외계 행성체의 검출 Giordano Bruno (1548 -1600) Christian Bartholméss, Jordano Bruno (Paris: Libaririe Philosophique de Ladrange, 1846), frontispiece. S. S. Hong http: //galileo. rice. edu/chr/bruno. html SNU, 05 -11 -05
지구인의 정체는 자신의 우주적 이웃과의 만남에서 확인될 것입니다. 우주적 이웃을 찾으려는 지구인의 노력은 이미 그 첫 발을 내디뎠습니다. 달 표면에 찍힌 이 발자국들이 우리의 확고한 의지를 드러내고 있습니다. 우리의 이웃과 손을 맞잡고 만남의 기쁨을 나누기까 지, 앞으로 얼마나 더 긴 세월을 기다려야 할지 아직 은 모르겠습니다. 하지만 우리의 최우선 과제는, 인류의 우주적 피붙 이들이 거주할 지구형 고체 행성의 존재를 확인하는 일입니다. S. S. Hong ; SNU 05 -11 -05
OBSERVATIONAL DETECTION OF EXTRA-SOLAR PLANETS 1. HUNTING OF EXTRA-SOLAR PLANETS 2. OCCULTATION OF CENTRAL STAR BY PLANET 3. CORONAGRAPH: An Occultation Maker 4. FRUITS OF DOPPLER SPECTROSCOPY 5. GRAVITATIONALLY REFRACTED RADIATION 6. THERMAL EMISSION FROM DEBRIS 7. PROSPECT OF THE IMMEDIATE FUTURE 8. SUMMARY AND CONCLUSION S. S. Hong ; SNU 05 -11 -05
REFERENCES : Gilmour, I. 2004, in An Introduction to ASTROBIOLOGY, Chap. 6 The Detection of Exoplanets, pp. 199 - 231. Ulmschneider, P. 2003, in INTELLIGENT LIFE IN THE UNIVERSE, Chap. 3 The Search for Extrasolar Planets, pp. 51 - 78. Lunine, J. I. 2005, ASTROBIOLOGY A Multidisciplinary Approach, Chap. 15 Life Elsewhere II: The Discovery of Extrasolar Planetary Systems and the Search for Habitable and Inhabited Worlds, pp. 474 - 508. Morrison, D. and Owen, T. 2003, THE PLANETARY SYSTEM, 3 rd Ed. Chap. 18 Distant Worlds, pp. 471 – 502. Im M. 2005, Why IR, a ppt file presented to an Astronomy Colloquium, SEES, Seoul National University. S. S. Hong ; SNU 05 -11 -05
1. HOW TO HUNT EXOPLANETS 1 -1 WHY NOT JUST LOOK AT IT The planet is going to be drowned in the flood of light from its much brighter central star, even in space. The Earth atmosphere makes things much worse for ground based observations by blurring the images. S. S. Hong ; SNU 05 -11 -05
Resolving Power of Telescope Light is subject to diffraction due to its wave nature. S. S. Hong ; SNU 05 -11 -05
The problem of diffraction is compounded by atmospheric blurring due to air turbulence. Although stars are almost point like sources, but they look like fuzzy disks through ground based optical telescopes. S. S. Hong ; SNU 05 -11 -05
Under the most ideal situation the minimum angle diffraction of separation a telescope can resolve is given by the ratio of wavelength to diameter D of the telescope aperture: diffraction = 1. 22 D = 0 . 126 [ 5, 000 Å ] [ 102 cm D ] In practice stellar images can not be sharper than the atmospheric seeing disk, which is of the order of 0. 1 even at world best observatory sites: The atmospheric turbulence beats the diffraction limit of 1 m telescope. Human eye commands at best about 30 of resolving power. For a hypothetical observer at 10 pc away from us, the Sun-Jupiter distance extends 0 . 52, which is four times the diffraction limit of 1 meter telescope. The diffraction limit of only meter class telescopes is good enough to resolve extrasolar Jovian planets and terrestrial ones as well. S. S. Hong ; SNU 05 -11 -05
Flooding of Light from Central Star Cause of the 1010 - fold Decrease (-16. 5) – (- 6. 8) = - 9. 7 geometrical dilution R 2 4 AU 2 1. 8 x 10 -9 Earth albedo = 0. 3 mean phase = 0. 5 in total 1. 8 x 10 -9 x 0. 3 x 0. 5 = 2. 7 x 10 -10 Visible light detectors with dynamic range 1010 are hard to come by. Therefore, it is impossible to detect the central starlight that is scattered or reflected by extra-solar planets. It may be possible to detect thermal emission from extra-solar planets, particularly in far IR wavelengths, since Sun overpowers Jupiter by 105~6 in FIR emission. S. S. Hong ; SNU 05 -11 -05
