At the heart of the galaxy OJ 287 – a blazar, as the researchers call it – there is a supermassive black hole that is emitting powerful jets of matter. One ? Perhaps two estimate astronomers today after going to see what is happening there.
You will also be interested
[EN VIDÉO] The blazars, giant black holes accelerating cosmic rays This is a great first! Scientists have succeeded in tracing the distant emission source of a high-energy neutrino, this ghost particle which generally passes through matter without interacting with it. Where does this neutrino come from? How was it detected? Answer in this video.
In the immensity of our Universethere are galaxies whose supermassive black hole central is said to be active. Because it swallows up the gas and the stars surroundings and emits, in doing so, powerful jets of matter. When these jets are aimed directly at our Earth, the astronomers qualify the galaxy in question of blazar. And it’s one of those remarkable objects, the galaxy OJ 287, that a international team of researchers just mapped with the highest resolution obtainable with astronomical observations, i.e. an angular resolution of 12 microseconds of arc in the range radio.
To do so, they mobilized the exceptional power ofinterferometry at a very long distance. Combining the signals received by twelve radio telescopes – including one on board a Russian satellite – they have in fact built a huge telescope virtual with a diameter of no less than 193,000 kilometers!
A supermassive black hole or maybe two
These interferometric images taken in four wavelengths different types provide researchers with information on the nature of the OJ 287 blazar. knots ofepisode in the jet, a curvature which increases with increasing angular resolution, a polarization of the radiation which betrays a magnetic field predominantly toroidal, a flare of parts of the internal plasma jet.
All this data seems to indicate that the galaxy OJ 287 actually hides not one, but two supermassive black holes rotating around each other. The secondary black hole on a orbit very narrow elliptical and crossing the accretion disk of the primary black hole twice every twelve years. The partners of this binary system suspect are now so close to each other that they should issue gravitational waves likely to soon become detectable. But the researchers are mindful that their observations could also be caused by other effects. To be continued…
On video: the secret of the blazars
New evidence for the existence of supermassive black holes at the heart of active galactic nuclei has just been brought about by a patient and high-resolution study by the Very Long Baseline Array (VLBA). This powerful technique of radio wave interferometry has enabled astrophysicists to dive inside the jet of charged particles produced by a blazar. The theory fits perfectly with the observations…
Article of Laurent Sacco published on 02/05/2008
The discovery of quasars in the early 1960s not only marked the return to prominence of general relativity but also marked the beginning of the end for Hoyle and Bondi’s model of stationary cosmology. Therefore, theastrophysics Relativism was to develop rapidly and powerfully under the impetus of giants like Chandrasekhar and Zeldovitch.
To explain the wonderful energy radiated by objects in a volume whose diameter had to be less than a light year, it was necessary to bring in stars generating a field of gravitation within the domain of general relativityEinstein.
According to the theory proposed in 1977 by Blandford and Znajek, quasars must derive their fantastic energy from the processes of accretion and relativistic magnetohydrodynamics produced by a black hole of Kerr in rotation and whose mass was to exceed one million solar masses. The powerful jets of particles observed would thus be aligned with the axis of rotation of the black hole. By twisting lines of magnetic fields generated by a dynamo effect, this rotation would be responsible for the processes of acceleration and expulsion of the particles present in the jet. But how to be sure?
A network of radio telescopes to watch for the shock wave
The theory naturally predicts that the winding of magnetic field lines by the rotation of the black hole involves a movement helical for accelerated particles moving along the jet. In addition, the radiation produced at different wavelengths will be more intense parallel to the jet and above all, past certain distances moving away from the central black hole along the jet, a shock wave must occur creating sudden emissions in the visible, but also X-rays and gamma.
Alan Marscher, an astrophysicist from Boston University, then undertook with his colleagues to observe BL Lacertae, a galaxy with an active nucleus and serving as a reference to define what are called BL Lac objects. Located at 950 millionlight years from the Earth, this object is a blazar, that is to say a quasar producing jets of particles, one of which is oriented in the direction of our Galaxy.
Using the network of radio telescopes known as the VLBA, researchers were able to track the movement of a package of particles ejected by the central black hole of BL Lacertae, emitting in radio waves. At the same time, other telescopes capable of observing optical, X-ray and gamma-ray emissions were mobilized for several years to observe the radiation coming from the blazar jet. When the packet of matter arrived exactly at the distance where theory predicted sudden bursts of gamma, X-ray and visible radiation would occur, the astrophysicists found that their calculations matched reality perfectly.
This is not only a theoretical success, greatly reinforcing confidence in the theory of black holes as the source of energy for quasars, it is also an impressive success from the point of view of observations because we has thus succeeded in closely following the details of the processes at the heart of a jet of quasars.
Interested in what you just read?