Die Vermessung der Milchstraße: Hipparcos, Gaia, SIM Vorlesung von Ulrich Bastian ARI, Heidelberg Sommersemester 2004

Gliederung Populäre Einführung I: Astrometrie Populäre Einführung II: Hipparcos und Gaia Wissenschaft aus Hipparcos-Daten I Wissenschaft aus Hipparcos-Daten II Hipparcos: Technik und Mission Astrometrische Grundlagen Hipparcos Datenreduktion Hauptinstrument Hipparcos Datenreduktion Tycho Gaia: Technik und Mission Gaia Global Iterative Solution Wissenschaft aus Gaia-Daten Sternklassifikation mit Gaia SIM und andere Missionen

Gaia: Wissenschaft

GAIA: spatial distributions, motions, physical properties 1 billion stars to V=20 Key objective: composition, formation and evolution of the Galaxy Plus: thousands of other objectives

Which stars can be observed ? Limit for 10-percent parallax

Ergebnisse der Gaia-Mission (Schätzungen): Stern-Entfernungen auf 10 %: 150 Millionen (HIP: 21000) 1 %: 20 Millionen (HIP: 100 ?) 0.1 %: 1 Million (HIP: keine) Veränderliche Sterne: 50 Millionen (HIP: 8000) Astrometr. Doppelsterne: 100 Millionen (HIP: 3000) davon mit Bahnen: 100 000 (HIP: 235) Direkte Sternmassen auf 1%: > 10 000 (bisher ein paar Dutzend ? ) Weiße Zwerge: 200 000 (bisher ein paar hundert?) Braune Zwerge: 50 000 (bisher ein paar Dutzend) Planetensysteme: 50 000 (bisher 120) Supernovae: 100 000 (bisher einige tausend) Kleinplaneten: 500 000 ? (bisher 65 000) Relativitätstheorie auf 0.5 10-6 (bisher 50 10-6, oder 10 10-6 ? ) Vollständige Sternzählungen, genaue Sternzählungen, überall.

GAIA: Key Science Objectives Structure and kinematics of our Galaxy: shape and rotation of bulge, disk and halo internal motions of star forming regions, clusters, etc nature of spiral arms and the stellar warp space motions of all Galactic satellite systems Stellar populations: physical characteristics of all Galactic components initial mass function, binaries, chemical evolution star formation histories Tests of galaxy formation: dynamical determination of dark matter distribution reconstruction of merger and accretion history  Origin, Formation and Evolution of the Galaxy

Simulation of the Galactic plane (50000 OB stars) -4000 -2000 0 2000 4000 Heliocentric x coordinate (pcs) 4000 2000 -2000 Heliocentric y coordinate -4000 -4000 -2000 0 2000 4000 Heliocentric x coordinate (pcs) 4000 2000 -2000 Heliocentric y coordinate -4000 Photometric distances Gaia distances (Drimmel, Smart & Lattanzi, 1997)

Halo accretion (Harding image) Halo Accretion (simulation: P. Harding) Halo accretion (Paul Harding): PS original modified by Jos to give black background, and horizontal structure removed.

 GAIA will identify details of phase-space substructure Tidal Streams in the Galactic Halo (simulation of accretion of 100 satellite galaxies)  GAIA will identify details of phase-space substructure

Gaia ist also nicht auf die Sterne mit guten Parallaxen beschränkt. Nebenbemerkung: kinematische Strukturen lassen sich sogar ganz ohne kinematische Daten entdecken. Beispiel: Gezeitenschwänze von Palomar 5, nur aus Mehrfarbenphotometrie mit Sloan Digitized Sky Survey. Gaia ist also nicht auf die Sterne mit guten Parallaxen beschränkt. Mehrfarbenphoto- metrie gibt‘s für alle 109 Sterne! Odenkirchen et al., in:

distance precision to members of the Hyades cluster Example performance distance precision to members of the Hyades cluster Ground Hipparcos GAIA

