Scientists have discovered the Jupiter-sized young exoplanet HD-114082b. The analysis results show that it is not like the two common gas giant planets. Simply put, it is too heavy. Astronomer Olga Zakhozhay of the Max Planck Institute for Astronomy in Germany and a research team are observing a 300 light-year exoplanet, only about 15 million years old, which is the youngest exoplanet so far. .
Exoplanets are generally understood through two methods: the transit method and the radial velocity method. The transit method is that when an exoplanet passes in front of its parent star, the brightness of the star will decrease. As long as the original brightness of the star, the degree of dimming and the length of time are known, the radius of the planet and the radius of its orbit can be estimated. The radial velocity law understands the mass of an exoplanet through the degree of star wobble, and the combination of the two can also know the orbital inclination.
In the past four years, researchers have analyzed the data of the parent star and planets. The radius of HD-114082b is equivalent to that of Jupiter, but its mass is 8 times that of Jupiter, which means that the density of HD-114082b is about twice that of Earth, or nearly 10 times that of Jupiter.
However, the size and mass of the young HD-114082b cannot be a super-large rocky planet. The upper limit of a rocky planet is 3 Earth radii and 25 Earth masses. As long as this value exceeds this value, the density of the celestial body and the gravity of the planet can retain a large amount of hydrogen and Helium makes up the atmosphere. It is obvious that HD-114082b exceeds this value and must be a gas giant planet, but astronomers still do not know the cause of HD-114082b’s value.
Scientists believe that giant planets are formed in two ways, “cold start” or “hot start”. The cold start is caused by the fragments surrounding the protoplanetary disk attracting each other due to static electricity, and then being attracted by gravity after the mass becomes larger, until the mass is large enough The uncontrolled accretion of hydrogen and helium is caused. This method will form a rocky core surrounded by a huge gas layer. When the gas falls to the core, it will lose heat, which is called a cold start. Hot start is also called disk instability, which occurs when the unstable rotation area of the protoplanetary disk directly collapses into a complete planet under the action of gravity. This method has no rocky core, and the gas will not release the gravitational potential energy by falling, and will retain More calories.
The cooling rates of the two methods are also different. The researchers believe that the properties of HD-114082b do not conform to the hot start model, but even if the cold start model is applied, the volume is still too large, unless the core is abnormally fragile or an unknown mechanism occurs. HD-114082b is one of the three exoplanets known to us that are less than 30 million years old, all of which are closer to the cold start model, but the three are very small sample sizes. Scientists need more planets of this kind to verify their conjectures. Maybe they should be more Improve the cold start model. The research was published in the journal Astronomy & Astrophysics.
(This article is reproduced with the authorization of Taipei Planetarium; the first picture is the gas giant planet in birth drawn by the artist, source: ESO)
