Mechanical and Aerospace Engineering: Discovering of Planets Outside the Solar System - Term Paper Example

 Recent discovering of planets outside the Solar System using telescopes 1.0 Introduction Whether it’s the Stone Age or the present day human has always looked up into the sky and wondered that, is there any other planet like planet earth, are they alone in this universe and will they be able to another home like earth. To fulfill the thirst of curiosity humans have exerted all their efforts to learn more and more about the universe. They started with the studies about moon and earth, and then to the relations of earth its orbit around the sun eluded their minds. Finally they concluded to the fact that it’s the earth which moves around the sun and not the sun moved around earth. This eagerness did not cease and they went further to discover the solar system around earth, discovering that the closest star to us was the “sun” and there are God knows how many more in this universe and other neighboring universe. With each star there is system of planets similar like our and this fact has given us hope that there might be another planet which we can call earth 2 one day. These ground breaking discoveries one after the other proved that there is much to learn and the universe is way vast then we think. On the other hand the population of the earth has reached a figure of over 6.9 billion The current population of the world is about 6.9 Billion (United States Census Bureau) with a growth rate of 1.1%. It is expected that this figure will rise to a value between 8 and 10 billion in 2040 to 2050, which is far beyond the carrying capacity of planet earth of about 4.5 billions. In order to sustain this population of the future we have to find a new place similar like earth soon. Space colonization is the idea we are targeting for, not just for accommodation but also to exploit the energy and mineral resources of that planet and fulfill the future requirements of the masses here. It is now an established fact that there is no planet in our solar system that can sustain life form of any type, Mars was one hope but the absence of oxygen and a protective layer such as ozone have created doubt in potential as prospective place of human existence. So now we have to look and search beyond this solar system into the neighboring systems. In order to understand and attain more knowledge we have to use new technologies and view the atmosphere and other specification of the planet more closely. Which can only be possible with latest and more accurate imaging systems? Engineers and scientist have employed telescopes for centuries to view far distant heavenly bodies. The concept remains the same but the methods employed are greatly advanced and the use of computer has revolutionized the speed of mathematical calculations therefore making observations much easier and the greatly enhanced the reach of the telescopes. Through these breakthrough technologies, till now we have discovered that there are about 496 exoplanets (The Extrasolar Planets Encyclopedia) and many yet to be discovered. 2.0 Extrasolar planet or Exoplanet: In general sense the planets which exist outside our solar system are called extrasolar planets or exoplanet. These are heavenly bodies which have there own star and revolve around it in a predefined manner or they might not even have their own star in which case they are known as rogue stars. But a definition which almost covers every thing was presented by working group on extra solar planets (WGESP) and which is “Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System.”(WGESP) These planets are very far away from earth and as we are aware of the fact that they do not possess any kind of light of their own in addition they are some times very small as well. These attributes of these planets makes it is very difficult to observe them through the conventional imagery technology or also known as Direct methods. 2.1 Direct Method: It is one of the most difficult and hardest method possible This is because of the extreme contrast between the light emitted by the parent star and by the companion planet. In order to have a clearer picture of the very small planet the light of the parent star has to be dimmed and then through trial the planet is located in the shadows. Various techniques are used to enhance the quality of image, one of these use the infrared radiations instead of visible light. Where as modifying the same concept the planets are detected on the basis of their heat emissions. Another method which is popular is by using coronagraph, whose working principle is that it masks the bright light of the central core and letting only the corona visible consequently the nearby planets have the chance to prove their existence. It is to taken into accounts here that direct imaging can provide you with limited data and information about the planet such as biosphere or water available on surface. In order to achieve higher resolution or information bigger telescopes have to be used which really is not possible at times and that’s where the need of indirect methods arouse. 