In a significant breakthrough in astrophysics, scientists have detected a gamma-ray source in a microquasar named SS 433, located 18,000 light-years away from Earth in our galaxy. This system, comprising a pair of stars and a black hole, has been known to astronomers for its emission of light in the X-ray and radio bands. However, this marks the first time that photons in the gamma-ray range have been observed.
In the SS 433 system, the black hole draws in matter from its companion star, forming an accretion disk. While most of this material is absorbed by the black hole, a small portion is ejected perpendicularly in two plasma jets at a speed reaching a quarter of the speed of light, as explained by Mathieu de Naurois, CNRS research director at LLR and deputy director of the H.E.S.S. collaboration.
The H.E.S.S. observatory, located in Namibia, detected the emission of very high-energy gamma photons, of a few tens of teraelectronvolts (TeV), in these jets. To put it in perspective, the energy of a photon with a visible wavelength is around one electronvolt, that of an X-ray photon is a thousand times greater, and a gamma photon is a thousand billion times greater.
This discovery is not just another entry in the gamma-ray astronomical zoology bestiary, which already includes several hundred entries. Thanks to SS 433’s unique position in the sky, scientists have been able to pinpoint, for the first time, where these gamma-ray photons were produced. Contrary to initial assumptions, they are not accelerated at the source of the jets, near the black hole, where velocity is highest. Instead, the phenomenon occurs at great distances, over 75 light-years from the black hole. At this distance, the previously disappeared jets suddenly re-emerge with X-rays and gamma rays, possibly due to a collision with an obstacle, likely a cloud of matter. This collision may accelerate particles, especially electrons, which then transmit their energy to photons.
Mathieu de Naurois comments, “The measurements are consistent with the theory. Moreover, the most energetic photons are emitted at the point of impact, and the particles gradually lose energy downstream.” This discovery provides astrophysicists with further insight into the mechanisms of cosmic particle accelerators, which are always more efficient than those built on Earth.
In a significant breakthrough in astrophysics, scientists have detected a gamma-ray source in a microquasar named SS 433, located 18,000 light-years away from Earth in our galaxy. This system, comprising a pair of stars and a black hole, has been known to astronomers for its emission of light in the X-ray and radio bands. However, this marks the first time that photons in the gamma-ray range have been observed.
In the SS 433 system, the black hole draws in matter from its companion star, forming an accretion disk. While most of this material is absorbed by the black hole, a small portion is ejected perpendicularly in two plasma jets at a speed reaching a quarter of the speed of light, as explained by Mathieu de Naurois, CNRS research director at LLR and deputy director of the H.E.S.S. collaboration.
The H.E.S.S. observatory, located in Namibia, detected the emission of very high-energy gamma photons, of a few tens of teraelectronvolts (TeV), in these jets. To put it in perspective, the energy of a photon with a visible wavelength is around one electronvolt, that of an X-ray photon is a thousand times greater, and a gamma photon is a thousand billion times greater.
This discovery is not just another entry in the gamma-ray astronomical zoology bestiary, which already includes several hundred entries. Thanks to SS 433’s unique position in the sky, scientists have been able to pinpoint, for the first time, where these gamma-ray photons were produced. Contrary to initial assumptions, they are not accelerated at the source of the jets, near the black hole, where velocity is highest. Instead, the phenomenon occurs at great distances, over 75 light-years from the black hole. At this distance, the previously disappeared jets suddenly re-emerge with X-rays and gamma rays, possibly due to a collision with an obstacle, likely a cloud of matter. This collision may accelerate particles, especially electrons, which then transmit their energy to photons.
Mathieu de Naurois comments, “The measurements are consistent with the theory. Moreover, the most energetic photons are emitted at the point of impact, and the particles gradually lose energy downstream.” This discovery provides astrophysicists with further insight into the mechanisms of cosmic particle accelerators, which are always more efficient than those built on Earth.