The List of Extrasolar Planets Known to Man - Essay Example

?PLANET 61 VIR C INTRODUCTION: On December 14, 2009, three planets were added to the list extrasolar planets known to man, making the number of exoplanets known till date to be 489 (Laughlin). These planets were discovered revolving around the star 61virginis which appears in the sky as a yellow orange heavenly body located at a distance of 27.8 light years from our solar system. The star is visible with naked eyes in a clear summer sky in vicinity of the southern margin of constellation virgo. The star has been known to be old and inactive, and photometrically stable (Vogt et al., 1366). The major properties of 61 Virginis are listed in table 1. The three planets forming the planetary system of 61 vir are vir b, vir c, vir d (table 2). They were discovered by a team of astronomers including Steven S. Vogt, Robert A. Wittenmyer, R. Paul Butler, Simon O’Toole, Gregory W. Henry, Eugenio J. Rivera, Stefano Meschiari, Gregory Laughlin, C. G. Tinney, Hugh R. A. Jones, Jeremy Bailey, Brad D. Carter, and Konstantin Batygin. The data leading to discovery of this planetary system was obtained from W. M. Keck observatory in Hawaii added to the observations made by Anglo-Australian Telescope (AAT) in New South Wales, Australia. The research was conducted in affiliation with National Science Foundation and NASA, who supported the research (Stephens). Table 1: Parameters of star 61 virginis 61 VIR Parameter Parameter Value References Year Stellar Type G5V Takeda et al. 2007 Mass 0.942(-0.029+0.034) solar masses Takeda et al. 2007 Radius 0.98±0.03 solar radius Takeda et al. 2007 Age 8.96 (-3.08+2.76) Gyr Takeda et al. 2007 Distance from Solar System 27.8 light years Takeda et al 2007 Planets 3- Vir b, vir c, vir d Vogt et al. 2010 Table 2: Characteristics of planet 61 vir c (Vogt et al., 1366) 61 VIR C CHARACTERISTICS Characteristic Value Distance from its star (Semi major axis) 0.2175 (±0.0001) AU Mass of Planet (M.sin i) 0.0573(±0.0035)MJ Discovery method/date code RV09 Sibling Planets Vir b and Vir d Orbital period 38.012±0.036 days (Epoch JD 2453369.166) 38.021±0.034 days (Keplerian orbital solutions) Eccentricity 0.14 61 VIRGINIS: 61 Viginis or HD 115617, is located at a distance of 28 light years (8.52 parsecs from the solar system, and is a part of the constellation virgo, along with many other stars namely Spica, ? virginis, ?virginis 70 virginis, chi virginis. The constellation virgo can easily be located on the basis of Spica, which is the brightest star of this constellation. Continuing on the curve formed by the seven major stars of ursa major, known as big dipper; to the star Arcturus of bootes constellation; the star spica can be located. The star belongs to the category of GV5 star, i.e. it is a main sequence star of G type while V is indicative of its luminosity. Main sequence refers to the stage of the life of a star. Stars occupying a position on Hertzsprung-Russel plot as a consequence of their absolute levels of brightness and colour index are known as main sequence stars (figure 1). Both of these properties are dependent on the mass of star which in turn is determined by the chemical composition and chemical reactions responsible for energy of the star (Habets and Heintze, 193). Figure 1: Hertzsprung-Russel plot (http://www.bibliotecapleyades.net) Thus the primary feature of a main sequence star is that it is in hydrostatic equilibrium, converting hydrogen in its core to helium by nuclear fusion; while simultaneously increasing in size. They form 91% of the stars known, are also known as dwarf stars in contrast to the rest which are known as white dwarfs (8%) and giants (1%). Our sun is a main sequence star and so is Virginis 61. The main sequence stars are further classified in to spectral classes depending on their temperature and other features such as luminosity and mass. Vir 61 belongs to spectral class G5, i.e. with a surface temperature of 10,000? C, Mass of 0.92 solar mass, luminosity 0.8 solar luminosity and lifespan of 15 billion years. (Habets and Heintze, 193). Planetary System of 61 Virginis: The architecture of 61Vir planetary system does share a few analogous characters with our solar system (figure 2), but there are no similarities between the two, despite the similarities between the system stars Sun and 61 Virginis. While our solar system has the following structure: Within 2AU: small rocky planets Between 2-4AU: Belt of rock and ice like asteroids Between 5-10AU: 2 gas giant planets Between 10-30AU: 2 ice giant planets 30-50AU: Region of rock and ice like objects extending as far as 100AU. 61 virginis planetary system on the other hand has: Within 0.50 AU: 2 ice giant planets of Neptune class, and another innermost super Earth like Ice giant planet Within 10AU: Region of rock and ice like bodies (Trilling et al. 1086). Besides these an extensive belt of cool debris has been found at about 8-10AU at the inner edge and between 96±5 and 195±10 at the outer edge, which could have been generated as a consequence of collisions of Edgeworth-Kuiper-Belt type icy objects (Trilling, 1086). Thus the planetary system of 61 vir and sun are similar in their radii, but the similarity ends here. Moreover there are still no planets found in the habitable zone of the planet, which lies between 0.76 and 1.52 AU. The three planets discovered are too close to the star, compared to solar system; where the closest planet mercury too is at a distance farther from farthest planet of 61 vir planetary system. Figure 2: Planetary system of 61 virginis and comparison to solar system (Laughlin) Planet Vir C: The planet vir c was discovered in the year 2009 using the radial velocity method (RV09). Radial velocity, spectroscopic or