PHYSICAL CHARACTERIZATION OF ASTEROIDS

1
PHYSICAL CHARACTERIZATION OF ASTEROIDS NEON
Group 5 Koraljka Mužic Nikola Vitas Grzegorz
Nowak Mario Mars Simone Marchi (tutor)
5th NEON SCHOOL, OHP, 2006
2
PHYSICAL CHARACTERIZATION OF ASTEROIDS
OUTLINE
Introduction
Photometry of 1980 Tezcatlipoca
Spectroscopy of 2 Pallas and 25 Phocaea
5th NEON SCHOOL, OHP, 2006
3
PHYSICAL CHARACTERIZATION OF ASTEROIDS
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
5th NEON SCHOOL, OHP, 2006
4
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
INTRODUCTION
Asteroid classification
Three spectral complexes
Asteroid classification
S type consisted mostly of silicates, with
addition of different elements Moderately steep
slope for ?lt0.7µm, 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
?lt0.55µm occasionally shallow absorption feature
at ?gt0.85µm
5th NEON SCHOOL, OHP, 2006
5
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
1980 Tezcatlipoca (NEO) DATA
Absolute magnitude, 13.92
Diameter, D 4.3 km (Gehrels, 1994)
Rotation period, P 7.2523 h (Wisniewski et
al, 1997)
Geometric albedo, g 0.25
Spectral type, S
Discovered 19/06/1950 by Wilson, A. G. at
Palomar
5th NEON SCHOOL, OHP, 2006
6
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
Orbit of Tezcatlipoca 25/07/2006 Sun Target
Earth angle 59º
5th NEON SCHOOL, OHP, 2006
7
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
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
5th NEON SCHOOL, OHP, 2006
8
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
1980 Tezcatlipoca in 12x12 star field
5th NEON SCHOOL, OHP, 2006
9
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
1980 Tezcatlipoca in 12x12 star field
5th NEON SCHOOL, OHP, 2006
10
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
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
5th NEON SCHOOL, OHP, 2006
11
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
The instrumental magnitude variation of 20
selected reference stars 25/07/2006
5th NEON SCHOOL, OHP, 2006
12
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
Tezcatlipoca / photometric observations line
original data, squares corrected values
5th NEON SCHOOL, OHP, 2006
13
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
Previous observations (Kaasalainen et al, 2004)
5th NEON SCHOOL, OHP, 2006
14
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
Composite light curve plot of the two
observations of Tezcatlipoca
5th NEON SCHOOL, OHP, 2006
15
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS PHOTOMETRY
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.
5th NEON SCHOOL, OHP, 2006
16
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Spectroscopy of Pallas (2)
General informations about Pallas.
Observations and data reduction.
Spectra and their slopes.
Variations of the spectrum.
5th NEON SCHOOL, OHP, 2006
17
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Discovery Discoverer Heinrich Wilhelm
Olbers Discovery date March 28, 1802 Orbital
elements Eccentricity (e) 0.231 Semi-major axis
(a) 2.773 AU Orbital period (P) 4.62
years Inclination (i) 34.840 Longitude of the
ascending node (O) 173.150 Argument of
perihelion 310.450 Physical
characteristics Dimensions 570x525x500
km Mass 2.2x1020 kg Density 2.8
g/cm3 Surface gravity 0.18 m/s2 Escape
velocity 0.32 km/s Rotational period 7.81
h Absolute magnitude 4.18 Spectral
class B-type asteroid
5th NEON SCHOOL, OHP, 2006
18
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Size comparison the first 10 asteroids
profiled against Earths Moon. Pallas is the
second on the left.
5th NEON SCHOOL, OHP, 2006
19
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
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.
5th NEON SCHOOL, OHP, 2006
20
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Reflectance spectra of C class asteroids
(Gaffey et al, 1993)
5th NEON SCHOOL, OHP, 2006
21
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
1. The spectra were obtained with the 1.93 m
telescope in conjunction with the CARELEC
spectrograph 26/07/2006. 2. We used solar-like
spectrum combined from three reference G2-type
stars to divide the asteroid spectra and obtain
the reflectivity of the asteroid.
5th NEON SCHOOL, OHP, 2006
22
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Reflectance spectra of C class asteroids
(Gaffey et al, 1993)
5th NEON SCHOOL, OHP, 2006
23
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Reflectance spectra of C class asteroids
(Gaffey et al, 1993)
5th NEON SCHOOL, OHP, 2006
24
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
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 9.954
h Inclination 21.58 Silicaceous-type
spectral class S
5th NEON SCHOOL, OHP, 2006
25
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
S-type asteroids
13-17 of known asteroids Composition
silicate Fe-Ni core Dominate the inner
asteroid belt Reflect 15
5th NEON SCHOOL, OHP, 2006
26
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Phocaea group in main belt
Mean orbital radius between 2.25 and 2.5 AU
Inclination between 18 and 32 Eccentricity
gt0.1 Distribution is determined
by Gravitational influence of Jupiter
Phocaea group
5th NEON SCHOOL, OHP, 2006
27
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Olivine pyroxene

• Fe2SiO4 fayalite and Mg2SiO4 forsterite
• XY(Si Al)2O6 XY calcium, sodium, magnesium,
  iron, chronium mixed mineral
• Pyroxene
• Olivine

5th NEON SCHOOL, OHP, 2006
28
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Reflectance spectra of C class asteroids
(Gaffey et al, 1993)
5th NEON SCHOOL, OHP, 2006
29
PHYSICAL CHARACTERIZATION OF ASTEROIDS
PHYSICAL CHARACTERIZATION OF ASTEROIDS
SPECTROSCOPY
Reflectance spectra of C class asteroids
(Gaffey et al, 1993)
5th NEON SCHOOL, OHP, 2006
30
THANK YOU FOR YOUR ATTENTION!
5th NEON SCHOOL, OHP, 2006