Why is IR So Important ? in visible light in infra - red S. S. Hong ; SNU 05 -11 -05
Even cold stuff can be ‘hot’ in IR ! brown dwarf Orion in visual and IR S. S. Hong ; SNU 05 -11 -05
before bouncing the ball after a few bouncings S. S. Hong ; SNU 05 -11 -05
Infrared Excess in the SED theoretical model simulations for the spectral energy distribution of the Solar system as observed by some intelligent beings 10 pc away from us S. S. Hong ; SNU 05 -11 -05
Direct Hunting versus Indirect Guessing Direct Methods : unambiguous recognition of those photons that left extra-solar planet • It is impossible to distinguish visible photons of planet origin from ones of the central star. Direct method works only for the Solar system. • It looks promising to distinguish origins of the IR photons. Indirect Methods : seek for observable consequences of the existence of planets orbiting around stars under consideration What might then be the observable consequences?
1 -2 INDIRECT DETECTION OF EXOPLANETS/ DEBRIS DISK Natural Occultation : transit of planet in front of the central star Coronagraph : blocking off the starlight by occulting disk Doppler Shift : Kepler Motion, gravitational wobbling Gravitational Lens : gravitationally refracted light Thermal Emission from Debris Disk : Dust is a better tracer than planet. Nulling Interferometry in Space : a promising future technology for direct detection to be employed in NASA TPF or ESA Darwin project S. S. Hong ; SNU 05 -11 -05
2. OCCULTATION OF CETRAL STAR BY PLANET 2 -1 OCCULTATION PHOENOMENON An accuracy better than 1% is required in photometry. If Doppler spectroscopy is done simultaneously, size of the planet, semi-major axis and inclination angle of the orbit can be fixed from the light and velocity curves. S. S. Hong ; SNU 05 -11 -05
2 -2 AN EXAMPLE OF OCCULTATION OBSERVATIONS HD 209458 S. S. Hong ; SNU 05 -11 -05
2 -3 DETERMINATION OF PLANET SIZE The three lines correspond to the three different-sized planets; from top to bottom : 1. 15, 1. 27, and 1. 40 RJ. S. S. Hong ; SNU 05 -11 -05
3. CORONAGRAPH: An Occultation Maker 3 -1 DIRECT DETECTION OF BROWN DWARF NASA IRTF on top of Mauna Kea, Hawaii IR image taken by a coronagraph with specially designed soft edge after heavy image processing with specially developed SWs S. S. Hong ; SNU 05 -11 -05
S. S. Hong ; SNU 05 -11 -05
3 -2 RECENT INNOVATIONS IN OCCULTATION THECHIQUE
Coronagraph + Adaptive Optics on 10 m Class Telescopes A brown dwarf of mass 60~80 MJ orbits around the central star at 20 AU distance. Occulting disk removes the central starlight; and a flexible secondary mirror corrects for atmospheric distortion. S. S. Hong ; SNU 05 -11 -05
4. FRUITS OF DOPPLER SPECTROSCOPY 4 -1 PRINCIPLE BEHIND THE DOPPLER EFFECT Letters written regularly by a traveling salesman ought arrive his wife at ever increasing intervals as he moves away from home. However, the letters written on his way back from the trip reach his wife at ever decreasing intervals. ( obs - o) o = vrad c or o = vrad c Measurements of the Doppler shift determine the relative velocity vrad of the source with respect to the observer. S. S. Hong ; SNU 05 -11 -05
4 -2 DOPPLER SHIFT OF SPECTRAL LINE In a star-planet system the star orbits the center of mass, as does the planet. On the other hand the center of mass draws a straight line in the sky plane. Although the planet can not be spotted by an Earth bound observer, the orbital motion generates periodic change in the radial velocity of the star. The Doppler shift measured by spectroscopic means may tell us the existence of circum-stellar planet or planets. S. S. Hong ; SNU 05 -11 -05
