Introduction
Astronomers have always strived to penetrate the sky and look at the invisible. It is very difficult to observe extrasolar planets directly. The radial velocity method and the transit methods are used to find them. The purpose of this research paper is to explore the current achievements in the search for extrasolar planets.
Main body
Several means are used to discover a planet. Detection methods include direct and indirect evidence. Extrasolar planets are hard to observe directly using images because they are outside the Solar System. It is extremely difficult to take a picture of an object that is located at such a big distance. Therefore, the means of indirect observations are used to discover extrasolar planets.
The Doppler or radial velocity method along with the transit method is the most commonly used indirect means to find extrasolar planets. The Doppler Effect allows analyzing the motion and properties of the star and planet (Howard 572). The spectrum of the star shifts with the movement of the planet. The Doppler technique is the best method to find large planets with a short orbital period.
The transit method is based on the shift in the brightness of the star. A planet dims the light of a star when it moves in front of it. With the help of this technique, the astronomers define the size and density of the planet taking into account the size of the star (Sullivan et al. 45). The disadvantage of this method is that only planets that pass directly between their star and the Earth can be measured.
The first extrasolar planet orbiting a main-sequence star was found in 1995 by Swiss astronomers Michael Mayor and Didier Queloz. They discovered a large gas giant near a star using the Doppler method. The scientists named the planet 51 Pegasi b (Howard 574). The parent star was 51 Pegasi, a yellow-orange star located about 50.1 light-years from the Solar System. The majority of detected extrasolar planets were massive and gaseous. Their orbits were not circular but largely eccentric.
The Kepler spacecraft originally detected transits of planets between their parent planets and the Earth in one region of the Milky Way galaxy. It discovered thousands of planetary candidates that could be confirmed as a planet by other methods or prove to be a false positive. According to the NASA Exoplanet Archive, there are 3 472 confirmed planets and 4 496 Kepler candidates (3).
Extrasolar planets located in the “habitable zone” of their stars can contain liquid water and life. Out of all confirmed planets, only twelve are in the “habitable zone”. The minimum length of time to detect a planet like the Earth from a 50 light-years distance is several years because one should look for repetitive transits. The minimum length of time to detect Jupiter-like planets is decades.
Conclusion
The detection of extrasolar planets is crucial for many reasons. It helps to outline the image of the universe and detect planets that can contain liquid water and life. Several methods are used to discover extrasolar planets. Direct techniques are ineffective because of the long distance. Indirect methods use the Doppler effect and observation of transits. The Kepler mission is one of the most prominent planet discovery projects. The detected planets are usually massive and gaseous. However, there are twelve planets in the “habitable zone”. These planets can be rocky, contain liquid water and life. Scientists continue to discover new planetary candidates with the help of new technologies.
Works Cited
“NASA Exoplanet Archive.” Ipac, 2017. Web.
Howard, Andrew W. “Observed Properties of Extrasolar Planets.” Science, vol. 340, no. 6132, 2013, pp. 572-576.
Sullivan, Peter, et al. “Finding the Nearest Extrasolar Planets with the Transiting Exoplanet Survey Satellite.” American Astronomical Society Meeting Abstracts# 224, vol. 224, 2014.