A young exoplanet with an unusual density puzzled astronomers

A group of astronomers led by the Institute for Astronomy of the Max Planck Society found that a sun-like

stars HD 114082 a giant exoplanet. Super Jupiter HD 114082 b is only 15 million years old. It is the youngest exoplanet of its type with a known mass and size.

For almost four years, researchersobserved the radial velocity of HD-114082. This is an indicator that shows the oscillations of a star caused by the gravitational influence of the planet. Using combined transit and radial velocity data, the researchers determined that the exoplanet HD-114082b has the same radius as Jupiter, but has an eight times the mass of the solar system's gas giant.


An exoplanet transits HD 114082. Video: Thomas Müller (MPIA/HdA)

This means that the average density of this gasThe planet is twice the density of the Earth. This is surprising, since the Earth is a rocky planet with an iron-nickel core, and not a gas giant composed mainly of hydrogen and helium (the lightest elements in the universe), like Jupiter.

Compared to currently accepted models, the density of HD-114082b is about two to three times that of a young gas giant just 15 million years old.

Olga Zakhozhaya, head of research from the Institute for Astronomy of the Max Planck Society

Planetary scientists have two models that describeformation of gas giants. The first of these, the "hot start" or disk instability theory, suggests that a planet is formed when a swirling region of instability in a protoplanetary disk collapses under the influence of gravity. The resulting body is a fully formed exoplanet with no rocky core.

The second possible explanation is the theory of "coldlaunch" - suggests the gradual formation of the planet from rocky debris inside the disk. Parts are attracted first by electrostatic forces, and then by gravitational forces. The more mass a protoplanet gains, the faster it grows until it becomes massive enough to cause uncontrolled accretion of light hydrogen and helium. As a result, a massive gas shell is formed around the stone core.

HD-114082b properties do not match any of thethese theories, scientists say. The high density of the planet indicates the presence of a rocky core, which contradicts the "hot start" theory. But even for the cold start theory, the planet is too massive for its age and size. Planetary scientists believe that further research will help refine theories of planet formation to account for unusual properties.

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On the cover: an artistic illustration of a gas giant around a Sun-like star. Image: NASA/JPL-Caltech/T. Pyle