As Futura had explained in a previous article, we can say that the greatest discoveries in Robert Oppenheimer’s physical-theoretical physics are those he made in 1939, laying the foundations for the theories of neutron stars and those of gravitational collapse, the led to the formation of neutron stars A black hole is constructed in the late 1950s and early 1960s. These are articles he wrote in collaboration with his then students: On Massive Neutron Cores, with Georges Volkoff (inspired by the ideas of the legendary Russian physicist Lev Landau), and On Continued Gravitational Contraction with Hartland Snyder.
Unfortunately, Oppenheimer didn’t live long enough to witness the discovery of pulsars in 1967, a discovery credited to radio astronomer Jocelyn Bell while she was doing her PhD with Antony Hewish (which will help her win the award). Nobel Prize in Physics in 1974 with Martin Ryle but without Jocelyn Bell – sparking a controversy that reverberates to this day). It was quickly recognized that these periodic radio-radio sources were precisely neutron stars (see explanation in the video below).
Oppenheimer also probably had no idea that the millisecond pulsars discovered later could be used to detect gravitational waves from colliding supermassive black holes. Waves that may have been spotted thanks to members of the International PulsarPulsar Timing Array (IPTA), which brings researchers together using data collected over about 15 years with several dozen radio telescopes on the planet. Among them are French radio astronomers using the famous Nançay radio telescope as part of the European Pulsar Timing Array (Epta).
A pulsar is a neutron star that emits beams of radiation that sweep across Earth’s line of sight. Like a black hole, it is a terminus in stellar evolution. The “pulses” of high-energy radiation we see from a pulsar are due to a misalignment of the neutron star’s spin axis and its magnetic axis. From our perspective, the pulsars appear to be pulsing because the neutron star’s rotation causes the beam of radiation generated in the magnetic field to enter and exit our field of view at regular intervals, much like the beam of light from a lighthouse. While the luminous flux is continuous, to a distant observer it appears to flicker in and out at regular intervals. For a reasonably accurate French translation, click the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © NASA Goddard Space Flight Center
Certain pulsars cause not only detectable emissions in the radio or X-ray range, but also X-rays. Article published in Astronomy & Astrophysics.
This is PSR J1023+0038, or J1023 for short, a pulsar known for its strange and enigmatic behavior, oscillating almost constantly between two luminosity modes observed around 4,500 years ago. -Light light years from the solar system in the Milky Way in the direction of the constellation Sextant, constellation Sextant.
Cosmic cannonballs fired in ten seconds
After combining observations from 12 ground and space telescopes, including three from ESO, we now understand that this behavior is the result of repeated ejections of packets of matter from the accretion disk of the pulsar, which is in orbit around a star, from which he drains GasGas and Plasma using his tidal powers, the tidal powers.
This is indeed what Maria Cristina Baglio, researcher at New York University Abu Dhabi affiliated with Italy’s National Institute for Astrophysics (Inaf) and lead author of the published article, explains in ESAO’s press release: “We have extraordinary ones Cosmic events are being experienced.” Huge amounts of matter, similar to cosmic cannonballs, are hurled into space in just a few seconds from a small celestial object that is rotating densely and at incredibly high speeds. »
This artistic animation shows the pulsar PSR J1023+0038 stealing gas from its companion star. This gas collects in a disk around the pulsar, falls slowly toward it, and is eventually ejected in a narrow jet. In addition, a particle wind is moving away from the pulsar, represented here by a cloud of very small dots. This wind collides with the molten gas, heating it and causing the system to glow in X-rays, ultraviolet, and visible light. Eventually, large amounts of hot gas are ejected by the jet and the pulsar reverts to its original, weaker state, repeating the cycle. This pulsar has been observed to continuously transition from one state to another every few seconds or minutes. © ESO, M. Kornmesser
At first, astrophysicists were puzzled by the fact that in a matter of seconds, J1023 went from a mode where the compact star emits X-rays, ultraviolet-ultraviolet, and visible light to a mode where it is weaker at those frequencies and emits more radio waves. as explained in the ESO press release.
So, hoping to better understand what was going on, for two nights in June 2021 they turned ESO’s Very Large Telescope (VLTVLT) and New Technology Telescope (NTT) instruments on the pulsar for visible and near-field observations To perform infrared observations complemented by those in the radio range accessible to the Atacama Large Millimeter/submillimeter Array (Alma). Astronomers have observed the pulsar cycle between its high and low light modes more than 280 times.
Thanks to a remarkable observing campaign involving 12 ground and space telescopes, including three from ESO, astronomers have discovered the strange behavior of a pulsar, a dead star spinning at very high speeds. This video summarizes the discovery. For a reasonably accurate French translation, click the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © M. Kornmesser, ESO, Angelos Tsaousis, UHD Team, C. Malin (christophmalin.com), Theofanis Matsopoulos
The ESO press release states that the solution to the puzzle surrounding the behavior of pulsar PSR J1023+0038 can be summarized as follows: “In deep mode, matter flowing towards the pulsar is ejected in a narrow jet perpendicular to the disk. ” . Gradually, this material accumulates closer and closer to the pulsar, at which point it is hit by the wind from the pulsing star, causing the material to heat up. The system is then in high mode, radiating heavily in X-rays, ultraviolet and visible light. In the end, the pulsar evacuates these masses of hot matter via the jet. “With less hot material in the disk, the system shines less brightly and goes back into low mode.”