Published On: Mon, Feb 8th, 2016

Preliminary Reference Earth Model Shows Earth-like Planets Have Earth-like Interiors

This artist’s painting compares a interior structures of Earth (left) with a exoplanet Kepler-93b (right), that is one and a half times a distance of Earth and 4 times as massive.

New investigate from a Harvard-Smithsonian Center for Astrophysics reveals that hilly worlds share identical structures, with a core containing about a third of a planet’s mass, surrounded by a layer and surfaced by a skinny crust.

Every propagandize child learns a simple structure of a Earth: a skinny outdoor crust, a thick mantle, and a Mars-sized core. But is this structure universal? Will hilly exoplanets orbiting other stars have a same 3 layers? New investigate suggests that a answer is approbation – they will have interiors really identical to Earth.

“We wanted to see how Earth-like these hilly planets are. It turns out they are really Earth-like,” says lead author Li Zeng of a Harvard-Smithsonian Center for Astrophysics (CfA).

To strech this end Zeng and his co-authors practical a mechanism indication famous as a Preliminary Reference Earth Model (PREM), that is a customary indication for Earth’s interior. They practiced it to accommodate opposite masses and compositions, and practical it to 6 famous hilly exoplanets with well-measured masses and earthy sizes.

They found that a other planets, notwithstanding their differences from Earth, all should have a nickel/iron core containing about 30 percent of a planet’s mass. In comparison, about a third of a Earth’s mass is in a core. The residue of any world would be layer and crust, usually as with Earth.

“We’ve usually supposed a Earth’s structure for a past hundred years. Now we can calculate a structures of planets orbiting other stars, even yet we can’t revisit them,” adds Zeng.

The new formula also can be practical to smaller, icier worlds like a moons and dwarf planets in a outdoor solar system. For example, by plugging in a mass and distance of Pluto, a group finds that Pluto is about one-third ice (mostly H2O ice though also ammonia and methane ices).

The indication assumes that apart exoplanets have chemical compositions identical to Earth. This is reasonable formed on a applicable abundances of pivotal chemical elements like iron, magnesium, silicon, and oxygen in circuitously systems. However, planets combining in some-more or reduction metal-rich regions of a universe could uncover opposite interior structures. The group expects to try these questions in destiny research.

The paper detailing this work, authored by Li Zeng, Dimitar Sasselov, and Stein Jacobsen (Harvard University), has been supposed for announcement in The Astrophysical Journal.

PDF Copy of a Study: Mass-Radius Relation for Rocky Planets formed on PREM

Source: Harvard-Smithsonian Center for Astrophysics

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