Exploration of the outer solar system by serendipitous occultations Françoise Roques (LESIA, Observatoire de Paris)
* serendipity : propensity for making fortunate discoveries while looking for something unrelated
* serendipity : propensity for making fortunate discoveries while looking for something unrelated
Search for Neptune rings 1984-1989 Tens of occultations observed between 1983 and 1989 Sicardy et al., 1991
Beyond Neptune :
Beyond Neptune : Large TNOs Sicardy et al., 2010
Beyond Neptune, some questions - break in the size distribution : size at which collisional processes take over gravitational ones r 0 = 90km (q=4.6-2) theory : 20-40 km? -2nd break in spectrum (~100m) Fuentes et al. 2009 -origine of the Jupiter family comets? -connection Kuiper belt - Oort cloud? -Sedna (500AU), capture of Triton - 10% of KBOs in binaries Bernstein et al., 2004
Beyond Neptune : direct detection Fuentes et al. 2008
Beyond Neptune : Small TNOs 0.4µm 1.2µm Roques et M oncuquet, 2000 Synthetic profile of 200 meters KBO at 40AU
Beyond Neptune, an invisible world Roques et al., 2008
Serendipitous stellar occultations 1976 : Can invisible' bodies be observed in the solar system?» (Bailey, 1976) 1987 : Occultation by small bodies, diffraction effects (Roques et al.) 1992 : Discovery of the first Kuiper Belt object Isolated event during 1980 Uranus occultation
«A Detection Method for SmallKuiper Belt Objects: The Search for Stellar Occultations» The Fresnel scale :! "D 2 λ: wavelength D: distance of the occultor The profile is smoothed by the star disc F S is scale factor for diffracting occultations. F s 0.4 µm 1.2 µm 50 UA 0.5 km 0.9 km 5000 UA 5 km 9 km Roques et Moncuquet, 2000
Serendipitous stellar occultations Ω Δ Nihei et al., 2007
Serendipitous stellar occultations dt = 1 sec dt = 0.2 sec! Roques et al.,2008
Research programs - Ultracam The instrument : ULTRACAM an ultra-fast, triple-beam CCD camera u : 0.36 µm, g :0.48 µm and i :0.77 µm 2 stars in a 2 FOV William Hershel Telescope - VLT 35 hours/* Roques et al., 2006
Research programs - Ultracam Variability index : (σ blue (int), σ red (int) ) Synthetic 200 meters KBO Doressoundiram et al., 2010
Research programs - Ultracam WHT run : no object in the Kuiper Belt 30-60 AU a cold extented disk of small objects? Roques et al., 2006
Research programs - Ultracam VLT g -r filters - f = 65Hz 20 hours/* Seeing mimics occultation by far objects dt=0.9 seconds depth = 7% stars separation : 79 NB : small FOV
Research programs Taiwan-American Occultation Survey 200 to 2000 stars/field 4Hz statistic analysis 3km radius KBO Scientific data collected since 2005 Alcock et al. 2003 ; Liang et al. 2004
FIRST RESULTS FROM THE TAIWANESE-AMERICAN OCCULTATION SURVEY (TAOS) Zhang L.W. et al. 2008 2 years of data with thousands of stars => no detection NB : small SNR
A SEARCH FOR SUB-km KUIPER BELT OBJECTS WITH THE METHOD OF SERENDIPITOUS STELLAR OCCULTATIONS Bickerton et al., 2007 180 cm Telescope 5 stars/field 40Hz cross correlation method 25 hours/* NB : 25 hours no detection
Research programs fromground University of New-South Wales Georgevits et al., 2007
Research programs fromground University of New-South Wales 6df/UKST Séminaire Temps & Espace 11/10/2010
Research programs fromground University of New-South Wales 6df/UKST Thousands of hours/* =>hundreds of events :? NB : instrumental noise, vibration Georgevits et al., 2007
RXTE Scopius 1 UV (lambda = 20m) 90 hours of observation 11 occultation events? NB : instrumental noise Chang et al., 2007
HST archive data 12000 h/* (various SNR, various latitudes) = one event : 500m at 45 AU NB : latitude Schlichting et al. 2009
