Most of the planetary scientists believe that there can be at least one exoplanet in our Milky Way galaxy, which has life. They have also figured out that 20% of the sun-like stars that exist on the Milky Way are circled by planets, which has the same dimensions as Earth. These planets are located in habitable zones around the stars as well. Therefore, life on exoplanets has become a popular topic among planetary scientists in the modern world.
The habitable zone of a planet can simply be defined as the area where the temperature is not too cold or too hot. These conditions help water to exist in those planets in the form of liquid. It is vastly known that life cannot survive without water in its liquid form. Therefore, while it has been figured out that there are about 2,000 exoplanets circling beyond our own sun, the possibility to have some sort of life in these planets depends on a variety of factors. The obliquity of the planet holds a prominent place among them. Obliquity can simply be defined as the angle of axis of a planet relative to its orbital axis around the parent starts.
The planet Earth has a low obliquity when compared to other planets. It rotates around an almost perpendicular axis of its own while rotating around the sun. Planetary scientists have figured out that the obliquity can vary from one planet to another. They believe that the planets with an extreme tilt have a very low chance of having life in it.
Recently some research scientists as the Massachusetts Institute of Technology figured out that water exists on planets that have a very high obliquity as well. Therefore, we can keep some hope that life can exist in the planets with a high obliquity. They also figured out a shallow ocean with a depth of about 50m in a specific planet, which has a comfortable temperature. According to their calculations, the average temperature of that planet was about 60-70 degrees Fahrenheit per year.
However, a planet with a high obliquity usually has an extreme and inhospitable climate. The North Pole would receive sunlight for a period of 6 months continuously and it would have to go through an unending night for the other six months. As a result, they believed that such a planet has a very little chance of having life. That’s mainly because the planet would freeze and boil throughout the year, which is really tough for life to exist. Nevertheless, this can differ under some conditions. For example, the oceans can store heat during the summer period and give it out during winter. This can create a somewhat mild climate in the planet. Therefore, we cannot neglect with extremely oblique planets by saying that they are not in a position to inhibit life.
It has been assumed that the Milky Way has about 200 billion stars. In addition, it has been calculated that there are about 11 billion planets with “habitable” living conditions. All these consist of hydrogen gas and they are seething hot. The planetary systems have been established circling such stars. In fact, sticky and fine dust particles melt together to create rocky cores, which eventually turns into major planets.
The very first exoplanet was discovered by research scientists 20 years ago. It was circling a sun like star and was named as 51 Pegasi b. Since then, they have discovered a large number of exoplanets, where most of them were smaller than their very first discovery. They even discovered an exoplanet, which is 150 smaller than 51 Pegasi b.
Many different methods are being used by research scientists in order to discover new exoplanets in the Milky Way. The Doppler Shift method can be considered as the most popular one. This is an effective method, which can be used to discover giant planets that exist closer to fiery stellar planets. This is a sensitive method and is associated with a higher chance of discovering earth-like planets.
Throughout the past two decades, scientists have figured out many other methods to discover exoplanets apart from the Doppler Shift method. The major drawback with the Doppler Shift method is that it cannot be used to discover smaller planets that have a wider orbit around the stars. However, the recently discovered methods are in a position to help the scientists with discovering such planets. At the end of 2015, they have been able to discover more than 1,900 exoplanets that belong to over 1,200 planetary systems.
The Kepler Space Telescope of NASA helps a lot for the scientists to discover new exoplanets. It was launched back in 2009 and has discovered few thousand candidate planets up to now. Most of these candidate planets were confirmed as exoplanets by scientists. Several statistical methods such as the verification by multiplicity were used by the scientists to figure out whether they are in a position to inhibit life or not. The Kepler Space Telescope follows a unique methodology when discovering exoplanets. It differs a lot from the Doppler Shift method. This method searches for extremely small dips in stellar brightness when a specific orbiting planet passes ahead of the glaring face of parent star.
In the meantime, the scientists at MIT spent their efforts in order to create a model of a highly oblique aqua-planet. This planet had the same dimensions of earth and it was positioned at a distance similar to the earth’s separation from sun. This 3D model simulated circulations among sea ice, atmosphere and ocean. The effects of winds and heat were also taken into consideration. They also created a motionless planet for comparison and discovered the possibility of having life in such a planet. They had the ability to control the obliquity of this planet and they discovered that the ocean absorbs heat during the summer period.
Given the scientific evidence and ongoing research therefore it appears that it is not science fiction to believe in life in other planets. While there is still a long way to go before we start packing, we can keep our fingers crossed for the prospect of habituating an exoplanet in the near future.
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