Astronomers have discovered a "super-Earth," a world larger than our planet, orbiting a star about 137 light-years away. The second planet is thought to be the same size as Earth and may also orbit the same star.
The super-Earth exoplanet, known as TOI-715b, orbits a red dwarf star that is cooler and smaller than the Sun. Astronomers discovered the planet using NASA's TESS (Transiting Exoplanet Survey Satellite) mission. A study detailing the findings was published in the January issue of the Monthly Notices of the Royal Astronomical Society.
The researchers determined that the planet is estimated to be one and a half times as wide as Earth, and it would only take a little over 19 Earth days to orbit its star. The planet is close enough to its star to exist within the habitable zone, or far enough from the star to provide the planet with a suitable temperature for the presence of liquid water on its surface.
Habitable zones are usually calculated based on factors such as the size, temperature, and mass of the star, as well as the reflectivity of the planet's surface. But the errors associated with these factors can be so large that they cast doubt on whether the planet is really in the habitable zone, said Dr Georgina Dr. Durlansfeld, lead author of the study and a postdoctoral fellow at the University of Birmingham's School of Physics and Astronomy. United Kingdom.
Astronomers believe that TOI-715b exists in a narrower and more optimized region around the star, called the conserved habitable zone, which is unlikely to be affected by the margin of error.
"This discovery is exciting because it is the first super-Earth discovered by TESS in a conserved, habitable zone," De Lansfeld said. In addition, due to the relatively close proximity, the system is suitable for further atmospheric surveys. ”
Since its launch in 2018, TESS has helped astronomers discover the planets around relatively close stars, which are planetsSuitable for follow-up observations through ground-based and space-based observatories.
"This allows us to gain a clearer picture of the diversity of exoplanetary systems orbiting various star types," Drasfeld said. ”
Telescopes can capture diminutions of starlight, which indicate that a planet is passing in front of its star, and these diminutions of starlight are known as transits. TOI-715b is closer to its star and orbits faster, meaning that the planet often passes in front of its star or transits its sun. Therefore, this exoplanet is the best candidate for future observations by the James Webb Space Telescope. The Webb telescope observes the universe through infrared light, which is invisible to the human eye, and can peek inside the planet's atmosphere.
As a planet passes by a star, the starlight passes through the star, allowing Webb to look for evidence of the atmosphere and even determine the composition of the planet's atmosphere. Knowing if planets have atmospheres can shed more light on whether they are potentially habitable for life.
"We really wanted to understand the mass of this planet with high precision to see if it was a true super-Earth or a member of the novel Ocean World category," Dransfeld said. He was referring to moons such as Jupiter's Europa or Saturn's Enceladus, which have the world's oceans. "This will allow us to really develop follow-up surveys and learn more about the demographics of the entire exoplanet. ”
To confirm the existence of a second planet, possibly the same size as Earth, researchers would need to make more successful observations of the planet's transit at different wavelengths of light, Dransfeld said.
If confirmed, the Earth-sized planet will be the smallest planet ever discovered by TESS in the habitable zone.
Red dwarfs are the most common stars in our galaxy, and many of them have been found to have small rocky worlds, such as the recently discovered Tripste system and its seven planets, located 40 light-years away. Planets closer to these smaller, colder stars may receive enough heat to be potentially habitable.
But a key question is whether these planets are close enough to be hit by stellar flares and radiation, which could erode their atmospheres, evaporate water, and limit their habitability for life.
The star of TOI-715b has only had a few flares in the past two years and is therefore not considered active, so it is an old star, Drensfeld said.
In the future, astronomers want to have the ability to search for planets around stars that are more similar to the Sun, which will require the ability to block out intense starlight to find faint Earth-sized planets.
Upcoming missions such as the European Space Agency's plato (Planetary Transits and Stellar Oscillations) will carry 26 cameras to study terrestrial planets in the habitable zone orbiting a sun-like star. The mission is expected to launch in 2026.
So far, no telescope has been able to do this, but it should be possible in the next ten years," Drensfeld said of Plato. "This will be one of the most anticipated discoveries, as it will begin to show us just how common planets that are truly similar to Earth are. ”