S. S. Hong SNU, 05 -11 -05
The amplitude of radial velocity curve depends on the star-to-planet mass ratio, the semi-major axis, and the orbital inclination. The radial velocity becomes zero : Maximum amplitude is obtained : S. S. Hong ; SNU 05 -11 -05
4 -3 ESTIMATES OF THE DOPPLER SHIFT FOR SUN BY EARTH Vrad, E = 30 km s-1 x m. E (M⊙ + m. E) = 3 x 106 cm s-1 x [6 x 1027 g/ 2 x 1033 g] = 9 cm s-1 max, E = 5000Å x 9 cm s-1 3 x 1010 cm s-1 = 1. 5 x 10 -6 Å BY JUPITER Vrad, J = 1. 4 x 106 cm s-1 x m. J (M ⊙ + m. J) = 13 m s-1 max, J = 2 x 10 -4 Å In principle semi-major axis and eccentricity can be determined for the orbit, but only lower limit can be given to the planet mass; since orbital inclination is unknown. How to measure the wavelength change so accurately, even if one may monitor for tens of years? S. S. Hong ; SNU 05 -11 -05
4 -4 WAVELENGTH CALIBRATION Noble Idea + Pioneer’s Dedication Michel Mayor on the right discovered the first extra-solar planet around star 51 Peg, together with Geoff Marcy on left who immediately confirmed it. Both men have gone on to discover many more wonderful new worlds. The gas provides them with a fine ruler for precise measurement of wavelengths. Extensive computing analysis is required for reducing large volume of data taken over a decade, and will be so over coming many decades. S. S. Hong ; SNU 05 -11 -05
4 -5 EARLY DISCOVERIES High Velocity resolution High Spectral Resolution • Large Telescope + High Quality Spectrograph + Decade Long Monitoring • Extremely Accurate Calibration of Wavelengths POISON GAS S. S. Hong ; SNU 05 -11 -05
An Example of High Quality Data S. S. Hong ; SNU 05 -11 -05
4 -6 CURRENT STATUS OF THE ART Discovery of terrestrial planets is still challenge of the generations to come. S. S. Hong ; SNU 05 -11 -05
4 -7 SOME OF THE HIGHLIGHT FINDINGS Hot Jupiters ! S. S. Hong ; SNU 05 -11 -05
Mass and Semi-major Axis of Extra-solar Planets planetary system S. S. Hong ; SNU 05 -11 -05
4 -8 OBSERVATIONAL BIAS massive planets ; short orbital periods ; small semi-major axis ; single component systems ; edge-on orbits ; nearby systems Is the Solar system an example of exceptional cases ? Have only exceptional systems been detected so far ? S. S. Hong ; SNU 05 -11 -05
5. GRAVITATIONALLY REFRACTED RADIATION 5 -1 GRAVITATIONAL LENS Einstein ring S. S. Hong ; SNU 05 -11 -05
5 -2 A SPLENDID FEAST OF GRAVIATIONAL MACRO-LENS 20세기 최고의 물리학자 앨버트 아인슈타인은 다음과 같이 말했습니다. "인생에는 두 가지 삶 밖에 없다. 한 가지는 기적 같은 건 없다고 믿는 삶. 또 한 가지는 모든 것이 기적이라고 믿는 삶. 내가 생각하는 인생은 후자이다. " S. S. Hong ; SNU 05 -11 -05
5 -3 PRINCIPLE BEHIND GRAVIATIONAL MICRO-LENS S. S. Hong ; SNU 05 -11 -05
5 -4 EXAMPLE OF GRAVIATIONAL MICRO-LENS A micro-lensing event can be confirmed by monitoring photometry at two wavelength bands, as the gravitational lensing affects all wavelengths in the same way. S. S. Hong ; SNU 05 -11 -05
6. THERMAL EMISSION FROM DEBRIS Why We are So Much Interested in Debris: Many small particles render much wider area than a single large particle of the same total debris mass: If a large mass body of radius R is divided into N small particles of size s, we expect an enormous enhancement in the total cross-sectional area: = [N s 2 R 2] = N [s R]2 = [R s]3 [s R]2 = [R s] This can be an enormously large number! S. S. Hong ; SNU 05 -11 -05
This is the reason why it is easier to observe proto-planetary disk than planet, and why Beta Pictoris demonstrates her charm and glory in IR emission and scattered visible light as well. This is the reason why we say “Small is better than Large!” S. S. Hong ; SNU 05 -11 -05
