The red dwarfs that make up almost 70% of the stellar population of the Milky Way are notably dimmer and smaller than the sun. So, the habitable zones of these stars, the range of the orbital distance where liquid water could be steady on the surface of a world, lie way closer in than they are in sun-like systems.
Habitable-zone red dwarf planets are tidally locked, which is not a good thing for habitability, as it can leave the world with a fright nightside and a scorching dayside. But in the case of a thick atmosphere, the heat can be globally distributed and mitigate extreme temperatures.
However, the newfound planets around GJ299A and GJ180, known as GJ299A c and GJ180 d respectively, orbit sufficiently enough to avoid tidal locking. The team members confirmed. This makes GJ 180 d a unique world. As per the team leader of the Carnegie Institution for Science in Washington, D.C., Fabo Feng, GJ180 d is the closest temperate super-earth that isn’t tidally locked to the star, which boosts its likelihood of supporting and hosting life. This super-Earth is slightly bigger than the Earth and has at least 7.5 times the Earth’s mass.
On the other hand, GJ299A is another super-Earth and is probably 7.9 times the Earth’s mass. GJ180 d finished one orbit in 106 Earth days while GJ299A c takes 122 Earth days for the same. GJ229 A c resides in a binary system containing a brown dwarf (which is called GJ229B) and a red dwarf. Brown dwarfs are bigger than the gas-giant planets but are too small to go through fusion reactions in the core. It is why they are also called failed stars.
Just like the name GJ180 d indicates, it is not a single world in its system. The astronomers had discovered two planets orbiting the red dwarf, GJ180 c, and GJ180 b previously. Although astronomers do not know much about these two newfound super-earths, they may learn a lot soon. Because these two planets are not too far from our solar system, they make high targets for research through substantial future investments like James Webb Space Telescope by NASA, which will launch next year.
Feng said that their discovery adds to the list of planets that could be imaged by the telescopes next generation. He said that ultimately they are working towards finding whether the planets orbiting close to stars host life. According to Jeff Crane of the Carnegie Institution, they eventually want to make a map of every world orbiting the nearest star to our solar system, specifically the ones that are possibly habitable.
Another newly discovered GJ 433 d or the cold Neptune does not seem to be a suitable candidate for life, but it is unusual for other reasons. Firstly, this planet is 4.9 times the size of Earth and orbits dims red dwarf that is only 29.5 light-years away from the Earth. Feng noted that GJ 433 d is the widest, coldest, and nearest Neptune-like planet detected until now. He also said that the alien world is a great candidate for the follow-up study that includes direct imaging.
These discoveries were made after researchers reanalyzed the data collected by the ESO’S (European Southern Observatory) UVES (Ultraviolet and Visual Echelle Spectrograph) instrument during the survey from 2000 to 2007 of almost thirty-three nearby red dwarfs. These were radial-velocity measures or observations that can reveal the stellar motion caused due to gravitational tugs of orbiting planets.
The team supplemented UVES data with measurements made by three other instruments – ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile, Carnegie Planet Finder Spectrograph (PFS) at Las Campanas Observatory in Chile, and High Resolution Echelle Spectrometer (HIRES) at the Keck Observatory in Hawaii. As a result, five newfound alien planets and eight unconfirmed exoplanet candidates were detected.
Teagarden Star b -Teagarden Star b was discovered in 2019 and is a kind of rocky exoplanet known as super-Earth. This planet orbits its star in 4.9 Earth day and weighs 1.05 times more than our world. This star system is just 12.5 light-years away from the Earth.
Teagarden Star c – It was discovered in 2019 alongside Teagarden Star b and is also possibly a rocky super-Earth. Teagarden Star c has an orbital time of 11.4 Earth days as well as a mass of 1.11 times the Earth. This star system is just 12.5 light-years away from the Earth.
K2-72 e was discovered in 2016 and orbited the K2072 star of the Aquarius constellation. It is an M-Warm Terran, rocky exoplanet only 217 light-years away from the Earth. Proxima Centauri b – It orbits the closest stellar neighbor of the Earth, Proxima Centauri, which is 4.22 light-years away. Proxima Centauri b is 1.27 heavier than the Earth and takes 11.2 Earth days to orbit its star. The scientists announced Proxima Centauri b in 2016.
