DOCSLIB.ORG

Gravitational Microlensing by Exoplanets and Exomoons

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

INTERNATIONAL SPACE SCIENCE INSTITUTE SPATIUM Published by the Association Pro ISSI No. 45, May 2020 Gravitational Microlensing by Exoplanets and Exomoons 200216_Spatium_45_2020_(001_016).indd 1 16.05.20 11:11 Editorial Since Copernicus (1473–1543) was world view abruptly. They seemed not able to measure brightness not to be inhabited as previously Impressum variations of the stars due to Earth’s assumed, and life appeared not to revolutionary motion around the be a matter of course. Astrophys- Sun, he inferred that stars must be ics and interdisciplinary science ISSN 2297–5888 (Print) very far away from Earth. During recognised the very special condi- ISSN 2297–590X (Online) the 16th and 17th Centuries schol- tions required to create life. More- ars began gradually to realise that over, these conditions need to be Spatium the Universe, i.e., the sphere of very selective and restricting, de- Published by the fixed stars enclosing our Solar pending not only on physical and Association Pro ISSI System, might not be finite but chemical parameters but particu- infinite. Philosophical arguments larly on stable and stabilising hab- by Thomas Digges (1546–1595) or itable environments in space and Giordano Bruno (1548–1600) sup- on ground. ported this view. Galileo (1564– Today, the existence of extra-ter- Association Pro ISSI 1642) provided evidence from ob- restrial life seems to be quite likely Hallerstrasse 6, CH-3012 Bern servations of the Milky Way using for statistical reasons. However, it Phone +41 (0)31 631 48 96 his telescope. is very hard to find evidence from see In his Cosmotheoros posthumously bio-markers identified in exoplan- www.issibern.ch/pro-issi.html published in 1698, Christiaan Huy- etary spectra as long as it is not clear for the whole Spatium series gens (1629–1695) estimated the dis- what life actually is. Furthermore, tances to the fixed stars by compar- our Solar System and particularly President ing the apparent magnitudes of the our Earth-Moon System have a Prof. Dr. Adrian Jäggi, Sun and Sirius. He found Sirius to special history resulting from a University of Bern be 27 664 times farther away from series of very unlikely events that Earth than the Sun. Already in 1690, happened successively in an assor- Editor he speculated about the existence of tative and even choreographic way. PD Dr. Andreas Verdun planets orbiting other stars than the Thereby it is supposed that the CH-3086 Zimmerwald Sun carrying extra-terrestrial life. Moon is ascribed a critical role for He thus may be considered the the origin and evolution of life on Printing “ inventor” of extrasolar planets. Earth. Stämpf li AG During the 17th and 18th centu- The topic of this issue is based on CH-3001 Bern ries, the value of the solar parallax the talk “Exoplanets: In Search of was measured using Mars opposi- Terra-2” by Prof. Dr. Joachim tions and transits of Venus with Wambsganss held on October 31, increasing accuracy. At least since 2018, in the Pro ISSI seminar se- that time it was realised that our ries. He pointed out that gravita- solar system and the cosmos must tional microlensing takes the po- be huge. As a reaction to this “hor- tential not only to detect Earth-like ror vacui” every celestial body was exoplanets, but even Moon-like thought to be inhabited, even the exomoons. He referred to results Title Caption Sun and the stars. The “plurality published by Liebig and Wambs- Simulation of the caustic structure of the worlds” became an estab- ganss (2010), from where material (magnification pattern) resulting from lished world picture prevailing un- was used for this issue. the configuration consisting of a host til the 20th century. star (left), exoplanet (right, larger structure), and exomoon, (right, Space probes sent out to almost all Andreas Verdun smaller structure within the exo- solar system bodies demolished this Zimmerwald, December 2019 planet’s caustic structure). SPATIUM 45 2 200216_Spatium_45_2020_(001_016).indd 2 16.05.20 11:11 Gravitational Microlensing by Extrasolar Planets and Moons By Prof. Dr. Joachim Wambsganss, Astronomisches Rechen-Institut (ARI), Zentrum für Astronomie der Universität Heidelberg (ZAH) and International Space Science Institute (ISSI), Bern Light Curve bly enhance the probability for the Figure 1 presents the observational discovery of extra-terrestrial life. data of the microlensing event Anomalies The role and importance of our OGLE-2005-BLG-390 – the dis- Moon for the origin of life on covery of a cool 5.5 Earth mass Earth was analysed by Benn (2001). exo planet (Beaulieu et al. 2006). He points out five possible criteria The signal of the exoplanet is The first time an extrasolar planet that may trigger and influence the super imposed on the light curve (or exoplanet) was discovered with evolution of life: (1) stabilisation of produced by the host star, a small- the method of gravitational micro- the planet’s rotational axis, (2) amplitude blip at day 10; it is lensing was