Solar System Science
and Future Sky Surveys
Pedro Lacerda, QUB
Summary
• Introduction to solar system
• Old view
• More recent discoveries
• Significance
• Ongoing surveys
• Important solar system goals for NGSS
The Old Solar System
%
!"#
$
&
$'()
• Nine planets
» 6 classic
» 2 modern
» Pluto
./"%0
+')*",
!"#$%&'
()%"'*
• Mysterious comets and asteroids
• Clockwork and immutable
-&#%"*&
More Recent
Discoveries
1992: The Kuiper Belt
(Jewitt & Luu 1993)
• Sun’s debris disc
• KBOs: icy relics from
planet formation
• frozen physics and
chemistry
• 1000+ KBOs
known
20
0
AU
!20
!50
!50
AU
0
0
50
50
AU
KB Orbital Distribution
0.6
Resonant
Scattered
q = qN
0.4
Classical
Eccentricity
0.8
Centaurs
1.0
0.2
0.0
20
30
Neptune
40
50
60
Semimajor Axis !AU"
70
80
Kuiper Belt Objects
• Numbers:
» Luminosity function
power-law α=0.65
» 1 deg–2 at mR=23.4
» N(D>100km) ~ 4!104
• Chemistry:
» Immense diversity in
surface colors.
» Featureless, methanoids,
and water-ice-covered.
!"#$%"&'&(#)%*##"$&+,,-
Kuiper Belt Objects
• Numbers:
» Luminosity function
power-law α=0.65
» 1 deg–2 at mR=23.4
» N(D>100km) ~ 4!104
• Chemistry:
» Immense diversity in
surface colors.
» Featureless, methanoids,
and water-ice-covered.
!""#$#%&'())#*++,
Kuiper Belt Objects
• Numbers:
» Luminosity function
power-law α=0.65
» 1 deg–2 at mR=23.4
» N(D>100km) ~ 4!104
• Chemistry:
» Immense diversity in
surface colors.
» Featureless, methanoids,
and water-ice-covered.
!"#$%&'(')("*+(,--.
Kuiper Belt Objects
• Numbers:
» Luminosity function
power-law α=0.65
» 1 deg–2 at mR=23.4
» N(D>100km) ~ 4!104
• Chemistry:
» Immense diversity in
surface colors.
» Featureless, methanoids,
and water-ice-covered.
!"#$%&'(&)*+&,--.
Kuiper Belt Objects
• Numbers:
» Luminosity function
power-law α=0.65
» 1 deg–2 at mR=23.4
» N(D>100km) ~ 4!104
• Chemistry:
» Immense diversity in
surface colors.
» Featureless, methanoids,
and water-ice-covered.
!"#$%&'(')("*+(,--.
The Largest KBOs
&"567"56
.+"'"#
,%"'/
)*+$'
!#2/
3"+76"
,%"#'(
012'(
-"#+("
&''(
!"#$%
3+4"
Kuiper Belt aftermath
• The solar system has a debris disk.
• Pluto is not strange, it is a KB member.
• Source of Centaurs, Jupiter comets,Triton,
•
•
(and possibly iSats and Trojans).
Neptune migrated outwards. Planets migrate.
Context for global models of the evolution
of the solar system.
“Nice” Model
Tsiganis, Gomes, Morbidelli, Levison 2005
2004: Main-Belt Comets
(Hsieh & Jewitt 2004)
• Comets with
asteroidal orbits
• Stable orbits, 4.5 Gyr
• Ice close to the Sun
4
2
0
!2
!4
!4
!2
0
2
4
Main-Belt Comets
• Only 5 MBCs known:
very low number statistics
•
Prototype MBC:
133P/Elst-Pizzarro
• Periodic activity (N=2):
Garradd
P/2010 A2
burried ice »
collisional activation » seasonal activity
• Distribution of ice in the solar system
Hsieh & Jewitt 2006
Solar System Zoo
Jupiter-Neptune
Source Zone
Asteroid Belt
Kuiper Belt
Centaurs
MBC
Trojans
JFC
Oort Cloud
iSats
HFC
LPC
NEOs
Ejection
Defunct Comets
Damocloids?
