Gravitation astrometric tests in the external Solar System: the QVADIS collaboration goals M. Gai, A. Vecchiato Istituto Nazionale di Astrofisica [INAF] Osservatorio Astrofisico di Torino [OATo] WAG 2015 M. Gai - INAF-OATo - QVADIS 1 High precision astrometry as a tool for Fundamental Physics Micro-arcsec astrometry: Current precision goals of astrometric infrastructures: a few 10 µas, down to a few µas 1 arcsec (1) 5 µrad 1 micro-arcsec (1 µas) 5 prad Reference cases: • Gaia – space – visible range • VLTI – ground – near infrared range • VLBI – ground – radio range WAG 2015 M. Gai - INAF-OATo - QVADIS 2 ESA mission – launched Dec. 19th, 2013 Expected precision on individual bright stars: 1030 µas WAG 2015 M. Gai - INAF-OATo - QVADIS 3 Spacetime curvature around massive objects 1.5 G: Newton’s 1".74 at Solar limb 8.4 rad gravitational constant GM 1 cos d: distance Sun- 1 1 observer c2d 1 cos M: solar mass 0.5 c: speed of light Deflection [arcsec] angle : angular distance of the source to the Sun 0 0 1 2 3 4 5 6 Distance from Sun centre [degs] Light deflection Apparent variation of star position, related to the gravitational field of the Sun ASTROMETRY WAG 2015 M. Gai - INAF-OATo - QVADIS 4 Precision astrometry for Fundamental Physics – Gaia WAG 2015 M. Gai - INAF-OATo - QVADIS 5 Precision astrometry for Fundamental Physics – AGP Talk A = Apparent star position measurement AGP: G = Testing gravitation in the solar system Astrometric 1) Light deflection close to the Sun Gravitation 2) High precision dynamics in Solar System Probe P = Medium size space mission - ESA M4 (2014) Design driver: light bending around the Sun @ μas fraction WAG 2015 M. Gai - INAF-OATo - QVADIS 6 Quantum Vacuum behaviour vs. Gravitation “Standard model”: matter and anti-matter attract each other Cosmological constant “catastrophe” Vacuum energy not consistent with Solar System dynamics (e.g. Mercury’s precession)? Alternative theories: matter and anti-matter repulse each other [matter attracts matter, A-M attracts A-M] Suggested e.g. from CPT symmetry Effects may be tested by astrometry [Villata, 2011; Hajdukovic, 2014; Kaplan et al., 2014; Villata, 2015] WAG 2015 M. Gai - INAF-OATo - QVADIS 7 The Cosmological Constant trouble Large “renormalisation” required Cosmological constant Dark Energy Constraints from Solar System dynamics WAG 2015 M. Gai - INAF-OATo - QVADIS 8 Polarisation of virtual pairs External gravitation field attracts particle and repulses anti-particle Separation: ~ Compton wavelength Hajdukovic talk Result: polarisation of virtual pairs Effect similar to electromagnetic case of charge in dielectric medium Modified effective gravitation field WAG 2015 M. Gai - INAF-OATo - QVADIS 9 Precision Astrometry in the Outer Solar System Binary system as test particle: Precession of binary orbit in external field Newtonian physics => Keplerian closed orbit Additional interactions => orbit perturbation, in particular precession Orbit no longer closed Rotation of ellipse on its plane Periastron precession Larger displacement of apastron Orbit monitoring detection of external force Requirement: Observation against field stars over several orbits WAG 2015 M. Gai - INAF-OATo - QVADIS 10 The QVADIS Collaboration Quantum Vacuum [effects] Astrometric Detection In the Solar system • International collaboration [Inst. Physics, Astrophysics, Cosmology (ME); INAF-OATo (I)] • Experimental approach: check of deviation from Newtonian dynamics on trans-Neptunian binaries • High precision narrow field astrometry from ground / space WAG 2015 M. Gai - INAF-OATo - QVADIS 11 Study case: UX25 Trans-neptunian binary system Newtonian precession from the Sun: ≅ 6 mas/orbit Estimated precession from vacuum polarisation: Δ휔푞푣 ≃ 