in 2004. In 2006, a elimination of primordial atmo- zoomed out in the extra diagram cool planet of 5.5 Earth masses sphere, (3) generation of the plan- on the top right side of the dia- was discovered with this method et’s magnetic field, (4) generation gram. This light curve illustrates (Figure 1, Beaulieu et al. 2006). of large tides, and (5) generation of the difficulty of the detection of Micro lensing is a very sensitive longer-period tides. These aspects exomoons. In order to be able to technique for detecting exoplanets certainly support the conditions of detect the much less significant with (projected) distances between life, so exomoons may play an es- microlensing effects caused by an roughly 0.5 and 10 AU from their sential role for the origin and evo- exomoon, tiny deviations in the host stars and with masses between lution of life on their host exo- structure of the light curve need roughly Earth mass and 10 Jupiter planets. This is why searching for to be identified, which is only pos- masses. Very frequent photometric microlensing effects through exo- sible if the resolution in time and measurements with observation moons might be an important is- photometric magnitude is much rates of about one frame per sue for the quest of extra-terrestrial higher than in this example (which 15 minutes and visual photometric life. was state of the art at the time). precision of about 20 mmag (milli- magnitudes)1 may in the future even allow to detect microlensing Figure 1: The light curve of the OGLE-2005-BLG-390 microlensing event events caused by extrasolar moons (differently coloured data points from different observatories) and best-fit model (or exomoons). This means that not plotted as a function of time. (Credit: Beaulieu et al. 2006) only the light curve of a micro- lensing host star and the deviation of this light curve caused by an exo planet have to be considered, but also anomalies superimposed on the exoplanet’s signal caused by its moon (or moons) have to be an- alysed. Simulations of convolved caustics and magnification patterns resulting from microlensing effects by exoplanets and exomoons sug- gest that massive extrasolar moons can in principle be detected. The detection of exomoons orbiting exoplanets of Earth-like masses in habitable zones would considera- 1 The (visual) brightness of a star is measured in “magnitudes”. By definition, 0 mag is the brightness of the star Vega (a Lyrae). SPATIUM 45 3 200216_Spatium_45_2020_(001_016).indd 3 16.05.20 11:11 Classical trast in brightness or magnitude planet applies to the spectroscopic between exoplanet and its host star. method. Here (projected) radial Methods In addition, such telescopes are not velocities are extracted from intended to be scheduled for sur- Doppler shifted spectral lines of to Detect vey or monitoring observation the order of a metre per second (or campaigns. smaller). To be successful, the host Extrasolar star must be bright enough in or- Planets der to produce a high enough flux Astrometry for an extremely high resolution spectrum containing a sufficient The gravitational pulls of exoplan- number of spectral lines, so that the Let us briefly summarise the ad- ets acting upon their host star force Doppler shifts can be analysed vantages and limits of the five clas- the star to move on a Keplerian or- properly. Although this method sical methods to detect exoplanets, bit around the barycentre of the was and still is very successfully in particular with respect to the exo system. If only one exoplanet used for the detection of exoplan- possibility of the detection of is present, the star’s motion is quite ets, it seems unimaginable that it exomoons. regular and can be measured (at will be able to detect exomoons: least with the Gaia satellite) if the The effect of the barycentre mo- exoplanet’s mass is of the order of tion of exoplanet plus exomoon Direct Imaging the mass of Jupiter. However, if cannot be disentangled into those more than two exoplanets are or- two components. Radial velocity By about 2025 (hopefully) three biting their host star, this motion measurements are most sensitive new ground-based optical tele- can become quite complicated. for exoplanets with very small scopes will become operational: Since the gravitational effect of an semi-major axes to their host stars The Giant Magellan Telescope exomoon upon the host star is van- because then their gravitational (GMT), the Thirty Meter Tele- ishingly small, there is no chance pull is strongest on the stars’ scope (TMT), and the European for this astrometric method to de- velocity. Extremely Large Telescope (ELT). tect exomoons at all. The ratio be- Equipped with newest generation tween the masses of host star and of advanced and dedicated techno- exomoon is so large that the angu- Transit logy in active and adaptive optics, lar resolution needed to detect a it is expected that these telescopes variation in the host star’s position The transit method uses the sim- will provide images in the optical would not be sufficient in any case.
Recommended publications
  • Copyrighted Material

