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Deep Impact & Spitzer : A Rosetta Stone for Comets and
Asteroids in the Solar System and Around Other Stars
Dr. Carey Lisse
Johns Hopkins University -Applied Physics Laboratory
Summary
• We have a new tool from the Deep Impact experiment, that
allows us to understand the makeup of comets and asteroids,
and to understand where and when comets and asteroids
formed and evolved.
• We have now successfully applied the tool to the ‘gold
standard’ of comet studies, Comet Hale-Bopp, and 2 bright
solar systems outside our own, the very young HD100546
and the mature star HD69830.
• We have learned that Hale-Bopp formed much earlier than
Tempel 1, and that the families of comets and asteroids
around other stars form and behave in much the same way
as they did in our own solar system.
Protostar
T < 104 yr
~5 M
Relics of Planetary System Formation
Disk & Jet
~105 yr
Comets,
Proto-planets,
Nebular Disks
~107 yr
Planetary System
+ Small Relic
Bodies (asteroids)
T > 108 yr
Orion Nebula
HH30
HR4796
Where Comets Come From
KBO’s, Pluto
Comet Structures
(C/West 1975)
Ion Tail
Dust Tail
33,000,000 km
(~0.2 AU)
Coma
Nucleus!
(1-10 km)
80,000 km
To Sun
(Pre-Post)/Pre = Ejecta/Pre-Impact Coma
Spitzer Observations of the Tempel 1 Ejecta
Spitzer IRS I+45 Min
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
344 Spectral Points
SNR 5 - 30 (2 error bars)
95% C.L. = 1.13
Simultaneous 5- 35 um
> 16 Sharp Features
Model : Sum of
Mineral Emissions
Carbonate (Chalk)
PAHs (Soot, Exhaust)
Water
Gas
Amorph Carbno (Soot)
Water Ice
Phyllosilicates (Clay)
Sulfidse (Fool’s Golds
Pyroxene (Rocks)
Olivines (Rocks)
Lisse et al. 2006
Fire, Mud, & Ice : Tempel 1 Contains Xtal Silicates, Annealed at T > 1000K + Ices,
Stable Only Below 200 K + Carbonates and Clays - Formed in Water
Crystal
Silicates
Carbonates
Clays
Comets
Strong Radial
PSN Mixing of
material from
inside the orbit of
Mercury to
outside the orbit
of Neptune (turnoff when giant
planet cores form)
Or Parent Body Aqueous Alteration over 4.5 Gyr
(1) Impulsive Cratering (2) Long Term Water Vapor Processing
SST-IRS P/Tempel 1 Ejecta Spectrum Compared to Comets, Exo-Systems. -Similar Spectra Due to Presence of Silicates, PAHs, Water, Sulfides.
- Differences Due to Relative Compositions, T, Particle Size
Comets Hale-Bopp, SW3, SW1
Disk Systems HD100546, HD69830, HD113766
10 Myr Be9V YSO w/ Disk Cavity
~15 Myr F3/F5 YSO
2-10 Gyr K0V w/ 3 Neptunes
Systems Studied
Comet Hale-Bopp : A huge comet formed near
the giant planets, early in the solar systems
history.
HD100546 (an infant giant star + forming solar
system)
HD69830 (a mature star slightly redder and
about the same age as the Sun, with at least
3 planets).
1.47 AU
JFC SW-3 B
Fragment
(SST; Sitko
et al. 2007)
Amorph
Carbon
PAHs
1.5 AU
JFC
Tempel 1
Ejecta
(SST; Lisse
et al. 2006)
Carbonates
Sulfides
Pyroxenes
Olivines
2.8 AU
5.7 AU
Carbonates
Pyroxenes
Olivines
JFC/Centaur
SW-1 Coma
(SST;
Stansberry
et al. 2005)
Oort Cloud
Hale-Bopp
Coma (ISO;
Crovisier
et al. 1997))
Water Ice
Smectite (clay)
Olivines
Lisse et al. 2007
“Spectral Fingerprints” of Cometary IR Mineralogy
T1 Spectral Model applied to other systems fits spectra well, extends results to Spitzer, ISO
database. We can now dig down below the dominant silicate emissions to find other species.
Hale-Bopp : No Fe-rich olivine. Much more water ice and amorphous carbon. Carbonates, clay.
SW1, SW3 : Much amorphous silicates, Mg-rich olivine. Only water gas for SW3, ice for SW1.
