In the quest to find potentially habitable planets outside our solar system, astronomers have searched for exoplanets similar to Earth. Now scientists have discovered a new class of habitable exoplanets, Hycean planets. These are hot planets covered in oceans, and the atmosphere is rich in hydrogen. They are much easier to find and observe.
Scientist has focused their efforts on seeking moons and planets of similar atmospheric composition, temperature, mass, and size to Earth. The recent discovery could lead to the search for living organisms outside our solar system. Researchers say that finding biosignatures of life outside our solar system within the next two or three years is a real possibility.
According to researchers, based on planet densities, these planets may include mini-Neptunes, rocky planets, super-Earth, icy giants, and gas giants. As compared to previously considered habitable planets, these plants are significant. With radii as large as 2.6 R⊕ for a mass of 10 M⊕.
In The Astrophysical Journal, a study was published. According to lead study author Nikku Madhusudhan, a reader in astrophysics and exoplanetary science at Cambridge University’s Institute of Astronomy, “Hycean planets open a whole new avenue in our search for life elsewhere.” Their research leads to a detailed study of the full range of stellar and planetary properties for certain conditions that can support life. Planets are considered suitable to live when they are located within the appropriate zone to live around the stars they orbit. This zone is a sweet spot.
According to scientists, the planets beyond our solar system are known as exoplanets. Outside of our solar system, there are more than 4,000 known exoplanets which NASA’s Kepler Space Telescope mainly detected. Most of the exoplanets discovered are in a relatively small region of our galaxy. They come in a wide variety of sizes and orbits. Some of them are huge and close to their parent’s stars, by measuring these planet’s sizes and masses composition ranging from very rock to gas-rich. In the Unified Astronomy Thesaurus, 15 types of exoplanets are currently listed. They are made of elements similar to the planets in our solar system, but their mixes of those elements may vary. Some may have ice or water, and others may have iron or carbon. Lots of research are being carried out by NASA on these planets.
The 1st exoplanets were discovered in 1990. In the last 30 years, thousands of exoplanets were found; many of them are between Earth and Neptune. Now we live in a universe of exoplanets. The count is rising and could rise to the tens of thousands within a decade.
Scientists say that mini-Neptunes are more than 1.5 times the size of Earth but still smaller than Neptunes. To have a rocky interior like Earth the size is too large. Beneath their atmosphere, the temperature and pressure are too high for life to endure. Planets in the super-Earth and mini-Neptune size range may be ocean planets, having liquid-water oceans hundreds of kilometres deep. Some rocky planets may be ultra-dry carbon and rocks are formed of silicon and carbon. Many exoplanet types depend on a planet’s size and location within a stellar system, like hot Neptunes and hot Jupiters, cold Neptunes and cold Jupiters. However, recent research by Madhusudhan and his colleagues determined that this inhospitable nature isn’t always the case. Depending on size, temperature, mass some planets could be habitable.
Prof Beth Biller, who studies exoplanets at the Institute of Astronomy at Edinburgh University, said so much diversity can be seen in exoplanets discovered until now. It makes sense to study non-Earth-like planets that can host life. He further said searching for biosignatures on Hycean planets is difficult. Searching for biosignatures on Earth’s twin is difficult. Scientists mostly have to rely on proving an atmosphere is not in equilibrium by detecting a combination of different biosignature gases that shouldn’t exist together in an equilibrium state. For the planets, from a significant number of bodies data have to be collected to find out which may be habitable.
Finding of the study –
- A new classification of Hycean planets.
- Six times the size of Earth, these planets can reach upto.
- These planets can reach upto 392 degrees Fahrenheit atmospheric temperatures.
- Under the atmosphere of these planets, oceans are there, and microbial life could exist in these oceans. The oceans could be similar to Earth in terms of temperature, pressure, or liquid water.
- Half of the part always has light from the star; it orbits in some of these planets, and the other half is dark. This means only one side of this planet is habitable.
- These planets all orbit red dwarf stars between 35 and 150 light-years away.
Past researches on exoplanets –
- In 1988, the 1st scientific detection of exoplanets was started. In 1992, the 1st confirmed detections were made where the discovery of many terrestrial-mass planets was discovered.
- In 1995 the 1st confirmation of an exoplanet orbiting a main-sequence star was made.
- The telescope has directly imaged some planets, but most were found by indirect method.
- Madhusudhan’s team published observations in 2019 of a mini-Neptune, dubbed K2-18b. It could support life in certain conditions. On the planet, they believe oxygen, ozone, methane and nitrous oxide are found.
- 4801 confirmed exoplanets are there as of 1 August 2021.
- NASA launched Transiting Exoplanet Survey Satellit in 2018 to perform an all-sky survey.
- Europe’s CHaracterising ExOPlanet Satellite was launched in December 2019, a partnership between ESA and Switzerland. The operation started in April 2020.
Future researches on exoplanets –
- The CSA/ESA/NASA James Webb Space Telescope will launch in late 2021. This will help in the better observation of exoplanets and their atmospheres by using several techniques. Compassionate spectroscopic observation of transiting planets – with similar characteristics in terms of size and mass – will usher in the era of comparative planetology for exoplanets.
- ESA’s PLAnetary Transits and Oscillations of stars mission will launch in 2026. This detects and characterizes many new extrasolar planetary systems by searching hundreds of thousands of bright stars for transiting planets.
- ESA’s Atmospheric Remote-sensing Infrared Exoplanet Large-survey will launch in 2029. This will conduct a chemical census of a large, well-defined, and diverse sample of exoplanets.
Among the range of known exoplanets, Hycean planets are common, but not much research has been done. It is essential to understand that the world with a habitable zone has the proper factors for life, searching for ozone, nitrous oxide, methane, oxygen or methyl chloride, and dimethyl sulfide. All of these are found on Earth. According to Madhusudhan, they are looking for these factors and focusing on planets similar to Earth. Ocean planets offer a better chance of seeing these factors.
Future telescopes will help scientists to learn more about Hycean planets but getting more information about their atmosphere. These planets can be a good subject for research. Scientist says that is good to see that habitable condition exists on planets that are different from Earth. They are planets of interest for scientists within and outside of our solar system. Factors like ozone, nitrous oxide, methane, oxygen are yet to be discovered other than Earth. Understanding of life in the universe could be changed if these factors are found. Scientists need to be open about where they can find life and what form life will take them.