- Astronomers have spotted the first jet from an S-shaped neutron starThe jet is part of the Circinus X-1 binary star system.
- The neutron star's jet sprays like a garden sprinkler.changing direction due to the motion of hot gas around the star.
- Astronomers had observed precession with jets around black holes. Before, but never with neutron stars.
The jet from a neutron star is like a garden sprinkler
On July 16, 2024, the Royal Astronomical Society released the first image of a strange “garden sprinkler-like” jet coming from a neutron starThe structure is S-shaped, created as the jet changes direction due to the wobbling of the hot gas disk around the star. The wobbling is due to a process called precessionAstronomers had previously observed precession with jets around black holes, but never with neutron stars.
This particular object is located in the binary system. Circinus X-1which is more than 30,000 light years of the Earth. It was formed from the core of a huge supergiant star which collapsed around the same time Stonehenge was built. It is so dense that a teaspoon of its material weighs as much as Mount Everest.
Binary systems have two stars held together by gravity. In the case of Circinus X-1, one of them is a neutron star.
Both neutron stars and black holes are cosmological monsters. They form when the largest stars in the universe die and collapse under their own gravity.
Black holes, however, are considerably more massive and scientists can only detect them through their gravitational effects. Meanwhile, scientists can directly observe neutron stars, despite their density. Neutron stars are some of the most extreme objects in the universe and have interiors composed almost entirely of neutrons.
Observing the neutron star jet
A team of astronomers from the University of Oxford used Suricata – a radio telescope in South Africa – to detect the jet emanating from the neutron star. The radio telescope created the most detailed high-resolution images of Circinus X-1.
The images, presented at this week's National Astronomy Meeting at the University of Hull, include the first image of an S-shaped jet emerging from a confirmed neutron star. It's a breakthrough that could help unravel the extreme physics behind the astronomical phenomenon.
The principal investigator Fraser Cowie Cowie, of Oxford University, said there was another system known for its S-shaped jets, called SS433, but recent results suggest the object is likely a black hole. saying:
This image is the first time we have seen solid evidence of a precessing jet from a confirmed neutron star. This evidence comes from both the S-symmetrical shape of the radio-emitting plasma in the jets and the fast, wide shock wave, which can only be produced when a jet changes direction. This will provide valuable insight into the extreme physics behind jet launching, a phenomenon that is still poorly understood.
Accretion from a binary system
The enormous density of the neutron star creates a strong gravitational force that pulls gas from the companion star. This hot gas forms a disk that spirals down toward the surface of the neutron star.
This process, known as accretionIt releases enormous amounts of energy every second, more powerful than a million suns. Some of this energy powers jets (or narrow beams of material flowing outward) from the binary system, which travel at close to the speed of light.
Recent improvements to the MeerKAT telescope have resulted in excellent sensitivity and higher resolution images. With them, the team saw clear evidence of an S-shaped structure, similar in shape to the spray of water from a garden sprinklerin the jet of the Circinus X-1.
Not only that, but the researchers also discovered mobile termination shock waves. These were the first ever recorded in an X-ray binary system. These are regions where the jet violently collides with the surrounding material, causing a shock wave.
Cowie's team measured the waves moving at about 10% of the speed. speed of lightThis confirmed that the fast-moving jet caused them and not something slower, such as a wind of material from stars, Cowie said:
The fact that these shock waves span a wide angle is consistent with our model, so we have two strong pieces of evidence that the neutron star jet is precessing.
What are jets made of?
Measuring the speed of shock waves will also help astronomers understand what the jets that produce them are made of.
Shock waves effectively act as particle accelerators in space, producing high-energy cosmic rays, and the maximum energy of the particles that can be accelerated depends on their speed. Cowie said:
Circinus X-1 is one of the brightest objects in the X-ray sky and has been studied for more than half a century. But despite this, it remains one of the most enigmatic systems we know of. Several aspects of its behaviour are not well explained. So it is very gratifying to help shed new light on this system, building on 50 years of work by others.
The next steps will be to continue observing the jets and see if they change over time in the expected way. This will allow us to more accurately measure their properties and continue to learn more about this puzzling object.
Bottom line: Astronomers using the MeerKAT radio telescope in South Africa have observed an S-shaped jet from a neutron star for the first time. The wobble of the star creates the S-shape of the jet.
Via the Royal Astronomical Society
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