Methods for Detecting Exoplanets

Methods for Detecting Exo orbitersA discussion and comparison of the radiate hurrying mode and the transportation p thermalometry system of spotting exo artificial sa spread abroadites.An exo satellite is a satellite that is turn asideside of our solar system orbiting a nonher hero, and so far (at 15/01/2017) 3560 exo satellites have been spy 1. Currently, with modern technology, the two main ways of detecting an exo monotonoust is use either the stellate velocity method or the transit photometry method, both of which having their advantages and disadvantages. Radial velocity works by the exo artificial satellite having a gravitational effect on the star it is orbiting causing the star to displace s faint-heartedly, starring(p) to its detected lite spectra being periodically shifted between red-shift and blue-shift as the major planet orbits it. The minimum galvanic pile back end then be calculated from the stars firing spectra. Transit photometry can be used to detect exoplanets by constabulary-abiding a periodic reduction in the intensity of descend detected from a star caused by the planet going directly in crusade of it between the star and the humankind. The size of the planet can be worked out by measuring the decrease in light and sometimes the composition of the planet can be deducedThe radial velocity method, in like manner known as the Doppler spectroscopy method, to detect exoplanets was the root proper method that worked potently. Orbiting planets cause a star to move slightly cod to their gravitational pull, since the planet has mass. This slight movement of the star being orbited affects the light spectrum from that star which is received by observers on Earth. Regular periodic shifts in the stars pass judgment spectrum, which would appear as a wobble, indicates the presence of an orbiting planet 2. If the exoplanet caused the star to move towards Earth then its light spectrum would be blue shifted, if the star trave l away from Earth the spectrum would be red shifted.The mass of the orbiting planet can then be determined, as Kelpers third law of temperamental work can be used to determine the orbital radius of the planet from the mass of the star, calculated using a Hertzsprung-Russell diagram, and the orbital period of the planet determined from the stars light spectrum. Then Newtons law of gravitation and the orbital law can be used to derive the equationto calculate the velocity of the orbiting planet. With the velocity of the planet, the equationcan be used to work out the mass of the detected planet 3.Using radial velocity is the most parking area method used to date to detect exoplanets, it has the advantage of not necessarily a actually long time comparative to the opposite methods and is therefrom useful in large scale surveys to husking dual exoplanets. Unfortunately, it does not give much specific nurture active the planet itself and hence must(prenominal) be combined with other techniques to obtain information like the planets chemical composition, density, and volume. Other methods could thus have more potential difference for the future for more in depth analysis of the detected planet 4.One major complication with radial velocity is that it is difficult tell mass of a detected planet easily, only the minimum mass based on how much star appears to move can be calculated, as it depends on the angle of the orbital plane of the planet. If the angle, , is the angle do by the plane perpendicular to the orbit of the planet from the plane of the smokestack from Earth, then the component in line with Earth is sin(). The detected mass, M, is thus the product of the true mass of the planet and sin(). The large , where 0 5. This gives arise to the problem that on a r atomic number 18 occasion a hapless mass star can be detected in a binary star system and mis pissn for a planet due to a mass being calculated much smaller than its actual mass and thus appears more similar to that of a planet because of the plane of its orbit with respect to earth.This method mainly detects planets that are very constraining to the star, massive, and have very short orbital periods so cause the largest wobbles that dont take very long to detect. Planets like this are often referred to as hot Jupiters, due to them being of similar size, mass, and composition to that of the planet Jupiter in our solar system besides they are much closer to the star they are orbiting, hence being hotter 6. A downside of this is that one of the main purposes of detecting exoplanets is to find planets capable of supporting life, and hot Jupiters are very unlikely to do this.Another main method of detecting exoplanets is called transit photometry. A planet may be detected by taking measurements of the dimming of light emitted by the star it orbits. When the planet passes directly in front of the star, as seen from Earth, it blocks out a fraction of the light that we receive. If this dimming occurs at regular