A "Super-Earth" called GJ 251c has recently been identified in the regular searches being carried out for possible signs of life. This one is less than 20 light years away putting it in the list of easily observed planets to look at regularly.
The planet, known as GJ 251c, orbits a red dwarf star 18.2 light-years away in the constellation of Gemini, the Twins. The planet's mass is four times greater than that of Earth, making it a 'super-Earth' — a rocky planet larger and more massive than our own.
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GJ 251c was discovered thanks to observations spanning over 20 years, during which scientists looked for a slight wobble of the world's parent star incurred by the planet's gravity. As the star wobbles ever so slightly toward and away from us, we see a Doppler shift in its radial velocity that can be measured with a spectrograph.
An interesting side note to this discovery is that there's another known planet in this system, named (brace yourself) GJ 251b. This one is a much smaller planet discovered in 2020 that orbits its star every 14 days at a distance of 7.6 million miles. By comparison, Mercury's orbit takes 88 days and it orbits our sun much farther away than GJ 251b, 36 million miles from the sun.
...Using archive data from telescopes worldwide, a team of astronomers, including Mahadevan, was able to refine the accuracy of the radial velocity measurements for planet GJ 251b
The team then combined this refined data with brand new, high-precision observations from the Habitable-Zone Planet Finder (HPF), which is a near-infrared spectrograph on the Hobby-Eberly Telescope at McDonald Observatory in Texas. This revealed a second planetary signal belonging to a four-Earth-mass world orbiting the star every 54 days. That was then confirmed by measurements with the NEID spectrograph on the 3.5-meter WIYN telescope at Kitt Peak National Observatory in Arizona.
Artist's impression of GJ 251c on the left with GJ 251b, in the middle, closer to its red dwarf star on the right. (Image credit: University of California, Irvine.)
GJ 251c is probably a bit too far away to use the James Webb Space Telescope (JWST) to search for or analyze its atmosphere. There are plans around for 30-meter-class telescopes that open other possibilities and even bigger, more specialized telescopes after that, out into the 2040s. The unmentioned elephant in the room is that red dwarf star.
At 36% of the mass of our sun, the star GJ 251 is a red dwarf. Astronomers have now found numerous rocky planets in the habitable zone of red dwarfs, including Proxima Centauri b, TRAPPIST-1e and f, and Teegarden's Star b. However, red dwarfs are notorious for having violent tempers that belie their diminutive stature, releasing regular powerful flares that can over time strip a planet of its atmosphere. For example, the JWST's observations of the inner three planets of TRAPPIST-1 find no evidence for an atmosphere, while its observations of the fourth planet, e, are so far inconclusive. Some astronomers are now growing skeptical that Earth-like worlds can thrive around red dwarfs.
The big picture is even a bit more complex than that because GJ 251 is a bit on the large side for a red dwarf, and that means the usual "Goldilocks zone" (the orbital shell where conditions are most favorable for life) is a little farther from the star and that might help.
It is possible that GJ 251c is far enough away from its star to have avoided the worst of its temper tantrums, and, if armed with a thick atmosphere and strong planetary magnetic field, it could have resisted the star's stellar wind from stripping its atmosphere away.
That makes the short version something like, "interesting, but don't sit on the edge of your seat waiting for news." The youngest of us might live long enough to see that news.
If it's over 1.5G, or the pressure's too high, or the radiation is too high (or too low) then, no, no life.
ReplyDeleteThe parameters that Earth met to start, yet alone sustain life as we know it are crazy.
Jovians that started in closer to the Sun that then moved out while cleaning the inner orbits of ash and trash. And then said jovians hanging around and cleaning up incoming ash and trash from outside the system.
A star just the right size and age and really meek in radiation activity.
A planetoidal moon of just the right size to get trapped by the planet's gravity and slow said planet's revolution and affect the water and the planetary crust (waves and flexing of the planet's crust.)
A planet, Earth, with just the right amount of heavy metals, and an active metallic core, and a functioning radiation shield, and a crust and lots of water, at just the right orbit from the local sun. And with just the right amount of gravity, not too light and not too heavy, that allowed chemicals to form at just the right gravity.
Periodic bombardments by meteor swarms to add just the right amount of spice to the planet.
And so much more.
All of that is the only reason we have life on this Earth. Almost a miracle, no?
And then to find another planet or planetoid that has 2/3rds of the 'coincidences' that the Earth had/has? Umpossible odds.