Science Case
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ELTsc Cover A4 A-W 28/6/05 3:35 pm Page 1 ELTsc Cover A4 A-W 28/6/05 3:35 pm Page 2 The science case for THE EUROPEAN EXTREMELY LARGE TELESCOPE THE ESSENTIAL NEXT STEP IN MANKIND’S DIRECT OBSERVATION OF THE NATURE OF THE UNIVERSE, THIS WILL PROVIDE THE DESCRIPTION OF REALITY WHICH WILL UNDERLIE OUR DEVELOPING UNDERSTANDING OF ITS NATURE. ELTsc pages A4 A-W 28/6/05 3:31 pm Page 1 INDEX/CONTENTS 1 Executive summary 2 4.3.1.1 Cluster photometry with adaptive optics 62 1.1 Astronomy with a 50metre–100metre telescope 5 4.3.1.2 Analysis and results 62 4.3.1.3 Conclusions 64 2 Introduction 6 4.3.2 Spectroscopic observations of star clusters 66 2.1 The power of Extremely Large Telescopes 6 4.4 The stellar initial mass function 67 2.2 Telescope design requirements 7 4.5 Extragalactic massive stars beyond the local group 70 3 Planets and Stars 9 4.6 Stellar kinematic archaeology 72 3.1 Exoplanets 10 4.7 The intracluster stellar population 75 3.1.1 Highlight Science Case: Terrestrial planets 4.8 The cosmic star formation rate from supernovae 76 in habitable zones – “Exo-earths” 10 4.9 Young, massive star clusters 78 3.1.1.1 “Exo-earths” around Solar type stars 10 4.10 Black holes – studying the monsters in galactic nuclei 80 3.1.1.2 Spectroscopic signatures of life: biomarkers 11 4.10.1 Introduction 80 3.1.2 Simulations of planet detection with ELTs 12 4.10.2 The future of massive black hole astrophysics: 3.1.2.1 On-going simulations 13 new opportunities with an E-ELT 82 3.1.3 Giant planets: evolution and characterisation 15 5 Galaxies and Cosmology 84 3.1.4 Mature gas giant planets 15 5.1 Cosmological parameters 85 3.1.5 Earth-like moons in the habitable zone 16 5.1.1 Dark energy 85 3.1.5.1 Detection from reflex velocity measurements 17 5.1.1.1 Type la supernovae as distance indicators 86 3.1.5.2 Moon-induced astrometric wobble of the planet 17 5.1.1.2 Gamma-ray bursts as distance indicators 88 3.1.5.3 Spectral detection of terrestrial moons of 5.1.2 Expansion history 90 giant planets 18 5.1.2.1 Cosmic expansion history from primary 3.1.5.4 Mutual planet/satellite shadows and eclipses 18 distance indictors 90 3.1.6 Rings around extrasolar planets 19 5.1.2.2 Codex: the COsmic Differential EXpansion experiment 91 3.1.7 Planets around young stars in the solar neighbourhood 20 5.2 Highlight Science Case: First light – the first galaxies 3.1.8 Free-floating planets in star clusters and in the field 21 and the ionisation state of the early universe 93 3.2 Our solar system 22 5.2.1 Introduction 93 3.2.1 Mapping planets, moons and asteroids 23 5.2.2 The highest redshift galaxies (z>10) 95 3.2.1.1 Large and nearby asteroids 23 5.2.3 Galaxies and AGN at the end of re-ionisation (5<z>10) 97 3.2.1.2 Small asteroids 23 5.2.4 Probing the re-ionisation history 101 3.2.1.3 Major and minor moons 23 5.2.5 Early chemical evolution of the IGM 103 3.2.2 Transneptunian objects (TNOs) 24 5.3 Evolution of galaxies 105 3.2.3 Comets and the Oort cloud 24 5.3.1 Introduction 105 3.2.4 Surface and atmospheric changes 26 5.3.2 Physics of high redshift galaxies 107 3.3 Stars and circumstellar disks 28 5.3.3 The assembly of galaxy haloes 109 3.3.1 Formation of stars and protoplanetary discs 28 5.3.4 The star formation rate over the history of 3.3.1.1 Probing birthplaces 30 the universe 115 3.3.1.2 Structure in inner disks 31 5.4 Fundamental constants 118 3.3.1.3 Embedded young stellar objects 33 3.3.1.4 Jets and outflows: dynamics and moving shadows 33 Annex A Summary of the dependence of the science 3.3.1.5 Debris disks around other stars 34 cases on telescope aperture 121 3.3.2 The lives of massive stars 35 A1.1 Exoplanet detection from ground-based ELTs 121 3.3.2.1 Early phases of evolution 35 A1.2 Resolved stellar populations 123 3.3.2.2 Mature phase outflows 36 A1.3 The very high redshift universe 124 3.3.2.3 Normal and peculiar stars 37 A1.4 Summary 126 3.3.2.4 Asteroseismology 38 Annex B New scientific opportunities in the extremely 3.3.2.5 Chemical composition: the challenge of chronometry 39 large telescope era 127 3.3.3 The death of stars 41 B1.1 The physics – astrophysics connection 127 3.3.3.1 Mass function of black holes and neutron stars 41 B1.2 The next generation of ground-based astronomical 3.3.3.2 Isolated neutron stars 41 and related facilities 128 3.3.3.3 Black holes in globular clusters 42 