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A globe larger than our planet, dubbed a “super-Earth,” has been found by astronomers orbiting a star some 137 light-years away. It’s possible that another planet, roughly the size of Earth, is circling the same star. The red dwarf star that TOI-715b, a super-Earth exoplanet, orbits is smaller and colder than our sun. Using NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, astronomers were able to identify the planet. January saw the publication of a study describing the discovery in the Monthly Notices of the Royal Astronomical Society. It takes the planet, which is thought to be 1.5 times wider than Earth, just over 19 Earth days to complete one orbit of its star, according to research. The planet is within the habitable zone—the range of a star’s temperature at which a planet can support liquid water on its surface—because it is close enough to the star to be in the habitable zone.

The size, mass, and temperature of a star as well as the surface reflectance of a planet are often used to determine the habitable zone. However, there may be significant error margins connected to these variables, raising concerns about whether a planet actually exists in the habitable zone, according to lead study author Dr. Georgina Dransfield, a postdoctoral scholar at the School of Physics and Astronomy at the University of Birmingham in the United Kingdom.

It is thought that TOI-715b is located in the conservative habitable zone, a more optimum and narrower area around the star that is less likely to be impacted by error margins. The fact that this is the first super-Earth discovered by TESS inside the conservative habitable zone makes the discovery fascinating, according to Dransfield. “In addition, the system is appropriate for additional atmospheric investigations due to its proximity.”

The planet hunter TESS

TESS has aided astronomers in identifying planets orbiting relatively nearby stars that are suitable for additional studies using space- and ground-based telescopes since its launch in 2018.

“This is giving us a much better understanding of the variety of exoplanetary systems circling a wide variety of star types,” stated Dransfield. Transits are the name for the dips in starlight that telescopes can detect, which show that a planet is passing in front of its star. Due to its near proximity to its star and short orbit, TOI-715b often transits—that is, passes in front of its star. Consequently, the exoplanet is a prime target for upcoming James Webb Space Telescope studies. The Webb telescope can see inside planets’ atmospheres and observe the universe in infrared light, which is invisible to the human eye.

Starlight pierces the planet’s orbit around the star, enabling Webb to search for signs of an atmosphere and potentially identify the composition of the planet’s atmosphere. Furthermore, knowing whether a planet has an atmosphere can help us learn more about whether or not life could exist there.

Dransfield stated, “We really want to know the planet’s mass with high precision to understand if it’s a true super-Earth or a member of the novel category of ocean worlds,” referring to moons of Jupiter and Saturn that have global seas, such Enceladus and Europa. “This will enable us to gain more insight into the overall demographics of exoplanets and truly shape our follow-up investigations.” Researchers need to successfully observe the planet’s transits at several light wavelengths in order to prove the existence of the likely Earth-sized second planet, according to Dransfield.The Earth-sized planet will be the smallest planet discovered by TESS in a habitable zone if it is verified.

The hunt for planets similar to Earth

The majority of stars in our galaxy are red dwarfs, and many of them have been found to be home to small, rocky planets. One such system is the recently discovered TRAPPIST system, which is 40 light-years away and has seven planets. Closer orbiting planets may receive enough heat from these smaller, cooler stars to be possibly habitable. The proximity of these planets to radiation and solar flares, which could weaken their atmospheres, evaporate water, and restrict their capacity to support life, is a crucial question.

The star TOI-715b is thought to be elderly because it hasn’t produced many flares in the last two years and isn’t thought to be active.

In the future, astronomers expect to be able to look for planets orbiting stars that resemble our sun more closely. To identify faint Earth-sized planets, they will need to be able to block bright starlight. In order to investigate Earth-like planets in habitable zone orbits around sun-like stars, upcoming missions like the European Space Agency’s PLATO, or PLAnetary Transits and Oscillations of stars, will be equipped with 26 cameras. Launch of the mission is scheduled for 2026. Referring to PLATO, Dransfield stated, “So far, no telescope has been capable of this, but it should be possible within the next decade.” “One of the most expected discoveries will be this one, as it will start to reveal how similar planets are to Earth in real life.”

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