K0V, 12 pc
“Mature” HD69830
•K0V, T = 5400 K, 2 - 10 Gyr old, 12 pc distant
•3 Neptune Sized Planets @ 0.08, 0.16, 0.63 AU
Lovis et al. 2006
B
C
D
Asteroidal Dust Belt
Lisse et al. 2007
T~ 400 K
Super Comet or Asteroid?
Carbonates
PAHs absent
Carbon attenuated
Water Ice
Pyrox all crystalline
Sulfides absent
Olivine Super-rich
Lisse et al. 2007
Beichman et al. 2005
“Near-solar” star. Small, icy, ephemeral dust replenished
by ongoing fragmentation. S.S. analogue : ~30 km radius
P/D asteroid disrupted @ 1 AU. Karins/Veritas 5-8 Mya?
HD69830 (a mature star slightly redder and about
the same age as the Sun, with at least 3 planets).
B
C
D
Asteroidal Dust Belt
Lisse et al. 2007
- The dust around HD69830 is substantially different from that found for comet
9P/Tempel 1 or C/Hale-Bopp 1995 O1 and comet-dominated YSO HD100546. It
lacks carbonaceous and ferrous materials but includes small icy grains.
- The composition of the HD 69830 dust resembles that of a disrupted P or D-type
asteroid. The amount of mass responsible for the observed emission is the equivalent
of
a
30
km
radius
asteroid.
- The temperature of the dust implies that the bulk of the observed material is at ~1.0
AU from the central source, outside the outermost of 3 Neptune-sized planets
detected
by
Lovis
et
al.
(2006).
- In our solar system, P and D-type asteroids are both large and numerous in the
outer main belt and near Jupiter (e.g. the Hildas and Trojans).
- Asteroids in our solar system have undergone similar major disruptive events to
produce debris disk-like structures (e.g the Karin and Veritas families 5-8 Myrs ago).
Comparative IR Mineralogy of Young Stellar Objects
HD100546 : Cometlike. Especially rich in
Mg-rich olivine and
amorphous pyroxene,
water ice. We find the
dust to be at ~13 AU,
consistent with the
inner disk cavity edge
of Grady et al. 2005.
Amorph
Carbon
HD113766 : Mainly has
Mg-rich olivine, Fe-rich
sulfides, and xtal pyroxene.
Little carbonates, clays,
PAHs, or amorphous
carbon present. Similar to
S-type asteroid. NOT an
older HD100546.
HD100546 Disk Herbig Be9V >10 Myr
PAHs
Carbonates
Water Ice
Clays
X
HD113766 Disk F3/F5 ~16 Myr
Sulfides
Pyroxenes
Olivines
Lisse et al. 2007
Sulfides
Pyroxenes
Olivines
Comet Hale-Bopp : A huge comet formed near
the giant planets, early in the solar systems
history. & HD100546 (an infant giant star +
forming solar system)
- We find similar emission signatures due to silicates, carbonates, phyllosilicates, water
ice, amorphous carbon, and sulfides in the two ISO-observed systems, Hale-Bopp and
HD100546,
but
there
are
significant
differences
as
well.
- T1, HB, and Hd100546 all show substantial emission due to silicates (rock forming
materials), water, PAHs (soot, exhaust) and metal sulfides (fool’s gold).
There are some differences : compared to Tempel 1, no Fe-rich olivines and few
crystalline pyroxenes are found in Hale-Bopp. The silicate and PAH material in HaleBopp is clearly less processed than in Tempel 1, indicating an earlier age of formation
for
Hale-Bopp.
- The observed material around HD 100546 is located ~13 AU from the central source,
and demonstrates an unusual composition due to either a very different, non-solar
starting mix of silicates or due to disk material processing during formation of the
interior disk cavity and planet(s) in the system.
Summary
• We have a new tool from the Deep Impact experiment, that allows us to
understand the makeup of comets and asteroids, and to understand
where and when comets and asteroids formed and evolved.
• We have now successfully applied the tool to the ‘gold standard’ of comet
studies, Comet Hale-Bopp, and 2 bright solar systems outside our own,
the very young HD100546 and the mature star HD69830.
• We have learned that Hale-Bopp formed much earlier than Tempel 1, and
that the families of comets and asteroids around other stars form and
behave in much the same way as they did in our own solar system.
By Measuring the Infrared Light
from the Tempel 1 Ejecta, We
Can Determine Dust
• Composition
• Temperature
• Particle Size