Scientists have discovered a unique binary system 1,400 light years away consisting of a hot Jupiter-like object orbiting a white dwarf, offering unparalleled insight into the study of hot Jupiters and the evolution of stars in binary systems. The hot Jupiter-like object, orbiting a star 10,000 times fainter than most stars, has extreme temperature variations and provides a glimpse into the effects of intense ultraviolet radiation on planetary atmospheres.
The newly discovered binary celestial system could improve our understanding of the evolution of planets and stars under extreme conditions.
The search for exoplanets – planets orbiting stars located outside our solar system – is a hot topic in astrophysics. Of the various types of exoplanets, there is one that is truly hot: hot Jupiters, a class of exoplanets that are physically similar to gas giant planets. Jupiter from our own neighborhood.
In contrast to “our” Jupiter, hot Jupiters orbit very close to their stars, completing a full orbit in just a few days or even hours, and – as their name suggests – have very high surface temperatures. They have great appeal to the astrophysics community. However, they are difficult to study because the glare from nearby stars makes them difficult to detect.
Now, in a study recently published in the journal Natural Astronomy, scientists report the discovery of a system consisting of two celestial bodies, located approximately 1,400 light years away, which, together, offer an excellent opportunity to study Jupiter’s hot atmosphere, as well as to improve our understanding of planetary and stellar evolution. The discovery of this binary system – the most extreme of its kind so far in terms of temperature – was made through analysis of spectroscopic data collected by the European Southern Observatory. Very Large Telescope in Chile.
“We have identified a hot Jupiter-like object orbiting a star that is the hottest object ever discovered, about 2,000 degrees hotter than the surface of the Sun,” said the study’s lead author, Dr. Na’ama Hallakoun, associated postdoctoral fellow. with the team of Dr. Sagi Ben-Ami is in the Department of Particle Physics and Astrophysics at the Weizmann Institute of Science. He added that, unlike hot Jupiters which are covered in glare, this object can be seen and studied because of its enormous size compared to the host star it orbits, which is 10,000 times fainter than a normal star. “This makes it a perfect laboratory for future studies of the extreme conditions of hot Jupiters,” he said.
An extension of the research he carried out in 2017 with Prof. Dan Maoz, a Ph.D. advisor at Tel Aviv University, Hallakoun’s new discovery makes it possible to gain a clearer understanding of hot Jupiters, as well as the evolution of stars in binary systems.
A massive brown dwarf with a “Moon-like” orientation.
The binary system that Hallakoun and his colleagues discovered involves two celestial bodies that are both called “dwarfs,” but whose properties are very different. One of them is a “white dwarf,” the remnant of a Sun-like star after its nuclear fuel has been exhausted. The other half of the pair, neither a planet nor a star, is a “brown dwarf” – a member of a class of objects that have a mass between gas giants like Jupiter and small stars.
Brown dwarfs are sometimes called failed stars because they are not large enough to power hydrogen fusion reactions. However, unlike giant gas planets, brown dwarfs are massive enough to survive the “pull” of their stellar partners.
“Stellar gravity can cause objects that are too close to be crushed, but this brown dwarf is dense, with a mass 80 times that of Jupiter so it is about the size of Jupiter,” said Hallakoun. “This allows it to survive intact and form a stable binary system.”
When a planet orbits very close to its star, the difference in gravitational forces acting on the near and far sides of the planet can cause the planet’s orbital and rotation periods to become synchronous. This phenomenon called “tidal locking” permanently locks one side of the planet in a position facing the star, similar to how Earth’s Moon always faces Earth, while the so-called “dark side” remains invisible. Tidal locking causes extreme temperature differences between the “dayside” hemisphere that is bombarded by direct stellar radiation and the other outward-facing “nightside” hemisphere, which receives much smaller amounts of radiation.
The intense radiation from their stars causes hot Jupiter’s surface temperatures to be very high, and calculations Hallakoun and his colleagues performed on the white dwarf-brown dwarf pair system show just how hot these objects are. By analyzing the brightness of the light emitted by the system, they were able to determine the surface temperature of the brown dwarf orbiting in both hemispheres. They found that daytime temperatures are between 7,250 and 9,800 Kelvin (around 7,000 and 9,500 Celsius), which is as hot as an A-type star – a Sun-like star that can be twice as massive as the Sun – and hotter than any giant planet known. is known. In contrast, temperatures on the night side are between 1,300 and 3,000 Kelvin (around 1,000 and 2,700 Celsius), resulting in an extreme temperature difference of about 6,000 degrees between the two hemispheres.
A glimpse into unexplored territory
Hallakoun said that the system he and his colleagues discovered offers an opportunity to study the effects of extreme ultraviolet radiation on planetary atmospheres. This radiation plays an important role in various astrophysical environments, ranging from star-forming regions, ancient gas disks where planets form around stars, to the atmospheres of the planets themselves. This intense radiation, which can cause gas evaporation and molecular breakdown, can have a significant impact on the evolution of stars and planets. But that’s not all.
“Only a million years since the formation of the white dwarf in this system – a very short time on an astronomical scale – we have rarely glimpsed the early days of this kind of compact binary system,” Hallakoun said. He added that, although the evolution of single stars is well known, the evolution of interacting binary systems is still poorly understood.
“Hot Jupiters are the opposite of habitable planets – they are very inhospitable to life,” Hallakoun said. “Future high-resolution spectroscopic observations of these hot Jupiter-like systems – ideally carried out with NASA’s new James Webb Space Telescope – may reveal how high heat and radiation conditions impact atmospheric structure, something that could help us understand exoplanets elsewhere in nature universe.”
Reference: “Irradiated Jupiter analog hotter than the Sun” by Na’ama Hallakoun, Dan Maoz, Alina G. Istrate, Carles Badenes, Elmé Breedt, Boris T. Gänsicke, Saurabh W. Jha, Bruno Leibundgut, Filippo Mannucci, Thomas R Marsh, Gijs Nelemans, Ferdinando Patat and Alberto Rebassa-Mansergas, 14 August 2023, Natural Astronomy.
DOI: 10.1038/s41550-023-02048-z
Research participants also included Prof. Dan Maoz of Tel Aviv University; Alina G. Istrate and Prof. Gijs Nelemans from Radboud University, Netherlands; Prof. Carles Badenes from the University of Pittsburgh; Elmé Breedt of Cambridge University; Prof. Boris T. Gänsicke and the late Prof. Thomas R. Marsh of the University of Warwick; Prof. Saurabh W. Jha of Rutgers University; Prof. Bruno Leibundgut and Dr. Ferdinando Patat of the European Southern Observatory; Filippo Mannucci of the Italian National Institute of Astrophysics (INAF); and Prof. Alberto Rebassa-Mansergas from the Polytechnic University of Catalonia.
Dr. Sagi Ben-Ami is supported by the Peter and Patricia Gruber Award; Azrieli Foundation; André Deloro Institute for Advanced Research in Space and Optics; and the Willner Family Leadership Institute for the Weizmann Institute of Science.
Ben-Ami is the incumbent of the Aryeh and Ido Dissentshik Career Development Chair.
2023-10-18 08:22:32
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