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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. There may also be a second planet, thought to be the size of Earth, 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 detected the planet using NASA’s TESS, or Transiting Exoplanet Survey Satellite mission. A study detailing the discovery was published in January in the Monthly Notices of the Royal Astronomical Society.
Researchers determined that the planet, which is estimated to be one and a half times as wide as our planet, takes just over 19 Earth days to complete one orbit around its star. The planet is either close enough to its star to be within the habitable zone or far enough away from a star that provides the right temperature for a planet to allow liquid water to exist on its surface.
The habitable zone is often calculated based on factors such as a star’s size, temperature, and mass, as well as the reflectivity of the planet’s surface. Lead study author Dr. But there can be large margins of error associated with these factors, which can raise the question of whether a planet is actually in the habitable zone, Georgina Dransfield said. United Kingdom.
Astronomers believe TOI-715b lies in a narrow, more favorable region around the star known as the conservative habitable zone, where it is less likely to be affected by margins of error.
“This discovery is exciting as TESS is the first super-Earth found in the conservative habitable zone,” Dransfield said. “Also, because it is relatively close, the system is suitable for further atmospheric research.”
TESS, planet hunter
Since its launch in 2018, TESS has helped astronomers detect planets around relatively nearby stars that are amenable to follow-up observations with ground- and space-based observatories.
“This allows us to get a much clearer picture of the diversity of exoplanet systems orbiting a wide variety of star types,” Dransfield said.
Telescopes can detect dips in starlight that indicate a planet is passing in front of its star, and these dips in starlight are called transits. TOI-715b has a fast orbit close to its star; This means that the planet often passes or transits in front of its star. As a result, the exoplanet is the best candidate for future observations with the James Webb Space Telescope. The Webb telescope sees the universe in infrared light invisible to the human eye and can look inside the atmospheres of planets.
As the planet passes in front of the star, starlight filters through the star, allowing Webb to look for evidence of an atmosphere and even determine the planet’s atmospheric composition. Understanding whether planets have atmospheres could reveal more about their ability to be potentially 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 the new category 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 really shape our follow-up research and learn more about exoplanet demographics as a whole.”
To confirm the existence of a possible second Earth-sized planet, researchers need more successful observations of the planet’s light transmission at different wavelengths, Dransfield said.
If confirmed, the Earth-sized planet would be the smallest planet TESS has found in the habitable zone.
Search for Earth-like planets
Red dwarf stars are the most common stars in our galaxy, and some of them have been found to host small, rocky worlds, such as the recently discovered TRAPPIST system, which has seven planets and is 40 light-years away. Planets orbiting closer to these smaller, cooler stars could potentially receive enough warmth to become habitable.
But the real question is whether these planets are also close enough to be exposed to starbursts and radiation that could erode their atmospheres, evaporate water, and limit their ability to be habitable for life.
Dransfield said TOI-715b’s star has shown only a few flashes in the past two years and is not considered active, making it a legacy star.
In the future, astronomers hope to have the ability to search for planets around stars more similar to our sun; This will require the ability to block intense starlight to find faint Earth-sized planets.
Upcoming missions like the European Space Agency’s PLATO, or PLAnetary Transits and Oscillations of stars, will carry 26 cameras to study Earth-like planets in habitable zone orbits around sun-like stars. The mission is expected to begin in 2026.
“No telescope has ever achieved 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 begin to show us how common planets that truly resemble Earth are.”
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