    Copyrighted Material

    Index Abulfeda crater chain (Moon), 97 Aphrodite Terra (Venus), 142, 143, 144, 145, 146 Acheron Fossae (Mars), 165 Apohele asteroids, 353–354 Achilles asteroids, 351 Apollinaris Patera (Mars), 168 achondrite meteorites, 360 Apollo asteroids, 346, 353, 354, 361, 371 Acidalia Planitia (Mars), 164 Apollo program, 86, 96, 97, 101, 102, 108–109, 110, 361 Adams, John Couch, 298 Apollo 8, 96 Adonis, 371 Apollo 11, 94, 110 Adrastea, 238, 241 Apollo 12, 96, 110 Aegaeon, 263 Apollo 14, 93, 110 Africa, 63, 73, 143 Apollo 15, 100, 103, 104, 110 Akatsuki spacecraft (see Venus Climate Orbiter) Apollo 16, 59, 96, 102, 103, 110 Akna Montes (Venus), 142 Apollo 17, 95, 99, 100, 102, 103, 110 Alabama, 62 Apollodorus crater (Mercury), 127 Alba Patera (Mars), 167 Apollo Lunar Surface Experiments Package (ALSEP), 110 Aldrin, Edwin (Buzz), 94 Apophis, 354, 355 Alexandria, 69 Appalachian mountains (Earth), 74, 270 Alfvén, Hannes, 35 Aqua, 56 Alfvén waves, 35–36, 43, 49 Arabia Terra (Mars), 177, 191, 200 Algeria, 358 arachnoids (see Venus) ALH 84001, 201, 204–205 Archimedes crater (Moon), 93, 106 Allan Hills, 109, 201 Arctic, 62, 67, 84, 186, 229 Allende meteorite, 359, 360 Arden Corona (Miranda), 291 Allen Telescope Array, 409 Arecibo Observatory, 114, 144, 341, 379, 380, 408, 409 Alpha Regio (Venus), 144, 148, 149 Ares Vallis (Mars), 179, 180, 199 Alphonsus crater (Moon), 99, 102 Argentina, 408 Alps (Moon), 93 Argyre Basin (Mars), 161, 162, 163, 166, 186 Amalthea, 236–237, 238, 239, 241 Ariadaeus Rille (Moon), 100, 102 Amazonis Planitia (Mars), 161 COPYRIGHTED
  • Exomoon Habitability Constrained by Illumination and Tidal Heating

    Exomoon Habitability Constrained by Illumination and Tidal Heating

    submitted to Astrobiology: April 6, 2012 accepted by Astrobiology: September 8, 2012 published in Astrobiology: January 24, 2013 this updated draft: October 30, 2013 doi:10.1089/ast.2012.0859 Exomoon habitability constrained by illumination and tidal heating René HellerI , Rory BarnesII,III I Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany, [email protected] II Astronomy Department, University of Washington, Box 951580, Seattle, WA 98195, [email protected] III NASA Astrobiology Institute – Virtual Planetary Laboratory Lead Team, USA Abstract The detection of moons orbiting extrasolar planets (“exomoons”) has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary “habitable edge”. We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons.
  • The Subsurface Habitability of Small, Icy Exomoons J