B1.3 Future astronimical space missions 130 3.3.4 Microlenses: optical and near-infrared counterparts 45 B1.3.1 Comparison with JWST imaging sensitivity 131 4 Stars and Galaxies 46 B1.4 Exoplanet detection from space 132 4.1 The interstellar medium 46 B1.5 Supporting multi-wavelength science via the 4.1.1 Temperature and density probes in the virtual observatory 133 thermal infrared 47 B1.6 Developments in instrumentation 134 4.1.2 Fine structure in the ISM from ultrahigh B1.6.1 Adaptive optics modes for ELTs 134 signal-to-noise spectroscopy 47 B1.6.2 The use of ELTs at mid-infrared wavelengths 134 4.1.3 The high redshift ISM 48 B1.6.2.1 Design considerations for an ELT operating in 4.1.4 Measuring dust properties via polarimetry 48 the mid-IR 135 4.1.5 Optical studies in heavily extinguished regions 49 B1.6.3 The use of ELTs at sub-mm wavelengths 135 4.2 Highlight Science Case: Resolved stellar populations 50 B1.6.3.1 Design considerations for an ELT operating in 4.2.1 The Hubble Sequence: Understanding galaxy the submillimetre 136 formation and evolution 52 B1.6.4 The potential of astronomical quantum optics 136 4.2.2 Chemical evolution – spectroscopy of old stars 52 Credits 139 4.2.3 The resolved stellar population targets for the European Extremely Large Telescope 55 References 140 4.2.4 Technical issues and design requirements 56 4.3 Resolved stars in stellar clusters 59 Section authors and general contributors 144 4.3.1 Modelling and simulated observations of stellar clusters 60 ELTsc pages A4 A-W 28/6/05 3:31 pm Page 2 1 Executive summary SCIENCE CASE FOR THE EUROPEAN EXTREMELY LARGE TELESCOPE Astronomy is in its golden age. Since the invention of the telescope, astronomers have expanded mankind’s intellectual horizons, moving our perception of the Earth from an unmoving centre of the Universe to being one of several small planets around a typical small star in the outskirts of just one of billions of galaxies, all evolving in an expanding Universe in which planets are common. The nuclear energy sources which provide System objects – planets, comets and starlight are identified, and we know that the asteroids, to the formation of stars and chemical elements of which we are made are galaxies, extreme states of matter and space the ash of that process: stardust. Exotic states (e.g. around black holes) and finally to of matter are known: neutron stars, black determine the global matter-energy content of holes, quasars, pulsars. We can show that the our Universe. In the past half-century a new Universe started in an event, the Big Bang, and generation of telescopes and instruments see the heat remnant of that origin in the allowed a golden age of remarkable new Cosmic Microwave Background. Tiny ripples discoveries: quasars, masers, black holes, in that background trace the first minute gravitational arcs, extrasolar planets, gamma inhomogeneities from which the stars and ray bursts, the cosmic microwave background, galaxies around us grew. By comparing the dark matter and dark energy have all been weight of galaxies with the weight of all the discovered through the development of a visible matter, astronomers have proven that succession of ever larger and more the matter of which we, the planets, the stars, sophisticated telescopes. and the galaxies, are made is only a tiny part In the last decade, satellite observatories and of all the matter which exists: most matter is the new generation of 8- to 10-metre diameter some exotic stuff, unlike what we are made of, ground based telescopes, have created a new not yet detected directly, but whose weight view of our Universe, one dominated by poorly controls the movements of stars in our Galaxy. understood dark matter and a mysterious This ‘dark matter’ or ‘unseen mass’, whatever vacuum energy density. This progress poses it is made of, is five times more abundant than new, and more fundamental, questions, the are the types of matter of which we are made. answers to some of which will perhaps unite Perhaps most exotic of all, some new force astrophysics with elementary particle physics seems to be stretching space-time, accelerating in a new approach to the nature of matter. the expansion of the Universe. The nature of Some discoveries, made using relatively modest this force, which controls the future of the technologies, will require vast increases in Universe, remains quite unknown.