Exoplanets are planets located outside our solar system. This exoplanet, called TOI-1231 b, completes a full orbit around its star every 24 Earth days.
It orbits a red or M-type dwarf star, known as NLTT 24399, which is smaller and weaker than stars like our Sun.
The discovery of the planet was detailed in a new study that will be published in a future issue of The Astronomical Journal.
“Although TOI 1231b is eight times closer to its star than Earth is to the Sun, its temperature is similar to Earth’s temperature thanks to its cooler and less bright host star,” said co-author Diana Dragomir, an assistant professor in the University of New Mexico’s department. for physics and astronomy, in a statement.
“However, the planet itself is actually larger than Earth and slightly smaller than Neptune ̵
Why this exoplanet may have clouds
The scientists were able to determine the radius and mass of the planet, which helped them calculate its density and deduce its composition.
The exoplanet has a low density, suggesting that it is a gaseous planet rather than a rocky one like Earth, but scientists do not yet know for sure the composition of the planet or its atmosphere.
“TOI-1231b is quite similar in size and density to Neptune, so we think it has a similarly large, gaseous atmosphere,” said author Jennifer Burt, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Pasadena, California.
“TOI1231b could have a large hydrogen or hydrogen helium atmosphere or a denser water vapor atmosphere,” Dragomir said. “Each of these would point to a different origin so astronomers could understand if and how planets form differently around M dwarfs compared to, for example, the planets around our sun.”
Scientists believe that the TOI-1231 b has an average temperature of 140 degrees Fahrenheit (60 degrees Celsius), making it one of the coolest of the small exoplanets available for future study of its atmosphere.
“Compared to most planets found so far, which often have burning temperatures in the many hundreds or thousands of degrees, the TOI-1231 b is positively frigid,” Burt said.
The cooler the exoplanet is, the more likely it is to have clouds in its atmosphere.
The corresponding small exoplanet K2-18 b, discovered in 2015, was recently observed in more detail, and scientists found signs of water in its atmosphere.
“TOI-1231 b is one of the only other planets we know of in a similar size and temperature range, so future observations of this new planet will let us determine how common (or rare) it is to form. water clouds around these temperate worlds, ”Burt said in a statement.
This makes the TOI-1231 b the perfect candidate for observations from the Hubble Space Telescope – or the James Webb Space Telescope, scheduled to launch in October. Webb has the ability to look into the atmospheres of exoplanets and help determine their composition. And Hubble is scheduled to observe the exoplanet later this month.
The search for exoplanets
Burt, Dragomir, and their colleagues discovered the planet using data from NASA’s Transiting Exoplanet Survey Satellite or TESS. The planet hunting satellite, launched in 2018, observes different areas of the sky for 28 days at a time. So far, TESS has helped scientists find large and small exoplanets orbiting stars like our sun as well as the smaller M dwarf stars. These diminutive stars are common in the Milky Way galaxy.
When a planet crosses in front of its star in orbit, it blocks a certain amount of light. This is called a transit, and it is a way astronomers search for exoplanets using missions like TESS.
Given that M dwarf stars are smaller, the amount of light blocked by a planet orbiting them is larger, making transit more detectable. Researchers are looking for at least two transits before finding out if they have found a candidate for the exoplanet. Follow-up observations were made using the Planet Finder Spectrograph on the Magellan Clay Telescope at the Las Campanas Observatory in Chile.
“One of the most exciting results of the last two decades of exoplanet science is that so far none of the new planetary systems we have discovered resemble anything in our own solar system,” Burt said.
“This new planet we’ve discovered is still weird – but it’s one step closer to being something like our neighborhood planets.”