X-ray emitting disk surrounding the black hole.

While some of the hot gas in the disk will cross the event horizon and fall into the black hole, some of it is instead blasted away from the black hole in a pair of jets. These jets are pointed in opposite directions, launched from outside the event horizon along magnetic field lines.

MAXI J1820+070’s black hole was discovered during its July 2018 outburst and was extensively monitored across the electromagnetic spectrum.

In November 2018 and February, May, and June of 2019, Université de Paris astronomer Mathilde Espinasse and colleagues used Chandra to observe jets in this system.

The main panel of the graphic is a large optical and infrared image of the Milky Way galaxy from the PanSTARRS optical telescope in Hawaii, with the location of MAXI J1820+070 above the plane of the galaxy marked by a cross. The inset shows the first observation of MAXI J1820+070 by Chandra on November 13, 2018 and the jet launched on July 7, 2018.

“Just how fast are the jets of material moving away from the black hole? From Earth’s perspective, it looks as if the northern jet is moving at 60% the speed of light, while the southern one is traveling at an impossible-sounding 160% of light speed,” the researchers said.

“This is an example of superluminal motion, a phenomenon that occurs when something travels towards us near the speed of light, along a direction close to our line of sight.”

“This means the object travels almost as quickly towards us as the light it generates, giving the illusion that the jet’s motion is more rapid than the speed of light.”

“In the case of MAXI J1820+070, the southern jet is pointing towards us and the northern jet is pointing away from us, so the southern jet appears to be moving faster than the northern one.”

“The actual velocity of the particles in both jets is greater than 80% of the speed of light.”

The team estimates that about 181 million billion kg of material was blown away from the black hole in these two jets launched in 2018.

“This amount of mass is comparable to what could be accumulated on the disk around the black hole in the space of a few hours,” the scientists said.

“Studies of MAXI J1820+070 and similar systems promise to teach us more about the jets produced by stellar-mass black holes and how they release their energy once their jets interact with their surroundings.”

The findings will be published in the Astrophysical Journal Letters.