Search For Other Worlds

SEARCH FOR OTHER WORLDS Roberto Bartali –

Abstract People always asked themselves: “Are we alone in the Universe?” The answer starts to come in 1995 when the first planet orbiting a star, which is not our Sun, was discovered. This work is about the search of those planets, focused on the methodologies employed for its detection from the ground and from space. The development of new technologies, in the last few years in the field of optic, electronic and mechanics, permitted the construction of giant telescopes, interferometers and space based observatories which show us many features totally new. Many theories were confirmed thanks to these powerful instruments and many others were placed in doubt. The first part of the work is focused to the description of each method used for the detection of exoplanets, describing the principle on which it is based, the kind of instruments it uses and where it is actually employed for the job. The second part is the description of the currently working and planned space missions aimed to the exoplanet search. Day after day, new discoveries came to light, the number of exoplanets grows rapidly, I will present a table of the principal characteristics of all known planets orbiting other stars. Our theories about the formation of the Solar System worked well until the discovery of giant planets orbiting very close to their parent stars. In the last section I will discuss why the old theory does not fit in the light of the newly discovered extrasolar planetary systems.

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Introduction People around the world always asked themselves: “Are we alone in the Universe?”, “Is the Sun the only star with a realm of planets?” The answer for the first question is: “Maybe yes, maybe not”, but, for the latter is “Yes!”. Now we know many other planetary systems in our Galaxy. From long ago, philosophers and astronomers though about the possibility of the existence of other planets around stars, but it was until 1995 when the first extrasolar planet, or exoplanet, was discovered. In this paper I will show how Figure 1 astronomers search for and detect exoplanets The first possible image of an exoplanet in the system of the star 2M1207 describing the techniques, the instrumentation From: http://www.eso.org/outreach/pressand the methods employed to find them. rel/pr-2004/pr-23-04.html The search for exoplanet is the newest field of Astronomy, so many new technologies was developed and many others must be developed in the future to achieve better and faster results. I will present, also, these new techniques and what kinds of researches are planned in the future, especially those devoted to the search for exoplanets from space. I will discuss, also, about the theories we have on the formation of a planetary system, the discovery of planets around stars, placed in doubt what we know until now. Even when the observation of an exoplanet is difficult, it is not a field exclusively for astronomers equipped with multimillion dollars equipments, a well skilled amateur, can do it and, also, discover a new planet with modest instruments.

Some history The idea of other planets orbiting stars came from the mind of many ancient philosophers, after the invention of the telescope, astronomers tried to find them for almost four centuries and now we have the evidence and possibly an image of an exoplanet. Figure 2 The Greek philosopher Democritus From: http://www-gap.dcs.stand.ac.uk/~history/Mathematicians/Democritus.html

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Democritus (460-370 BC) (Figure 2), and Epicurus ((341-270 BC) were Greek philosophers of the Atomist group [1], they were many centuries ahead of their time, because they believed in the infinite number of other worlds

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Unfortunately, astronomy, and science in general, were strongly influenced by Aristotle (384-322 BC) who believed in the Earth as the only planet in the Universe. • Many centuries later, an Italian philosopher, Giordano Bruno (1548-1600), retakes the Atomist theories saying that there are an infinite number of stars and an infinite number of planets, like Earth, orbiting around them; but that affirmation was sufficient to be condemned burnt at the stake [2]. • Christian Huygens (1629-1695) was the first to search for exoplanets [1]; • For many years Peter van de Kamp (1901-1995) tried, without any result, to find planets around the Barnard star [3],[9]. • Otto Struve (1897-1963) [4] proposed, in 1952, that studying changes in radial velocity with a spectroscope first, and, then Figure 3 measuring variations of the Mayor and Queloz, discoverers of the first exoplanet luminosity with a photometer, it From: http://www.obscould be possible to detect a planet hp.fr/www/nouvelles/51orbiting a star [5]. peg.html • Frank Drake (Figure 4) developed, in 1961, an equation “The Drake Equation” [6],[7],[8] for calculating (statistically) the number of possible planets with technological civilizations around other stars in the Galaxy. • Michel Mayor and Didier Queloz (Figure 3) discovered the first exoplanet orbiting the star 51 PEG in 1995 (October 5) with the Hamilton Spectrograph at the Lick Observatory. [11] • The ESO VLT/NAOS adaptive optics imaging facility, take what is seems to be the first picture of an exoplanet (Figure 1) on September 10, 2004. [12]

The Drake Equation The first attempt to evaluate the number of possible planets in the Galaxy was issued by Frank Drake in 1961. He proposed an equation where the result could be as true as possible depending on the certainty of Figure 4 the value of Frank Drake and his famous equation each term. From:http://www.seti.org/site/pp.asp? c=ktJ2J9MMIsE&b=179073

Unfortunately we can only “guess” about the value of all of the terms of the equation [7],[8]. The purpose of that formula is to get an approximate number of civilizations with technological skills sufficient to send interstellar messages in the form of electromagnetic 3

waves. For this work, I am interested only in the second (Fp = fraction of stars with planets) and, only partially, in the third (Ne = number of planets per system) terms. I will explain, briefly, each term of the Equation: N = R* Fp Ne Fl Fi Fc L Where: • N = number of civilizations in the Galaxy transmitting electromagnetic waves. • R* = rate of long living star formation per year. • Fp = fraction of those stars with planetary systems. • Ne = number of planets suitable for life. • Fl = fraction of suitable planets on which life appears. • Fi = fraction of planets on which intelligent life emerges. • Fc = fraction of technological and communicating civilizations. • L = length of time, in years, such civilizations are transmitting signals. The best “guess” value for each term depends on who fits all the numbers in the equation; for example, Shostak [7] gives this set of possible values: R* = 5; Fp = 0.5; Ne = 1; Fl = 1; Fi = 1; Fc = 1; L = 10,000; so N = 25000 .

Earth based detection methods and projects There are several methods used by astronomers to detect exoplanets, most of them are indirect [16]. The light we receive, from the planet, is millions of times lesser than the

Figure 5: Diagram of methods used for exoplanet search by M. Perrymann (ESA) From: http://astro.estec.esa.nl/SA-general/Projects/Staff/perryman/planet-figure.pdf

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light emitted by the host star because they are orbiting at very short distance from it and their diameters are tens of times lesser than the diameter of the star. The figure 5 represents a summary of, all currently and planned for the future, methods for the detection of exoplanets, it is created by M. Perryman of the European Southern Observatory (ESA). I will describe the concept behind each of the methods currently used. As we see in the above diagram there are three main approaches based on: • Dynamical effects o Radial velocity o Astrometry o Pulsar timing • Microlensing • Photometric signals o Imaging direct detection o Transit Radial Velocity This is the most successful method for indirect exoplanet detection. Almost 90% of the known planets orbiting other stars than our Sun were discovered with it. It is based on the Doppler Effect. If a star has a planetary system, the center of mass of the system is not the same as the center of the star, it is shifted. An orbiting planet asserts a pull on the star and the star shows a wobble in its movement which period is the same as the orbital period of the planet (Figure 6). The amount of the change in the radial velocity (figure 7) is proportional to the mass of the planet respect to the mass of the star and to the radius of the planet orbit. For example: if the planet mass is 0.001 Figure 6 times the mass of the star and the planet is The planet and the star moves around orbiting at a speed of 20 km/s (20,000 m/s), the the center of mass of the system From: www.star.ucl.ac.uk/ star suffer from an oscillation (a variation in its ~rhdt/diploma/lecture_2/ radial velocity) of 20 m/s. If the orbital period of the planet is 1 year, we can detect a periodical variation of +/- 20 m/s on the velocity profile of the star each year, the effect is more evident if the planet is orbiting at short distance. If the orbit is not circular (it has some eccentricity) the spectra is red and blue shifted in irregular form showing that eccentricity. This effect is detectable from Earth by using a spectrometer with sufficient resolution. What we see is a Doppler shift in the spectral lines of the star (Figure 8), when the planet is orbiting toward us the lines are blueshifted but, if the planet is going away, the lines are redshifted. Actual spectroscopic technology is able to resolve changes in the radial velocity of a star as low as 1 m/s or less [10].

