They discovered a potentially habitable “super-Earth” 137 light years away

(CNN) — Astronomers have discovered a “super-Earth”, a world larger than our planet, orbiting a star about 137 light years away. Another Earth-sized planet could also be orbiting the same star.

The super-Earth exoplanet, known as TOI-715b, orbits a red dwarf star that is cooler and smaller than our Sun. Astronomers discovered the planet thanks to NASA’s TESS (Transiting Exoplanet Survey Satellite) mission. A study about the discovery was published in the journal Monthly Notices of the Royal Astronomical Society in January.

Researchers have determined that the planet, which is estimated to be one and a half times the width of our planet, takes just over 19 Earth days to complete one orbit around its star. The planet is close enough to its star to be in the habitable zone, that is, at a distance far enough from the star that the planet gets the right temperatures for liquid water to exist on its surface.

The habitable zone is usually calculated based on factors such as a star’s size, temperature, and mass, as well as the reflectivity of the planet’s surface. But there can be a large margin of error associated with these factors, raising questions about whether a planet actually resides in the habitable zone, said Dr. Georgina Dransfield, lead author of the study and a postdoctoral researcher in the School of Physics and Astronomy at the university. They say. of Birmingham, United Kingdom.

Astronomers believe TOI-715b exists in a narrower, more optimal region around the star known as the conservative habitable zone, which is less likely to be affected by the margin of error.

“This discovery is exciting because it is the first super-Earth discovered by TESS within the conservative habitable zone,” says Dransfield. “Also, being relatively close, the system is suitable for future atmospheric research.”

TESS, planet hunter

Since its launch in 2018, TESS has helped astronomers detect planets around relatively nearby stars, suitable for follow-up observations with ground-based and space-based observatories.

“This allows us to get a much clearer picture of the diversity of exoplanetary systems orbiting a wide range of stellar types,” Dransfield said.

Telescopes can catch the dip in starlight that indicates a planet is passing in front of its star, and that dip in starlight is called a transit. TOI-715b is close to its star and has a fast orbit, meaning the planet frequently passes, or transits, in front of its star. As a result, the exoplanet is an optimal candidate for future observations with the James Webb Space Telescope. The Webb telescope observes the universe in infrared light, which is invisible to the human eye, and can peer into planetary atmospheres.

As the planet passes the star, light from the star is filtered through it, allowing Webb to look for signs of an atmosphere and even determine the planet’s atmospheric composition. And knowing whether planets have atmospheres can reveal more about their ability to be potentially habitable for life.

“We want to know the mass of the planet very precisely to know whether it is a true super-Earth or a member of a new class of ocean worlds,” Dransfield said, referring to moons with global oceans like Europa on Jupiter. telling. , or Enceladus, on Saturn. “This will allow us to really shape our follow-up investigations and learn more about the demography of the exoplanet as a whole.”

Dransfield said that to confirm the existence of a possible second Earth-sized planet, researchers need more successful observations of the planet’s transit at different wavelengths of light.

If the existence of an Earth-sized planet is confirmed, it would become the smallest TESS has ever found in the habitable zone.

discovery of earth like planets

Red dwarf stars are the most common in our galaxy, and many of them have been found to host small rocky worlds, such as the recently discovered Trappist system, whose seven planets lie 40 light years away. Planets orbiting close to these small, cool stars could potentially get warm enough to be habitable.

But a key question is whether these planets are also close enough to be vulnerable to stellar flares and radiation, which could destroy their atmospheres, evaporate water and their ability to be habitable to life. Can be limited.

TOI-715b’s star has only shown a few flashes over the past two years and is not considered active, making it an old star, Dransfield said.

In the future, astronomers hope to have the ability to search for planets around stars like our Sun, which will require the ability to block intense starlight in order to find faint Earth-sized planets.

Upcoming missions such as the European Space Agency’s PLATO (Planetary Transit and Oscillation) will carry 26 cameras to study Earth-like planets in habitable zone orbits around Sun-like stars. The mission is scheduled to launch in 2026.

“So far, no telescope is capable of this, but within the next decade it should become possible,” Dransfield said, referring to PLATO. “This will be one of the most anticipated discoveries, as it will begin to show us how common Earth-like planets really are.”