HomeScience and ResearchSpaceAstronomers find a featherweight sub-Earth exoplanet as dense as pure iron

Astronomers find a featherweight sub-Earth exoplanet as dense as pure iron

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‘GJ 367 b’ is a featherweight among extrasolar planets. The newly discovered planet is one of the lightest among the over 5000 exoplanets known today, with a mass half that of Earth.

It takes about eight hours for the extrasolar planet to orbit its parent star. GJ 367 b is slightly larger than Mars, with a diameter of just over 9000 kilometers. The planetary system is only 31 light years away from Earth, making it a great candidate for further study.

The discovery shows that even the tiniest, least massive exoplanets may have their features correctly determined. Such research is crucial to comprehending how terrestrial planets form and evolve.

GJ 367 b is a fast-moving planet with an orbital period of only one-third of an Earth day.

“From the precise determination of its radius and mass, GJ 367b is classified as a rocky planet,” said Kristine W. F. Lam, lead researcher.

“It seems to have similarities to Mercury. This places it among the sub-Earth sized terrestrial planets and brings research one step forward in the search for a ‘second Earth’.”

A quarter-century after the first extrasolar planet was discovered, the attention has switched to better characterizing these planets as well as finding new discoveries. For most known exoplanets, it is now possible to create a far more detailed profile.

Many exoplanets have been identified using the transit method, which involves measuring minute variations in a star’s radiated light, or apparent magnitude, as a planet passes in front of it (with respect to the observer).

With the help of NASA’s Transiting Exoplanet Survey Satellite, GJ 367 b was also identified using this method.

GJ 367 b is an ‘ultra-short period’ (USP) exoplanet, meaning it orbits its star in less than 24 hours.

“We already know a few of these, but their origins are currently unknown,” said Kristine Lam.

“By measuring the precise fundamental properties of the USP planet, we can get a glimpse of the system’s formation and evolution history.”

Following the finding of this planet using TESS and the transit method, the radial velocity method was used to study the spectra of its star from the ground. The mass was determined using the HARPS instrument on the 3.6m telescope of the European Southern Observatory. The planet’s radius and mass were established with great care and a mixture of several evaluation methods: its radius is 72 percent of Earth’s radius, and its mass is 55 percent of Earth’s mass.

The researchers were also able to make conclusions about the exoplanet’s inner structure by calculating its radius and mass with an accuracy of 7 and 14 percent, respectively. It is a rocky planet with a low mass but a higher density than Earth.

“The high density indicates the planet is dominated by an iron core,” explained Szilárd Csizmadia.

“These properties are similar to those of Mercury, with its disproportionately large iron and nickel core that differentiates it from other terrestrial bodies in the Solar System.”

However, due to its close proximity to its star, the planet is subjected to extremely high levels of radiation, more than 500 times greater than the Earth. The surface temperature might rise to 1500 degrees Celsius, melting all rocks and metals. As a result, GJ 367 b cannot be deemed a “second Earth.”

This recently discovered exoplanet’s parent star, a red dwarf dubbed GJ 367, is only half the size of the Sun. This helped its detection because the transit signal of the circling planet is extremely important.

Red dwarfs are not just smaller than the Sun, but they are considerably cooler. This makes it easier to locate and characterize the planets that are linked with them.

They are among the most common star objects in our cosmic neighborhood, making them good exoplanet research candidates.

These red dwarfs, also known as ‘class M stars,’ are thought to be orbited by two to three planets on average, according to researchers.

Source: 10.1126/science.aay3253

Image Credit: SPP 1992 (Patricia Klein)

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