Issue |
A&A
Volume 513, April 2010
|
|
---|---|---|
Article Number | A26 | |
Number of page(s) | 7 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/200913609 | |
Published online | 16 April 2010 |
Origin of the near-Earth asteroid Phaethon and the Geminids meteor shower
J. de León1 - H. Campins2 - K. Tsiganis3 - A. Morbidelli4 - J. Licandro5,6
1 - Instituto de Astrofísica de Andalucía-CSIC, Camino Bajo de Huétor 50, 18008 Granada, Spain
2 -
University of Central Florida,
PO Box 162385, Orlando, FL 32816.2385, USA
3 -
Department of Physics, Aristotle University of Thessaloniki,
54 124 Thessaloniki, Greece
4
- Departement Casiopée: Universite de Nice - Sophia Antipolis,
Observatoire de la Côte d'Azur, CNRS 4, 06304 Nice, France
5 -
Instituto de Astrofísica de Canarias (IAC),
C/Vía Láctea s/n, 38205 La Laguna, Spain
6 -
Department of Astrophysics, University of La Laguna,
38205 La Laguna, Tenerife, Spain
Received 5 November 2009 / Accepted 26 January 2010
Abstract
Aims. In this paper we establish a compositional and
dynamical connection between two B-type objects: main belt asteroid (2)
Pallas and near-Earth asteroid (3200) Phaethon. The final purpose is to
help understand the origin of this very interesting object.
Methods. We first compare visible and near-infrared spectra of
asteroids Phaethon and Pallas. We then compare the reflectance spectra
of Phaethon with all the available visible spectra of B-type asteroids
belonging to the Pallas family. One last spectral comparison is then
performed to search for any correspondence between Phaethon and any
B-type asteroid in the main belt. Numerical simulations are also
carried out to explore the dynamical connection between the orbital
neighborhoods of Pallas and Phaethon.
Results. Main differences between Phaethon and Pallas lie in the
visible wavelength part of their reflectance spectra. We have also
found that the nine asteroids belonging to the Pallas family have
visible spectra that are different from that of Pallas and strikingly
similar to that of Phaethon. Spectral comparison excludes any other
B-type asteroid in the main belt as a possible parent body of Phaethon.
Numerical simulations establish a dynamical pathway that connects
Phaethon with Pallas and its family members.
Conclusions. The spectral similarities between Phaethon and
Pallas family members, together with their established dynamical
connection, supports Pallas as the most likely parent body of Phaethon
and therefore, the associated Geminids meteor stream. We suggest that
differences in asteroid sizes are the most likely explanation for the
differences in the visible reflectance spectra between Phaethon and
Pallas.
Key words: minor planets, asteroids: general - techniques: spectroscopic - methods: numerical
1 Introduction
Asteroid (3200) Phaethon is a remarkable near-Earth asteroid (NEA). It
was the first asteroid associated with a meteor shower, namely the
Geminid stream (Whipple 1983),
and together with 2005 UD and 2001 YB5 is one of the 3 NEAs with
associated meteor showers. Phaethon's unusual orbit has a high
inclination (
)
and a very low perihelion distance (0.14 AU). Its reflectance
spectrum suggests a connection with primitive meteorites, best fitting
with CI/CM carbonaceous chondrites (Licandro et al. 2007; Emery et al. 2008), aqueously altered and rich in hydrated silicates. Following the most recent taxonomy of DeMeo et al. (2009),
it is classified as a B-type object. Recent studies suggest a
connection with the population of main-belt comets (Hsieh & Jewitt 2006), classifying Phaethon as an activated asteroid.
Asteroid Pallas is one of the largest objects in the main asteroid belt, with a diameter of 550 km. This asteroid has also unusual orbital parameters for such a large body: it has a highly inclined orbit (
)
and a high orbital eccentricity (e=0.23).
Classified as a primitive, B-type object, it has been widely related to
carbonaceous chondrites (Chapman & Salisbury 1973; Johnson & Fanale 1973; Johnson & Matson 1975) and with evidence of hydration (Lebofsky 1980; Rivkin et al. 2002). Lemaitre & Morbidelli (1994) were the first to note the existence of a possible collisional family around Pallas.