    The Subsurface Habitability of Small, Icy Exomoons J

    A&A 636, A50 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937035 & © ESO 2020 Astrophysics The subsurface habitability of small, icy exomoons J. N. K. Y. Tjoa1,?, M. Mueller1,2,3, and F. F. S. van der Tak1,2 1 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands e-mail: [email protected] 2 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands 3 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands Received 1 November 2019 / Accepted 8 March 2020 ABSTRACT Context. Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. Aims. We intend to investigate under what thermal and orbital circumstances small, icy moons may sustain subsurface oceans and thus be “subsurface habitable”. We pay specific attention to tidal heating, which may keep a moon liquid far beyond the conservative habitable zone. Methods. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat.
  • Astrophysics with New Horizons: Making the Most of a Generational Opportunity

    Astrophysics with New Horizons: Making the Most of a Generational Opportunity

    Draft version October 3, 2018 Typeset using LATEX twocolumn style in AASTeX62 Astrophysics with New Horizons: Making the Most of a Generational Opportunity Michael Zemcov,1, 2 Iair Arcavi,3, 4 Richard Arendt,5 Etienne Bachelet,6 Ranga Ram Chary,7 Asantha Cooray,8 Diana Dragomir,9 Richard Conn Henry,10 Carey Lisse,11 Shuji Matsuura,12, 13 Jayant Murthy,14 Chi Nguyen,1 Andrew R. Poppe,15 Rachel Street,6 and Michael Werner16 1Center for Detectors, School of Physics and Astronomy, Rochester Institute of Technology, Rochester, NY 14623, USA 2Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 3Einstein Fellow at the Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA 4Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA 5CRESST II/UMBC Observational Cosmology Laboratory, Code 665, Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA 6Las Cumbres Observatory, 6740 Cortona Dr Ste 102, Goleta, CA 93117-5575, USA 7U. S. Planck Data Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA 8Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA 9NASA Hubble Fellow, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 10Henry A. Rowland Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA 11Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD
  • Using the Microlensing Technique, Astronomers Discover an Earth-Like Planet Outside Our Solar System

    Using the Microlensing Technique, Astronomers Discover an Earth-Like Planet Outside Our Solar System

    S&TR July/August 2006 11 Using the microlensing technique, astronomers discover an Earth-like planet outside our solar system. OOKING out to the vastness of the L night sky, stargazers often ponder questions about the universe, many wondering if planets like ours can be found somewhere out there. But teasing out the details in astronomical data that point to a possible Earth-like planet is exceedingly difficult. To find an extrasolar planet—a planet that circles a star other than the Sun— astrophysicists have in the past searched for Doppler shifts, changes in the wavelength emitted by an object because of its motion. When an astronomical object moves toward an observer on Earth, the light it emits becomes higher in frequency and shifts to the blue end of the spectrum. When the object moves away from the observer, its light becomes lower in frequency and shifts to the red end. By measuring these changes in wavelength, astrophysicists can precisely calculate how quickly objects are moving toward or away from Earth. When This artist’s rendition shows the Earth-like extrasolar planet discovered in 2005. (Reprinted courtesy of the European Southern Observatory.) Lawrence Livermore National Laboratory 12 An Earth-Like Extrasolar Planet S&TR July/August 2006 a giant planet orbits a star, the planet’s About the New Planet we consider the number of stars out there,” gravitational pull on the star produces a According to Livermore astrophysicist Cook says, “the fact that we stumbled on small (meters-per-second) back-and-forth Kem Cook, OGLE-2005-BLG-290-Lb is a one small planet means that thousands Doppler shift in the star’s light.
  • Abstracts of the 50Th DDA Meeting (Boulder, CO)

    Abstracts of the 50Th DDA Meeting (Boulder, CO)