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If the star has more than one planet, each one pulls the star proportionally of its mass and semimajor axis. This method is very effective. About 122 planets were discovered by it. We can calculate many parameters for the system: • Mass of the planet • Orbital period • Orbital semimajor axis • Eccentricity of the orbit • Possible detection of more planets in the same system There is a problem that arises using this method because it works well only if the plane of the orbit of the planet is aligned with our line of sight. In this case all the parameters measured corresponds to the real parameters of the system, but if the orbit is inclined, Figure 7 there is a factor of 1/sin i to compensate Radial velocity curve variations for the star for (where i is the inclination of the Gliese876 orbit). From: http://www.obsIf the value of the inclination is hp.fr/www/nouve not known, we only calculate the least lles/gl876-fr.html possible mass of the planet [15]; but the value of i, the inclination, is measurable with the aid of very precise astrometric observations, because we have to measure the movement of the star relative to the background sky. This method is suitable only for the detection of massive planets and /or planets orbiting closely to the parent star (with our current technology). This is a list of working projects operating in the field of exoplanet search by the method of Radial Velocity: • Absolute Astronomical Accelerometer EMILIE Spectrograph. http://www.aero.jussieu.fr/experience/AAA/ Operating on the Observatoire de HauteProvence • The Advanced Fiber-Optic Echelle (AFOE) spectrometer http://cfa-www.harvard.edu/afoe/afoe.html Operating on Whipple Observatory • High resolution Echelle Spectrometer Anglo Australian Planet Search www.aao.gov.au • California and Carnegie Planet Figure 8 Search Diagram of the Doppler shift of spectral lines from the star www.exoplanet.org From: www.star.ucl.ac.uk/ • Coralie at Leonard Euler Swiss ~rhdt/diploma/lecture_2/ Telescope 6

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Operating at La Silla http://obswww.unige.ch/~udry/planet/coralie.html ELODIE is a fixed-configuration, cross-dispersed Echelle Spectrograph http://obswww.unige.ch/~udry/planet/elodie.html Operating on the Observatoire de Haute-Provence Exoplanet tracker with dispersed fixed-delay interferometer http://www.astro.psu.edu./users/jian/project10 Operating at the KPNO 2.1m telescope Doppler planet search with Fringing spectrometer http://www-phys.llnl.gov/H_Div/doppler/ High Accuracy Radial Velocity Planetary Search (HARPS) http://obswww.unige.ch/Instruments/harps/Welcome.html Operating at La Silla Observatory 3.6m ESO Telescope Hobby Eberly Telescope http://www.as.utexas.edu/astronomy/research/ss.html Operating at Mc Donald Observatory TNG High Resolution Spectrograph http://www.pd.astro.it/new_sites/ESP/resultspage.htm#Risultato%20metallicita%20binarie

Operating at Telescopio Nazionale Galileo Spectrographe pour l´observation des Phenomenes Sismologiques et Exoplanetaires (SOPHIE) http://www.obs-hp.fr/www/technique/sophie/sophie.htm Operating on the Observatoire de Haute-Provence • Extrasolar Planet Search Project http://www.spectrashift.com/ • Ultra Violet Visual Echelle Spectrograph (UVES) http://www.eso.org/instruments/uves/ Operating at ESO •

Astrometry Astrometry is the field of Astronomy which is interested to measure the position of a star respect to some reference frame. With this in mind, it is possible to detect a planet revolving around a star by accurately measuring the position of the star respect to some other background stars [9]. This is because in a planetary system, the star gravity maintains the planet in orbit, but the planet also pushes the star with a force proportional to its Figure 9 Diagram of the displacement of the movement of the star caused by a planet orbiting it. From: www.star.ucl.ac.uk/ ~rhdt/diploma/lecture_2/

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mass and the distance to the star (Figure 9). If the plane of the orbit is perpendicular to our line of sight (or with a small inclination) it is possible to see measure the star wobble. The star is oscillating, respect to the reference “fixed” stars with a period equal to the orbital period of the planet. Knowing the period, it is possible to calculate the semimajor axis of the orbit and the mass of the planet. Even when this method can be used to confirm detections made with other methods, the only one that can be used to confirm a detection made by astrometry is the direct imaging. This is because the planet is always aside of the star, like a double star system. Some suspected exoplanets were detected y this method, but they are not confirmed yet. It is very difficult to detect a planet this way from ground because the atmospheric turbulence reduce the resolution of the telescope, but new telescope technologies, like optical interferometry and adaptive optics, may improve the probability to find planets. The best result will be achieved from space (see Space based detection methods and projects). There are a few projects, not operating yet, forwarded to exoplanet searching: • Keck Interferometer http://www2.keck.hawaii.edu • Palomar Testbed Interferometer http://huey.jpl.nasa.gov/palomar/ • Phase-Referenced Imaging and Micro-arcsecond Astrometry PRIMA http://www.eso.org/projects/vlti/instru/prima/index_prima.html • ESO-VLT Single Telescope Extrasolar Planet Survey STEPS http://huey.jpl.nasa.gov Pulsar timing

Figure 10 Pulse repetition rate from a pulsar orbited by a planet changes From: http://www.astro.psu.edu/users/alex/pulsar_ planets_text.html

After a supernova explosion event, the star collapses and forms a neutron star. This neutron star has a very intense magnetic field but not aligned with the spin axis, this misalignment produces beamed radio pulses (hence the name of pulsar); if the rotation axis is toward our line of sight we can detect those pulses. The radio pulses emitted are very constant (but in a large timescale, the frequency slowly decay), so if a planet or another star is revolving around the pulsar, the effect is a change in the pulse repetition rate (Figure 10), which depends on the orbital period of the planet. This is relatively easy to measure with modern radiotelescopes. Basically, we need a very precise reference timer, like atomic clocks, to compare it with the pulse repetition rates

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of a millisecond pulsar. pulsar. A few planets were discovered by this method, but it holds two records: the oldest and the farthest planet detected [14],[18],[19]. This is a list of projects, working or under test, in the pulsar timing planet search: • Pulsar Planet Detection http://www.astro.psu.edu/users/alex/pulsar_planets.htm Operating at Penn. State University • Nancay Decametric search for Exoplanets Under test on Nancay Radiotelescope • Low Frequency Array LOFAR http://www.lofar.org/ Project Gravitational micro lensing

Figure 11 Diagram of the microlensing effect From: http://www.macalester.edu/astronomy /courses/physics50/spring2002.html

The Theory of Relativity formulated by Einstain at the beginning of the XX century, forecast the lensing effect. It consists of the deviation of light from a distance source when passing close to a massive object (Figure 11 and 12) due to the gravity of the interfering object. More massive the object, between the source and the observer, more deviated is the light. With this in mind, astronomers tried to detect exoplanets when they pass in front of the parent star. This implies that the orbit plane is parallel to our line of sight. This method is capable to detect planets with mass of several Jupiter mass and as low as the Earth mass, even if the planet is orbiting at distances from 1 to 4 astronomical units from the star. This technique is the best for the search of exoplanets from ground based telescopes because is the only one capable to detect Earth mass objects. The lensing effect may be very large as we see for the MACHO (Massive Compact Halo Objects) 98-BLG-35 (figure 13), the planet in that system is also the smallest encountered yet, with an approximate mass of 4x10e-5 star masses. Figure 12 Amplification effect of the light from the star due to the microlensing microlensing phenomenon From: http://www.nd.edu/~srhie/MPS/

