Water is an absolute necessity of life. This is why when astronomers are looking for life in the universe, they are actually on the lookout for water. Astronomers have discovered such a planet called K2-18b, which is at the perfect distance from its star K2-18 that allows water to exist in liquid state therein. This star is a red dwarf (which means that it is smaller and colder than the Sun) and the exoplanet is a super-Earth planet (a planet whose size is between that of the Earth and Neptune).
Watch Dr. Salman Hameed’s [Urdu] video on Kainaati Gupshup, as he reveals how these properties, along with other features of this discovery have exciting implications for the human race:
K2-18b was discovered by an indirect detection method, called the eclipsing or transit method. The planet is at a substantial distance of more than 120 light years from the Earth, which makes it all the more difficult for astronomers to observe it directly. Instead, the astronomers focus on the star it revolves around. When the planet passes between the Earth and the star, the star’s light dims as in an eclipse, and that’s how you know that a planet is journeying around it.
When K2-18b revolved around its star, the dimming of light reoccurred every 33 days. This implies that this extrasolar planet takes around 33 days to complete a revolution around its star. In comparison, the Earth takes 365 days to complete its revolution around the Sun. This leads to the conclusion that this exoplanet is closer to its star than the Earth is to the Sun. However, since K2-18 is also colder than the Sun, this planet is at a balanced distance such that water can exist in liquid form despite being closer to its star. This region is called the habitable zone. The habitable zone does not ensure the presence of life, but it certainly indicates a possibility of it. If water can exist in liquid form there, so can life.
Another interesting fact related to the discovery of this planet lies in its composition. All atoms and molecules have particular signatures. This explains how we know the composition of the Sun without actually having visited the Sun. Similarly, when K2-18b passed in front of its star, astronomers observed how its atmosphere was absorbing the star’s light. The observation revealed the presence of ample hydrogen as well as water, which are indispensable to life.
However, before one gets carried away and declares this planet as habitable, a few facts must be taken into consideration. This planet is a super-Earth, which means that it is greater in size than the Earth (3 times) but smaller than Neptune. Planets with these properties do not exist in the Solar System. Therefore, it is difficult to predict the properties of super-Earths i.e. whether they are gaseous like Neptune, or terrestrial like the Earth. Nevertheless, It is hoped that since this exoplanet is in the habitable zone, droplets may form in its atmosphere that cause rain, as it happens on the Earth.
There are other potential problems as well. Since the planet is closer to its Sun, it is probably tidally locked like the Moon which is close to the Earth and tidally locked, so you can only see one facet of it. It entails that one of the surfaces of K2-18b will point towards its sun at all times. There will always be a colder facet and a hotter facet. Astronomers are unsure if its atmosphere will be able to balance the varying temperatures. The temperature difference could be somewhere between 0 and 40 degrees, which is a lot like the temperature extremities in Lahore and Karachi’s weather. So, there is a probability of life there but once again no certainty.
The presence of strong magnetic fields in such red dwarves is another hitch. A lot of flares are expected. However, there is an upside to this as well. Such red dwarves have a very long life span. The Solar System’s Sun will survive for 10 billion years. However, red dwarves of this sort can live up to hundreds of billions of years, which means that it has ample time to develop life.
The discovery of K2-18b is a milestone for the scientific community. The mere fact that astronomers have telescopically figured out the composition of a planet that is at a distance of more than 120 light years, thereby bypassing the need to physically visit a place to find out what’s going on there, is a huge accomplishment on its own. Furthermore, it is an embryonic answer to the pressing question of the possibility of extraterrestrial life. The invention of more powerful telescopes is underway as we speak. These telescopes can potentially enable us to detect oxygen in the extrasolar atmospheres. Since the oxygen in our planet’s atmosphere came from life, it is considered a signature of life. Technological advancements in the form of such discoveries and inventions open up exciting possibilities of life and a lot more, in systems within our reach and beyond.