    Abstracts of the 50th DDA Meeting (Boulder, CO) American Astronomical Society June, 2019 100 — Dynamics on Asteroids break-up event around a Lagrange point. 100.01 — Simulations of a Synthetic Eurybates 100.02 — High-Fidelity Testing of Binary Asteroid Collisional Family Formation with Applications to 1999 KW4 Timothy Holt1; David Nesvorny2; Jonathan Horner1; Alex B. Davis1; Daniel Scheeres1 Rachel King1; Brad Carter1; Leigh Brookshaw1 1 Aerospace Engineering Sciences, University of Colorado Boulder 1 Centre for Astrophysics, University of Southern Queensland (Boulder, Colorado, United States) (Longmont, Colorado, United States) 2 Southwest Research Institute (Boulder, Connecticut, United The commonly accepted formation process for asym- States) metric binary asteroids is the spin up and eventual fission of rubble pile asteroids as proposed by Walsh, Of the six recognized collisional families in the Jo- Richardson and Michel (Walsh et al., Nature 2008) vian Trojan swarms, the Eurybates family is the and Scheeres (Scheeres, Icarus 2007). In this theory largest, with over 200 recognized members. Located a rubble pile asteroid is spun up by YORP until it around the Jovian L4 Lagrange point, librations of reaches a critical spin rate and experiences a mass the members make this family an interesting study shedding event forming a close, low-eccentricity in orbital dynamics. The Jovian Trojans are thought satellite. Further work by Jacobson and Scheeres to have been captured during an early period of in- used a planar, two-ellipsoid model to analyze the stability in the Solar system. The parent body of the evolutionary pathways of such a formation event family, 3548 Eurybates is one of the targets for the from the moment the bodies initially fission (Jacob- LUCY spacecraft, and our work will provide a dy- son and Scheeres, Icarus 2011).
  • Report by the ESA–ESO Working Group on Extra-Solar Planets

    Report by the ESA–ESO Working Group on Extra-Solar Planets

    Report by the ESA–ESO Working Group on Extra-Solar Planets 4 March 2005 Summary Various techniques are being used to search for extra-solar planetary signatures, including accurate measurement of radial velocity and positional (astrometric) dis- placements, gravitational microlensing, and photometric transits. Planned space experiments promise a considerable increase in the detections and statistical know- ledge arising especially from transit and astrometric measurements over the years 2005–15, with some hundreds of terrestrial-type planets expected from transit mea- surements, and many thousands of Jupiter-mass planets expected from astrometric measurements. Beyond 2015, very ambitious space (Darwin/TPF) and ground (OWL) experiments are targeting direct detection of nearby Earth-mass planets in the habitable zone and the measurement of their spectral characteristics. Beyond these, ‘Life Finder’ (aiming to produce confirmatory evidence of the presence of life) and ‘Earth Imager’ (some massive interferometric array providing resolved images of a distant Earth) arXiv:astro-ph/0506163v1 8 Jun 2005 appear as distant visions. This report, to ESA and ESO, summarises the direction of exo-planet research that can be expected over the next 10 years or so, identifies the roles of the major facilities of the two organisations in the field, and concludes with some recommendations which may assist development of the field. The report has been compiled by the Working Group members and experts (page iii) over the period June–December 2004. Introduction & Background Following an agreement to cooperate on science planning issues, the executives of the European Southern Observatory (ESO) and the European Space Agency (ESA) Science Programme and representatives of their science advisory structures have met to share information and to identify potential synergies within their future projects.
  • Meeting Program