7. PROSPECT OF THE IMMEDIATE FUTURE Comparison of Planet Hunting Methods as observed at 5 pc away from the Solar system S. S. Hong ; SNU 05 -11 -05
Limitations and Promises S. S. Hong ; SNU 05 -11 -05
8. SUMMARY AND CONCLUSION 1. The problem of atmospheric blurring can be handled comfortably by adaptive optics even on ground and of course on space platform. 2. Light flooding is a target for coronagraph. 3. With two decades of dedicated struggle the Doppler spectroscopy has revealed a glimpse of the Promised Land, I mean, Gardens of Eden for extra-solar intelligent beings. 4. Yet, extra-solar counterparts of the terrestrial planets defy all our hunting effort with contemporary innovations. 5. Nulling interferometry in space and monitoring of micro-lensing events on the Earth and from the space as well promise us to witness extra-solar terrestrial planets in a coming decade. 6. Large millimeter radio telescope arrays being built, like ALMA some 5, 000 m above the sea level in Northern Chile, will be available for us within a decade to probe fine details in dense molecular cores, proplyds, and debris disks. 7. The sub-millimeter radio interferometry will eventually detect biological signs, if intelligent beings enjoy civilizations that are advanced at least as ours. S. S. Hong ; SNU 05 -11 -05
In Conclusion : I may proclaim you are the blessed generation of human beings; after so many millions of years we humans are soon to hear about news from our cosmic neighbors. You are the first members of the species to receive such a good news. Let us think about Fr. Giordano Bruno of the 16 th century. And let us pay a special tribute to our beloved poet Ji Yong Chung, who wrote in 1937 : 별 똥 떨 어 진 곳 마 음 에 두 었 다 다 음 날 가 보 려 벼 르 다 이 젠 다 자 랐 소. It is not Ji Yong but Seungsoo who has ‘grown up’ too early. This is the very reason why I envy you so much. I, therefore, ask each one of you to live a cosmopolitan life in its fuller and truer sense. S. S. Hong ; SNU 05 -11 -05
Appendix: Kepler’s Third Law spectroscopic observations maximum radial velocity orbital velocity spectral type of the central star mass M of the star mass m of the planet orbital period P, star mass M sin i , planet mass m semi-major axis a S. S. Hong ; SNU 05 -11 -05
Giordano Bruno (1548 -1600) Filippo Bruno was born in Nola, near Naples, the son of Giovanni Bruno, a soldier, and Fraulissa Savolino. He took the name Giordano upon entering the Dominican order. In the great Dominican monastery in Naples (where Thomas Aquinas had taught), Bruno was instructed in Aristotelian philosophy. His exceptional expertise in the art of memory brought him to the attention of patrons, and he was brought to Rome to demonstrate his abilities to the Pope. During this period he may also have come under the influence of Giovanni Battista Della Porta, a Neapolitan polymath who published an important book on natural magic. Bruno was attracted to new streams of thought, among which were the works of Plato and Hermes Trismegistus, both resurrected in Florence by Marsilio Ficino in the late fifteenth century. Hermes Trismegistus was thought to be a gentile prophet who was a contemporary of Moses. The works attributed to him in fact date from the turn of the Christian era. Because of his heterodox tendencies, Bruno came to the attention of the Inquisition in Naples and in 1576 he left the city to escape prosecution. When the same happened in Rome, he fled again, this time abandoning his Dominican habit. For the next seven years he lived in France, lecturing on various subjects and attracting the attention of powerful patrons. From 1583 to 1585 he lived at the house of the French ambassador in London. S. S. Hong ; SNU 05 -11 -03