In this paper we show a possible connection between near-Earth asteroid
Phaethon and main belt asteroid Pallas. For Pallas to be considered as
a likely source for Phaethon, it must fulfill the following
requirements. First, Phaethon must be spectroscopically similar to
Pallas and its family members, which would suggest similar surface
composition. Second, a dynamical mechanism must exist, such that Pallas
fragments of Phaethon's size (a diameter of 5
km) can develop planet-crossing orbits and become highly-inclined NEAs.
In the following sections we show that both requirements are met.
2 Data compilation and family members comparison
To explore the compositional connection between Phaethon and Pallas, we
have compiled the relevant spectra from several databases. The visible
spectra (
m) of Pallas, Pallas family members and Phaethon, were taken from the SMASS survey (Bus & Binzel 2001a,b; Binzel
et al. 2001, 2004). The near-infrared spectra (
m) of both Pallas and Phaethon were taken from the MIT-UH-IRTF survey (Binzel et al. 2008).
For the sake of comparison we have also used visible and near-infrared
spectra of Phaethon from the NEOSS database (de León et al. 2010), previously published by Licandro et al. (2007).
![]() |
Figure 1:
Determination of asteroids that belong to the Pallas family.
a) Number of asteroids against the velocity cut-off
|
Open with DEXTER |
To determine which asteroids belong to the Pallas family, we apply the hierarchical clustering method (HCM, Zappalà et al. 1995) on the latest catalog of numerically computed proper elements of all numbered asteroids (provided by the AstDyS service, http://hamilton.unipi.it/astdys). The number of asteroids linked to Pallas changes with the considered value of velocity cut-off, ,
which is a measure of the distance between two bodies in proper
elements space. We can identify a family of 40-80 members, for a
velocity cut-off in the range
m s-1. The number of asteroids linked to the family varies with
,
reaching a plateau for
m s-1
(see Fig. 1a). These high values of
suggest that this family represents a cratering event (also indicated by observations, e.g. Schmidt et al. 2009), rather than a catastrophic disruption, given that Pallas probably contains
of the family's mass. In that case, multi-kilometer sized fragments
could have been ejected from Pallas with relative velocities comparable
to the escape velocity of Pallas (
m s-1; see e.g. Asphaug 1997, for the Vesta case).
Table 1: Proper orbital elements and physical parameters for Pallas and 9 Pallas family members classified as B-types.
For a velocity cut-off of
m s-1,
we find 71 possible Pallas family members. Visible spectra are
available only for six of these asteroids, all of which are classified
as B-types. The proper orbital elements and some physical parameters of
Pallas and its family members are shown in Table 1. We include the semi-major axis (a), eccentricity (e) and inclination (i) of their orbits, as well as their absolute visual magnitude (H) and their visual geometric albedo (
), the later taken from IRAS database (Tedesco 1992). Diameter is estimated from H and
following the expression of Fowler & Chillemi (1992),
.
The differences between the albedo of Phaethon and Pallas family members are within the error bars
. For asteroid Phaethon, osculating orbital elements have been used, taken from JPL Horizons online database (http://ssd.jpl.nasa.gov). Its albedo value has been taken from Harris (1998),
where they use the NEATM model, more appropriate for a small and fast
rotating asteroid than the STM model used within IRAS database.
![]() |
Figure 2:
Spectral comparison between asteroid Phaethon, Pallas and Pallas family members. a)
The visible and near-infrared reflectance spectrum of asteroid Phaethon
is shown in blue. This composite spectrum results from averaging the
spectra taken from two different databases (Binzel et al. 2008;
Licandro et al. 2007), after interpolating with a step of 0.005 |
Open with DEXTER |
The distribution of the Pallas family members in proper semi-major axis and absolute visual magnitude (
)
appears to be ``V''-shaped (see Fig. 1b), a phenomenon known to be associated both with size-dependent ejection velocities field as well as with a drift in
due to the Yarkovsky effect. Note that the Pallas family is contained
within and abruptly terminates at the location of two mean motion
resonances (MMRs) with Jupiter (the 8:3 MMR, at
2.71 AU, and the 5:2 MMR, at
2.82 AU). The minimum value of absolute magnitude (H) of asteroids near the inner truncation distance (the 8:3 MMR with Jupiter) is
14.2, which translates to a diameter D = 4.95 km (using a mean albedo of
),
i.e. these bodies are the size of Phaethon. Thus, some Phaethon-sized
Pallas family fragments could have been able to reach these resonances.
