Every student knows the basic structure of the Earth: a thin crust, a thick mantle and a core the size of Mars. However, is such a structure universal? Will rocky exoplanets orbiting other stars have the same three layers? The results of a new study provide a positive answer to this question.
“We wanted to understand how similar these rocky planets are to Earth. It turns out that they are very similar to our planet, - said the lead author of the study Li Zeng.
To reach this conclusion, Zeng and his colleagues used the PREM computer model, which is the standard model for the interior of the Earth. They added the ability to change the mass and composition of the planet and modeled six known rocky exoplanets with known mass and size.
It turned out that other planets, despite their differences from Earth, all must have a nickel-iron core, which makes up about 30 percent of the planet's mass. For comparison: about a third of the Earth's mass is concentrated in its core. The rest of each planet will make up its mantle and crust, just like the Earth.
“We understood the inner structure of the Earth just a few hundred years ago. Now we can study the structure of planets orbiting other stars, although we cannot visit them,”added Zeng.
The new computer model could also be used to study small, cold worlds such as satellites and dwarf planets in the Outer Solar System. For example, having entered the mass and size of Pluto into the system, scientists have determined that it consists of one third of ice (mainly water, but also ammonia and methane).
The model assumes that exoplanets have a similar chemical composition to Earth. This assumption is based on an analysis of the abundance of key chemical elements such as iron, magnesium, silicon, and oxygen in neighboring stellar systems. Nevertheless, the planets formed in more or less metal-rich parts of the galaxy will have a different internal structure. Scientists are going to pay attention to such worlds in their next studies.
Andrey Barabash
Promotional video: