Artistic representation of a binary star system, International University of Valencia
Let the Sun not confuse.
Despite the fact that the star closest to the Earth shines alone, the most common is that the stars orbit in company in the universe.
The coexistence between two or more stars is called binary systems, a category that embraces a great diversity of stellar pairs.
But in particular there is one that fascinates astronomers, the X-ray Be binary stars, which focus on Valencia, until this Friday, the International Congress BeXRB2021, organized by the International University of Valencia (VIU) in collaboration with the European Space Agency (THAT).
The event brings together in a virtual way more than a hundred researchers of about twenty nationalities, from centers such as the universities of Oxford or George Washington and from institutions such as NASA.
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Be-companion X-ray binary systems (BeXRBs), as these types of stars are known in modern astronomy, still represent one of the great enigmas of cosmic history.
The union consists of joining a “Be” -type star - between eight and ten times more massive than the sun and which resembles Saturn due to its characteristic disk around the equator, sculpted with the material that escapes it - with an object compact, a neutron star or a black hole, whose elliptical orbit around the massive star makes both are doomed to live in pairs.
The interaction, which emits X-rays, between the disk and the compact object, gives rise to a very interesting physics and phenomenology that goes to the limit of what we know, helps us to promote models and confirm theories, for example, such as Einstein's, on the structure of space-time and the behavior of matter under extreme conditions
Pere Blay, professor at VIU and support astronomer at the Instituto de Astrofísica de Canarias
“There is an interaction, which emits X-rays, between the disk and the compact object, which gives rise to a very interesting physics and phenomenology that goes to the limit of what we know, helps us to promote models and confirm theories, for example, like those of Einstein, on the structure of space-time and the behavior of matter under extreme conditions.
The natural interest in these objects has increased in recent years ”, explains Pere Blay, professor and researcher at the International University of Valencia and previously an astronomer at the Canary Islands Observatories (OOCC) and the Nordic Optical Telescope (NOT).
Illustration of the black hole Cygnus X-1 swallowing matter from the star with which it forms a binary system.NASA |
CXC |
M.WEISS
The formation of the discs of the Be stars still forms one of the oldest unsolved mysteries in astronomy.
“Although these stars have been known since the late 19th century, we still do not know how they are capable of forming their circumstellar disks.
When the material of this disk is trapped by a black hole or a neutron star in a BeXRB, through its study, we expand the frontier of our knowledge about its structure or even about the structure of matter ”, observes Blay.
Parents of gravitational wave systems
Peter Kretschmar, responsible for supervising the work on the XMM-Newton telescope at the European Center for Space Astronomy, has highlighted the “totally different” scale of this type of cosmic pairs, with a magnetosphere of hundreds of thousands of kilometers, the localized matter in a star with a radius of 12 kilometers and a column from which X-rays of only a few meters or kilometers emerge, tiny areas from which a luminosity tens of thousands of times greater than the Sun emerges.
“BeXRBs are interesting because they are light sources with multiple emissions and different levels of activity, with a regular spacing determined by the orbital period, but it doesn't always happen. Sometimes it is quite regular and sometimes it is not, and this is one of the most important questions. The ways of understanding it are varied. They are working very hard to design models. The simplest ones follow the light curve as matter approaches and emission occurs, but 20 years ago it began with another one on which the interaction of the tidal force of the small object can sometimes cause an emission. Other more elaborate models propose that the disk is elongated or deformed ”, describes Kretschmar, who adds, as a factor of interest, the study along the electromagnetic spectrum."Some of these binary systems reach not only X-rays, but also gamma rays, so they can be followed with optical, infrared or radio telescopes."
The origin of this type of binary system occurs in the union of two stars, one rotating around the other, in which the most massive one evolves faster and explodes as a supernova, an alternation that changes the configuration of the system with a speed of different movement
The origin of this type of binary system occurs in the union of two stars, one rotating around the other, in which the most massive one evolves faster and explodes as a supernova, an alternation that changes the configuration of the system with a speed of different movement. A compact object remains from the explosion, a neutron star or black hole, the result of which, together with a massive star, is a binary X-ray system. cataclysmic event of these characteristics ”, notes Blay, PhD in the multifrequency study of binary X-ray systems.
As important as analyzing the past is knowing what will happen to these binary stars in the future.
“The massive star also evolves and its natural form is exploding like a supernova, of which a neutron object or a black hole will also remain.
If after the explosion the system survives and the objects remain together we will have, we will have a system that we can study with the LIGO or LISA detectors, because the binary X-ray systems are the progenitors of the systems that are later detected in gravitational waves ", he describes Blay, coordinator of the conference, in whose presentation he analyzed the relationship between mobiles, the invisible universe and binary X-ray systems.
The connection with the mobile
Many of the components of smartphones are scarce in the earth's crust, which is a headache for the industry. An explanation to understand why elements such as precious metals, germanium, thallium, tungsten or neodymium are so scarce is found precisely in these binary stars. Almost all the components of our smartphone occur in rare cosmic events such as binary X-ray systems.
In the nucleus of the stars, where a factory of atoms is cooked, fission phenomena occur that generate from the simplest such as hydrogen to more complex reaction chains that produce heavier elements such as iron. But to get the ingredients that allow the design of smart phones, another more sophisticated process is needed, which forces us to leave the interior of the star. “For the heaviest elements, scenarios are needed in which the energy contribution is very large and we have proof of how they are produced in supernovae, but theories have not yet been able to explain the heaviest elements such as gold, silver, tungsten. . The heaviest materials need even greater inputs of energy such as kilonovas, neutron star mergers in the invisible universe,or of a neutron star and a black hole, from a binary system. That is why these elements are so rare in the universe, ”explains Blay.
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