2.2 Indirect Methods: This method is highly effective and is majorly responsible for the discovery of most of the extrasolar planets. The basic principle of this method is that a planet is detected through the effect of the planet on it host star and vice versa. This method also takes into account the gravitation effect of star and planet and then considers the orbital path of the planet. The change in the contrast of the images while movement in the system also depicts the presence of the planet. There are majorly five ways of detection through Indirect methods: 1. Radial velocity Tracking 2. Astrometry 3. Pulsar Timing 4. Transits 5. Gravitational Microlensing 2.2.1 Radial velocity Tracking In this method the relative movement of the star about the planet and then the increase and decrease of distance from earth during its orbital is considered. Therefore the radial velocity of the star along its orbital path is transferred into a spectrum employing Doppler effect, where the redness the images shows the star is relative distance from us in increasing and the blue color indicates the proximity. There are some periodic changes in star’s orbital velocity because of our inclination as observer to the orbit of the star. This method also known as Doppler spectroscopy has been really helpful as planet finder and its ranges up to planets with in a range of 160 light yeas from earth. Latest advanced telescopes such as HARPS (High Accuracy Radial Velocity Planet Searcher) spectrometer at the ESO 3.6 meter telescope in La Silla Observatory, Chile and HIRES spectrometer at the Keck telescopes have taken precision to the next level. 2.2.2 Astrometry Being the oldest method employed for the cause the concept is very simple which is that when a smaller body is moving in a prescribed orbit which is due to the masses of the two bodies should move in the similar manner through out but if there is any sudden or unusual change in its path then it can be said that there is some other nearby body that effects and changes the orbit. Although the method seems to be promising but no success story has been seen in finding a planet yet. 2.2.3 Pulsar Timing Normally Pulsar are the stars which are in the continuous process of emitting radio waves while their radial movement which are just like signals these signals are very regular and have a definite cycle time. If there is planet in the vicinity of the star then this timing is disturbed hence affecting the regularity of the signals. Hence this phenomenon can be used to detect planets around a pulsar (star). The scarcity of pulsars in the universe is the reason of unpopularity this method of detection. One of the few success is the discovery of planets around the pulsar PSR 1257+12.( A. Wolszczan & D. A. Frail, 1992). 2.2.4 Transits: When the planet passes between the star and the earth this phenomenon is called transit. As we are aware of the fact that the star is emitting light and when the it is blocked by the planet there is a substantial decrease in the brightness of the star consequently this abrupt change is sensed through photometry and the amount of light that pass through is measured. The combination of transit photometry and radial velocity has been a real success. Through this combination now we can not only gauge the size and shape of the planet but also the surface and density and atmosphere of the planet. A significant break through of this technology is the measurement of temperature of the planet two teams has successfully acquired the temperature of two planets TrES-1 and HD 209458b. Harvard-Smithsonian Center for Astrophysics, led by David Charbonneau, worked on TrES-1 and discovered that planet' temperatures: 1,060 K (790°C) [Cha05]. Where as on the other side Goddard Space Flight Center, led by L. D. Deming, studied HD 209458b and came to a conclusion that temperature is 1,130 K (860°C) for HD 209458b. [emi05] These ground breaking technologies are followed by the two biggest missions, firstly the French Space Agency mission, COROT, which began in 2006 and secondly by NASA mission Kepler launched in 2009. 2.2.5 Gravitational Microlensing The gravitational effect of very large planets and celestial masses cause the bend in the light which is coming from the distant objects (stars) which are amplified and acts as a magnifying lens. The basic concept employed here is that when light from one heavenly body moves towards the earth it bends and by passes any massive bodies which come in their way. The size and shapes of the amplified light curve gives us the knowledge about the distance and size of the exoplanet. The extrasolar planet OGLE 2003-BLG-235/MOA 2003-BLG- 53 was the first planet discovered using this technique, in 2003. The hurdle in using this method is that the arrangement in which accurate reading can be taken comes once after a long time and you need to have luck that all the arrangement of bodies are as you expect them to be. 3.0 Recent discoveries of planets outside the Solar System using