During this period he published the books that are most important for our purposes, Cena de le Ceneri ("The Ash Wednesday Supper") and De l'Infinito, Universo e Mondi ("On the Infinite Universe and Worlds"), both published in 1584. In Cena de le Ceneri, Bruno defended the heliocentric theory of Copernicus. It appears that he did not understand astronomy very well, for his theory is confused on several points. In De l'Infinito , Universo e Mondi, he argued that the universe was infinite, that it contained an infinite number of worlds, and that these are all inhabited by intelligent beings. Wherever he went, Bruno's passionate utterings led to opposition. During his English period he outraged the Oxford faculty in a lecture at the university; upon his return to France, in 1585, he got into a violent quarrel about a scientific instrument. He fled Paris for Germany in 1586, where he lived in Wittenberg, Prague, Helmstedt, and Frankfurt. As he had in France and England, he lived off the munificence of patrons, whom after some time he invariably outraged. In 1591 he accepted an invitation to live in Venice. Here he was arrested by the Inquisition and tried. After he had recanted, Bruno was sent to Rome, in 1592, for another trial. For eight years he was kept imprisoned and interrogated periodically. When, in the end, he refused to recant, he was declared a heretic and burned at the stake. It is often maintained that Bruno was executed because of his Copernicanism and his belief in the infinity of inhabited worlds. In fact, we do not know the exact grounds on which he S. S. Hong ; SNU 05 -11 -03
was declared a heretic because his file is missing from the records. Scientists such as Galileo and Johannes Kepler were not sympathetic to Bruno in their writings. Sources: A convenient introduction to Bruno is the article by Frances Yates in the Dictionary of Scientific Biography. Several of Bruno's works have been translated into English. See The Ash Wednesday Supper, tr. Stanley L. Jaki (The Hague: Mouton, 1975); Sidney Greenberg, The Infinite in Giordano Bruno, with a Translation of his Dialogue Concerning the Cause, Principle, and One (New York: King's Crown Press, 1950); Jack Lindsay, Cause, Principle, and Unity; Five Dialogues (New York: International Publishers, 1964); Dorothea Waley Singer Giordano Bruno, his Life and Thought. With Annotated Translation of his Work, On the Infinite Universe and Worlds (New York: Schuman). The crucial work on Bruno's thought is Frances Yates, Giordano Bruno and the Hermetic Tradition (Chicago: University of Chicago Press, 1964). See also Walter Pagel, "Giordano Bruno: The Philosophy of Circles and the Circular Movement of the Blood, " Journal of the History of Medicine and Allied Sciences 6 (1951)): 116 -125; Angus Armitage, "The Cosmology of Giordano Bruno, Annals of Science 6 (1948): 24 -31. S. S. Hong ; SNU 05 -11 -03
별똥이 떨어진 곳 정 지용 밤뒤 1를 보며 쪼그리고 앉았으려면, 앞집 감나무 위에 까치 둥우리가 무섭 고, 제 그림자가 움직여도 무섭다. 퍽 추운 밤이었다. 할머니만 자꾸 부르고, 할머니가 자꾸 대답하셔야 하였고, 할머니가 딴 데를 보지나 아니하시나 하 고, 걱정이었다. 아이들 밤뒤 보는 데는 닭 보고 묶은 세배를 하면 낫는다고, 닭 보고 절을 하 라고 하셨다. 그렇게 괴로운 일도 아니었고, 부끄러워 참기 어려운 일도 아 니었다. 둥우리 안에 닭도 절을 받고, 꼬르르 소리를 하였다. 별똥을 먹으면 오래 산다는 것이었다. 별똥을 주워 왔다는 사람이 있었다. 그날 밤에도 별똥이 찌익 화살처럼 떨어졌다. 아저씨가 한번 메추라기를 산 채로 훔켜잡아 온, 뒷산 솔 포대기 2 속으로 분명 바로 떨어졌다. S. S. Hong ; SNU 05 -11 -10
별똥 떨어진 곳 마음에 두었다 다음날 가보려 벼르다 이젠 다 자랐소. 『소년』, 1937. 12. ─『정지용전집』, 민음사, 1988 에서 재수록 ─『모던 수필』, 향연, 2003 에서 재재수록 ssh S. S. Hong ; SNU 05 -11 -10
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