Scientists spot smallest planet outside our solar system

Scientists have discovered one of the tiniest planets ever outside our solar system, a scorching-hot globe about the size of Mars and about as dense as pure iron that orbits its star every eight hours. 

The researchers announced on Thursday that they were able to detect the planet, which is only 31 light years away from Earth, and deduce some of its key characteristics, demonstrating recent advances in the ability to characterise smaller-sized planets beyond our solar system.

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Exoplanets, as these alien worlds are known, have intrigued scientists’ as potential habitats for life. GJ 367b, a newly discovered one with ferocious surface temperatures and possibly a molten lava surface on the side facing its star, cannot harbour life, they said. Other small exoplanets discovered and studied using the same methods, on the other hand, may turn out to be good candidates for sustaining extraterrestrial life. 

Scientists have turned their attention to characterising exoplanets more precisely a quarter century after the first discoveries, in order to gain a better understanding of their diversity, which ranges from large gas giants like Jupiter to smaller rocky Earth-like planets where life could thrive.

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“Gas giants such as Jupiter, as we know it, are not habitable because they have more extreme temperatures, weather, pressures and a lack of essential building blocks to support life,” astronomer Kristine Lam of the Institute of Planetary Research at the German Aerospace Center (DLR), lead author of the study published in the journal Science, told India Today. 

“Unlike gas giants, small terrestrial worlds like Earth are more temperate and consist of important ingredients, such as liquid water and oxygen, to harbor life forms. Although not all terrestrial exoplanets are habitable, searching for smaller worlds and identifying the type of planets they are can help us understand how planets were formed, what makes a planet habitable and if our solar system is unique,” Lam added.

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GJ 367b is the tiniest exoplanet ever discovered and studied. It measures about 5,600 miles (9,000 kilometres) in diameter, compared to Earth’s 7,900 miles (12,700 kilometres) and Mars’ 4,200 miles (6,800 kilometres). It has a mass of 55% that of Earth and is much denser, resembling pure iron. GJ 367b is composed of 86% iron, with an interior structure similar to Mercury, the closest planet to our sun, according to the researchers.

They’re wondering if the planet’s core was once encased in an outer mantle.”Perhaps like Mercury, GJ 367b could have experienced an episode of giant impact which stripped away the mantle, leaving behind a large iron core. Or maybe the exoplanet is a remnant of a Neptune or super-Earth sized gaseous planet, where the atmosphere of the planet has completely blown away as the planet is blasted by a large amount of radiation from the star,” Lam said.According to astronomer and study co-author Szilard Csizmadia, also of the DLR’s Institute of Planetary Research, it orbits very close to a red dwarf star that is smaller, cooler, and less luminous than our sun – more than 99% closer than Earth’s distance to the sun. 

GJ 367b orbits its star once every 7.7 hours, putting it in the “ultra-short period” category of exoplanets that orbit their stars in less than 24 hours. With surface temperatures of about 2,700 degrees Fahrenheit, one side of GJ 367b is likely to face its star at all times (1,500 degrees Celsius).”This temperature is high enough to evaporate any atmosphere that GJ 367b might have had in the past, as well as melting any silicate rocks and metallic iron on the planet,” Lam said.