    Meeting Program

    A A S MEETING PROGRAM 211TH MEETING OF THE AMERICAN ASTRONOMICAL SOCIETY WITH THE HIGH ENERGY ASTROPHYSICS DIVISION (HEAD) AND THE HISTORICAL ASTRONOMY DIVISION (HAD) 7-11 JANUARY 2008 AUSTIN, TX All scientific session will be held at the: Austin Convention Center COUNCIL .......................... 2 500 East Cesar Chavez St. Austin, TX 78701 EXHIBITS ........................... 4 FURTHER IN GRATITUDE INFORMATION ............... 6 AAS Paper Sorters SCHEDULE ....................... 7 Rachel Akeson, David Bartlett, Elizabeth Barton, SUNDAY ........................17 Joan Centrella, Jun Cui, Susana Deustua, Tapasi Ghosh, Jennifer Grier, Joe Hahn, Hugh Harris, MONDAY .......................21 Chryssa Kouveliotou, John Martin, Kevin Marvel, Kristen Menou, Brian Patten, Robert Quimby, Chris Springob, Joe Tenn, Dirk Terrell, Dave TUESDAY .......................25 Thompson, Liese van Zee, and Amy Winebarger WEDNESDAY ................77 We would like to thank the THURSDAY ................. 143 following sponsors: FRIDAY ......................... 203 Elsevier Northrop Grumman SATURDAY .................. 241 Lockheed Martin The TABASGO Foundation AUTHOR INDEX ........ 242 AAS COUNCIL J. Craig Wheeler Univ. of Texas President (6/2006-6/2008) John P. Huchra Harvard-Smithsonian, President-Elect CfA (6/2007-6/2008) Paul Vanden Bout NRAO Vice-President (6/2005-6/2008) Robert W. O’Connell Univ. of Virginia Vice-President (6/2006-6/2009) Lee W. Hartman Univ. of Michigan Vice-President (6/2007-6/2010) John Graham CIW Secretary (6/2004-6/2010) OFFICERS Hervey (Peter) STScI Treasurer Stockman (6/2005-6/2008) Timothy F. Slater Univ. of Arizona Education Officer (6/2006-6/2009) Mike A’Hearn Univ. of Maryland Pub. Board Chair (6/2005-6/2008) Kevin Marvel AAS Executive Officer (6/2006-Present) Gary J. Ferland Univ. of Kentucky (6/2007-6/2008) Suzanne Hawley Univ.
  • Simon Porter , Will Grundy

    Simon Porter , Will Grundy

    Post-Capture Evolution of Potentially Habitable Exomoons Simon Porter1,2, Will Grundy1 1Lowell Observatory, Flagstaff, Arizona 2School of Earth and Space Exploration, Arizona State University [email protected] and spin vector were initially pointed at random di- Table 1: Relative fraction of end states for fully Abstract !"# $%& " '(" !"# $%& # '(# rections on the sky. The exoplanets had a ran- evolved exomoon systems dom obliquity < 5 deg and was at a stellarcentric The satellites of extrasolar planets (exomoons) Star Planet Moon Survived Retrograde Separated Impacted distance such that the equilibrium temperature was have been recently proposed as astrobiological tar- Earth 43% 52% 21% 35% equal to Earth. The simulations were run until they Jupiter Mars 44% 45% 18% 37% gets. Triton has been proposed to have been cap- 5 either reached an eccentricity below 10 or the pe- Titan 42% 47% 21% 36% tured through a momentum-exchange reaction [1], − Sun Earth 52% 44% 17% 30% riapse went below the Roche limit (impact) or the and it is possible that a similar event could allow Neptune Mars 44% 45% 18% 36% apoapse exceeded the Hill radius. Stars used were Titan 45% 47% 19% 35% a giant planet to capture a formerly binary terres- Earth 65% 47% 3% 31% the Sun (G2), a main-sequence F0 (1.7 MSun), trial planet or planetesimal. We therefore attempt to Jupiter Mars 59% 46% 4% 35% and a main-sequence M0 (0.47 MSun). Exoplan- Titan 61% 48% 3% 34% model the dynamical evolution of a terrestrial planet !"# $%& " !"# $%& " ' F0 ets used had the mass of either Jupiter or Neptune, Earth 77% 44% 4% 18% captured into orbit around a giant planet in the hab- and exomoons with the mass of Earth, Mars, and Neptune Mars 67% 44% 4% 28% itable zone of a star.
  • The Interior Structure of Super-Earths