Disintegration
Comparative studies
Sun/Planet Impact
needed to establish
interrelationships
Scientific Value
• No longer N=1
• solar system vs extrasolar systems
• Detailed studies
• Small bodies
• many - everywhere - all sizes
• interrelations - evolution
Transient Phenomena
• Motion -› discovery (pairs)
• Photometric variability
• Cometary activity
Brightness
Lightcurve
Comet 17P/Holme
Time
s
Photometric Variability
Magnitude
Lightcurves
Elongated
Objects
•∆m < 0.7 mag
•Period ~ 5-10hr
Close
Binaries
Rotational Phase
•∆m > 0.9 mag
•Period ~ 10-20hr
Spins — Shape — Density
Primordial rotation — Collisions — Inner structure
where between these two extremes.
4.1. Albedo Models
Crane 2001), but hemispherically averaged color variations
occur only at the 0.01 mag level and are so small that they
would not be detected in the present work (Table 4). From
the example set by Pluto, we conclude that the absence of
color variations on Varuna larger than a few times 0.01 mag
places no useful constraint on the albedo modulation
hypothesis.
If Varuna is spherical and rotating at period P, we can
obtain a lower limit to the density by requiring that the body
not be in a state of internal tension. Simple force balance
Extreme Lightcurves
A complex distribution of albedo markings could produce the observed light curve. If so, the DmR = 0.42 ! 0.02
mag photometric range would imply an albedo contrast
100:4DmR " 3 : 2 or greater (depending on the projection of
into the line of sight). Some spherical
Fig. 2.—Phased data from all the observations in 2002 and 2003 of 2001 QG . The period has been the
phased torotation
6.8872 hr, which isvector
the best-fit single-peaked
riod. Filled colored symbols are data taken in the B band (blue), V band (green), and R band (red) at the Keck I Telescope on UT August 30. All other
mbols are R-band data from the various nights of observations at the UH 2.2 m telescope. The B and
V points have
been shifted
according to their
color
outer
solar
system
bodies
show large albedo contrasts,
ferences from the R band (V!R = 0.60 and B!V = 1.00). No color variation is seen between maximum and minimum light. The uncertainty on each
298
otometric observation is "0.03 mag.
2001QG298
∆m=1.14mag P=13.8hr
Sheppard&Jewitt’04
Varuna
∆m=0.42mag P=6.3hr
Jewitt&Sheppard’02
Fig. 2.—Phase dispersion minimization (PDM) plot computed from the
entire R-band data set of Varuna (February and April observations). The
best fit is the frequency near 3.78 cycles day$1 (double-peaked period of
6.34 hr). The other large peaks flanking the 3.78 frequency are the 24 hr
sampling aliases. The single-peaked period is at 7.57 cycles day$1 (period of
3.17 hr), with associated flanking 24 hr alias periods.
Fig. 3.—Same as Fig. 2, but for a period phased to 13.7744 hr, which is the best-fit double-peaked period. There appear to be two distinct minima. The minima
pear to be more ‘‘notched’’ compared with the flatter maxima. No color variation is seen between maximum and minimum light. The uncertainty for each
otometric observation is "0.03 mag.
Hektor
∆m=1.2mag P=6.9hr
Dunlap&Gehrels’69
Haumea
∆m=0.28mag P=3.9hr
Lacerda et al ‘08
Fig. 4.—R-band photometry of Varuna, phased according to the double-peaked rotation period Prot = 6.3442 hr. The April data have been
brightened by 0.09 mag to correct for the dimming effects of a higher phase
angle (see Sheppard & Jewitt 2002) and greater distance of Varuna compared with the February observations.
where between these two extremes.
