NASA Discovery Alert: A “Super-Earth” in the Habitable Zone Only 137 Light-Years Away

A new super-Earth, TOI-715 b, found 137 light-years away could harbor conditions for life, orbiting within the habitable zone of a red dwarf star. A possible second Earth-sized planet in the same system suggests a rich area for further study.

Discovery of a Super-Earth

Astronomers have identified a “super-Earth” exoplanet that merits further examination, orbiting a small, reddish star that is, by astronomical standards, fairly close to us – only 137 light-years away. This system may also contain a second planet, about the size of Earth.

Key Facts About the Planetary System

The bigger planet, dubbed TOI-715 b, is about one and a half times as wide as Earth, and orbits within the “conservative” habitable zone around its parent star. That’s the distance from the star that could give the planet the right temperature for liquid water to form on its surface.

Several other factors would have to line up, of course, for surface water to be present, especially having a suitable atmosphere. But the conservative habitable zone – a narrower and potentially more robust definition than the broader “optimistic” habitable zone – puts it in prime position, at least by the rough measurements made so far.

The smaller planet could be only slightly larger than Earth, and also might dwell just inside the conservative habitable zone.

This illustration shows one way that planet TOI-715 b, a super-Earth in the habitable zone around its star, might appear to a nearby observer. Credit: NASA/JPL-Caltech

Advances in Exoplanet Research

Astronomers are beginning to write a whole new chapter in our understanding of exoplanets – planets beyond our solar system. The newest spaceborne instruments, including those onboard NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NASA’s James Webb Space TelescopeThe James Webb Space Telescope (JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope. It covers longer wavelengths of light, with greatly improved sensitivity, allowing it to see inside dust clouds where stars and planetary systems are forming today as well as looking further back in time to observe the first galaxies that formed in the early universe.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>James Webb Space Telescope, are designed not just to detect these distant worlds, but to reveal some of their characteristics. That includes the composition of their atmospheres, which could offer clues to the possible presence of life.

The recently discovered super-Earth, TOI-715 b, might be making its appearance at just the right time. Its parent star is a red dwarf, smaller and cooler than our Sun; a number of such stars are known to host small, rocky worlds. At the moment, they’re the best bet for finding habitable planets.

These planets make far closer orbits than those around stars like our Sun, but because red dwarfs are smaller and cooler, the planets can crowd closer and still be safely within the star’s habitable zone. The tighter orbits also mean those that cross the faces of their stars – that is, when viewed by our space telescopes – cross far more often.

In the case of planet b, that’s once every 19 days, a “year” on this strange world. So these star-crossing (“transiting”) planets can be more easily detected and more frequently observed.

That’s the case for TESS (the Transiting Exoplanet Survey Satellite), which found the new planet and has been adding to astronomers’ stockpile of habitable-zone exoplanets since its launch in 2018. Observing such transits for, say, an Earth-sized planet around a Sun-like star (and waiting for an Earth year, 365 days, to catch another transit) is beyond the capability of existing space telescopes.

Potential for Further Discovery

Planet TOI-175 b joins the list of habitable-zone planets that could be more closely scrutinized by the Webb telescope, perhaps even for signs of an atmosphere. Much will depend on the planet’s other properties, including how massive it is and whether it can be classed as a “water world” – making its atmosphere, if present, more prominent and far less difficult to detect than that of a more massive, denser and drier world, likely to hold its lower-profile atmosphere closer to the surface.

If the possible second, Earth-sized planet in the system also is confirmed, it would become the smallest habitable-zone planet discovered by TESSLaunched on April 18, 2018, aboard a SpaceX Falcon 9 rocket, NASA’s Transiting Exoplanet Survey Satellite (TESS) is a space telescope mission to search nearby stars for undiscovered worlds with a goal of discovering thousands of exoplanets around nearby bright stars.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>TESS so far. The discovery also exceeded early expectations for TESS by finding an Earth-sized world in the habitable zone.

An international team of scientists led by Georgina Dransfield of the University of BirminghamFounded in 1825 as the Birmingham School of Medicine and Surgery, the University of Birmingham (informally Birmingham University) is a public research university located in Edgbaston, Birmingham, United Kingdom. It is a founding member of both the Russell Group, an association of public research universities in the United Kingdom, and Universitas 21, an international network of research-intensive universities. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>University of Birmingham, United Kingdom, published a paper in January 2024 on their discovery, “A 1.55 R_⊕ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole,” in the journal, “Monthly Notices of the Royal Astronomical Society.” An international array of facilities used to confirm the planet included Gemini-South, Las Cumbres Observatory telescopes, the ExTrAThe French national Exoplanets in Transits and their Atmospheres (ExTrA) project is comprised of three 60-centimeter telescopes located at ESO’s La Silla Observatory in northern Chile. ExTrA searches for Earth-sized worlds around stars by looking for slight dips in light from a star.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>ExTrA telescopes, the SPECULOOS network, and the TRAPPIST-south telescope.

Reference: “A 1.55 R⊕ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole” by Georgina Dransfield, Mathilde Timmermans, Amaury H M J Triaud, Martín Dévora-Pajares, Christian Aganze, Khalid Barkaoui, Adam J Burgasser, Karen A Collins, Marion Cointepas, Elsa Ducrot, Maximilian N Günther, Steve B Howell, Catriona A Murray, Prajwal Niraula, Benjamin V Rackham, Daniel Sebastian, Keivan G Stassun, Sebastián Zúñiga-Fernández, José Manuel Almenara, Xavier Bonfils, François Bouchy, Christopher J Burke, David Charbonneau, Jessie L Christiansen, Laetitia Delrez, Tianjun Gan, Lionel J García, Michaël Gillon, Yilen Gómez Maqueo Chew, Katharine M Hesse, Matthew J Hooton, Giovanni Isopi, Emmanuël Jehin, Jon M Jenkins, David W Latham, Franco Mallia, Felipe Murgas, Peter P Pedersen, Francisco J Pozuelos, Didier Queloz, David R Rodriguez, Nicole Schanche, Sara Seager, Gregor Srdoc, Chris Stockdale, Joseph D Twicken, Roland Vanderspek, Robert Wells, Joshua N Winn, Julien de Wit and Aldo Zapparata, 18 May 2023, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad1439