intervals, then it may be deduced that this planet is in orbit and passing in front of the star once every orbital period 7.The amount of dimming that occurs reflects the ratio of size between the star and planet since the size of such a star may be determined from its spectrum we may then view the planets size. For planets orbiting the same sized star with the same luminosity and same light e foreign mission spectra, planets orbiting it will decrease the amount of light received on earth by different amounts depending on the size of the planets 8. A planet with a radius three times larger than another orbiting planet will lead to a drop in the amount of light received nine times that of the other planet. Hence, the decrease in light received from the star due to a planets transit is proportional to the solid of the planets radius and so proportional to the planets cross-sectional area.When this method is combined with radial velocity an alysis which gives an estimated mass, the density may be calculated, giving a much clearer picture of the composition of the planet. The planets atmospheric conditions may also be unc everywhereed by analysing the depth of the transit at different wavelengths of light. ignitor emitted by the star will be absorbed by gases in the planets atmosphere to different degrees at different wavelengths 9. Therefore, by studying its spectra elements in the atmosphere may be determined. For such analysis to be carried out, searches must continuously cover large portions of the sky and its cluttered light sources over long periods of time.Transit photometry only works, however, when a planet passes directly between its star and the Earth, which is uncommon. For a star one astronomical unit (approximately about 150 million kilometres) away from its star, and the star being the same as the sun earth orbits, the probability of an orbiting planet producing a detectible transit is 0.47%, give that the planet has a random orbital alignment 10. A planets orbital period could be a very long time, months, or years, but its transit directly in front of the star between it and earth could only be a couple of hours. Despite this, in very large scale exoplanet finding surveys spanning over extended periods of time and applications programme potentially thousands of stars, the transit photometry method has been found to be more effective than the radial velocity method at finding a larger number of exoplanets 11. However, transit photometry has a much larger detection straddle of false positives, meaning an exoplanet was thought to be detected using this method but after further investigation was found to be a false detection. A 2012 study found that in single winding systems, the number of false detections was up to 40%, based on the observations from the Kepler mission 12. This means that, in the case of single planetary systems, a planetary detection using transit photometry mus t be verified using another method, which is often radial velocity and sometimes the less common method of orbital brightness modulation. References1 Schneider, J. 2017. Interactive Extra-Solar Planets Catalogue. The Extrasolar Planets Encyclopedia. Online. Accessed 15/01/2017. available from http//exoplanet.eu/catalog/2 Astronomy Notes. 2007. The Velocities of Stars. Online. Accessed 15/01/2017. Available from http//www.astronomynotes.com/starprop/s8.htm3 Fischer, D. 2010. Radial Velocity. Yale University. Online. Accessed 15/01/2017. Available from http//exoplanets.astro.yale.edu/ shop class/EPRV/Bibliography_files/Radial_Velocity.pdf4 Zechmeister, M. 2011. Precision radial velocity surveys for exoplanets. beginning(a) ed. S.l. s.n..5 The Planetary Society. 2016. Radial Velocity. Online. Accessed 15/01/2017. Available from http//www.planetary.org/ look/space-topics/exoplanets/radial-velocity.html6 Sasselov, D. 2008. Astronomy Extrasolar planets. Nature. 451(7174). pp.29-31.7 Sh annon, L. and Russell, D. 2012. Exoplanet Transits Light Curve Photometry. Bangor University. Online. Accessed 15/01/2017. Available from http//www.baylor.edu/content/services/document.php/181811.pdf8 The Planetary Society. 2016. Transit Photometry. Online. Accessed 15/01/2017. Available from http//www.planetary.org/explore/space-topics/exoplanets/transit-photometry.html9 Shore, L. 2014. Searching for Exoplanets. Exploratorium Teacher Institute. Online. Accessed 15/01/2017. Available from http//www.exo.net/pauld/Venus/ExoPlanets%20and%20Transits.pdf10 Carroll, M. 2017. Earths of Distant Suns. 1st ed. Cham Springer International Publishing. p.50.11 Hidas, M. et al. 2005. The University of New South Wales Extrasolar Planet Search methods and first results from a field centred on NGC 6633. Monthly Notices of the Royal Astronomical Society. 360(2). pp.703-717.12 Santerne, A., Daz, F., Moutou, C., Bouchy, F., Hbrard, G., Almenara, M., Bonomo, S., Deleuil, M., Santos, C. 2012. SOPHIE velo cimetry of Kepler transit candidates. Astronomy Astrophysics. 545. p.A76.