Wolf 1061 c – This planet takes only 17.9 Earth days to orbit its M-type star, which lies 14 light-years away from the Earth. It has a significant mass, almost 3.41 times the Earth’s. Tau Ceti f – It is a super-Earth exoplanet that orbits a G-type star every 1.7 Earth years. The star is visible from the Earth and sits only 12 light-years away. It has a mass of almost 3.93 times the Earth’s. However, scientists have questioned Tau Ceti f’s and its neighbor’s habitable status. Then, a 2015 study claimed that this label was generous as the exoplanets did not enter habitable zone until under a billion years and cosmically recently.
TRAPPIST – 1 d – Scientists discovered Trappist – 1 way back in 1999. But it was only in 2016 that they discovered its surrounding exoplanets. This star system is only 40 light-years away from the Earth. Some data suggest that this planet may possess a ring of water around its terminator or the line, which demarcates the chilly night side and the warm day side of the planet. TRAPPIST – 1 f – Revolving around TRAPPIST – 1, this planet takes 9.4 Earth days to do so and weighs .68 times of the Earth.
TRAPPIST – 1 e – It is the fourth one out of the TRAPPIST – 1 exoplanets as well as the second one within the habitable zone. In 2018, a paper was published, which suggests that this planet may have an iron core like the Earth and, thus, may possess a protective magnetosphere. TRAPPIST – 1 g – It is the largest TRAPPIST – 1 exoplanet, as well as the sixth from TRAPPIST – 1. It is thought to possess an atmosphere that is not rich in hydrogen. That means that it has evolved over a period of millions of years. Also, this means that it may be a rocky body, just like its TRAPPIST – 1 neighbors.
GJ 667C c- This rocky world is amongst the six exoplanets revolving around GJ 667C and also the only one that lies in the habitable zone. It completes the orbit in 28.1 Earth days and is 3.8 times heavier than the Earth. It is 22 light-years away from us and debuted in 2011. GJ 667C e – This planet takes 62 Earth days to circle its star, as well as it is 2.7 Earth’s mass. It is one of the three worlds that orbit the star GJ 667C. Because this star is located 22 light-years away from the Earth, it is not visible from the Earth. GJ 667C f – This planet also has 2.7 times the Earth’s mass but completes its orbit around GJ 667C in 39 Earth days.
GJ 1061 c – It is amongst the three exoplanets that orbit the red dwarf star Gliese 1061. This star lies almost 12-light years away from our planet and is the twentieth nearest star to the Earth. GJ 1061 c takes 6.7 Earth days to complete one orbit. GJ 1061 d – GJ 1061 d orbits the star Gliese 1061, which can be detected in the Horologium constellation. It takes 12.4 Earth days for this planet to circle its star. GJ 3323 b – It takes 5.4 days for this super-Earth to complete one orbit around its M-type star. GJ 3323 b has a mass 2.02 times the Earth’s and is nearly 12 light-years from the Earth.
Kepler – 186 f – It was the first exoplanet of the size of the Earth found in a habitable zone and had an orbit of one hundred and thirty Earth days and is nearly 10% larger than the Earth. It seems like Kepler – 186 f would be a good candidate to have liquid water, and probably life. However, it is 490 light-years away from the Earth, in the Cygnus constellation.
Kepler-62 f – This planet circles around Kepler-62, nearly 1,200 light-years away from the Earth. As per recent research, astronomers believe that this exoplanet may be water-world, similar to the Earth. It is almost 1.4 times bigger than the Earth. Kepler-1229 b – It orbits a K-type star. However, this super-Earth takes almost 86.8 days to complete an orbit around an orange dwarf, Kepler- 1229 that is 770 light-years away from the Earth.
Life on other planets than the Earth has fascinated humans for thousands of years. There are endless questions regarding the same, which need years of research and practice. But one thing is imperative to support life on any planet – water. Other factors that determine whether a world can support growth are its size, orbiting period, distance from its star, and the star type it is revolving around.
The recent discovery of TOI 770 d and the usage of advanced technologies may help us know more about the unknown worlds out there. Whatever we are going to discover is definitely going to be intriguing and unexpected.