Those that have been trapped in resonance, presumably had their orbital
eccentricities increased to values that would render them Mars- or even
Earth-crossers.
Before discussing in more detail the dynamical connection
between Phaethon and Pallas, we establish a spectroscopic one. As can
be seen in Fig. 2a, the spectra of Pallas and Phaethon are quite similar beyond 1 m,
showing a smooth decay in reflectance with a negative slope, suggesting
a similar surface composition. In fact, the only significant
differences between the two spectra lie in the visible band, between
0.5 and 0.9
m,
indicated by a dashed-line box. For this reason we decided to compare
the visible spectrum of Phaethon not only with that of Pallas, but also
with those of the Pallas family members.
In the visible, Phaethon's spectrum is strikingly similar to those of the Pallas family members (Fig. 2c), while it is markedly different from that of Pallas itself (Fig. 2b). Differences in size can explain these spectral variations. While Pallas has a diameter of
550 km,
its family members have diameters that range from 5 to 26 km.
Variations in the reflectance spectra with respect to grain size have
been studied before for carbonaceous chondrite meteorites (Johson &
Fanale 1973; Sheppard et al. 2008).
In particular Johson & Fanale studied the reflectance spectra of
separates of different sizes of CV3 meteorite Grosnaja, finding that
the spectra got bluer (negative spectral slope) and darker with coarser
grain size. Hence, it is possible that smaller asteroids are covered
with coarser grains. This is also consistent with recent results,
showing that smaller asteroids present higher thermal intertia (Delbo
et al. 2007). Large objects
(e.g. Pallas), covered by dusty regolith, tend to have small thermal
inertia because of their fine-powdered surface. Smaller objects could
have lost their regolith during the collisional event that created them
(in the case of collisional families), not being able to develop or
retain a new regolith, thus preserving preferentially larger grains on
their surfaces.
![]() |
Figure 3:
Dynamical evolution of a fictitious Pallas fragment towards a Phaethon-like orbit. The time evolution of its semi-major axis (top), eccentricity (middle) and inclination (bottom)
are shown. The particle was initially injected in the 8:3 MMR with
Jupiter. The horizontal dotted lines superimposed on each graph
correspond to |
Open with DEXTER |
3 Dynamical link between Pallas and Phaethon: long-term evolution of Pallas fragments in the NEA space
We now show how a dynamical link between Pallas and Phaethon can be
established. To show that Pallas fragments can become Mars-crossers and
subsequently develop Phaethon-like orbits, we integrated the orbits of
fictitious Pallas fragments, initially injected in the 8:3 and
5:2 MMRs that border the Pallas family (notice that the 8:3 MMR had not been considered as a potential NEA source in the NEO model of Bottke et al. 2000, 2002).
First, we generated a population of fragments, their initial conditions
being selected using the equations of Gauss from Zappalà et al. (1995) and assuming isotropic ejection from Pallas with V=300 m s-1.
We then selected only those particles that were injected in the two
resonances, as verified by a short-term numerical integration of their
orbits. These resonant particles were then cloned, in order to generate
a population of
1000
resonant particles. The orbits of the resonant particles were then
integrated for a time interval of 100 My. During this integration,
95% of the particles ended their life by falling on the Sun, while the rest (
5%) encountered Jupiter and were swiftly ejected from the system. Of all these objects, 21 (i.e.
2%) spent several My on Mars- and Earth-crossing orbits with a < 2 AU, before ending their life. According to our simulations, Pallas fragments, injected in the 8:3 MMR have a
3
higher probability of reaching a < 2 AU than particles starting from the 5:2 MMR. Figure 3 shows the orbital evolution of a fictitious Pallas fragment starting from the 8:3 MMR. The particle has an eccentricity of
0.2 at t = 0, since it is a Pallas fragment. When it becomes decoupled from the resonance and goes towards the NEA space (around t
= 14 My), its eccentricity starts oscillating between 0 and 0.9,
and when it reaches the NEA region (the last few Myrs), having
AU
and high inclination Phaethon-like orbit, its eccentrity has
oscillations that cover almost the same band as Phaethon's statistical
sample (i.e. between 0.40 and 0.82). So the fictitious Pallas fragment
becomes a NEA and develops an orbit quite similar to that of Phaethon.