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Another very interesting case is the planetary detection in multiple star systems. This technique is also unique for detecting planets in binary and multiple star systems. If the orbit is inclined (not parallel to our line of sight) more than the lensing zone, this technique is not usable. Figure 13 Highest microlensing effect detected to date. From: Rhie S.H., et al, 1999

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These are some projects in the field of microlensing planet search: Hungarian Automated Telescope Network (HATN) http://cfa-www.harvard.edu/~gbakos/HAT/Net/main.html Operating at Whipple Observatory MACHO project http://wwwmacho.mcmaster.ca/ Operating in Australia and North America Microlensing Observations in Astrophysics MOA http://www.physics.auckland.ac.nz/moa/ Operating in Australia and Japan Microlensing Planet Search Project http://www.nd.edu/~srhie/MPS/ National Science Foundation The Optical Gravitational Lensing Experiment OGLE http://sirius.astrouw.edu.pl/~ogle/ Operating on Las Campanas Observatory Microlensing Transits Doppler Tomography http://star-www.st-and.ac.uk/~yt2/WEB_GROUP/top.html Operating at University of St. Andrews

Transit Photometry This technique is based on the precise measurement of the star luminosity. If the star is not a variable star, its luminosity is constant, but if a planet pass in front of it, eclipsing the star, the luminosity decrease by an amount of 0.01% to 5 %. This occurs only if the planetary orbit is aligned with our line of sight or the inclination is very low. The amount of the luminosity reduction [45],[47] depends on the diameters of both the star and the planet transiting in front of the star. The duration of the eclipse depends on the mass of the star and on the distance of the planet from it (orbital semimajor axis). If the observation is made also by a spectroscopic technique, it is possible to calculate the mass

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and the size of the star. The period of one revolution of the planet is the time elapsed from an eclipse to another one. Detecting the repetition of these eclipses is the best proof of the reality of the phenomenon. Photometric measurements mast be done with high accuracy because a change of 0.01 magnitudes is very hard to detect. With modern CCD devices and good photometric data reduction software, even a skilled amateur, with a medium aperture telescope (8 to 12 inch diameter) can do a scientific useful work or may discover a new planet. In the figure 14 we see a planet eclipsing a star. The light from the star Figure 14 decrease as the planet passes in front of it. Diagram of a planet transiting in front of a A combination of this method with the star From: spectroscopic analysis of the light from the http//:iac.es/proyect/tep/transitmet.html star when the planet is transiting, may in the future, show the chemical composition of the planetary atmosphere, if it exists, and also if there are the signature of biological activities. As well as the microlensing method, this is suitable for the detection of small planets tens of times the Earth mass and, possibly in the near future, also a terrestrial type planet. A real plot of a light curve is visible in figure 15. It is from data of the Hubble Space Telescope (HST), from the ground it is not possible to get a light curve as clean as that. These are some operating and future development issued to the observation of transiting planets: • TennesseeState/ Smithsonian Automatic Photoelectric Telescope http://schwab.tsuniv.edu/index.html Operating at Fairborn Observatory • Transit Search Figure 15 http://www.transitsearch.org/ Light curve of the star Operating HD209458 observed by the HST. • Vulcan South From: http://www.polartransits.org/ http://reductionism.net.sea Operating at Antarctica nic.net/HD209458/ExoPlane t.html • Permanent All Sky survey PASS http://www.iac.es/proyect/pass/ Project

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The Monitoring Network of Telescopes MONET http://www.uni-sw.gwdg.de/~hessman/MONET/ Project Hungarian Automated Telescope Network http://cfa-www.harvard.edu/~gbakos/HAT/Net/main.html Project Search For Trojan Extrasolar planets http://www.trojanplanets.appstate.edu/Intro.htm Project Stellar Astrophysics & Research on Exoplanets STARE http://www.hao.ucar.edu/public/research/stare/stare.html Project STELLA http://www.aip.de./stella/ Project

Direct Imaging detection The most challenging method to planetary detection is the direct image because the difference in luminosity between the planet and the parent star is in the order of millions to billions. The angular distance of the planet from the star is so small that is in the order of fractions of arcseconds. Figure 1 is an example of the results achieved by this technique; it is the first picture of a planet outside our Solar System. The light emitted by the planet is the Figure 16 reflected light from the parent star [48], it is The VLT complex of 4 8 m telescopes of well visible only when it is in the “full” phase, ESO, their light can be combined forming that is when it is behind the star. This method of an optical interferometer From: www.astrosurf.com/ lombry/astrodetection works best if the planetary orbit is outils2.htm inclined respect to our line of sight. In this case it is visible for most of the orbit, but the planet present phases (just like the inner planets of our solar System Mercury and Venus) that depends on the tilt of the plane of the orbit. It is very difficult to detect a planet with mass less than several times the mass of Jupiter. The observations in the middle infrared are more effective because the difference in luminosity is much less than they are in the visible. This is the approach followed by most projects in this field; obviously the best place to do this kind of research is from Antarctica, but the results obtained by the ESO VLT (Figure 16) are very impressive. The future of this detection method is the use of optical interferometers (Figure 17) and the nulling technique [50]. The latter is based on the shifting of the phase of one element an amount equal to half wavelength to cancel the light at the center of the image.

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This way the star became just a point and it is possible to see a planet or a protoplanetary disk. Figure 17 The scheme of an optical interferometer From: www.astrosurf.com/ lombry/astrooutils2.htm

This is a list of projects working toward the detection and direct imaging of exoplanets:

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Very Large Telescope Interferometer VLTI http://www.eso.org/projects/vlti/ Operating at ESO • Astronomical Nulling Interferometer ANI http://zero.as.arizona.edu/~phinz/nulling.html Project • Mid-InfraRed Large-well Imager MIRLIN http://cougar.jpl.nasa.gov/mirlin.html Operating at Palomar and Keck II telescopes

Space based detection methods and projects Just 30 years ago, our knowledge of the Solar System was very poor and the interest on the observation of planets and their satellites were dissipated because the power of telescopes were not sufficient to shows more than that we know. The construction of giant telescopes, optical interferometers, adaptive optics and super sensitive megapixels CCD were just a dream. The race for the space conquest, changed dramatically that attitude, and astronomers gets new dreams: a telescope in space and spacecrafts to planets became true in just a few years. Missions like Mariner, Pioneer, Viking, and Galileo uncovered many secret of the planets and their satellites, opening a new great interest in our Solar System. Very soon, thanks to the discovery of the first exoplanet in 1995, astronomers started to plan space missions with the aim to uncover the planetary formation secrets and discover many other planetary systems in our Galaxy and, eventually, life! The Hubble Space Telescope (HST) (Figure 18) and the Hipparcos placed the basis for the future space based researches. The former because without the atmospheric aberration shows a completely new Universe discovering the first steps of stars and planetary systems formation. With the precision of the astrometric measurement of the Figure 18 Hubble Space Telescope From: http://oposite.stsci.edu/ftp/pubi nfo/HST/HST_FREE.JPG

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Hipparcos satellite, astronomers will be able to measure very small movement of the stars, revealing the presence of planets revolving around them. I will show in this section only the approved satellite missions (Table 1), briefly describing their scientific goals related to the exoplanet search. There are a lot more missions waiting for approval or under a feasibility study stage. Table 1 Detection methods used by satellites for the search of exoplanets

DETECTION METHOD Transit Photometry Astrometry Astrometry IR imaging Transit Photometry Imaging Photometry Astrometry/Imaging IR Imaging

Figure 19 Artistic impression of COROT From: http://www.astrspmrs.fr/images/satel.gif

SATELLITE COROT GAIA HST JWST KEPLER MOST SIM SPITZER

COROT Convection Rotation and Planetary Transit ( http://www.obspm.fr/encycl/corot.html ) (Figure 19) is a French developed and funded mission with the participation of Austria, Belgium, Brazil, Germany, Spain, ESA and ESTEC. The science project consists of stellar seismology and the study of extrasolar planets with a 30 cm telescope coupled to an array of CCD detectors. It will monitor light curves of selected stars trying to find planets in the Habitable Zone. It is the first approved space mission dedicated to these subjects and it will be launched in June 2006. GAIA

Figure 20 ESA GAIA spacecraft From: http://www.rssd.esa.int/gaia/i mage_gallery.html

(http://sci.esa.int/sciencee/www/area/index.cfm?fareaid=26 ) (Figure 20) is an ESA mission for creating a three dimensional catalog of all objects in the Galaxy with an unprecedented positional and radial velocity. The goal is to get data from 10e9 stars during a period of 5 years, monitoring each object 100 times. It contains 170 CCD cameras with 9 Mpixels each. It will discover planets and brown dwarfs. It will be launched in 2011 and will be doing observations from the L2 point at 1.5 million Km from Earth.

