Despite the rapid improvement in technology the past few years, the current technology is not capable of yielding a completely successful mission that would travel to other stars and search for habitable exoplanets. Fortunately, the number of solar systems and exoplanets discovered is increasing. Direct images received from those exoplanets have a very low resolution but provide plenty of useful information. This essay will examine how this information when compared to the figures of Earth can offer a hint on which exoplanets might be habitable and have potential life.
The astronomical definition of a habitable world is a place that has liquid water, or maybe just any form of liquid since different living organisms might not necessarily require water to survive. However, it takes more than liquid itself for life to exist. The following also play an important role in the existence of life: size, mass, gravity, magnetic field, atmosphere, minerals, chemicals, temperatures, soil, land, distance from star, type of star and distance our solar system.
We can get an exoplanet’s mass by measuring its gravity and then find its density. Density shows what the world is made of. The Earth has a mantle made of rock and a solid core made of iron. In addition, we can estimate how the material is factored with the help of the moment of inertia factor. Every material has a rotating body that accelerates and decelerates. The speed depends on how the mass is distributed within in the body. Smaller numbers means that the mass is concentrated more and more at the center. Earth is not a uniform shape and most of its mass is concentrated at the center.
Gravity can also be an indication of what molecules are held on a planet. The Earth has enough gravity that can hold oxygen, water, methane, ammonia, nitrogen and carbon dioxide. Earth can’t hold onto helium and hydrogen at Earth’s temperature they are moving too fast. Holding on molecules retains the atmosphere of a planet. Finding oxygen in its pure form will be a strong indicative of life. Detecting the atmosphere of the exoplanet through the spectra of atmospheres, can tell us something about its ability to host life. Almost all of the oxygen we have in the atmosphere is from life. Therefore, if we actually saw oxygen in the atmosphere of an exoplanet it would mean there might be Earth-like life on that planet.
Moreover, in order to determine the features and structure of any planet, a property called the albedo is used. Albedo is the percentage of sunlight that reflects off a surface. The Earth’s albedo changes depending on the season. For example, in December on the northern hemisphere temperatures can get very cold and the sunlight is reflected from the snow, an indication of ice. We can use the albedo and the density to find out all of the objects and materials found on the planet.
Besides the content and surface of planets, also important for potential life is the magnetic field. Earth has a pretty strong magnetic. A strong magnetic field protects the planet from the star’s emissions of high-energy particles. Since Earth is rotating and has a solid inner core, with an extremely hot liquid outer core it causes a magnetic field. There are big loops of fields from the earth. There is a magnetic north and a magnetic south.
Different stars have different effects on our ability to view planets. If you have a really big star that is really hot then the habitable zone will be further out. Around a cooler star it will be closer in. Similarly, if you have a bigger star you might have a bigger disk to form planets in. more material to form more planets. Stronger tidal force from bigger stars as well as stronger gravity and vice versa. Stars can be classified with the Hertzsprung–Russell diagram which plots luminosity and temperature/color. On the diagram yellow colored stars or G type stars are similar to our Sun.
Distance from our solar system to another solar system is important as well. Time and distance are closely related. Everything we study in astronomy is in the past. The further you look the deeper into the past you look. Similarly, the further you find a star the longest time it will take to reach it. Bearing in mind that the age of the solar system is 4.56 billion years and that humans started developing their technology the past decades it is clear that what we see in an exoplanet located million or even billion light year away might not depict the current situation.
Once finding an exoplanet with all the characteristics similar to the figures of Earth it is when it is important to establish a budget and hire aeronautical engineers who will build a spacecraft. The spacecraft should be capable reaching a certain distance where it will be more possible to send back more clear images. The images will determine the possibility of extrasolar life. The biggest challenge still remains to find the appropriate exoplanet. Estimations predict that it is a matter of time an exoplanet with potential life to be found.
West, A. A. (2012). Lecture 1 –Lecture 24 [PDF slides]. Retrieved from http://blackboard.bu.edu
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