A new planet equivalent to Earth in size, made of solid iron, has been discovered orbiting a nearby star.
Trying to understand nature without understanding its diversity is difficult for us, and this is evident in exoplanetary science, and in the theories and ongoing research related to their formation.
Strange extreme natural phenomena pose constraints on our scientific models, and an incentive for scientists to dig deeper.
Gliese 367b is certainly an outlier in the exoplanet catalogue, which includes more than 5,000 planets, so Gliese 367b is not unique in these characteristics, but on the other hand it is considered very dense, about twice as dense as our planet. .
Therefore, it would likely be pure iron.
Astronomers discovered the planet Tahai in the data of TESS in 2021, which is a survey of planets transiting the sun, but recent research contained in the Astronomical Journal of Physical Letters shows the development in the process of measuring the mass and diameter of this strange planet, as those researches also led to the discovery of the existence of two brothers of this planet. Planet.
The title of the research is: A group of very high-density planets with a short-term orbital period around the non-terrestrial planet (Gliese 367b), discovery of two new low-mass planets within a time period of 11.5 to 34 days.
The research was recorded by lead researcher Elisa Gofo, a PhD student at the University of Turin.
TESS discovered the planet Gliese 367b in 2021, when it detected a very weak transit signal from the red dwarf star Gliese 367.
This indicates the limits of Tess’s observational power, so scientists verified its small size, which is roughly the size of Earth.
In 2021, researchers used the High Radial Velocity Spectroscopic Planetary Research Device (HARPS) at the European Southern Observatory, with the aim of determining the mass and density of (Gliese 367b), as they found in their research that the diameter of that planet is 72% of the diameter of the Earth, and its mass is about 55% of Earth mass, which means it is likely an iron planet, specifically part of a leftover core from another gas planet, which was large at an earlier time.
In their new study, the researchers used the HARPS spectrometer to reveal the dimensions of that small planet, and relied on 371 observations from HARPS to determine the planet’s characteristics.
This recent study showed that the planet is denser than the last study found in 2021. Instead of 55% of the Earth’s mass, scientists found in their new research that it is equivalent to 63% of the Earth’s mass, and that a drop is equivalent to 70% of the Earth’s diameter.
The density of the new planet (Gliese 367b) is twice the density of our planet.
How did the planet acquire its current shape? This shape is uncommon to find in nature, possibly the core of another planet stripped of its lithosphere.
“Gliese 367b can be compared to a planet that is similar to our Earth but has lost its rocky crust,” said lead author Joffo.
“This may have had a major impact on the formation of the planet, which we assume may have formed in the same way that our Earth formed, as it has a dense core made of pure iron, and is covered by a crust rich in silicates.”
It appears that something extraordinary happened to the small planet and caused it to lose some of its mass. Gufo explained that the small planet underwent an unusual event that caused it to lose its rocky crust, leaving its dense core bare. Possible collisions between it and other planets early in its life may have removed its outer layer.
Another possibility, according to Govoe, is that the fast-rotating planet might be in an unusually iron-rich region in the cometary disk, but this seems unlikely.
The third and final possibility appeared for the first time when astronomers discovered the planet (Gliese 367b) in 2021, as it was most likely the remains of a large gas giant like Neptune.
If this theory is correct, it is likely that the planet formed separately from its star, then migrated into orbit around the star, and that its position is now so close to the star that the intense radiation coming from the red dwarf vaporized the planet’s atmosphere.
(Gliese 367b) belongs to a very small class of exoplanets, called super-Mercury planets. Its composition is identical to that of Mercury, but it is larger and denser, and although it is rare, one system includes two of them.
It is also possible that Mercury suffered the same fate (Gleize 367b), perhaps carrying a mantle and a large crust, but external influences removed them.
The paper stated: Thanks to approximate measurements of the new planet’s mass and radius, he explored its internal composition and core structure, and found that it was expected to have an iron core with a mass composition of 0.91 of its mass.
What happened in this system? How could Gliese 367b be in this position with its orbit so close to its star?
Scientists also found two other planets in this system, Gliese 367c and Gliese 367d.
Astronomers believe that fast-rotating planets are always found in systems with double planets, so new research strengthens this hypothesis.
Tess could not observe such planets because they do not transit their star, and scientists discovered their presence in HARPS observations, and their discovery limited the possible formation scenarios.
Co-author David Gandolfi, a professor at the University of Turin, said: “Thanks to our extensive observations and research, as well as the spectroscopic observations of HARPS, we have discovered the presence of two additional lower-mass planets, with an orbital period between 11.5 and 34 days, which also reduces the number of possible scenarios leading to Such dense planets form.”
These companion planets orbit close to the star, but with lower masses, which poses constraints on which of them might have formed in an iron-rich environment, but it is a hypothesis that is not beyond doubt.
On the other hand, Gordolfi explained: “Gliese 367b may have formed in a dense iron environment, but we do not rule out scenarios that include violent and extreme events such as the collision of giant planets.”
In the conclusion of that research paper, the team delved into possible formation scenarios. In one formation scenario, the exoplanetary disk surrounding Gliese 367b should contain an iron-rich part, but scientists are not sure whether this type of rich regions exists, and they added: “One possible path involves formation of more iron-rich material than is typically assumed in protostar-forming disks. “However, it is not clear whether there are actual discs with high iron content, especially near the inner rim, where most of the material can be obtained.”
In fact, a separate 2020 study suggested that work on planetary formation failed to replicate the extreme iron enrichments needed to explain Mercury’s formation.
If disk models cannot explain how iron-rich Mercury formed, they cannot explain how Gliese 367b formed.
It seems most likely that it was different in the process of formation, and then took on its present form over time.
Impact erosion occurs when a planet’s outer crust is lost through repeated space collisions.
Because our planet’s outer layer is less dense than the inner material, repeated impacts would cause the overall density to increase, removing lighter surrounding material. However, there is at least one problem, the authors added: Bulk density measurements of Gliese 367b suggest that impact erosion It should be clearly effective in removing non-metallic materials from the planet’s mass, even if it is the only process taking place, which is significantly impressive, but not impossible.
There are now three possibilities: either the planet formed in an iron-rich environment, or the planet was previously more massive and lost its outer crust through collisions, or it is the nucleus of a once-existing massive gas giant that migrated closer to its star, stripping it of its gaseous envelope.
Perhaps what happened was a combination of the previous three scenarios.
At the end of the paper, the researchers concluded that this system, which hosts such a rapidly rotating body, is an unusual target for further investigation and scientific research, in order to find scenarios for the formation and migration of rapidly rotating space systems.
