Moving ‘sunspots’ on the surface of a neutron star

Une vue d'artiste d'un magnétar avec sa croûte solide et ses boucles coronales. © Nasa, CXC, M.Weiss

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[EN VIDÉO] Gamma-ray bursts: Neutron star collisions illuminate the universe
Gamma-ray bursts are the brightest phenomena in the universe in the field of electromagnetic waves. We can observe an average of one day in the galaxy and they occur in distant galaxies. There are two types, short and long. This video explains the nature of short bursts.

Neutron stars are celestial bodies Exotic Its existence was predicted in the 1930s, when they could form when a star exceeded 8 Masses Sun light. There comes a time when thermonuclear reactions are produced Pressure Resistant radiationDecline Under their own Gravity These stars are stopped. Their heart Iron The CEA at the bottom of this article will generate the sequence of complex events discussed in the video and this will lead to an explosion, more precisely what it is called Supernova Type II. In many cases, the remainder adds up to a compact star Volume Some have a mass of approximately ten kilometers in diameter (among others, this one) Black hole It develops). Abstraction forces most electrons and Protons Before the eruption the star’s iron core converges following a decay reaction Beta On the contrary, it produces neutrons, hence the name of these alien stars.

Theories of neutron galaxies and the gravitational pull leading to the formation of black holes are the first works built in the late 1950s and early 1960s, dating back to 1939, and we are indebted to them. Robert Oppenheimer. Essays written with his students during that time are: On massive neutron cores », With Georges Volkoff, and Continuing gravity abstraction With Heartland Snyder.

What is a neutron star? What is the difference between these stars and our sun? Interpretations by Roland Lehuk, an astronomer at the CEA. Video co-produced by L’Esprit Sorcier. © CEA Research

From pulsars to magnets

It is necessary to observe the first pulsar of Jocelyn Bell and wait until 1967 with its description.Neutron star In rotation by Thomas Gold and Franco Pacini, the community of astrophysicists confirms the existence of these. Stars Attractive with strange properties. They are but elephants Thing A teaspoon is as dense as the weight of a mountain on earth. Department of Gravity y is so serious, it is necessary to appeal to the theory General relativity They are also laboratories to describe them and to test other theoretical theories of gravity, for example, Trapped relativity.

It has been known for some years that some neutron stars have extraordinarily strong magnetic fields. So we talk Magnet To mark these magnetic stars. An ordinary neutron star is already strongly magnetized because of its intensity Magnetic field Is on average 10 billion times larger than a magnet Refrigerator. But a magnet is usually a thousand times stronger.

The magnets rotate like this The sun Also, like all neutron stars, they have high surface temperatures. So it can create phenomena like its magnetic plasma on the surface of the sun, especially in the coronal loops.

Neutron stars with coronal loops?

Remember the coronal loops, and so on Sun pointsIs strongly connected to the solar magnetic field and the events form the active areas of the sun. Will explode Occurs frequently with lines of intense and dynamic magnetic fields, which can save a lotEnergy Before releasing her.

However, the surface of a neutron star is often believed Solid And made of iron cores, the interior of which is filled with more and more dominant neutrons, as one travels to the depths of the star, until pressures and temperatures give way to appearance. The position of the object Nuclear power is not yet properly understood and probably Formation of a guacma.

However, we can try to better understand the structure and evolution of neutron stars in many ways, especially by studying Their X-ray emissionsThis is exactly what astronomers do with their instruments Internal composition of the neutron star Explorer (Sweet) Of NASA aboardISS.

Nisar allowed them to take a closer look at a magnet already found and named SGR 1830-0645 (SGR 1830 for short). This was particularly marked by a strong eruption X-rays On October 10, 2020, it was discovered from space by the Neil Kehrels Laboratory Swift From NASA.

SGR 1830 Presentation of invention made with magnet. To get the most accurate French translation, click on the white rectangle in the lower right. English verses appear later. Then click on the nut to the right of the rectangle, then “Verses” and finally “Auto Translate”. Select “French”. © NASA’s Goddard Space Flight Center

Plate tectonics in neutron star?

SGR 1830 is located somewhere Milky Way Towards Constellation Sobiski’s armor (scutum), a small galaxy just east of the snake’s tail. As explained in the video and a post above Letters from the Journal of Astronomy, Swift’s vision and Niger’s vision show a sequence of continuous pulses in the X – ray field, indicating that the detected neutron star rotates on its axis every 10.4 seconds.

However, on closer inspection, the stimuli are tripled and finally doubled. The best way to interpret these observations is to initially cover three areas, which are particularly hot and therefore bright, as the temperature is above one million degrees. In fact, the theory behind these areas is that they are equivalent to the sunspots and the legs of the sun’s coronal loops. The two of them move and eventually merge, reducing these particularly bright areas from three to two. During these trips The Top tile Melted internally in the star Movements Such as Tectonic plates It also occurs in contact with the kinetics of magnetic coronal loops on Earth.

It is certain that this is the first time we have seen the evolution of “sunspots” on the surface of a neutron star.

The explosion of very large stars in gravitational supernovae enriches the galactic medium with chemical components synthesized by nuclear fusion, while the collapse of the center of the star forms a neutron star or black hole. The transition between the collapse of the center and the ejection of the star envelope poses a challenge to the theoretical understanding of supernovae. A hydraulic experiment designed and carried out at CEA made it possible to reproduce by analogy one of the cases of hydrodynamic instability that facilitates explosion. This experimental approach complements numerical simulations. Discover this animation experience and detailed descriptions of supernova explosions and the formation of neutron stars. The animated film was produced and co-sponsored by CEA and ERC, and was directed by Studio Anemia. Scientific and technical design: T. Foglizzo, J. Guilet, G. Durand (CEA). © CEA Research

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