    The Interior Structure of Super-Earths

    FACULTY OF SCIENCE The interior structure of super-Earths Kaustubh HAKIM Supervisor: Prof. Tim Van Hoolst Thesis presented in Affiliation (KU Leuven) fulfillment of the requirements for the degree of Master of Science in Astronomy and Astrophysics Academic year 2013-2014 Scientific Summary Since many centuries, philosophers have wondered about the existence of life away from our home planet. Once it got established that the Sun is just a star similar to the ones that light up our night sky, astronomers started looking for hidden Earth-like worlds with their telescopes. Until the 1990s, there was no sign of any other planetary system. But today, with the discovery of about 800 extra-solar planets early in the year 2014 itself, the total exoplanet count is 1794. These discoveries also led us to a new class of rocky exoplanets called super-Earths. With the possibility of atmospheres and water, they have the potential to sustain life. To explore their surface and internal dynamics, it is necessary to know what they are made up of. The advent of inter-planetary space missions gave scientists the opportunity to ex- plore the interiors of terrestrial planets and satellites other than the Earth. In this thesis, we extend the methods of interior structure modeling developed for terrestrial planets to the super-Earths. As super-Earths are massive with high internal pressures (>1 TPa), extrapolation of these methods needs extreme care. Recently published ab initio data for the behavior of iron at such pressures is compared with the equations of state (EOS) from the literature to arrive at a suitable EOS for the core of super-Earths.
  • Keith Horne: Refereed Publications Papers Submitted: 425. “A

    Keith Horne: Refereed Publications Papers Submitted: 425. “A

    Keith Horne: Refereed Publications Papers Submitted: 427. “The Lick AGN Monitoring Project 2016: Velocity-Resolved Hβ Lags in Luminous Seyfert Galaxies.” V.U, A.J.Barth, H.A.Vogler, H.Guo, T.Treu, et al. (202?). ApJ, submitted (01 Oct 2021). 426. “Multi-wavelength Optical and NIR Variability Analysis of the Blazar PKS 0027-426.” E.Guise, S.F.H¨onig, T.Almeyda, K.Horne M.Kishimoto, et al. (202?). (arXiv:2108.13386) 425. “A second planet transiting LTT 1445A and a determination of the masses of both worlds.” J.G.Winters, et al. (202?) ApJ, submitted (30 Jul 2021). (arXiv:2107.14737) 424. “A Different-Twin Pair of Sub-Neptunes orbiting TOI-1064 Discovered by TESS, Characterised by CHEOPS and HARPS” T.G.Wilson et al. (202?). ApJ, submitted (12 Jul 2021). 423. “The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc” M.L.Silverstein, et al. (202?). AJ, submitted (24 Jun 2021). 422. “A temperate Earth-sized planet with strongly tidally-heated interior transiting the M8 dwarf LP 791-18.” M.Peterson, B.Benneke, et al. (202?). submitted (09 May 2021). 421. “The Sloan Digital Sky Survey Reverberation Mapping Project: UV-Optical Accretion Disk Measurements with Hubble Space Telescope.” Y.Homayouni, M.R.Sturm, J.R.Trump, K.Horne, C.J.Grier, Y.Shen, et al. (202?). ApJ submitted (06 May 2021). (arXiv:2105.02884) Papers in Press: 420. “Bayesian Analysis of Quasar Lightcurves with a Running Optimal Average: New Time Delay measurements of COSMOGRAIL Gravitationally Lensed Quasars.” F.R.Donnan, K.Horne, J.V.Hernandez Santisteban (202?) MNRAS, in press (28 Sep 2021).
  • The Nature of the Giant Exomoon Candidate Kepler-1625 B-I René Heller

    The Nature of the Giant Exomoon Candidate Kepler-1625 B-I René Heller

    A&A 610, A39 (2018) https://doi.org/10.1051/0004-6361/201731760 Astronomy & © ESO 2018 Astrophysics The nature of the giant exomoon candidate Kepler-1625 b-i René Heller Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany e-mail: [email protected] Received 11 August 2017 / Accepted 21 November 2017 ABSTRACT The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indi- cate the presence of a hitherto unknown kind of gas giant moon, if confirmed. Three transits of Kepler-1625 b have been observed, allowing estimates of the radii of both objects. Mass estimates, however, have not been backed up by radial velocity measurements of the host star. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e., via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0:4 MJup) to a brown dwarf (BD; up to 75 MJup) or even a very-low-mass star (VLMS; 112 MJup ≈ 0:11 M ). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water–rock companion of about +19:2 180 M⊕. Furthermore, the planet–moon dynamics during the transits suggest a total system mass of 17:6−12:6 MJup.