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HST ASTROMETRY ( http://clyde.as.utexas.edu/SpAstNEW/ASTindex.html ) Figure 21 The Fine Guidance Sensor Camera of the HST From: http://www.stsci.edu/instruments/fgs/handb ook/FGS.Cycle11.IHB.pdf

It is a University of Texas program aimed to do precise astrometric measurements of selected objects using the Hubble Space Telescope Fine Guidance Sensor camera (Figure 21). In addition to variable star studies it was used to search for exoplanets around Proxima Cen. JAMES WEBB SPACE TELESCOPE JWST ( http://www.jwst.nasa.gov/ ) it is a NASA optimized infrared space telescope to be launched in 2011 and will be stationary in the L” point of the Earth orbit at 1.5 million km from Earth (Figure 22). The principal instrument will be a 6.5 m IR telescope for wavelength between 6 and 22 micron. The operating temperature will be 50K. The scientific goal is the study of the formation of the Universe and the planetary systems formation. Figure 22 Artistic impression of the JWST From: www.coseti.org/hstjwst.htm

KEPLER (http://discovery.nasa.gov/kepler.html ) is a NASA mission (figure 23) specifically designed for exploring the structure of extrasolar planetary systems and to detect Earth mass planets within the Habitable Zone. Its main instrument will be a photometer with a 95 cm lend diameter. Kepler will monitor 100 thousand Sun-like stars detecting transiting planets. It is programmed for launching in 2007.

Figure 23 Artistic impresión of Kepler satellite From: http://discovery.nasa.gov/kepler.html

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MOST Microvariability and Oscillations of Stars ( http://www.astro.ubc.ca/MOST/ ) Figure 24 Canadian MOST satellite From: http://www.astro.ubc.ca/MOST/media_p ack/most_view.jpg

It is a tiny Canadian space telescope satellite (65x65x30 cm) with a 15 cm telescope measuring small luminosity variations (one part in a million) from a selected catalog of stars up to the 6th magnitude. It will detect the reflected light from exoplanets orbiting very closely to the parent star to study their sizes and atmospheric composition. It was launched in 2003 and it is still operating in a polar orbit. SIM Space Interferometry Mission ( http://planetquest.jpl.nasa.gov/SIM/sim_project.html ) Figure 25 Artist concept of SIM From: http://planetquest.jpl.nasa.gov/images/sim _concept2002_lrg.jpg

Is a NASA mission to be launched in 2009 (Figure 25). It is an astrometric satellite capable to measure the position of the 250 nearest stars to a precision of 1 microarcsecond and of 3 microarcseconds for the next 2000 stars. With this precision it will be able to discover Neptune and Jupiter sized planets around Sun-like stars. Another goal is the study of Hot Jupiter-like planets around young stars to understand how planetary systems are formed. The principal instrument is an optical interferometer with a 10 m diameter for science and an 8,5 m diameter mirror for the guidance. Both mirrors are optimized for the visible part of the EM spectrum. The stability of the fringes will be better than 1/100 of wavelength, the same as the VLA, but for the visible. SPITZER IR Space Telescope ( http://www.spitzer.caltech.edu/index.shtml ) is a NASA space telescope for the IR part of the EM spectrum Figure 26). It was launched in 2003 and still operating. The telescope is Figure 26 The Spitzer IR space telescope From: http://www.spitzer.caltech.edu/picturega llery/galleryimages/model2.jpg

0.85 m diameter optimized for the Infra red spectrum between 3 and 180 micron wavelength and the instruments are cryogenically cooled to near absolute zero. The telescope is protected by a shield. It is observing from a Earth trailing solar orbit. It will be

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used to study the origin and composition of planets, in special case the protoplanetary disk around stars and dust clouds.

Catalogue of known exoplanets The Table 2 is divided in two sections. Table 2a contains: Planet name, parent star, Constellation, Year of discovery and Orbital radius. Table 2b contains: Planet name, Period, K m/s, Parent star mass, eccentricity, R.A. (2000) and DECL. (2000). These tables are a recompilation and an integration of several tables found over the WEB about exoplanets characteristics. They contain all planets detected until now. Unfortunately, this is not an official catalogue, I found many differences in the data presented by various catalogues and not all field are filled because some data I was not able to find yet [39],[40],[41],[42],[43],[44]. Table 2a List of all exoplanet confirmed until now Orbital Radius 0.3 AU 0.19 AU 0.36 AU 0.46 AU 40 AU 0.05 AU

Planet

Star

Constellation

Year

Discovered By

HD 114762 b PSR 1257 a PSR 1257 b PSR 1257 c PSR 1257 d 51 Pegasi b

Coma Berenices

1989 1991 1991 1994 1994 1995

David Latham et al, Alexander Wolszczan Alexander Wolszczan

Michel Mayor and Did

Andromedae

1996

Geoffrey Marcy and R

0.05 AU

55 Cancri b 47 Ursae Majoris b

HD 114762 PSR 1257 PSR 1257 PSR 1257 PSR 1257 51 Pegasi Upsilon Andromedae 55 Cancri 47 Ursae Majoris

Cancer Ursa Major

1996 1996

San Francisco State University of Califo

tau Boo

tau Bootis

Bootes

1996

San Francisco State

70 Virginis b

70 Virginis rho Coronae Borealis 16 Cygni HD 217107 HD 210277 HD 187123 Gliese 876 HD 195019 HD 168443 HD 168443 14 Herculis HD 209458 HD 192263 HD 37124 HD 130322 HD 177830 HD 134987 HR 810 Upsilon Andromedae Upsilon Andromedae HD 222582

Virgo

1996

San Francisco State

0.118 AU 2.1 AU 0.0462 AU 0.43 AU

Corona Borealis

1997

Smithsonian Astrophy

0.23 AU

Cygnus Pisces Aquarius Cygnus Aquarius Delphinus Serpens Serpens Pegasus Aquila Taurus Virgo Taurus Libra Horologium

1997 1998 1998 1998 1998 1998 1998 1998 1998 1999 1999 1999 1999 1999 1999 1999

San Francisco State Keck and Lick Observ Keck Observatory Keck Observatory Haute-Provence Keck and Lick observ Keck and Lick observ Keck and Lick observ Haute-Provence Obser San Francisco State Keck Precision Veloc Keck Precision Veloc Geneva Observatory Keck Precision Veloc Keck Precision Veloc ESO La Silla observa

1.7 AU 0.07 AU 1.097 AU 0.042 AU 0.21 AU 0.14 AU 0.29 AU 2.87 AU 2.5 AU 0.045 AU 0.15 AU 0.585 AU 0.088 AU 1 AU 0.78 AU 0.925 AU