These results show that there exists a dynamical pathway, through which
fragments of Pallas can evolve into Phaethon-like orbits. Thus,
Phaethon can be directly linked to the Pallas family, not only
spectroscopically but also dynamically. Note that, during this
evolution towards the NEA space, the mean inclination changes only by a
few degrees. Thus, asteroids escaping from the region of Pallas, which
itself follows a high-inclination orbit (proper i
33
), would preferentially populate the high-inclination parts of the NEA space, where Phaethon is located.
The mean time interval that an average Pallas fugitive spends within different parts of the (a,e) and (q,i) space (for a<2 AU) is shown in Figs. 4a and b, where both planes have been divided into
cells. As shown in this figure, these Pallas fugitives spend a small,
but non-negligible, fraction of their lifetime on Phaethon-like orbits;
this is indicated by the proximity of Phaethon to the dark grey region
(i.e. cells visited for at least 105.5 yrs). The orbital space visited by Phaethon is indicated by its mean location, along with 1-
error bars, calculated after an integration of 21 ``clones'' of
Phaethon. A similar computation was done for Rudra (100 Rudra
``clones''), a Mars-crossing object whose spectrum is quite close to
that of Phaethon and the Pallas family members (see next section) and
whose orbit also intersects the region of evolved Pallas fragments. The
clones were chosen by adding small, random deviations (of size 10-4 in a and e and
in the angles) in the initial values of the orbital elements of
Phaethon (resp. Rudra). The orbits of these 21 Phaethon (resp. 100
Rudra) clones were integrated for a time span of 100 My (resp.
150 My) or until they collided with the Sun or one of the planets.
The region of orbital elements space covered by these objects, during
their evolution, is depicted by computing the mean value and standard
deviation in each element (a, e, i and q), over the entire time interval and over all clones.
![]() |
Figure 4:
Long-term orbital evolution in the NEA space. In the top panels ( a) and b)) the (a,e) and the (q,i) projections are shown, where
q = a (1-e) is the perihelion distance. The
quantity plotted in grey-scale is the logarithm of the mean time (in
years) that our Pallas-fugitives spend in different regions of the NEA
space. Thus, black regions correspond to residence times TR
> 10 5.5 yrs, while white regions correspond to TR < 104 yrs. Bottom panels ( c) and d))
are the same but only particles spending more than 30 My as NEAs
are taken into account. The fact that the present positions of Phaethon
and Rudra are in better agreement with the residence time distributions
of panels c,d than a,b, suggests that the distribution of B-types in
the NEA space is not kept in steady state by a continuous flux of
Pallas fragments. The mean values of the respective orbital parameters
of Phaethon (resp. Rudra) are indicated by a red (resp. green) solid
circle. The red (resp. green) error-bars correspond to |
Open with DEXTER |
Given these results one might expect to find many more B-type NEAs in the black and dark-gray regions of Figs. 4a, b, if the population of B-type NEAs were kept in steady state by a continuous flux of Pallas family members, escaping from their source region. This is not observed. However, Phaethon and Rudra reside on orbits that are some of the longest-lived among those reachable from the Pallas family (see Figs. 4c, d). Indeed, the median dynamical lifetimes of Phaethon and Rudra are 26 My and 106 My respectively, i.e. much longer than the typical NEA dynamical lifetime (a few My). This suggests that the injection of Pallas family members in the 8:3 resonance was higher in the past (presumably during or soon after the family-forming event). In fact, in this case we would expect that the B-type NEAs that still survive today should be in the longest-lived orbits, in agreement with the observed orbital positions of Phaethon and Rudra (Figs. 4c, d).
4 Spectral comparison with other B-types
For a unique connection between Pallas and Phaethon to be established, one would have to exclude, if possible, all other candidates, or at least show that they are far less likely to be Phaethon's parent bodies than Pallas. The first requirement to be met is the spectral match, both in the visible and the near-infrared. A good match between the complete spectrum of two objects is a strong indication of a similar composition. Unfortunately, there is a lack of near-infrared spectra of B-type asteroids, neither for the Pallas family members nor for other plausible parent bodies, so we restrict our comparison to the visible region. In this sense, data is being currently collected by the authors in the near-infrared of B-type asteroids of the main belt in order to improve the compositional comparison.