Stellar Astrophysics Comprehensive luminosity calibration, for example: distances to 1% for 18 million stars to 2.5 kpc distances to 10% for 150 million stars to 25 kpc rare stellar types and rapid evolutionary phases in large numbers parallax calibration of all distance indicators e.g. Cepheids and RR Lyrae to LMC/SMC Physical properties, for example: clean Hertzsprung-Russell sequences throughout the Galaxy solar neighbourhood mass function and luminosity function e.g. white dwarfs (~200,000) and brown dwarfs (~50,000) initial mass and luminosity functions in star forming regions luminosity function for pre main-sequence stars detection and dating of the oldest (disk and halo) white dwarfs

Binary and Multiple Stars Constraints on star formation theories Orbits for > 100,000 resolved binaries (separation > 20 mas) Masses to 1% for > 10,000 objects throughout HR diagram Full range of separations and mass ratios Interacting systems, brown dwarf and planetary companions Photocentric motions: ~108 binaries Photometry: >106 eclipsing binaries Radial velocities: >106 spectroscopic binaries

Astrometric detection of extra-solar planets : Solar motion at 100 pc Planet B Star 10 mas = hairwidh at 1000 km !

Extra-solar planets: detection domains for astrometry and for radial velocity

Expected Exo-Planet Astrometric Discoveries Monitoring of hundreds of thousands of F-G-K stars to 200 pc for 1MJ planets and P < 10 years: complete census of all stellar types (P = 2-9 years) masses, rather than lower limits (m sin i) Large-scale detection and physical characterisation: 20,000- 30,000 planets expected to 150-200 pc e.g. 47 UMa: astrometric displacement 360 as orbits for many (5000) systems (~ 30% to 100 pc) mass down to 10 MEarth to 10 pc

Photometric detection of extra-solar planets : transits -0.1 0.1 days I 1.00 0.99 0.98 HD 209458 - ap = 0.045 UA Charbonneau et al., 1999 I t P Central  0 inclination Efficiency unaltered by distance !

GAIA: Studies of the Solar System Deep and uniform detection of all moving objects: complete to 20 mag (well, not really, due to scanning law) discovery of ~105 - 106 new objects (65,000 presently known) taxonomy and mineralogical composition versus heliocentric distance diameters for ~1000 asteroids masses for ~100 objects orbits: 30 times better than present, even after 100 years Trojan companions of Mars, Earth and Venus Kuiper Belt objects: ~300 to 20 mag + binarity + Plutinos Near-Earth Objects: e.g. Amors, Apollos and Atens (442: 455: 75 known today) ~1600 Earth-crossing asteroids > 1 km predicted (100 currently known) GAIA detection: 260 - 590 m at 1 AU, depending on albedo

General Relativity/Metric From positional displacements:  to 510-7 (cf. 10 -5 presently)  scalar-tensor theories effect of Sun: 4 mas at 90o; Jovian limb: 17 mas; Earth: ~40 as From perihelion precession of minor planets:  to 310-4 - 310-5 (10-100 better than lunar laser ranging) Solar J2 to 10-7 - 10-8 (cf. lunar libration and planetary motion) From white dwarf cooling curves: dG/dT to 10-12 - 10-13 per year (cf. PSR 1913+16 and solar structure) Gravitational wave energy: 10-12 < f < 10-9 Hz Microlensing: photometric (~1000) and astrometric (few) events Cosmological shear and rotation (cf. VLBI)

Nebenbemerkung: Die Robertson-Parameter Sie modifizieren die Metrik um einen kugelymmetrischen Körper gegenüber der Allgemeinen Relativitätstheorie (ART): ART besagt: Brans-Dicke (eine alternative Gravitationstheorie) besagt: wobei w ein freier Parameter der Theorie ist Die klassischen Tests der ART: light bending ~(g+1)/2, radar delay ~(g+1)/2, geodetic precession of orbiting gyros ~(2g+1)/3, perihelion precession of planets ~(2-b+2g)/3. -> Gaia kann g und b bestimmen.

Light Bending by Solar System Bodies

ICRF: Source distribution Defining sources (212) Candidate sources (294) Other sources (102)