Andromedae

1999

San Francisco State

0.83 AU

Andromedae

1999

San Francisco State

2.5 AU

Aquarius

1999

Keck Observatory

1.35 AU

Upsilon Andromedae b

rho CrB 16 Cygni b HD 217107 b HD 210277 b HD 187123 b Gliese 876 b HD 195019 HD 168443 b HD 168443 c 14 Herculis b HD 209458 b HD 192263 b HD 37124 b HD 130322 b HD 177830 b HD 134987 b HR 810 b Upsilon Andromedae c Upsilon Andromedae d HD 222582 b

Pegasus

17

HD 10697 b HD 83443 b HD 16141 b HD 168746 b HD 46375 b HD 108147 b HD 75289 b BD -10 3166 b HD 6434 b Epsilon Eridani b

HD 10697 HD 83443 HD 16141 HD 168746 HD 46375 HD 108147 HD 75289 BD -10 3166 HD 6434 Epsilon Eridani

Andromeda Vela Cetus Scrutum Monoceros Crux Vela Crater Phoenix Eridanus

1999 2000 2000 2000 2000 2000 2000 2000 2000 2000

McDonald Observatory

HD 38529 b

HD 38529

Orion

2000

San Francisco State

HD 179949 b HD 82943 b HD 121504 b HD 52265 b HD 27442 b HD 160691 b HD 19994 b HD 92788 b HD 12661 b HD 169830 b GJ 3021 b Gliese 86 b HD 190228 b HD 89744 b HD 162020 b HD 4208 b HD 82943 c HD 114783 b HD 142 b HD 4203 b HD 68988 b HD 213240 b 47 Ursae Majoris c HD 23079 b HD 80606 b HD 28185 b HD 178911 b HD 106252 b HD 33636 b HD 39091 b HD 141937 b Iota Draconis b HD 41004A b

HD 179949 HD 82943 HD 121504 HD 52265 HD 27442 HD 160691 HD 19994 HD 92788 HD 12661 HD 169830 GJ 3021 Gliese 86 HD 190228 HD 89744 HD 162020 HD 4208 HD 82943 HD 114783 HD 142 HD 4203 HD 68988 HD 213240 47 Ursae Majoris HD 23079 HD 80606 HD 28185 HD 178911 HD 106252 HD 33636 HD 39091 HD 141937 Iota Draconis HD 41004A

Sagittarius Hydra Centaurus Monoceros Reticulum Ara Cetus Sextans Aries Sagittarius Hydrus Eridanis Vulpecula Ursa Major

2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2001 2002 2002

Anglo-Australian Pla CORALIE survey for s CORALIE survey for s Geneva Observatory Anglo-Australian Pla Anglo-Australian Pla Geneva Observatory San Francisco State San Francisco State ESO La Silla Observa

Canis Major

2002

Ara

2002 2002

La Silla Observatory Geneva Observatory Advanced Fiber-Optic ESO La Silla Observa Keck Precision Veloc Geneva Observatory Keck Precision Veloc Anglo-Australian Pla Keck Precision Veloc Keck Precision Veloc Geneva Observatory University of Califo Anglo-Australian Pla ESO La Silla Observa CORALIE survey for s Geneva Observatory Geneva Observatory Keck Precision Veloc Anglo-Australian Pla Geneva Observatory Lick Observatory Geneva Observatory European Southern Observatory Lick Observatory Anglo-Australian Pla

Sculptor Hydra Virgo Phoenix Pisces Ursa Major Grus Ursa Major Reticulum Ursa Major Eridanus Lyra Virgo Orion Mensa Libra Draco Phoenix

Keck Precision Veloc Geneva Observatory Marcy G., Butler P., Geneva Observatory Marcy G., Butler P., Geneva southern extr CORALIE survey for s California Planet Se

HD 47536 b

HD 47536

HD 136118 b HD 160691 c

HD 136118 HD 160691

HD 49674 b

HD 49674

2002

Keck Observatory

HD 108874 b HD 128311 b HD 72659 b HD 40979 b HD 114386 b HD 150706 b HD 147513 b

HD 108874 HD 128311 HD 72659 HD 40979 HD 114386 HD 150706 HD 147513

2002 2002 2002 2002 2002 2002 2002

Keck Observatory Keck Observatory Lick and Keck observ Geneva Observatory Geneva Observatory Geneva Observatory

2 AU 0.038 AU 0.35 AU 0.066 AU 0.041 AU 0.098 AU 0.046 AU 0.046 AU 0.015 AU 3.3 AU 0.1293 AU 0.045 AU 1.16 AU 0.32 AU 0.49 AU 1.18 AU 1.65 AU 1.3 AU 0.94 AU 0.789 AU 0.823 AU 0.49 AU 0.11 AU 2.31 AU 0.88 AU 0.072 AU 1.69 AU 0.73 AU 1.2 AU 0.98 AU 1.09 AU 0.071 AU 1.6 AU 3.73 AU 1.48 AU 0.439 AU 1 AU 0.32 AU 2.61 AU 2.62 AU 3.34 AU 1.49 AU 1.3 AU

2.335 AU 2.3 AU 0.0568 AU 1.07 AU 1.01 AU 3.24 AU 0.818 AU 1.62 AU 0.82 AU 1.26 AU

18

HD 20367 b HD 30177 b HD 196050 b HD 23596 b Gliese 777A b 55 Cancri c 55 Cancri d HD 37124 c HD 12661 c HD 38529 c HD 114729 b HD 216437 b HD 73526 b HD 76700 b HD 2039 b Tau 1 Gruis b gamma Cephei b

HD 20367 HD 30177 HD 196050 HD 23596 Gliese 777A 55 Cancri 55 Cancri HD 37124 HD 12661 HD 38529 HD 114729 HD 216437 HD 73526 HD 76700 HD 2039 Tau 1 Gruis gamma Cephei

Grus (the crane Cepheus

2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 2002

Epsilon Eridani c

Epsilon Eridani

Eridanus

2002

HD 216770 b HD 104985 b HD 70642 b HD 3651 b

HD 216770 HD 104985 HD 70642 HD 3651

Pegasus Draco Puppis Pegasus

2003 2003 2003 2003

Geneva Observatory Anglo-Australian Obs Anglo-Australian Obs Geneva Observatory Geneva Observatory Lick Observatory Lick Observatory Keck Observatory Keck and Lick observ Keck and Lick observ Keck Observatory Anglo-Australian Tel Anglo-Australian Pla Anglo-Australian Pla Anglo-Australian Pla Anglo-Australian Pla McDonald Observatory Alice Quillen, University of Roches Geneva Observatory Okayama Astrophysica Anglo-Australian Tel California & Carnegi

OGLE-TR 56

OGLE-TR-56

Sagittarius

2003

Harvard-Smithsonian

HD 73256 b HD 10647 b HD 111232 b Gliese 876 c HD 142415 b HD 169830 c HD 219449 b HD 330075 b HD 37605 b HD 50554 b HD 59686 b HD 65216 b HD 74156 b HD 74156 c HD 8574 b OGLE 2003-BLG235/MOOGLE 2003BLG-235/MOA 2003BLG-53

HD 73256 HD 10647 HD 111232 Gliese 876 HD 142415 HD 169830 HD 219449 HD 330075 HD 37605 HD 50554 HD 59686 HD 65216 HD 74156 HD 74156 HD 8574

Canis Major Phoenix Musca Aquarius

2003 2003 2003 Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown Unknown

CORALIE survey for e Geneva Observatory Geneva Observatory

OGLE-TR-113 b OGLE-TR-132 b TrES-1

Cancer Cancer Taurus Aries Orion

Sagittarius Aquarius

Gemini

Hydra Hydra Pisces

Coralie Survey Coralie Survey for E Lick Observatory HARPS McDonald Observatory Geneva Observatory Lick Observatory Coralie Survey for E Geneva Observatory Geneva Observatory Geneva Observatory

