TESS finds inviting world sized between Earth and Venus

The use of observations by NASA’s TESS (Transiting Exoplanet Survey Satellite) and several other instruments, two international teams of astronomers have discovered a planet between the sizes of Earth and Venus only 40 light-years away. Several factors make it a candidate well-suited for further study using NASA’s James Webb Space Telescope.

TESS stares at a tidy swath of the sky for approximately a month at a time, tracking the brightness changes of tens of thousands of stars at intervals ranging from 20 seconds to 30 minutes. Detecting transits—brief, periodic dimmings of stars caused by the passage of orbiting worlds—is one of the mission’s primary goals.

“We have now found the closest, transiting, temperate, Earth-sized world discovered to date,” said Masayuki Kuzuhara, a mission assistant professor at the Astrobiology Center in Tokyo, who co-led one research team with Akihiko Fukui, a mission assistant professor at the University of Tokyo. “Although we do not yet know whether it has an atmosphere, we have been thinking of it as an exo-Venus, with the same size and energy received from its host star as our planetary neighbor in the solar system.”

The host star called Gliese 12, is a faint red dwarf located nearly 40 light-years away in the constellation Pisces. The star is only about 27% of the Sun’s size, with about 60% of the Sun’s surface temperature. The newly discovered world, named Gliese 12 b, orbits every 12.8 days and is Earth-sized or slightly smaller—comparable to Venus. Assuming it has no atmosphere, the planet has a surface temperature estimated at around 107 degrees Fahrenheit (42 degrees Celsius).

Astronomers note that the small sizes and low masses of red dwarf stars make them ideal for discovering Earth-sized planets. A smaller star produces a deeper dimming for each transit, and a lower mass means an orbiting planet can induce a larger reflex motion of the star. These effects make smaller planets easier to detect.

The lower luminosities of red dwarf stars also mean their habitable zones—the range of orbital distances where liquid water could exist on a planet’s surface—lie closer to them. This makes it easier to detect transiting planets within habitable zones around red dwarfs than around stars that emit more energy.

The gap between Gliese 12 and the unusual planet is just 7% of the distance between Earth and the sun. The planet receives 1.6 times more energy from its host star as Earth does from the sun and about 85% of what Venus experiences.

“Gliese 12 b represents one of the best targets to study whether Earth-sized planets orbiting cool stars can retain their atmospheres, a crucial step toward understanding habitability on planets across our galaxy,” said Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland in Australia. He co-led a separate research team with Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London.

Each and every teams imply that studying Gliese 12 b would possibly perchance perchance perchance succor free up some aspects of our have solar system’s evolution.

“It is known that Earth’s and Venus’s first atmospheres were stripped away and then replenished by volcanic outgassing and bombardments from residual material in the solar system,” Palethorpe said. “Earth is habitable, but Venus is not due to its total lack of water. Because Gliese 12 b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability pathways planets take as they form.”

One crucial factor in retaining an atmosphere is the storminess of its host star. Red dwarfs tend to be magnetically active, leading to frequent, intense X-ray flares. However, analyses by both teams show that Gliese 12 exhibits no signs of harmful behavior.

A paper led by Kuzuhara and Fukui appears in The Astrophysical Journal Letters. The Dholakia and Palethorpe findings were published in Monthly Notices of the Royal Astronomical Society on the same day.

In some unspecified time in the future of a transit, the host significant individual’s gentle passes via any atmosphere. Different gas molecules rob up completely different colors, so the transit affords a predicament of chemical fingerprints that would possibly perchance perchance perchance additionally be detected by telescopes treasure Webb.

“Everyone knows of only a handful of temperate planets similar to Earth that are both close enough to us and meet the various criteria needed for this type of observation, called transmission spectroscopy, using advanced instruments,” said Michael McElwain, a research astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-author of the Kuzuhara and Fukui paper. “To better understand the diversity of atmospheres and evolutionary outcomes for these planets, we need more examples like Gliese 12 b.”

TESS is a NASA Astrophysics Explorer mission managed by NASA Goddard and operated by MIT in Cambridge, Massachusetts. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes, and observatories worldwide are participants worldwide are involved in the mission.