6.5m MMT Observatory/Megacam shutterless continuous readout mode 200 Hz - SNR ~ 25 VI detection method Efficiency recovery 10% for a 0.7km KBO (40 AU) NB : small SNR and large stars Bianco et al. 2009
And also : Kepler (Gaudi): very good precision but long time exposure Corot : data analysis in progress ESO guiding cameras (Roques et Hainaut) : suspended project Today :Numerous approachs and very few detections Adapted instrumentation is missing fast photometry + high SNR (atmosphere,photon noise ) + small stars = Survey or Space or Large Telescope
A critical parameter, the star size Wang et al., 2010 O5 B5 A5 F5 G5 K5 M5 m >11.112.413.814.615.617.3 20 Minimum magnitude for diffracting occultations Roques et M oncuquet, 2000
Star size impact 10 km at 5000 AU 3km at 5000 AU
Pan STARRS video mode lightcurves Sky survey for the detection of NEA May 2010 Tel de 1.8m FOV : 7 deg 2 30 Hz Selection of (240) 60 guide stars of the prototype telescope Expected number of detections in 3 years with PS1 NB : sky survey Wang et al., 2010
Occultation from space projects Whipple Smithsonian Astrophysical Observatory, Ball Aerospace, Jet Propulsion Laboratory Spacecraft based on Kepler design 95 cm Schmidt optical system 100 square degree field of view Articulated solar arrays Hybrid CMOS focal plane array (Rockwell HyViSI/Hawaii-2RG) 140,000 stars, 40 Hz readout
Kepler (Gaudi 2004) Whipple
Occultation from space projects : Whipple 3 km at 42 AU, 40 Hz Kuiper belt + Oort Cloud! 10 km at 10 4 AU, 5 Hz 600 m at 42 AU, 40 Hz 4 km at 3000 AU, 10 Hz Nihei et al., 2007
NB : expensive
Oort Could Explorer for Dynamic Occultation Events Ocledocle JJ Kavellars (HIA Vctoria) Canadian Space Agency To achieve the primary scientific goal, the OCLE-DOCLE payload is designed to stare at a target star cluster over long periods, reporting high-precision photometry on approximately 1000 stars simultaneously at a continuous rate of 30-40 Hz. NB : space is expensive
Occultation from ground UltraPhot-VLT Paris observatory-lesia, Paris Observatory -GEPI, National Tsin Hua University A high speed photometric mode for FLAMES FOV : 25 diameter Number of fibres : 100-150 100 Hz
UltraCam data UltraPhot - aperture size maximum diameter = 4.3
UltraPhot - Optical design The optical design below allows to throw 3 images of fibres in 3 different spectral ranges. The parabolic mirror collimates the beam and allows to use a dichroic mirror. The camera reduces the image size of the entrance field to the dimensions of the detector. David Horville, GEPI
UltraPhot - camera A 2 km comet at 5000 AU ~100 fibres expected event rate Kuiper : 1 event/week Oort could : 1 event/2 months
UltraPhot Science : Variable targets, transits, occultations ULTRAPHOT will allow high speed photometry of large number of faint objects on timescales of seconds to milliseconds. Potential interested scientific fields are numerous : Exploration of Outer Solar System Objects Kuiper Belt,?Oort Cloud? Extrasolar Planets Transits (Transit Timing) Compact objects (pulsars, X binaries) Blue cataclysmic variables in Globular Cluster Young Stellar Objects
MEFOS, a 29 fibers spectrograph has been upgraded and and mounted on the 1.93m telescope of the OHP 29 image fibres 10 Hz first light : March 2010 Séminaire Temps & Espace 11/10/2010
Miosotys, selection of targets Boissel, Doressoudiram, 201O
Beyond Neptune Françoise Roques, Bruno Sicardy, Thomas Widemann Alain Doressoundiram, Yannick Boissel, Frederic Dauny, Paul Felenbok, Andrée Fernandez, Jean Guerin, Stephen Shih, Joe Liu (Lesia, Observatoire de Paris) Hsiang-Kuang Chang (Institute of Astronomy National Tsing Hua University, Taiwan) François Colas, Jean Lecacheux (Institut de Mécanique Céleste et de Calcul des Ephémérides, Observatoire de Paris) Isabelle Guinouard (GEPI)