Astronomers observe a “giant Earth” 137 light-years away

Astronomers observe a “giant Earth” 137 light-years away


An artist’s illustration depicts the “super-Earth” exoplanet TOI-715b orbiting within the habitable zone around a red dwarf star.

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Astronomers have discovered a “super-Earth,” or a world larger than our planet, orbiting a star about 137 light-years away. It is also possible that another planet, thought to be Earth-sized, orbits the same star.

The giant exoplanet, known as TOI-715b, orbits a red dwarf star that is cooler and smaller than our sun. Astronomers discovered the planet using NASA’s TESS mission, or the Transiting Exoplanet Survey Satellite. A detailed study of the discovery was published in January in the Monthly Notices of the Royal Astronomical Society.

The researchers found that the planet, which is estimated to be one and a half times wider than our planet, takes a little more than 19 Earth days to complete one orbit around its star. A planet is close enough to its star to be within the habitable zone, or the distance from the star that provides the planet with the right temperature for liquid water to exist on its surface.

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

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

“This discovery is exciting because it is the first TESS super-Earth to be found within the habitable zone,” Dransfield said. “In addition, due to its relative proximity, the system is suitable for further aerial investigations.”

Since its launch in 2018, TESS has helped astronomers discover planets around relatively nearby stars Suitable for follow-up observations using ground and space 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 pick up dips in starlight that indicate a planet passes in front of its star, and those dips in starlight are called transits. TOI-715b is close to its star and has a fast orbit, meaning the planet passes in front of or crosses its star frequently. As a result, the exoplanet is an ideal candidate for future observations using the James Webb Space Telescope. The Webb telescope sees the universe in infrared light, which is invisible to the human eye, and can peer into planetary atmospheres.

As the planet passes the star, starlight filters through, allowing Webb to search for evidence of an atmosphere and even determine the composition of the planet’s atmosphere. Understanding whether planets have atmospheres could reveal more about their potential to be habitable for life.

“We really want to know the mass of the planet with high precision to understand 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 such as Jupiter’s Europa or Saturn’s Enceladus. “This will allow us to shape our follow-up investigations and learn more about the demographics of exoplanets 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 transits in different wavelengths of light.

If an Earth-sized planet is confirmed, it will become the smallest planet in a habitable zone TESS has discovered to date.

Red dwarf stars are the most common stars in our galaxy, and a number of them have been found to host small rocky worlds, such as the recently discovered TRAPPIST system with its seven planets, located 40 light-years away. Planets orbiting closer to these smaller, cooler stars could receive enough warmth to be habitable.

But the key question is whether these planets are also close enough to be exposed to stellar flares and radiation, which could erode their atmospheres, evaporate water, and limit their ability to be habitable.

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

In the future, astronomers hope to be able to search for planets orbiting stars more similar to our Sun, which will require the ability to block intense starlight to find faint Earth-sized planets.

Upcoming missions such as the European Space Agency’s PLATO, or Planetary Star Transits and Oscillations, will carry 26 cameras to study Earth-like planets in habitable zone orbits around Sun-like stars. The mission is expected to launch in 2026.

“So far, no telescope has been able to achieve this, but it should be possible within the next decade,” Dransfield said, referring to Plato. “This will be one of the most anticipated discoveries, because it will show us how similar common planets really are to Earth.”

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