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| An artist's impression of the GJ 251 system. (Michael Marcheschi/m2design/University of California, Irvine) |
Recently, a new exoplanet candidate emerged that could be one of the best alien worlds to look for extraterrestrial life on yet.
A super-Earth with a minimum mass of around 3.84 times that of our planet, GJ 251c, is only 18 light-years away. The most thrilling aspect? It is in the habitable zone of its star, which is an orbital distance that is just right for life to exist.
According to astronomer Suvrath Mahadevan of Pennsylvania State University, "the exoplanet is in the habitable or 'Goldilocks Zone,' the right distance from its star that liquid water could exist on its surface, if it has the right atmosphere,"
The intricate combination of elements that constitute a planet where life might flourish is still being figured out by scientists, but before looking more closely at a contender, there are a few important broad traits to consider.
The first two things scientists search for are whether the planet is at a distance from its star where temperatures allow for liquid water, the so-called "solvent of life," and whether it has a solid, rocky composition like Earth, since it is the only planet that we know for sure sustains life.
Surprisingly few exoplanets in the millions of worlds found so far fit both of these criteria. Thus, a treasure among riches is one that not only checks those boxes but is also close enough for in-depth examination.
The near proximity of [GJ 251c] to its host star—just around 18 light-years away—makes it particularly useful, according to astronomer Paul Robertson of the University of California, Irvine. "Cosmically speaking, it's practically next door."
The exoplanet revolves around a red dwarf star, GJ 251, which is around one-third the mass and diameter of the Sun. The habitable zone is significantly closer to the star than the habitable zone in the Solar System since it is tiny and chilly. Because they have shorter orbits, the signals from numerous orbits are simpler to notice and stack, which can actually make it easier to find any worlds that may be hanging around there.
In an effort to find low-mass neighboring worlds that would make suitable direct imaging candidates, a group of astronomers led by UC Irvine's Corey Beard selected GJ 251 for monitoring. The exoplanet GJ 251b, a super-Earth 3.85 times Earth's mass with a 14.2-day orbit that is too near to the star for habitability, was already known to exist on this star, which is why it was selected. Additionally, astronomers have gathered data about the star for almost 20 years.
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| Animation showing how radial velocity is measured, one of the ways a planet can affect the light of its star. (Alysa Obertas/Wikimedia Commons, CC BY-SA 4.0) |
In order to supplement this data, the researchers conducted new, higher-resolution measurements to examine the star's minute movements as it is pulled by the gravitational pull of any planets orbiting it. To their great joy, they discovered evidence of a second world in the star's habitable zone, with an orbital period of 53.6 days, in addition to the signal of the existing planet.
Our knowledge about GJ 251c is quite limited. Although its mass has been measured due to the gravitational pull it has on the star, its diameter and other characteristics cannot be determined without more information because it does not pass in front of the star.
In order to supplement this data, the researchers conducted new, higher-resolution measurements to examine the star's minute movements as it is pulled by the gravitational pull of any planets orbiting it. To their great joy, they discovered evidence of a second world in the star's habitable zone, with an orbital period of 53.6 days, in addition to the signal of the existing planet.
Our knowledge about GJ 251c is quite limited. Although its mass has been measured due to the gravitational pull it has on the star, its diameter and other characteristics cannot be determined without more information because it does not pass in front of the star.
"We are at the cutting edge of technology and analysis methods with this system," Beard asserts. Because of the ambiguity of our sensors and methodologies, we are still determining the planet's status even if its finding is highly statistically significant. To directly photograph this contender, we need the newest telescopes, but we also need community support."
Whether or not GJ 251c has an atmosphere that retains heat to enable seas of water to swirl around on its surface will be revealed by the next generation of telescopes, which are tantalizingly close.
"While we can't yet confirm the presence of an atmosphere or life on GJ 251c, the planet represents a promising target for future exploration," Mahadevan continues. "We made an exciting discovery, but there's still much more to learn about this planet."
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