A recently suspended exoplanet has puzzled astronomers.
By taking measurements of a very small Jupiter-sized exoplanet called HD-114082b, scientists found that its characteristics do not match either of the two popular models for the formation of gas giant planets.
Simply put, he is too heavy for his age.
“Compared to currently accepted models, HD-114082b is two to three times denser for a young gas giant just 15 million years old,” he said. explains astrophysicist Olga Zakhazy from the Max Planck Institute for Astronomy in Germany.
This exoplanet, orbiting a star called HD-114082 at a distance of about 300 light-years, has been the subject of an intense data collection campaign. At only 15 million years old, HD-114082b is one of the youngest exoplanets ever discovered, and understanding its properties could provide clues to how planets form, a process that is not fully understood.
Two types of data are needed to comprehensively characterize an exoplanet based on its influence on the host star. The transit data is a record of how the light of a star dims when an orbiting exoplanet passes in front of it. If we know how bright the star is, this slight dimming could reveal the exoplanet’s size.
On the other hand, radial velocity data is a record of how much a star wobbles in response to the gravitational pull of the outer planets. If we know the mass of a star, the amplitude of its oscillations can give us the mass of an exoplanet.
For nearly four years, the researchers have been collecting observations of the radial velocity of HD-114082. Using data collected on transit and radial velocity, the researchers determined that HD-114082b has a similar radius. Jupiter – But the mass of Jupiter is 8 times greater. This means that the density of the exoplanet is almost twice that of the Earth, and about 10 times that of Jupiter.
The size and mass of this small exoplanet means it is unlikely to be a very large rocky planet; top borders around it 3 earth radius It’s in 25 earth masses.
Rocky exoplanets also have a very small density band. Above this range the body becomes more intenseAnd the planet’s gravity begins to contain an important atmosphere of hydrogen and helium.
HD-114082b significantly exceeds these parameters, which means it is a gas giant. But astronomers don’t know how it happened.
“We think that the giant planets could have formed in two possible ways.” says astronomer Ralf Lönnhardt mpiya. “Both occur within a protoplanetary disk of gas and dust distributed around a young central star.”
Both methods are called “cold start” or “warm start”. During a cold start, an exoplanet is thought to form, pebble by pebble, from the debris of a disk orbiting a star.
Parts are attracted to each other first electrostatically and then gravitationally. The larger the mass, the faster it grows until it becomes massive enough to cause the runaway accumulation of hydrogen and helium, the two lightest elements in the universe, creating a huge shell of gas around the rocky core.
Given that gases lose heat as they fall towards the planet’s core and form an atmosphere, this is considered a relatively cool option.
Hot start is also known as disk instability and is believed to occur when a swirling region of instability in the disk collapses directly on itself under the force of gravity. As a result, the object is a fully formed exoplanet without a rocky core, as the gases hold more heat.
Exoplanets that experience a cold start or a hot start must cool at different rates, leading to different features that we should observe.
The researchers say the performance of the HD-114082b is not suitable for a hot start model. Its size and mass are more consistent with primary accretion. Even so, he is still quite large for his size. Either it contains an unusual core, or something else is going on.
“It is too early to abandon the idea of a hot start” Lennhardt says🇧🇷 “All we can say is that we still don’t quite understand the formation of giant planets.”
Exoplanets are one of three planets less than 30 million years old for which astronomers have obtained radius and mass measurements. So far, all three seem to be inconsistent with the disk instability model.
Three is clearly too small for the sample size, but three to three indicates that primary accumulation is probably the more common of the two.
“While more planets of this type are needed to confirm this trend, we think theorists need to start rethinking their calculations.” Zahozay says.
“It’s amazing how the results of our observations fit into the theory of planet formation. They help improve our knowledge of how these giant planets grow and tell us where there are gaps in our understanding.”
Research published in astronomy and astrophysics.