PHYSICAL CHARACTERIZATION OF ASTEROIDS NEON Group 5: Koraljka Mužić Nikola Vitas Grzegorz Nowak Mario Mars Simone Marchi (tutor) 5 th NEON SCHOOL, OHP, 2006

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 OUTLINE # Introduction # Photometry of 1980 Tezcatlipoca # Spectroscopy of 2 Pallas and 25 Phocaea

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Asteroid observations # Photometry: information about the shape of the body and scattering properties of the surface # Spectroscopy: information about the chemical composition and homogeneity of the surface

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 Asteroid classification Three spectral complexes: S – type: consisted mostly of silicates, with addition of different elements Moderately steep slope for λ<0.7μm, silicon absorption feature at 1 μm C - type: carbon rich silicate composition Flat spectra, shallow absorption features, if present at all Very low albedos X – type: carbon rich and metal rich; a generally featureless spectra, with slight to moderately red slope; A subtle UV absorption feature, at λ<0.55μm; occasionally shallow absorption feature at λ>0.85μm PHYSICAL CHARACTERIZATION OF ASTEROIDS: INTRODUCTION

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # 1980 Tezcatlipoca (NEO): DATA # Absolute magnitude, # Diameter, D = 4.3 km (Gehrels, 1994) # Rotation period, P = h (Wisniewski et al, 1997) # Geometric albedo, g = 0.25 # Spectral type, S # Discovered 19/06/1950 by Wilson, A. G. at Palomar PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Orbit of Tezcatlipoca [25/07/2006] Sun – Target – Earth angle = 59º PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Observations of 1980 Tezcatlipoca at OHP # Two nights: 25/07/2006 (63 frames), 30/07/2006 (55 frames) # Telescope: 1.20 cm # Detector: CCD TK1024 # Filter: R # Exposure time: 120 s PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # 1980 Tezcatlipoca in 12’x12’ star field PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # 1980 Tezcatlipoca in 12’x12’ star field PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Selected reference stars and 1980 Tezcatlipoca # Photometry: information about the shape of the body and homogeneity of the surface # Spectroscopy: information about the chemical composition PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # The instrumental magnitude variation of 20 selected reference stars [25/07/2006] PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Tezcatlipoca / photometric observations: line = original data, squares = corrected values PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Previous observations (Kaasalainen et al, 2004) PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Composite light curve plot of the two observations of Tezcatlipoca PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Model of Tezcatlipoca or What did we conclude? # Rough dimensions a/b = 1.4, b/c = 1.4 (Kaasalainen et al, 2004) # Considerable irregularities # The high solar phase angles and shadowing effects can explain high amplitudes of the light curve even if the model is not highly elongated. # The “barrel-like” model may also represent a “bone” shape of the asteroid… # …though we cannot expect narrow “waist” if the object is not highly elongated. # New observations are necessary to confirm the model and to explain the systematic effects indicated by the difference between data obtained with R and V filter. PHYSICAL CHARACTERIZATION OF ASTEROIDS: PHOTOMETRY

PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY 5 th NEON SCHOOL, OHP, 2006 Spectroscopy of Pallas (2) # General informations about Pallas. # Observations and data reduction. # Spectra and their slopes. # Variations of the spectrum.

PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY 5 th NEON SCHOOL, OHP, 2006 Discovery Discoverer Heinrich Wilhelm Olbers Discovery dateMarch 28, 1802 Orbital elements Eccentricity (e)0.231 Semi-major axis (a)2.773 AU Orbital period (P)4.62 years Inclination (i) Longitude of the ascending node (Ω) Argument of perihelion Physical characteristics Dimensions 570x525x500 km Mass 2.2x10 20 kg Density2.8 g/cm 3 Surface gravity 0.18 m/s 2 Escape velocity0.32 km/s Rotational period 7.81 h Absolute magnitude4.18 Spectral classB-type asteroid

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Size comparison: the first 10 asteroids profiled against Earth’s Moon. Pallas is the second on the left. PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # B-type # Relatively uncommon type of carbonaceous asteroid, falling into the wider C-group, # generally similar to the C-type objects, # ultraviolet absorption below 0.5 um is small or absent, # spectra is rather slightly bluish than reddish, #the albedo also tends to be greater than the generally very dark C- type. PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Reflectance spectra of C class asteroids (Gaffey et al, 1993) PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, The spectra were obtained with the 1.93 m telescope in conjunction with the CARELEC spectrograph 26/07/ We used solar-like spectrum combined from three reference G2-type stars to divide the asteroid spectra and obtain the reflectivity of the asteroid. PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Reflectance spectra of C class asteroids (Gaffey et al, 1993) PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Reflectance spectra of C class asteroids (Gaffey et al, 1993) PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 Spectroscopy of Phocaea (25) # Discovered by J. Chacornac on April 6, 1853 # Member of the main asteroid belt # Distance ~3 AU # Diameter 75.1 km # Rotation period h # Inclination 21.58° # Silicaceous-type [spectral class S] PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # S-type asteroids # 13-17% of known asteroids # Composition silicate & Fe-Ni core # Dominate the inner asteroid belt # Reflect ~15% PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Phocaea group in main belt # Mean orbital radius between 2.25 and 2.5 AU # Inclination between 18° and 32° # Eccentricity >0.1 # Distribution is determined by Gravitational influence of Jupiter Phocaea group PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Olivine & pyroxene # Fe 2 SiO 4 [fayalite] and Mg 2 SiO 4 [forsterite] # XY(Si; Al) 2 O 6 [XY = calcium, sodium, magnesium, iron, chronium mixed mineral] Pyroxene Olivine PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Reflectance spectra of C class asteroids (Gaffey et al, 1993) PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

PHYSICAL CHARACTERIZATION OF ASTEROIDS 5 th NEON SCHOOL, OHP, 2006 # Reflectance spectra of C class asteroids (Gaffey et al, 1993) PHYSICAL CHARACTERIZATION OF ASTEROIDS: SPECTROSCOPY

THANK YOU FOR YOUR ATTENTION! 5 th NEON SCHOOL, OHP, 2006