telescopes: 3.1 Exoplanets of prime importance: One of the vital reasons for searching of planets outside the solar system is for an alternative earth and to find that are we alone in this universe? And can we go some where else if the capacity of earth exhausts. The most significant leap forward yet was taken in the Lick-Carnegie Exoplanet Survey, led by principal investigator Steven S. Vogt, professor of University of California, Santa Cruz along with co-investigator R. Paul Butler of the Carnegie Institution of Washington. Discovered a planet Gliese 581 g which is identical to the planet Earth in many of its aspects. This exoplanet is orbiting the Gliese 581 also known as red dwarf star. This is estimated that this exoplanet is 20.5 light-years (1.94×1014 km) from Earth in the constellation of Libra. The discovery was made using radial velocity measurements, combining 122 observations obtained over 11 years from the High Resolution Echelle Spectrometer (HIRES) instrument of the Keck 1 telescope with 119 measurements obtained over 4.3 years from the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument of the European Southern Observatory's 3.6 m telescope at La Silla Observatory.( Steven S. Vogt). Further in his journal the principal investigator has told that the planet has an orbital period if about 36 days and according to the calculations by the method employed such as radial velocity and usage of Keck 1 telescope, the radius of the planet is about 1.3 to 2.0 times that of earth and when working on the grounds of mass Gliese 581 g is estimated to be 3.1 to 4.3 times heavier. The most significant and blissful attribute of this planet is the hope that it’s temperature and specific gravity of atmosphere is very much similar to earth and in addition to that the presence of ice has really glared the hope of life on this planet. Other planets where there life is conducive are Gliese 581 c, Gliese 581 g, Gliese 581 d and OGLE-2005-BLG-390Lb and they are one way or the other very similar to the earth. The major issues in finding more about these planets and many other like these one, is that we at present do not have the technology and systems to probe more into their atmosphere and for that purpose many scientist and engineers are working on more advanced telescopes. These missions include the Darwin which was proposed by ESA mission and specifically designed for habitual planets. Then COROT mission, was initiated in 2006 by the French Space Agency to have a better picture. Lastly the Kepler Mission and Terrestrial Planet Finder were recently launched by NASA to improve the observations. There are more than 490 confirmed extra-solar planets discovered till now and in order to understand the range of their size and mass of such planets we have to look know about the biggest and the smallest ones first, later followed by the average ones. Satter and Jordan claimed of discovering the smallest planet known to us till date it is in planetary system HD 10180 located in the southern constellation of Hydrus with distance 127 light years from Earth. This extra solar system also contains the other smallest planets of the universe. The planets were detected using the HARPS spectrograph, in conjunction with the ESO's 3.6 m telescope at La Silla Observatory in Chile, using Doppler spectroscopy. Where as the largest exoplanet discovered is TrES-4b it was claimed by Trans-Atlantic Exoplanet Survey using the transit method. It is 1,400 light-years (430 pc) away in the constellation Hercules. It is 1.799 times the diameter of Jupiter. TrES-4's orbital radius is 0.05091 AU, giving it a predicted surface temperature of about 1782 K.( Mandushev) 3.2 Most significant Exoplanetry mission and Telescopes: There are majorly four missions working at the moment for the exploration and research of exoplanet using the state of the art telescopes and imagery systems. They are 1. MOST (Micro variability and Oscillations of Stars telescope) 2. COROT (Convection Rotation and planetary Transits) 3. ESO (European Southern Observatory) 4. Kepler (NASA) 3.2.1 MOST (Micro variability and Oscillations of Stars telescope) It is also the smallest space telescope in the world (for which its creators nicknamed it the “Humble Space Telescope”, in reference to one of the largest, the Hubble)[MOST]. MOST is the first spacecraft dedicated to the study of aster seismology. It employs telescopes of with a telescope style of Maksutov catadioptric. The major accomplishment of this telescope is that it has altered the fact that star Procyon does not oscillate to the extend that was expected and then later in 2006 observations taken from MOST discovered the new class of variable stars, the "slowly pulsating B supergiants" (SPBsg). 3.2.2 COROT (Convection Rotation and planetary Transits): It is the space mission led by the French Space Agency (CNES) and in collaboration of European Space Agency (ESA) with the primary purpose of finding new exoplanets and it has been really successful in it. The COROT optical path consists of a 27 cm (10.6 in) diameter off-axis afocal telescope housed in a two-stage opaque baffle specifically designed to block sunlight reflected by the Earth and a camera consisting of a dioptric objective and a focal box.