Artist's impression of the nearby planetary system with the super-Earth and another planet located closer to the star in the system (University of California, Irvine.)
A super-Earth has been discovered in the habitable zone of its planetary system
This is an exoplanet that moves around a star close to our solar system. An exoplanet that belongs to the super-Earth category and is located in the habitable zone of its parent star has been discovered at a distance of less than 20 light years, placing it high on the list of the closest and best places to search for life beyond our solar system. Astronomers use the term super-Earth (or super-Geo) to refer to planets in other star systems whose size is larger than that of Earth but smaller than that of the large gas planets of our solar system such as Uranus and Neptune. The planet, known as GJ 251c, orbits a red dwarf at a distance of 18.2 light years in the constellation Gemini. Its mass is four times that of Earth. “While we cannot yet confirm the existence of an atmosphere or life on GJ 251c, the planet is a promising target for future exploration,” said Suvrath Mahadevan, a professor of astronomy at the University of Pennsylvania. The habitable zone, also known as the “Goldilocks zone,” is the region that allows the potential development of planets where there are conditions (atmosphere, temperature and, most importantly, liquid water) friendly to the presence of life.
The discovery GJ 251c was discovered thanks to observations lasting more than 20 years, during which scientists looked for a small wobble of its parent star caused by the planet’s gravity. As the star moves slightly towards and away from us, a Doppler shift in its radial velocity is observed that can be measured with a spectrograph. There is another known planet in the same system, GJ 251b, discovered in 2020 and orbiting its star every 14 days at a distance of 12.2 million kilometers. Using archival data from telescopes around the world, a team of astronomers including Mahadevan improved the precision of their radial velocity measurements of GJ 251b. The team then combined this data with new, high-precision observations from the Habitable-Zone Planet Finder (HPF), an infrared spectrometer on the Hobby-Eberly Telescope at McDonald Observatory in Texas. They found a second signal that corresponds to a planet with a mass four times that of Earth and an orbital period of 54 days. The discovery was confirmed by measurements from the NEID spectrograph on the WIYN (3.5-meter) telescope at the Kitt Peak National Observatory in Arizona. Now that we know the planet exists, astronomers can plan future observations. GJ 251c is likely to be a little further from its star than the James Webb Space Telescope can directly detect its atmosphere. The next generation of 30-meter telescopes may be able to detect its atmosphere through reflected light, but a full analysis of the planet is expected to be possible only with the Habitable Worlds Observatory, a giant space telescope planned for launch in the 2040s. “We are at the limits of technology and resolution with this system. "We need the next generation of telescopes to directly image this candidate world," said Cory Beard of the University of California, Irvine.
The star Although GJ 251c is considered by Mahadevan to be "one of the best candidates for searching for atmospheric traces of life," there is one major issue: its star itself. With a mass equal to 36% of the Sun, GJ 251 is a red dwarf. Several rocky planets have been found in the habitable zone of such stars — including Proxima Centauri b, TRAPPIST-1e and f, and Teegarden's Star b — but red dwarfs are notorious for their powerful flares that can strip planets of their atmospheres over time. For example, James Webb’s observations of the three inner planets in the TRAPPIST-1 system have shown no evidence of an atmosphere, while the results for the fourth, TRAPPIST-1e, remain inconclusive. This has led some astronomers to question whether life-friendly planets around red dwarfs are actually possible. However, GJ 251c has an advantage. It is a little further from its star than other habitable planets around red dwarfs. This is because GJ 251 is a little more massive and hotter than most stars of its type, so the habitable zone extends further. If the planet has a thick atmosphere and a strong magnetic field, it may have withstood the flares and solar winds of its star. But that remains a hypothesis for now. "We made an exciting discovery but we still have a lot to learn about this planet," said Mahadevan.
Artist's impression of the nearby planetary system with the super-Earth and another planet located closer to the star in the system (University of California, Irvine.)
A super-Earth has been discovered in the habitable zone of its planetary system
This is an exoplanet that moves around a star close to our solar system.
An exoplanet that belongs to the super-Earth category and is located in the habitable zone of its parent star has been discovered at a distance of less than 20 light years, placing it high on the list of the closest and best places to search for life beyond our solar system.
Astronomers use the term super-Earth (or super-Geo) to refer to planets in other star systems whose size is larger than that of Earth but smaller than that of the large gas planets of our solar system such as Uranus and Neptune. The planet, known as GJ 251c, orbits a red dwarf at a distance of 18.2 light years in the constellation Gemini. Its mass is four times that of Earth.
“While we cannot yet confirm the existence of an atmosphere or life on GJ 251c, the planet is a promising target for future exploration,” said Suvrath Mahadevan, a professor of astronomy at the University of Pennsylvania. The habitable zone, also known as the “Goldilocks zone,” is the region that allows the potential development of planets where there are conditions (atmosphere, temperature and, most importantly, liquid water) friendly to the presence of life.
The discovery
GJ 251c was discovered thanks to observations lasting more than 20 years, during which scientists looked for a small wobble of its parent star caused by the planet’s gravity. As the star moves slightly towards and away from us, a Doppler shift in its radial velocity is observed that can be measured with a spectrograph.
There is another known planet in the same system, GJ 251b, discovered in 2020 and orbiting its star every 14 days at a distance of 12.2 million kilometers. Using archival data from telescopes around the world, a team of astronomers including Mahadevan improved the precision of their radial velocity measurements of GJ 251b.
The team then combined this data with new, high-precision observations from the Habitable-Zone Planet Finder (HPF), an infrared spectrometer on the Hobby-Eberly Telescope at McDonald Observatory in Texas. They found a second signal that corresponds to a planet with a mass four times that of Earth and an orbital period of 54 days. The discovery was confirmed by measurements from the NEID spectrograph on the WIYN (3.5-meter) telescope at the Kitt Peak National Observatory in Arizona. Now that we know the planet exists, astronomers can plan future observations. GJ 251c is likely to be a little further from its star than the James Webb Space Telescope can directly detect its atmosphere. The next generation of 30-meter telescopes may be able to detect its atmosphere through reflected light, but a full analysis of the planet is expected to be possible only with the Habitable Worlds Observatory, a giant space telescope planned for launch in the 2040s. “We are at the limits of technology and resolution with this system. "We need the next generation of telescopes to directly image this candidate world," said Cory Beard of the University of California, Irvine.
The star
Although GJ 251c is considered by Mahadevan to be "one of the best candidates for searching for atmospheric traces of life," there is one major issue: its star itself. With a mass equal to 36% of the Sun, GJ 251 is a red dwarf. Several rocky planets have been found in the habitable zone of such stars — including Proxima Centauri b, TRAPPIST-1e and f, and Teegarden's Star b — but red dwarfs are notorious for their powerful flares that can strip planets of their atmospheres over time.
For example, James Webb’s observations of the three inner planets in the TRAPPIST-1 system have shown no evidence of an atmosphere, while the results for the fourth, TRAPPIST-1e, remain inconclusive. This has led some astronomers to question whether life-friendly planets around red dwarfs are actually possible.
However, GJ 251c has an advantage. It is a little further from its star than other habitable planets around red dwarfs. This is because GJ 251 is a little more massive and hotter than most stars of its type, so the habitable zone extends further.
If the planet has a thick atmosphere and a strong magnetic field, it may have withstood the flares and solar winds of its star. But that remains a hypothesis for now. "We made an exciting discovery but we still have a lot to learn about this planet," said Mahadevan.