Doppler method is based on the Doppler’s principle of spectrum shift (figure 3). Minor shifts in the spectral patterns of a star indicate the movements of star towards or away from the Earth or the viewer’s position. If the star’s spectral pattern exhibits a shift to shorter wavelengths i.e. towards blue part of the spectrum, it is indicative of the star moving towards the Earth and vice versa. A regular pattern of spectral shift of a star indicates that it is periodically being pulled back and forth or ‘wobbled’ by a planet, which is revolving around it. Thus even though the planet is not actually visible its presence becomes known. Thus a planet can be successfully detected using this method; in fact most of the exosolar planets detected have been detected using RV method (The Planetary society). However, the method suffers from a serious drawback that it fails to provide accurate values of the mass of a planet, which leads to uncertainties in the planetary mass values. Since mass is the primary criteria of distinction between a planet and a star, it becomes difficult to categorize a newly discovered extrasolar body as a star or planet. This problem arises when the planetary orbit of the planet is face on, that is the planet moves in a plane perpendicular to the line of vision. In this case the planet during its orbit neither moves away nor towards the Earth. Further in face on position mass is determined using angle of inclination (i) (eq1) Eq 1: Where, M is the mass of Earth. Thus if the value of ‘i’ is closer to 90?, it means that the planet is close to edge on position and therefore the estimated mass value would be closer to the actual mass of planet. However, if the value of ‘i’ is low, the planet is in face on position, thus the actual mass of the planet would be much higher than the estimated value (The Planetary Society). On ground explorations of the planets have to await the technology for interstellar transportation faster than the speed of light, which seems unlikely within next 50 years. A journey to planet 61vir c from earth would mean covering a distance of 27.8 light years. The fastest manned flights till date, Apollo 10 had a speed of 11.1km/s, which is 0.0037% of speed of light. Travelling at this speed, a simple calculation will provide the time taken to travel a distance of 27.8 light years. Time = distance/speed 1 light year = 9.461*1012 kms Time taken to travel to vir 61 c= 27.8 light years/ 11.1 km/s =27.8*9.461*1012/11.1 = 23.695 1012s = 7.509*105years Just a look at the value of time needed to travel to 61 vir c can guide us to the conclusion that it is simply impossible for any human being to reach 61 vir c alive, or even plan a mission to this planet on the basis of present technology available. Even if in coming years technology is developed to travel at the speed of light, it will still take 27.8 years to reach this planet, which again seems an improbable and almost impossible mission. The possibility of life on planet vir c is highly improbable, since the planet is too hot for sustaining any lifeform. Scientifically, the existence of life on vir c has been ruled out. Planet mercury, which is at a distance of .37 AU from Earth, has a temperature of 450.C, which is too high for life sustenance. Thus it is difficult to imagine life on vir c, which is at a distance of 0.27 AU from its star (61 vir which is similar to Sun). Both the temperature and light intensity on planet would certainly be too high. Thus, neither the 61 vir c nor its sibling planets have the climatic conditions suitable for holding life and this can be concluded since they lie very close to the star and consequently, have an extremely high temperature. Conclusively, even if life from Earth is introduced on the planet 61 vir c, or if humans manage to reach there, the planet would be completely uninhabitable, primarily due to high light intensity and temperatures. There is expected to be neither any water on the planet nor any food source for life sustenance. The probability of having life sustaining atmospheric gases is also negligible. Thus planet 61 vir c is completely uninhabitable and also unapproachable for man. Works Cited 1. Dickinson, Terence. “The Zeta Reticuli Incident” Web. Feb 2011. http://www.bibliotecapleyades.net/vida_alien/zetareticuli_incident01.htm 2. Habets, G. M. H. J. and Heintze, J. R. W. “Empirical bolometric corrections for the main sequence.” Astronomy and astrophysics supplementary series 46 (1981): 193-237. Print. 3. Laughlin, G. Web. Feb 2011. http://oklo.org 4. NASA, “Warp drive, when.” Web. Feb 2011. http://www.nasa.gov/centers/glenn/technology/warp/scales.html 5. Stephens, T. “New planets discoveries suggest low mass planets are common around nearby stars.” Web. Feb 2011. http://news.ucsc.edu/2009/12/3439.html 6. Takeda, G., Ford, E. B., Sillis, A., Rasio, F. A., Fischer, D. A., and Valenti, J. F. “Structure and evolution of nearby stars with planets. II. Physical properties of 1000 cool stars from the SPOCS catalog.” The astrophysical journal supplementary series 168.2 (2007): 297-318. Print. 7. The planetary society. Web. Feb 2011. http://www.planetary.org/exoplanets/howwefind.php 8. Trilling D. E., Bryden, G.; Beichman, C. A.; Rieke, G. H.; Su, K. Y. L.; Stansberry, J. A.; Blaylock, M.; Stapelfeldt, K. R., Beeman, J. W., and Haller, E. E. "Debris Disks around Sun-like Stars". The Astrophysical Journal 674.2 (2008): 1086–1105. Print 9. Vogt, S. S., Wittenmyer, R. A., Butler, R. P., O’Toole, S., Henry, G. W., Rivera, E. J., Meschiari, S., Laughlin, G., Tinney, C. G., Jones, H. R. A., Bailey, J., Carter, B. D., and Batygin K. “A super Earth and two neptunes orbiting the nearby sun like star 61 Virginis.” The astrophysical journal 708 (2010): 1366-75. Print. Read More