0.23 arcsec/orbit [Hajdukovic, 2014, hal-00908554] Cumulative effect on 5 years (~200 orbits): 46 arcsec WAG 2015 M. Gai - INAF-OATo - QVADIS 12 Previous observations… [M. E. Brown, ApJL 2013] WAG 2015 M. Gai - INAF-OATo - QVADIS 13 …and reconstructed orbit Semi-major axis angular amplitude: ~150 mas System unresolved by conventional telescopes Faint visible magnitude: • 20 mag primary • 22 mag secondary WAG 2015 M. Gai - INAF-OATo - QVADIS 14 Observing problem - I Orbit variation over 5 years Orbit Unperturbed variation orbit (1D) (1D) Challenge: reliable µas astrometry [Gai & Vecchiato, 2014, on faint objects, narrow field arXiv:1406.3611] WAG 2015 M. Gai - INAF-OATo - QVADIS 15 Observation setup Multiple images taken over orbital period along several orbits Determination of positions and velocity against field stars Orbital fit: parameter estimate WAG 2015 M. Gai - INAF-OATo - QVADIS 16 Observing problem - II Small variation of observed vs. nominal orbital positions over a few years Requirement: few µas final precision Small field (~10-20 arcmin) to have several reference stars (e.g. from Gaia) Simulation for ~100 µas precision on individual measurements WAG 2015 M. Gai - INAF-OATo - QVADIS 17 Performance on 8 m telescope with adaptive optics Observation in near infrared bands Photon noise, near diffraction limited imaging Exploit best instrument performance Feasible with 8 m AO telescope from ground – 10 nights/year Best candidate: James Webb Space Telescope (~2020) – 30 hours/year WAG 2015 M. Gai - INAF-OATo - QVADIS 18 Third-body perturbations Need for cross-check: precession may be induced by mass cluster in external regions of the Solar system Sun effect estimated 10 smaller than QV effect [Hajdukovic 2014] Measurement sensitive to any perturbation from known dynamics: MOND, unknown objects, … WAG 2015 M. Gai - INAF-OATo - QVADIS 19 Additional trans-neptunian binaries as candidates After first detection, larger survey? • confirm the effect • identify dependency on system parameters Dedicated space mission? (55637) 2002 UX25 (136199) Eris and Dysnomia (136108) Haumea, Hi'iaka, and Namaka (50000) Quaoar and Weywot (66652) Borasisi and Pabu (42355) Typhon and Echidna … WAG 2015 M. Gai - INAF-OATo - QVADIS 20 Orbit disturbances from object shape Celestial bodies are neither spheres nor point sources… 243 Ida 433 Eros Vesta 951 Gaspra [different viewpoints] Tidal effects orbit perturbations WAG 2015 M. Gai - INAF-OATo - QVADIS 21 Example: Polyhedron-Polyhedron Systems Chappaz, L., and Howell, K., "Bounded Motion near Binary Systems Comprised of Small Irregular Bodies," AIAA/AAS Astrodynamics Specialist Conference, San Diego, California, August 2014. Near Earth Asteroid (NEA) 1999 KW4 Shape model [Ostro et al. 2006]: primary and secondary WAG 2015 M. Gai - INAF-OATo - QVADIS 22 Higher-Fidelity Dynamical Models: perturbed elliptical orbit WAG 2015 M. Gai - INAF-OATo - QVADIS 23 Considerations on UX25 in-depth study Long term monitoring with significant cadence sampling required: - measure time sequence of positions AND velocity - measure shape / brightness distribution - measure albedo / surface composition - deduce mass distribution - cross-check actual dynamics with high fidelity model predictions Fundamental Physics result confidence on system parameters WAG 2015 M. Gai - INAF-OATo - QVADIS 24 Conclusions High precision astrometry: tool for Fundamental Physics Gravitation aspects of Quantum Vacuum need investigation Quantum Vacuum polarisation effects close to state of the art Experimental requirements of QV effects detection Crucial constraints to e.g. MOND and local Dark Energy Contributions to science case and implementation welcome! WAG 2015 M. Gai - INAF-OATo - QVADIS 25 .