A Gas Giant Exoplanet Has Been Discovered With Twice The Density of Earth

Astronomers are perplexed by a recently weighed exoplanet.

Scientists have found that the properties of a very young Jupiter-sized exoplanet don't match the models of gas giant planet formation.

It is too heavy for its age.

HD-114082b is too dense for a young gas giant with only 15 million years of age.

The exoplanet HD-114082 was the subject of an intense data collection campaign. HD-114082b is one of the youngest exoplanets ever found, and understanding its properties could yield clues as to how planets are formed.

There are two types of data needed for a characterization of an exoplanet. The way a star's light dims is recorded in transit data. The exoplanet's size can be revealed if we know the star's brightness.

A record of how much a star wobbles in place is called radial velocity data. The exoplanet's mass can be given if we know the mass of the star.

The researchers were able to collect radial velocity observations for four years. The researchers found that HD-114082b has the same radius as Jupiter but is 8 times Jupiter's mass. The density of the exoplanet is ten times that of Jupiter.

The size and mass of this young exoplanet make it unlikely to be a large rocky planet, the upper limit is around 3 Earth radii and 25 Earth mass.

A small density range can be found in rocky exoplanets. The body becomes denser and the planet's gravity starts to hold more hydrogen and helium.

HD-114082b is a gas giant. Astronomers don't know how it ended up like that.

The astronomer says that giant planets can be formed in two different ways. There is a disk of gas and dust surrounding a young central star.

Both ways are referred to as a cold start or a hot start. pebble by pebble is the idea that the exoplanet was formed from debris in the star's disk.

The pieces are attracted with two different ways of attraction. When it's massive enough to cause runaway accretion of hydrogen and helium, the lightest elements in the Universe, the faster it grows.

As gasses fall towards the planet's core, it's seen as a relatively cool option.

A hot start is when a swirling region of instability in the disk collapses under the weight of gravity. The result is a body that doesn't have a rocky core.

We should be able to observe the characteristics of planets that experience cold starts and hot starts.

HD-114082b's size and mass are more consistent with core accretion than its properties would suggest. It is too large for its size. Something else is going on, either it has an unusual core or it isn't.

It's too early to abandon the idea of a hot start. We do not understand the formation of giant planets very well.

One of the three that we know of are younger than 30 million years old. The disk instability model seems to be inconsistent with the others.

Three is a very small sample size, but three for three suggests that core accretion is more common than the other.

While more such planets are needed to confirm the trend, we believe that theorists should reexamine their calculations.

Our results feed back into the theory. They help us understand how giant planets grow and how we can better understand them.

The research was published in astronomy and astrophysics.