( Auvergne et al) The achievement of corot is the that it has discovered smallest exoplanet which is named as COROT-7b and later COROT-9b which is claimed to be first temperate planet. In addition to this corot has discovered more than 14 exoplanet. Special thing about Corot is that it detects planets with help of sensing the black contrast created when the planet moves from in front of its sun and the image is taken from its potent telescopes. 3.2.3 ESO (European Southern Observatory) The European Southern Observatory has numerous telescopes just for the purpose of discovering new exoplanents. One of which is HARPS (High Accuracy Radial Velocity for Planetary Searcher) on the ESO 3.6-metre telescope at La Silla for radial velocity high resolution spectroscopy. It can measure velocities with a precision greater than 1 m/s (or 3.6 km/h).( ESO, Observatory). Another is 1.2-metre Swiss Telescope at La Silla, used for high resolution spectroscopy, another is 1.54-metre Danish Telescope at La Silla for long-term monitoring. 3.2.4 Kepler (NASA) This is by far the most relevant and productive space program of NASA space observatory launched in 2009 and which is designed for the sole purpose to find exoplanets that are identical to planet earth and can be habitable. The Kepler uses the transiting technique of indirect method along with Doppler spectroscopy to come to its results and discovery of new planets. Through kepler scientist have researched on 7500 stars from the initial target list. The Kepler is one of the sources that confirm the candidacy of a new exoplanet and then its relevant information. So far the kepler itself has detected more than 12 exoplanets 4.0 Conclusion With the tremendous growth in the technology and advance telescopic imagery we have come to a conclusion that the universe is so large that we might not be able to see its other end. Everyday our telescopes and instruments show us a new picture, they show us new horizon a horizon with numerous exo-solar systems which have multiple stars and those stars with a many planets. The exponentially increasing number of exoplanets every day increases the probability of find the one planet we can call earth. We have witnessed a great improvement in the efforts to find the exoplanets where now all large space agencies are coming aboard to solve the problems encountered The ground breaking methods such as transiting and gravitational microlensing, to detect new planets have made it quicker and easier to locate and pinpoint their location. Further the ESO’s advance telescopes and recent mission such as by Keplers (NASA) have given us an insight to the surface and shape attributes of these heavenly bodies. Now these technologies have enabled man to decide sitting here about on earth, hundreds of light year far from the location that whether the planet have clouds or not or whether it possess water or not. These rapidly improving methods and instrumentation have proved to us that there is more than that meets the eye and it is now evident that the universe has a full potential to have another planet like earth. 5.0 References 1. US. Census Bureau, Population Division. (11/01/10). World Population Clock Projection. Available: http://www.census.gov/ipc/www/popclockworld.html. Last accessed 11/10/10. 2. (WGESP). "POSITION STATEMENT ON THE DEFINITION OF A "PLANET"." February 28, 2003. WORKING GROUP ON EXTRASOLAR PLANETS (WGESP) OF THE INTERNATIONAL ASTRONOMICAL UNION. . 3. Schneider, J. The Extrasolar Planets Encyclopaedia. . 4. Charbonneau et al.; Allen, Lori E.; Megeath, S. Thomas; Torres, Guillermo; Alonso, Roi; Brown, Timothy M.; Gilliland, Ronald L.; Latham, David W. et al. (2005). "Detection of Thermal Emission from an Extrasolar Planet". The Astrophysical Journal 626 (1): 523–52 5. Deming, D.; Seager, S.; Richardson, J.; Harrington, J. (2005). "Infrared radiation from an extrasolar planet" . Nature 434 (7034): 740 – 743 6. Vogt, Steven S.; Butler, R. Paul; Rivera, Eugenio J.; Haghighipour, Nader; Henry, Gregory W.; Williamson, Michael H. (2010-09-29). "The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581". accepted by the Astrophysical Journal. Retrieved 2010-09-29. 7. Steven S. Vogt, R. Paul Butler, Eugenio J. Rivera, Nader Haghighipour, Gregory W. Henry, Michael H. Williamson. "The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581." 07-nov-2010 . 8. Mandushev, Georgi; et al. (2007). "TrES-4: A Transiting Hot Jupiter of Very Low Density". The Astrophysical Journal Letters 667: L195–L198. 9. MOST. Micro variability and Oscillations of Stars telescope. 2010 11 09 . 10. Auvergne et al.; Bodin, P.; Boisnard, L.; Buey, J.-T.; Chaintreuil, S.; Epstein, G.; Jouret, M.; Lam-Trong, T. et al. (2009). "The CoRoT satellite in flight: description and performances". Astronomy and Astrophysics 11. European Southern Observatory, Telescopes and Instrumentation. 10 11 2010 . Read More