Unknown

Microlensing Observations in Astrophysics

OGLE-TR-113

Unknown

Las Campanas Observa

OGLE-TR-132 GSC 0265201324

Unknown

OGLE (Optical Gravit

Unknown

1.25 AU 2.6 AU 2.5 AU 2.72 AU 3.65 AU 0.24 AU 4.9 AU 2.95 AU 2.61 AU 3.51 AU 2.08 AU 2.7 AU 0.66 AU 0.049 AU 2.2 AU 2.5 AU 2.1 AU

0.46 AU 0.78 AU 3.3 AU 0.284 AU 0.0225 AU 0.037 AU 2.1 AU 2.07 AU 0.13 AU 1.05 AU 3.6 AU 0.3 AU 0.044 AU 0.26 AU 2.38 AU 0.8 AU 1.37 AU 0.276 AU 4.47 AU 0.76 AU

0.0228 AU 1.15 AU 0.003 AU

19

Table 2b Planet HD 114762 b PSR 1257 a PSR 1257 b PSR 1257 c PSR 1257 d 51 Pegasi b Upsilon Andromedae b 55 Cancri b 47 Ursae Majoris b tau Boo 70 Virginis b rho CrB 16 Cygni b HD 217107 b HD 210277 b HD 187123 b Gliese 876 b HD 195019 HD 168443 b HD 168443 c 14 Herculis b HD 209458 b HD 192263 b HD 37124 b HD 130322 b HD 177830 b HD 134987 b HR 810 b Upsilon Andromedae c Upsilon Andromedae d HD 222582 b HD 10697 b HD 83443 b HD 16141 b HD 168746 b HD 46375 b HD 108147 b HD 75289 b BD -10 3166 b HD 6434 b Epsilon Eridani b HD 38529 b HD 179949 b HD 82943 b HD 121504 b HD 52265 b HD 27442 b HD 160691 b HD 19994 b HD 92788 b HD 12661 b HD 169830 b GJ 3021 b Gliese 86 b HD 190228 b HD 89744 b HD 162020 b HD 4208 b HD 82943 c

Orbit Period K (m/s)

Mstar (suns) 0.82

e

RAh

RAm

RAs

dec

D

‘

“

0.334

12 00 00 00 00 57

21 01 01 01 01 27

+ + + + + +

17 12 12 12 12 20

31 40 40 40 40 46

01 00 00 00 00 04

84.03 25.262 66.5 98.2 62050 4.23

616.7

55.0

1.06

0

13 13 13 13 13 22

0.1 0.02

4.62

10.2

1.30

0.034

01

36

48

+

41

24

38

14.66 1095 3.3128 116.6 39.645 804 7.11 437 3.1 61.02 18.3 57.9 2135 1650 3.52 24.4 155 10.724 391 260 320.1

72.2 49.3 471.4 315.2 64.2 51.2 140.2 39.5 68.0 210.0 271.4 472.7 289.0

1.03 1.03 1.30 1.10 0.95 1.01 0.98 0.99 1.06 0.32 1.02 1.01 1.01

86.5 50.5 28.8

1.05 0.79 0.91

37.7 49.3

1.17 1.05

0.03 0.096 0.018 0.4 0.028 0.67 0.14 0.45 0.03 0.27 0.05 0.54 0.2 0.326 0 0 0.19 0.048 0.43 0.25 0.161

08 10 13 13 16 19 22 22 19 22 20 18 18 16 22 20 05 14 19 15 02

52 59 47 28 01 41 58 09 46 53 28 20 20 10 03 13 37 47 05 13 42

37 29 17 25 3 51 15 29 57 13 17 04 04 23 10 59 02 32 20 28 31

+ + + + + + + + + + + + -

28 40 17 13 33 50 02 07 34 14 18 09 09 43 18 00 20 00 25 25 50

20 25 27 46 18 31 23 32 25 15 46 35 35 49 53 52 43 16 55 18 48

02 46 22 43 51 03 42 32 15 13 12 34 34 18 04 00 50 53 14 33 12

241.2

53.9

1.30

0.18

01

36

48

+

41

24

38

1266.6

61.1

1.30

0.41

01

36

48

+

41

24

38

576 1083 2.99 75.8 6.409 3.024 10.9 3.51 3.487 22.09 2502.1 14.41 3.093 444.6 64.6 118.96 423 743 454 340 264.5 230.4 133.82 15.78 1127 256 8.4 829 221.6

191.3 114.2 58.0 11.2 27.0 34.5 27.3 53.5 59.9 37.0

1.00 1.10 0.79 1.00 0.92 1.00 1.20 1.15 1.10 0.99

54.7 118.0 46.0 45.0 38.8 30.7 42.8 45.0 98.6 75.0 83.0

1.39 1.24 1.05 1.02 1.13 1.20 1.08 1.35 1.07 1.07 1.40

375.9 90.0 275.3 813.0 18.2 34.0

0.86 1.20 1.40 0.70 0.93 1.05

0.71 0.12 0.08 0.28 0 0 0.558 0.054 0 0.3 0.608 0.28 0.05 0.41 0.13 0.29 0.02 0.62 0.2 0.36 0.33 0.34 0.505 0.046 0.43 0.7 0.277 0.04 0.54

23 01 09 02 18 06 12 08 10 01 03 05 19 09 13 07 04 17 03 10 02 18 00 02 20 10 17 00 09

41 44 37 35 21 33 25 47 58 04 32 46 15 34 57 00 16 44 12 42 04 27 16 10 03 22 50 44 34

51 55 11 19 49 12 46 40 28 40 55 34 33 50 17 18 29 08 46 48 34 49 12 14 00 10 38 26 50

+ + + + + + -

05 20 43 03 11 05 64 41 10 39 09 01 24 12 56 05 59 51 01 02 25 29 79 50 28 41 40 26 12

59 04 16 33 55 27 01 44 46 29 27 10 10 07 02 22 18 50 11 11 24 49 51 50 18 13 19 30 07

08 59 19 38 21 46 19 12 13 17 29 05 45 46 24 01 07 02 45 01 51 00 04 00 24 46 06 56 46

20

HD 114783 b HD 142 b HD 4203 b HD 68988 b HD 213240 b 47 Ursae Majoris c HD 23079 b HD 80606 b HD 28185 b HD 178911 b HD 106252 b HD 33636 b HD 39091 b HD 141937 b Iota Draconis b HD 41004A b HD 47536 b HD 136118 b HD 160691 c HD 49674 b HD 108874 b HD 128311 b HD 72659 b HD 40979 b HD 114386 b HD 150706 b HD 147513 b HD 20367 b HD 30177 b HD 196050 b HD 23596 b Gliese 777A b 55 Cancri c 55 Cancri d HD 37124 c HD 12661 c HD 38529 c HD 114729 b HD 216437 b HD 73526 b HD 76700 b HD 2039 b Tau 1 Gruis b gamma Cephei b Epsilon Eridani c HD 216770 b HD 104985 b HD 70642 b HD 3651 b OGLE-TR 56 HD 73256 b HD 10647 b HD 111232 b Gliese 876 c HD 142415 b HD 169830 c HD 219449 b HD 330075 b HD 37605 b HD 50554 b HD 59686 b HD 65216 b HD 74156 b HD 74156 c HD 8574 b OGLE 2003-BLG235/MOOGLE 2003-

501 338 406 6.276 759 2594 627.3 111.78 385 71.487 1500 1553 2115.3 658.8 547.5 655 712.13 1209.6 1300 4.948 401 414 2185 260 872 264 540.4 500 1620 1289 1558 2613 44.28 5360 1942 1407 2189.5 1136 1294 190.5 4 1190 903 102200 118.3 198.2 2231 62.23 1.2119 2.5486 1056 1138 30.1 386.3 2102 182 3.37 54.23 1279 303 613.1 51.61 2300 228.8

