Astronomers have finally determined that black hole jets are composed of matter, rather than a combination of matter and antimatter particles.
Certain objects, black holes prominently, emit narrow beams of high speed matter called jets. “Although they have been observed for decades, we’re still not sure what they are made of, or what powers them,” says Dr. María Díaz Tringo from the European Southern Observatory. Now, an international team of astronomers may finally have found some answers.
The team was observing a small black hole with a mass a few times the size of our sun. The team was studying the X-Ray and radio waves emitted by the black hole and originally didn’t find anything remarkable about it and no jets seemed to be present. However, a few weeks later when they took a second look, things had changed. The radio waves showed evidence of the sudden presence of a jet, and the X-ray spectrum showed absorption lines, a clear sign that atoms were appearing around the hole.
“Intriguingly, we found the lines were not where they should be, but rather were shifted significantly,” Dr James Miller Jones from the Curtin University node of the International Centre for Radio Astronomy Research. This shift is essentially a different version of the doppler effect: It’s the same phenomenon you’ll hear when a siren passes you; the pitch of the siren appears to change because of the relative motion of the audio source as compared to you. “It led us to conclude the particles were being accelerated to fast speeds in the jets, one directed towards Earth, and the other one in the opposite direction,” said Dr Simone Migliari from the University of Barcelona.
The X-Ray spectrum, more importantly, finally explained exactly what is in these jets. Scientists already know electrons are present, but to maintain a net neutral charge, the jets also have to contain some type of particle with a positive charge: “Until now it wasn’t clear whether the positive charge came from positrons, the antimatter ‘opposite’ of electrons, or positively charged atoms. Since our results found nickel and iron in these jets, we now know ordinary matter must be providing the positive charge,” said Dr. Miller Jones.
Those jets are fast!
Since these positively charged ions are much heavier than positrons, it suggests the energy release involved in these jets is higher than might have been previously expected. The team measured the particles’ speed at around 66% of light speed, or 198,000km/s. This is the most accurate measure to date of the speed of such jets. Now remains the question of whether the disk of matter around the black hole is responsible for the jets, or whether it is the spin of the black hole itself that projects them. “Our results suggest it’s more likely the disk is responsible for channeling the matter into the jets, and we are planning further observations to try and confirm this,” said Dr Miller Jones.