4.1. Albedo Models
Crane 2001), but hemispherically averaged color variations
occur only at the 0.01 mag level and are so small that they
would not be detected in the present work (Table 4). From
the example set by Pluto, we conclude that the absence of
color variations on Varuna larger than a few times 0.01 mag
places no useful constraint on the albedo modulation
hypothesis.
If Varuna is spherical and rotating at period P, we can
obtain a lower limit to the density by requiring that the body
not be in a state of internal tension. Simple force balance
Extreme Lightcurves
A complex distribution of albedo markings could produce the observed light curve. If so, the DmR = 0.42 ! 0.02
mag photometric range would imply an albedo contrast
100:4DmR " 3 : 2 or greater (depending on the projection of
into the line of sight). Some spherical
Fig. 2.—Phased data from all the observations in 2002 and 2003 of 2001 QG . The period has been the
phased torotation
6.8872 hr, which isvector
the best-fit single-peaked
riod. Filled colored symbols are data taken in the B band (blue), V band (green), and R band (red) at the Keck I Telescope on UT August 30. All other
mbols are R-band data from the various nights of observations at the UH 2.2 m telescope. The B and
V points have
been shifted
according to their
color
outer
solar
system
bodies
show large albedo contrasts,
ferences from the R band (V!R = 0.60 and B!V = 1.00). No color variation is seen between maximum and minimum light. The uncertainty on each
298
otometric observation is "0.03 mag.
2001QG298
∆m=1.14mag P=13.8hr
Sheppard&Jewitt’04
Varuna
Observationally
∆m=0.42mag P=6.3hr
intensive
Jewitt&Sheppard’02
Fig. 2.—Phase dispersion minimization (PDM) plot computed from the
entire R-band data set of Varuna (February and April observations). The
best fit is the frequency near 3.78 cycles day$1 (double-peaked period of
6.34 hr). The other large peaks flanking the 3.78 frequency are the 24 hr
sampling aliases. The single-peaked period is at 7.57 cycles day$1 (period of
3.17 hr), with associated flanking 24 hr alias periods.
Fig. 3.—Same as Fig. 2, but for a period phased to 13.7744 hr, which is the best-fit double-peaked period. There appear to be two distinct minima. The minima
pear to be more ‘‘notched’’ compared with the flatter maxima. No color variation is seen between maximum and minimum light. The uncertainty for each
otometric observation is "0.03 mag.
Hektor
∆m=1.2mag P=6.9hr
Dunlap&Gehrels’69
Haumea
∆m=0.28mag P=3.9hr
Lacerda et al ‘08
Fig. 4.—R-band photometry of Varuna, phased according to the double-peaked rotation period Prot = 6.3442 hr. The April data have been
brightened by 0.09 mag to correct for the dimming effects of a higher phase
angle (see Sheppard & Jewitt 2002) and greater distance of Varuna compared with the February observations.
Duffard et al. 2009
Most lightcurves
are boring.
Sparse Sampling
• density estimates
• abundance close vs. distant
• test models
• binary formation
• mass vs time
• mixing
Fraction detected !!"
100
!
"
!
"
3
4
5
6
7
8
9
Number of observations per KBO
10
"m # 0.6 mag
!
80
"
40
!
20
"
2
"
!
"
!
"
"
!
60
"
0!
1
!
!
"m # 0.9 mag
"
Small Body Domain
Virtually Unexplored
• KBOs: discovered 1992 - 2% known today
• MBCs: discovered 2004 - 5 known today
• Understanding of interrelations in its infancy
• Entire populations may await discovery
Ongoing Surveys
PanSTARRS
• Moving Object Processing pipeline System
• ~5 new asteroids discovered
4000 rediscovered (400000 known)
• Outer solar system in standby
• Cometary activity in standby
• Plan: everything <23.5mag will be known
Next Generation
Sky Surveys
discover more objects
• To
statistics – patterns – outliers – new
Main
G o als
identify interesting objects
• To
variability – activity – odd dynamics – links
(follow-up) observations
• Monitoring
physical properties – surface chemistry