28.5 31.6 49.3 189.7 91.0 11.1 55.3 411.0 161.0 343.0 150.4 164.5 196.9 234.5

0.92 1.10 1.06 1.20 1.22 1.03 1.10 0.90 0.99 0.90 0.96 0.99 1.10 1.00

74.0

0.70

212.9

1.24

13.1 49.6 84.9 42.3 108.0 27.0 33.0 31.0 29.0 142.2 48.5 126.0

1.00 1.01 0.80 0.95 1.08 0.75 0.98 0.92 1.12 0.95 1.10 1.29

0.1 0.37 0.53 0.14 0.31 0.1 0.06 0.927 0.06 0.1243 0.54 0.39 0.62 0.4 0.7 0.39 0.2 0.366 0.8 0 0.2 0.21 0.18 0.26 0.28 0.38 0.52 0.23 0.22 0.28 0.314

13.0 49.3 32.4 27.0 169.1 17.6 37.5 114.8 25.0 127.8

1.03 1.03 0.91 1.07 1.39 0.93 1.07 1.02 1.00 0.98

0.34 0.16 0.4 0.224 0.34 0.33 0.34 0.34 0 0.69 0.2

33.0 0.0 32.0 15.9

0.90 1.50 1.00 0.79

0.32 0.03 0.1 0.63

267.0

1.05

168.0 81.0 52.0 36.0

0.78 0.32 1.03 1.40

0.038 0.32 0.25 0.27

81.9

1.06

0.737 0.42

37.0 112.0 125.0 64.0

0.92 1.05 1.05 1.10

0.41 0.649 0.359 0.4

0.33

13 00 00 08 22 10 03 09 04 19 12 05 05 15 15 05 06 15 17 06 12 14 08 06 13 16 16 03 04 20 03 20 08 08 05 02 05 13 22 08 08 00 22 23 03 22 12 08 00 17 08 01 12 22 15 18 23 15 05 06 07 07 08 08 01

12 06 44 18 31 59 39 22 26 09 13 11 37 52 24 59 37 18 44 51 30 36 34 04 10 31 24 17 41 37 48 03 52 52 37 04 46 12 54 37 53 24 53 39 32 55 05 21 39 56 36 42 48 53 57 27 15 49 40 54 31 53 42 42 25

43 19 41 22 00 29 43 37 26 03 29 46 09 17 55 49 47 55 8 30 26 00 03 29 39 17 01 40 54 51 00 37 37 37 02 34 34 44 39 16 55 20 37 20 55 53 15 28 21 35 23 29 51 13 40 49 53 37 01 42 48 41 25 25 12

+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

02 49 20 61 49 40 52 50 10 34 10 04 80 18 58 48 32 01 51 40 22 09 01 44 35 79 39 31 58 60 40 29 28 28 20 25 01 31 70 41 66 56 48 77 09 26 76 39 21 29 30 53 68 14 60 29 09 49 06 24 17 63 04 04 28

15 04 26 27 25 25 54 36 33 35 02 24 28 26 57 14 20 35 50 52 52 44 34 15 03 47 11 07 01 38 31 53 20 20 43 24 10 52 04 19 48 39 35 37 27 39 54 42 15 32 02 44 25 15 12 49 05 57 03 14 05 38 34 34 34

54 30 56 38 59 46 57 13 02 59 29 12 08 09 57 22 23 32 02 03 47 47 5 37 17 23 34 37 14 04 50 48 02 02 50 51 05 24 25 08 03 00 53 56 29 31 20 19 01 21 15 27 30 13 00 00 15 48 38 44 09 50 41 41 00

18

05

16

-

28

53

42

21

BLG-235/MOA 2003-BLG-53 OGLE-TR-113 b OGLE-TR-132 b TrES-1

1.4 1.7 3.03

0

10 10 00

52 50 00

24 34 00

+

61 61 00

26 57 00

48 25 00

Planetary system formation theories Leucippus (480-420 BC) [1], some 2500 years ago, though about the formation of the planets as follows: “The worlds come into being as follows: many bodies of all sorts and shapes move from the infinite into a great void; they come together there and produce a single whirl, in which, colliding with one another and revolving in all manner of ways, they begin to separate like to like”. He was not too far from our actual theories. But, in the past years, these theories were brought on the carpet after the discovery of many giant planets orbiting very close to the parent star, too close to fit in our actual knowledge of the only one Figure 27 planetary system under our eyes: our Solar System. Protoplanetary disk in Orion The conventional theory for the formation of our From: rst.gsfc.nasa.gov/ planetary system is based on a large dust and gas cloud Sect20/A11.html condensation. After some time, a series of events like these might be occurred: • Some perturbing event, like a supernova explosion or a shock wave from an encounter with another gas cloud, produced the compression of some part of the cloud. • The gravity then, does the rest. Particles and gas continued to condense. • As the density increase, the temperature goes warmer. • The condensing cloud strart to rotate and after some times it begins to flattens. • The density and the temperature of the inner part is growing rapidly and the disk spins faster. • The temperature and the density in the center are so high that can initiate a thermonuclear process: the star is born. • The star continues to rotate and to drag the disk material under its gravity. • Dust particles and gas begins to condense at certain distance from the star. This condensed cloud is called Protoplanetary disk (Figure 26). • Giant gaseous and light planets might be formed in the outer part of the disk. • Rocky, less massive but denser ones, in the inner part of the disk. • Satellites, with some exceptions like the Moon and trapped asteroids, would be formed by the same process and at the same time. • After the formation, each planet stabilize itself in a circular, or very small eccentric, orbit revolving around the central star in the same direction as the star rotate and the protoplanetary disk does. The reason to have small rocky planets in the inner part of a planetary system is because the temperature in the inner part would be too high to let forming a gaseous planet like Jupiter (light elements like Hydrogen and Helium would be expelled due to the 22

temperature). The quantity of available material would be too low to produce Jupiter like giant planets. Heavy elements would be trapped in the inner part of the disk by gravity On the opposite side of the disk, matter is too sparse and cold to coalesce and form a rocky denser planet (Pluto is an exception in our Solar System). The quantity of material available is too much to let forming giant planets. The quantity of light elements is much more than the quantity of heavy elements, so giant Jupiter-like planets are almost gaseous, maybe they have a little rocky nucleus. This model was accepted and not contrasted for decades, but, in 1995, the evidence demonstrates exactly the opposite: giant Jupiter like planets orbiting less than an AU from the star and planets with very high eccentricity were found. What is wrong? Maybe our simple and elegant theory needs a deep revision, because it explains well the inner planets (Mercury to Mars) and Jupiter and Saturn. Uranus and Neptune are too small and cold; and Pluto is very small and maybe rocky. Recently a new theory appeared: the “Disk Instability”. According to this theory, planets do not grow through accretion, but with a collapse directly from the disk, so they do not needs a core. This might works well, because planets with any size can forms anywhere in the disk, but it do not explain why giant gaseous planets are too close to the star and why Uranus and Neptune are small. There is a “patch” to this theory. Our Sun, long time ago, was an element of a binary or multiple star system. The companion star might be photoevaporated Uranus and Neptune (they was much bigger, but the radiation from the companion star heated the gases and blown them out). But where is that star? Why not Saturn and Jupiter? Another theory called the “Migration theory” try to explain the case of Hot Jupiters (Jupiter like planets very close to the parent star) proposed in 1980 by Goldreich and Tremaine. Basically it states that a giant planet is formed far from the star and then migrates inward. The problem is to explain why the migration may initiate and how to stop it; otherwise we can not see any planet around stars. The possible reasons for entering in the migration process could be: gravitational drag, interaction with nearby star or interaction with a large nearby planet. The possible mechanisms that may stops the migration could be: running out of disk, magnetic fields interacting with the planet or tidal interaction from the star locking the planet at some distance from the star. We are observing protoplanetary disks around young stars (younger the star, densest the disk) and not circling old stars. This implies that, if the migration is not stopped until the disk dissipates, all planets were falling into the star and no planetary systems might exist.

