[▲ Imagination of a cataclysmic star seen from a revolving exoplanet (Credit: Departamento de Imagen y Difusion FIME-UANL / Lic. Debahni Selene Lopez Morales DR 2022)]
Nuevo Leon Autonomous University (UANL)Dr. Carlos ChavezThe research team led byA new method for discovering exoplanetsWe announced the research results on.The research team focused on white dwarfs and stars, a type of variable star known for its drastic changes in brightness.“Catalysmic Star”It is a star system called.
■ Possibility of detecting exoplanets and brown dwarfs based on changes in the brightness of cataclysmic stars
white dwarfIs like the sunRelatively light star(Mass less than 8 times that of the sun)red starLost gas after evolving intoA celestial body with only the core remainingThat thing.The diameter is about the same as the earthbut,Mass is about three-quarters of the sunIt is a high-density celestial body that is said to have some.
In a cataclysmic starWhite dwarfs and stars revolve in orbits close to each otherAndGas flowing out of a star falls on a white dwarfIt is believed to be.When this gas leads to a runaway thermonuclear reaction, the surface layer of the white dwarf blows away.“New Star”A phenomenon called (Nova, a classical nova) occurs. Also, when the gas continues to accumulate and the mass of the white dwarf reaches about 1.4 times that of the Sun (Chandrasekhar limit),“Supernova”(Supernova)“Type Ia supernova”Is believed to occur.
However, the gas does not go straight toward the white dwarf, but falls around the white dwarf by drawing a spiral.“Accretion disk”CalledThin disk structureIs said to form. The temperature of the accretion disk is very high, and its brightness overwhelms the brightness of white dwarfs and stars.Most of the light from cataclysmic stars comes from the accretion diskIt is called.By the way, smaller explosions than novae are repeated“Dwarf Nova”(Dwarf nova) is thought to be caused by changes in the state of the accretion disk surrounding the white dwarf.
[▲ Imaginary view of a binary star consisting of white dwarfs and stars (video)]
（Credit: ESO/M. Kornmesser）
Temporarily, this cataclysmic starplanetorbrown dwarfEven ifrevolves, it is the same as a planet that revolves around a general star.Difficult to discover directlyProbably.However, it revolves around a cataclysmic star“Third celestial body” such as planetsFlows out of a star and creates an accretion disk around a white dwarfAffects gas via gravityBy exertingPossibility of changing the brightness of cataclysmic starsIs considered. If you can catch this change in brightness,It may be possible to indirectly detect the “third celestial body” that revolves around a cataclysmic star.
Maybe.
*… It is thought that the lower limit of the mass of a celestial body between a star and a planet is 13 to 15 times that of Jupiter, and the upper limit is about 75 to 80 times that of Jupiter.Therefore, Chavez et al. Analyzed the observation data of four cataclysmic stars in order to verify the method of detecting dark objects such as planets based on the change in the brightness of the cataclysmic stars. as a result,“LU Camelopardalis” “QZ Serpentis” “BK Lyncis”About threeThe “third celestial body”, which has a relatively light mass, may be revolving.
Is said to have been shown.Of the three cataclysmic stars, the estimated mass of the celestial body that revolves around “QZ star in Serpens” is0.63 times that of JupiterIt is within the range of the planet (about 200 times that of the earth).On the other hand, the estimated mass of the celestial body that revolves between “LU star in Camelopardalis” and “BK star in Lynx” isAround 90 times that of Jupiter
So, it seems that it may be slightly above the upper limit of brown dwarfs.It has been 30 years since the discovery of an exoplanet that revolves around a pulsar in 1992.Number of known exoplanetsAs of July 18, 20225063
(From NASA’s exoplanet database). The research team is convinced that the new method used this time is promising for searching for exoplanets that revolve around binary stars.
Related: The pulsar where an exoplanet was found for the first time in history, may it be a rare existence?
- Source
- Image Credit: Department of Image and Diffusion FIME-UANL/ Lic. Debahni Selene Lopez Morales DR 2022
- Royal Astronomical Society – A New Method to Detect Exoplanets
Chavez et al. – Testing the third-body hypothesis in the cataclysmic variables LU Camelopardalis, QZ Serpentis, V1007 Hercules and BK Lyncis
Text/Matsumura Takehiro
