Title: Osservazioni nellIR termico dei corpi minori del sistema solare
1Osservazioni nellIR termico dei corpi minori del
sistema solare
- Marco Delbò
- INAF Osservatorio Astronomico di Torino
2Why thermal IR ?
Asteroids and comets are cold objects
- By measuring the thermal emission of asteroids
- Albedos and Sizes (Radiometric technique)
- Physical information such as surface roughness
and thermal inertia
3Radiometric technique
4Thermal model
5What do we need ?
6Thermal IR multiwavelength coverage
- Allows deriving the temperature of the object
through a thermal model fit - A single measurements at 10?m cannot distinguish
the two temperature distributions
7NEO size distribution
8Our level of knowledge
About 2000 NEOs discovered to-date Less than 60
objects for which we know diameter and albedo
H18 Geom. Albedo0.05 ? D1.5 km H18 Geom.
Albedo0.3 ? D0.6 km
9Asteroid size distribution
- The asteroid size distribution is uncertain for
objects smaller than 20 30 km
10What we can do with LBT
- Next slides show example targets that we have
observed with the Keck 1 10m telescope on Mauna
Kea Hawaii - LBT thermal IR sensitivity should be very close
11Some examples
- 2002 BM26
- D?0.6 km
- Keck LWS
- Unpublished results
- By R. Binzel (MIT)
- H.W. Harris (DLR)
- M. Delbo (INAF-OATo
12Goals of the project
- Origin of NEOs
- Physically based size distribution
- Correlation with spectral types
- Thermo-Physical properties
- Improve thermal models
13Preliminary results
- Increasing albedo with decreasing size
- Albedos of small objects seem higher than the
value that one would expect from the taxonomic
class - FRM (i.e. very high thermal inertia) can be ruled
out
14Increasing albedo with decreasing size
- Is this a selection effect ?
- Many low albedo observed at small sizes.
- Targets selected well below the discovery limit
- Does it applies for Main Belt Asteroids ?
- Is this due to some inadequacies in the thermal
models we adopt?
15Access to a LBT class telescopewill help to
solve these and other related questions
16Exploiting LBT interferometric capabilities
- Simulation of the reconstuction of a asteroid
surface temperature distribution with LBT
17Asteroid temperature distribution
A
18LBT psf
P
19Asteroid temperature distribution
- 140km _at_1AU
- IA P
- R IP/(P2u)
A
I
R
20T distrib. Of 1.4km NEA _at_ 0.01AU
- Object
- Blurred
- Reconstruction
21The measured temperature distribution will help
for...
22Calibration of thermal models
- Which assume a temperature distribution up to now
23Study of the Yarkovsky thermal force
Which is due the asimmetrical thermal emission
force
Which causes a secular variation of the asteroid
orbital elements...