Conclusion Our Solar System is not unique; there are a lot of stars with a planetary system in the Galaxy. The search for planets outside our Solar System is difficult because they are orbiting very close to the star and their luminosity is millions of times lower than that of the parent star. The techniques developed for that search are pushing the actual technology to the edge. They also helps to the development of new methods and to the design of instruments

23

capable of observing and measuring the physical properties of the newly discovered planets and allow to the discovery of many more. Each method employed has some benefits and some drawbacks because it is designed to realize measurements of only one or a few properties of the exoplanet or the system in which it resides. If we want to know how the planets in the system behave, we have to observe them with two or more techniques, because each one is capable to show us some details, but never the full panorama. Combining ground based observations with those made from space, we can be able to detect many more planets, including Earth mass (or lower) planets. Space telescopes, without, the atmospheric aberrations, can detect very fine details and even, in a near future, determine if the planet has an atmosphere and which are its components, then , the next step, will be the detection of biological activity with high resolution spectroscopy. Until now the best method to detect exoplanet was the measurement of the Doppler Shift of the light from the star orbited by one or more planets (radial velocity measurement). This one, with the accurately determination of the position and the movement of the star relative to other reference stars (astrometry) and the shift of the repetition rate of the pulses from a Pulsar (Pulsar timing), are all indirect, this means that we do not see the planet, but we knows it is there because we can measure the effect it exert on the parent star. Microlensing and Transit are a more direct technique, because they measure the change of the luminosity of the star. The combination of the two methods may lead to the determination of the orbital parameters, and hence the mass of the planet. When a transit occurs, the planet decreases the light from the star because it passes in front of it. A microlensing effect occurs when the planet either behind or in front of the star. The direct imaging detection is better when the planet is on one side of the star because what we see is the reflected light. If we are combining all methods to observe a star with planets, we can realize a full orbit diagram. The search for exoplanets is a new and growing field of Astronomy and Astrophysics. As many extrasolar planetary systems are discovered, refinements of the actual theories about their formation, evolution and ends, must be done. All theories must explain our solar System as well as all other extrasolar planetary systems. Actually each one may explain some part of the solar System and in part some other planetary system, it is necessary to discover many new systems and study them statistically. Maybe each system was formed in a similar way, but if we see it in depth, maybe it does not fit exactly with the general model. This is because the conditions of the first stages of the protoplanetary disk were slightly different, but in general terms there must be no great differences. All models we have now are failing to predict the formation of some planets in certain conditions, the discussion on this topic was issued by the discovery of giant planets very close to their parent star. So, a lot of new observations must be done to really see if the Solar System is something common in the Galaxy or in The Universe.

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Reference [1] http://www.hao.ucar.edu/public/research/stare/search.html [2] http://galileo.rice.edu/chr/bruno.html [3] http://www.astronomiaonline.com/informacion/exoplanetas/ [4] http://en.wikipedia.org/wiki/Otto_Struve [5] Struve O., Proposal for a project of high precision stellar radial velocity work, 1952 [6] http://www.seti.org/site/pp.asp?c=ktJ2J9MMIsE&b=179073 [7] Shostak S., Sharing the Universe, Berkeley Hills Books, 1998 [8] Sagan C., Comunicacion con inteligencias extraterrestres, Planeta, 1985 [9] http://www.public.asu.edu/~sciref/exoplnt.htm [10] Butler R.P. et al, Ultra High precision velocity measurements of oscillations in Alpha Centauri A, The Astrophysical Journal Vol. 600, 2004 [11] http://mthamilton.ucolick.org/techdocs/instruments/hamspec/hamspec_index.html [12] http://www.eso.org/outreach/press-rel/pr-2004/pr-23-04.html [13] http://cfa-www.harvard.edu/planets/searches.html [14] http://www.space.com/scienceastronomy/oldest_planet_030710-1.html [15] http://astron.berkeley.edu/~gmarcy/0398marcy.html [16] Ksanfomaliti L.V., Extrasolar Planetery Systems, Russian Academy of Science, 2000 [17] http://www.physics.usyd.edu.au/~ptitze/work/xsol.htm [18] http://hubblesite.org/newscenter/newsdesk/archive/releases/2003/19/text/ [19] http://xxx.lanl.gov/ftp/astro-ph/papers/0307/0307339.pdf [20] Rhie S.H., et al, On planetary companions to MACHO-98-BLG-35 lensing star, AAS Jan 99 meeting, 1999 [21] Bennet D.P., Gravitational microlensing evidence for a planet orbiting a binary star system, Nature 402,57, 1999 [22] Bennet D.P., Rhie S.H., Detecting Earth-mass planets with gravitational microlensing, APJ 472, 1996 [23] Bennet D.P. et Al., Planetary microlensing from the MACHO project, AstroPh/9612208, 1996 [24] http://www.nd.edu/~srhie/MPS/ [25] http://www.nsf.gov/od/lpa/news/press/99/pr9968.htm [26] http://www.macalester.edu/astronomy/courses/physics50/spring2002.html [27] Stairs I.H. et al, Evidence for free precession in a pulsar, Nature Vol. 406, 2000 [28] Sigurdsson S., A young White Dwarf companion to pulsar B1620-26: Evidence for early planet formation, Science Vol. 301, 2003 [29] Perryman M.A.C., Extra-solar planets, Rep. Prog. Phys Vol. 63, 2000 [30] Bouchy F. et al, Doppler follow-up of OGLE transiting companions in the galactic bulge, Astro-ph/0410346 V1, 2004 [31] Butler R.P. et al, A Neptune-mass planet orbiting the nearby M Dwarf GJ436, ApJ, 2004 [32] West F., Monitoring nearby stars for transits by extrasolar Jovian planets, II : transits of M-Type (red) dwarf stars by close extrasolar giant (Jovian) planets, JAAVSO Vol. 27, 1999 [33] Borucki W. et al, Laboratory demonstration of high-precision transit photometry for extra-solar planet detection, 2004

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[34] Perryman M.A.C., Extra-solar planets, 2000 [35] Jones H.R.A. et al, Extra-solar planets around HD196050, HD216437 and HD160691, Astro-ph/0206216 v1, 2002 [36] Charbonneau D. et al, Detection of planetary transit across a Sun-like star, Astrophysical Journal Letters, 1999 [37] Abe F. et al, Search for low mass Exoplanets by gravitational microlensing at high magnification, Science vol.305, 2004 [38] Bazot M., Vauclair S., Astroseismology of exoplanets hosts stars : test of internal metallicity, astro-ph/0407544 v2, 2004 [39] http://exoplanets.org/planet_table.shtml [40] http://planetquest1.jpl.nasa.gov/atlas/atlas_search.cfm [41] http://www.planeten.ch/exoplanets/index.php?menu=exoplanets&submenu=epistellargasgiants [42] http://www.obspm.fr/encycl/cat1.html [43] http://obswww.unige.ch/~naef/who_discovered_that_planet.html [44] http://www.all-science-fairprojects.com/science_fair_projects_encyclopedia/List_of_stars_with_confirmed_extrasolar _planets [45] http://iac.es/proyect/tep/transitmet.html [46] Lattanzi M.G. et al, GAIA and the hunt for extra-solar planets, 2004 [47] http://www.public.asu.edu/~sciref/exoplnt.htm [48] http://iac.es/proyect/jovian/index.html [49] Castellano T.,The Detection of Transits of Extrasolar Giant Planets with Inexpensive Telescopes and CCDs, 2004 [50] http://zero.as.arizona.edu/~phinz/nulling.html

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