Portuguese Institute of Astrophysics and Space Sciences (IA)Susana BarrosThe research team is led byConfirmed planetary system with a total of 5 exoplanetspublish the results of the research. 2 of every 5 planetsSimilar to Mercuryhas been noted,Why do dense rocky planets form?It is hoped that this will lead to clarification
■ 5 exoplanets have been confirmed, 3 of which are lighter than Earth
What was reported this time is a fixed star about 127 light years away in the direction of “Reticule” in the southern sky「HD 23472」5 orbiting exoplanets「HD 23472 d」HD 23472 a」HD 23472 f」HD 23472 b」HD 23472 c(in order of distance from the star*). In this article, it is written as “planet d” below.
Two of the outer planets b and c were said to have been discovered in 2019, and the three inner planets d, planet e, and planet f were reported by the research team. The three outer are rocky planets with larger radii than the Earth, as it is called“super earth”It has been with. The orbital period, radius, and mass of each planet are given as follows.
●HD 23472 d
・Revolution period: 3.98 days
・Radius: about 0.75 times the earth
・ Mass: about 0.55 times that of earth
● HD 23472 e
・ Period of revolution…7.90 days
・Radius: about 0.82 times that of Earth
・ Mass: about 0.72 times that of earth
●HD 23472 f
・ Period of revolution: 12.16 days
・Radius: About 1.14 times that of Earth
・ Mass: about 0.77 times that of earth
●HD 23472 b
・ Period of revolution: 17.67 days
・Radius: about 2.00 times the Earth
・ Mass: about 8.32 times that of Earth
●HD 23472 c
・ Period of revolution: 29.80 days
・Radius: about 1.87 times that of Earth
・ Mass: about 3.41 times that of earth
The parent star, HD 23472, is slightly smaller than the Sun.K star(The radius is about 0.71 times that of the Sun, the mass is about 0.67 times that of the Sun, and the surface temperature is about 4400 degrees Celsius). The equilibrium temperatures of the five planetary surfaces areAround 200 to 630 degrees CelsiusBoth are considered to be seriously high temperatures for terrestrial life.
* The name of the exoplanet is the name of the star with lowercase letters added in order starting with “b”. The alphabet is given according to the order in which the planets were discovered and the distance from the star, but even if a new planet is discovered later in the same planetary system, the name that has already been named will not be changed . The order of distance from the star is not necessarily alphabetical, and in some cases, planet d is closer to the star than planet c, as in this case.
■ Maybe we can get a clue to approach the mystery of Mercury’s formation?
This time, the focus is on the interiorgood planet planet ein two. When the research team estimated the average density and internal composition of each planet, planet da planet eHigh iron content and high average density(planet d is 7.5-3.1+3.9 g/cm3the planet e is 7.5-3.0+3.9 g/cm3),Possibility that the core (nucleus) accounts for about 45% of the masswas shown.
There are four rocky planets in the solar system, but the innermostMercury has a large core made of iron and nickelIt is known thatAccording to the research team, the newly discovered exoplanets are a good planet e similar to Mercury.“Super-Mercury”Also known as「K2-229 b」It is said that only six were known, including This is the first time that two supermercuries have been discovered in the same planetary system.
According to the research team, it is not yet known why Mercury has such a large core.part of the mantle that covers the coreButlost in a massive collisionorevaporated by high temperatureIt is said to be possible. The two supermarkets have just been discoveredClues to solve the mystery of Mercury’s formationcan give you the Institute for Happy Astrophysics (IAC), which took part in the researchAlexander Suarezhe said, “The chance of a collision forming a supermercury has already decreased significantly, as two massive impacts in the same planetary system seem unlikely.”
Also, the IACs who participated in the studyJonay Gonzalezstates that knowing more about the composition of the newly discovered exoplanet is essential to understanding how it was formed. The European Southern Observatory (ESO) is being built“European Very Large Telescope (ELT)”We look forward to future observations using , to study the composition of planetary surfaces and atmospheres.
Related: Direct image of an exoplanet 355 light years away from the James Webb Space Telescope
- Image Credit: NASA/JPL-Caltech; NASA Applied Physics Laboratory/Johns Hopkins University/Carnegie
- IA – Two rare supermercuries discovered around the same star
- IAC – Astronomers discover a planetary system with three super-Earths and two super-Mercuries
Text / Matsumura Takehiro