A recently discovered exoplanet has left astronomers in awe.
After measuring Jupiter’s dwarf star HD-114082b, scientists have found that its properties don’t quite match the two types of giant gas planets.
In short, he is very difficult for his age.
Astronomer Olga Zakhozhay of the Max Planck Institute for Astronomy in Germany said: “Compared to today’s accepted models, HD-114082b is two to three times more dense than a small gas giant that is only 15 million years old.
Orbiting a star called HD-114082 about 300 light-years away, the exoplanet has been the subject of a data-gathering campaign. At only 15 million years old, HD-114082b is one of the youngest exoplanets ever discovered, and understanding how planets form is a poorly understood process.
Two types of data are needed to find out more about an exoplanet, depending on how it affects its host star. Transit data is a record of how the star’s light changes when an orbiting exoplanet passes in front of it. If we know the brightness of the star, this reddening can reveal the size of the exoplanet.
On the other hand, the radial velocity data is a record of how much the star wobbles in its position in response to the exoplanet’s gravitational pull. If we know the mass of the star, then the amplitude of its vibration can give us the mass of the exoplanet.
For nearly four years, the researchers collected radial velocity measurements of HD-114082. Using a combined method and radial velocity measurements, the researchers determined that HD-114082b has the same radius as Jupiter – but it is 8 times that of Jupiter. This means that the exoplanet is about twice the mass of Earth, and about 10 times the mass of Jupiter.
This small exoplanet size and mass means that it is unlikely to be a super large rocky planet; the upper limit for them is around 3 Earth radii and 25 Earth masses.
There is also a very small density in the rocks of exoplanets. Above this, the body becomes solid, and the Earth’s gravity begins to hold the essential hydrogen and helium gases.
HD-114082b is the most abundant of those parameters, which means it is a gas giant. But astronomers don’t know how it got that way.
“We think that giant planets can form in two ways,” says astronomer Ralf Launhardt of the MPIA. “All of this happens within a protoplanetary disk of gas and dust distributed around the central star.”
These two methods are called ‘cold start’ or ‘hot start’. In the early cold, the exoplanet is thought to form, rock by rock, from debris in the disk surrounding the star.
Particles are attracted, first electrostatic, then gravity. The more abundant they are, the faster they grow, until they are so massive that they form hydrogen and helium, the lightest elements in the universe, creating the largest envelope around rocks.
Since these gases lose heat when they fall to the center of the earth and form the atmosphere, it is considered the most efficient way.
A hot start is also known as a disc instability, and is thought to occur when a rotating part of the instability in the disc collapses in on itself under the force of gravity. A well-formed exoplanet body does not have a rocky core, where the gases retain their heat.
Exoplanets that experience a cold or hot start must cool at different rates, producing different conditions that we should look for.
The properties of HD-114082b do not match the original hot model, the researchers say; its size and weight are closely related to the increase in the center. But even so, it is still very large because of its size. Either it has a weirdly moist bloom, or something else is going on.
“It’s too early to give up on the idea of a hot start,” Launhardt says. “What we can say is that we don’t really understand the formation of the giant planets.”
The exoplanet is one of three we know of that are younger than 30 million years, for which astronomers have obtained measurements of their orbits and masses. At this point, all three seem to be incompatible with the default disk format.
Obviously, three is the smallest sample size, but three for three suggests that perhaps the larger expansion may be the more common of the two.
“Although such planets are needed to confirm this phenomenon, we hope that theologians will begin to reevaluate their calculations,” says Zakhozhay.
“It’s exciting how our observational results feed back into the theory of planet formation. It helps advance our understanding of how these giant planets grow and tells us where the gaps in our understanding are.”
Research has been published in Astronomy & Astrophysics.
