Now, maybe you’ve probably heard, and read, a lot of crazy stories and theories involving aliens, extraterrestrials, and possible life outside planet Earth. But the biggest catch is: it is possible. And we have some exoplanets to prove that!
But what exactly makes an exoplanet habitable? According to NASA, a planet can be considered habitable if it has what it takes to sustain life for a period of time. Like drinkable water sources, atmosphere that allows unaided breathing, and climates that don’t reach extreme temperatures.
The planet usually resides in what’s called the habitable zone; not too close to their host star as to make the planet’s surface unbearably hot, and not too far away from the host star to freeze the planet.
Now that you know the requirements to classify habitable exoplanets, we have gathered a list of some of them that might become the next Earth.
Check them out:
- Proxima Centauri b
- Ross 128 b
- Tau Ceti f
- Wolf 1061 c
- Teegarden’s Star b
Proxima Centauri b
Proxima Centauri b orbits around the habitable zone of the red dwarf star Proxima Centauri (the closest star to the Sun and part of a triple star system).
The exoplanet was discovered in August 2016 by using the radial velocity method, where periodic Doppler shifts of the parent star’s spectral lines suggest an orbiting object.
The Proxima Centauri (the habitable zone where it orbits around), with the correct planetary conditions and atmospheric properties, may present the existence of liquid water on the surface of the planet, which makes the Proxima Centauri b exoplanet habitable.
In 1935, Murray Leinster’s short story “Proxima Centauri” puts human travelers into the Proxima Centauri system. The story received mixed reviews, but caught the eye of Isaac Asimov, who talks about it in the anthology Before the Golden Age.
Plus, Stephen Baxter predicted the existence of Proxima b three years before it was actually discovered with his book, Proxima!
Ross 128 b
Ross 128 b is an earth-sized exoplanet orbiting within the inner habitable zone of the red dwarf Ross 128.
It was found using a decade’s worth of radial velocity data from the European Southern Observatory’s HARPS spectrograph (High Accuracy Radial Velocity Planet Searcher) at the La Silla Observatory in Chile.
Ross 128 b’s orbital patterns haven’t been completely confirmed, but it tends to stay within its habitable zone. However, if it has an Earth-like atmosphere, the planet could distribute the energy received from the star around the planet to allow more areas to potentially hold liquid water.
Tau Ceti f
Tau Ceti f is a super-Earth or mini-Neptune orbiting Tau Ceti.
This exoplanet was discovered in 2012 by statistical analyses of the star’s variations in radial velocity, based on data received by HIRES, APPS, and HARPS.
In October 2020, Tau Ceti f was confirmed to be the most potentially habitable exoplanet orbiting a Sun-like star.
The exoplanet has an estimated equilibrium temperature of only 190 Kelvin. But with a thicker atmosphere and a larger ocean, the temperature could be similar to Earth’s.
The Tau Ceti system has fascinated science fiction writers for decades, as it has been a part of literature by Arthur Clarke, Dan Simmons, Lois McMaster Bujold, and most recently, Andy Weir with Project Hail Mary.
Wolf 1061 c
Orbiting within the habitable zone of the red dwarf star Wolf 1061 in the constellation Ophiuchus, Wolf 1061 c is the fifth-closest known potentially habitable zone, classified as a super-Earth.
Since it is so close to its star and possibly tidally locked, the results show that on one side, it is permanently facing the star and the other side permanently facing away.
This could mean the existence of an extreme variations of temperatures, but the terminator line that separates the illuminated side and the dark side could potentially be habitable, as the temperature there could be suitable for liquid water to exist.
A larger portion of the exoplanet could also be habitable if it has a thick enough atmosphere to facilitate heat transfer away from the side facing the star.
image from Wikipedia
Teegarden’s Star b
An exoplanet discovered in July 2019 by a peer-review article in Astronomy & Astrophysics published by Mathias Zechmeister and more than 150 other scientists.
This peer-review was published as a part of the CARMENES survey, supporting the existence of two candidate exoplanets orbiting Teegarden’s Star.
The radial velocity method detected possible habitable exoplanets due to the Teegarden Star’s alignment and faintness. After three years of observation, two periodic radial velocity signals emerged from Teegarden’s Star b at 4.91 days.
It orbits around the habitable zone of its host star, indicating the possibility of existing stable liquid water on the surface, thanks to its atmospheric composition.
The host star’s composition also bodes well for the exoplanet’s habitability. Most red dwarfs emit powerful flares, which can strip off other planets’ atmospheres and cause them to be uninhabitable. However, Teegarden’s Star is relatively quiet and inactive, making Tegarden’s Star b a good candidate for human life.
New Habitable Exoplanets Everyday!
In July 2020, an article at the Science Daily News reported a study from the University of Arizona that pinpointed the existence of methane in plumes of Saturn’s moon Enceladus, the sixth-largest moon of Saturn, measured by the Cassini spacecraft on Saturn’s icy moon.
This could be a sign of possible life on the moon since the information received by Cassini is compatible with the characteristics of a habitable environment.
So there might be a potentially hospitable exoplanet closer than we think!
If you liked this article, I highly suggest you check out Nasa’s Exoplanet Exploration website. It has a lot of cool facts and an expansive exoplanet catalog.