In order to do so, we have searched all available spectroscopic
databases for other objects with visible spectra similar to that of
Phaethon, but outside the Pallas family. Spectra for a total of 105
bodies, classified as B-types, were compiled. We use a
test to compare the visible spectra of all selected asteroids with the
mean spectrum of Phaethon. The mean spectrum of Phaethon has been
computed as a weighted mean of three spectra from 2 different databases
(Binzel et al. 2008; Licandro et al. 2007). Weights have been chosen to favour spectra with higher S/N. The resultant mean spectrum is shown in Fig. 2c.
Most of the data we are using for this spectral comparison belongs to
SMASS database, but there are also spectra from the S3OS2 (Lazzaro
et al. 2004) and NEOSS (de Leon et al. 2010,
submitted) databases. Therefore, we apply a wavelength interpolation to
all the spectra to yield the same resolution as SMASS data: a step of
0.0025
m, from 0.435 to 0.925
m.
The
statistic is defined as

where yi is the reflectance of the asteroid to be compared with Phaethon, Yi is the reflectance of Phaethon and n is the number of data points of the spectra. The smaller the value of









Two more objects were found near the 2:1 MMR with Jupiter, and belong to two high-inclination collisional families: asteroid (1101) Clematis, which belongs to the (702) Alauda family, and asteroid (1901) Moravia, which is the largest member of the Moravia family (Gil-Hutton 2006). Five of the members of the Alauda family have taxonomic classification, with three of them being B-types. In the case of the Moravia family, only two objects have taxonomic classification, and both are B-types. Nevertheless, due to the proximity of these two asteroids to the 2:1 MMR, they are far less likely NEA sources than Pallas. Moreover, we did not find other asteroids, belonging to those families that match Phaethon's spectra. The next six bodies to consider are listed here in increasing order of similarity:

Asteroids (282), (2816) and (4997) are isolated B-types, do not have any other dynamically related and smaller asteroids in their surroundings and do not belong to any collisional family. From a dynamical point of view, (4484) Sif is located in a very dispersed (in semi-major axis), high-inclination band of asteroids between the 3:1 (






The remaining 4 candidates are dynamically classified as Mars-crossers, since their orbits currently have eccentricities 0.4 and perihelion distances
1.7 AU: these are (3581) Alvarez, (5690) 1992 UB, (6500) Kodaira and (2629) Rudra. Rudra is a high-inclination (30
)
true Mars-crosser. Its orbit intersects the ecliptic at a minimum nodal distance of
1.35 AU.
However, this is not true for the other three bodies. Integrating their
orbits we found that their perihelion distance becomes q = 1.7 AU only when the argument of perihelion is
90
.
Since their mean inclination is
33
,
this means that they only reach q
= 1.7 AU when they are well above or below the ecliptic; their
nodal distance is always larger than 1.9 AU, so they never cross
the orbit of Mars.
More importantly, the secular oscillations of their orbital elements
are nearly identical to those found for Pallas; they are just on
different phases of very similar evolution cycles. We estimated their
proper elements, by time-averaging their osculating values (see
Table 1)
over a period of 1 My and found that all three asteroids lie
within the borders of the Pallas family. Thus, these three objects are
most likely dynamically misclassified members of the Pallas family.
This ambiguity comes from the fact that their orbital eccentricities
are currently larger (
0.4) than that of Pallas (
0.23). This raises the total number of Pallas members that match
Phaethon's visible spectrum to nine. Therefore, the last asteroid in
our list of possible candidates is (2629) Rudra, a small (
4.5 km diameter) Mars-crosser that, therefore, cannot be Phaethon's parent body, but it is likely (see Figs. 4c, d) an object escaped from the Pallas family as well.
The above results show that Phaethon can be directly linked to the Pallas family not only spectroscopically but also dynamically. Since Pallas is the only large B-type asteroid that can be linked both spectroscopically and dynamically with Phaethon, we belive that our results strongly support that Phaethon most likely originated from Pallas. Hence, the Geminids are also very likely pieces of the asteroid Pallas. Furthermore, the Pallas collisional family may constitute an important and previously unidentified source of primitive-type material that can reach the neighborhood of the Earth.
5 Conclusions
We have compared reflectance spectra of asteroids Phaethon, Pallas, and
all the available spectra of Pallas family members and other main belt
objects classified as B-types. Several important conclusions can be
extracted from the obtained results.
- 1.
- Pallas is the most likely parent body of Phaethon.
- 2.
- We found that visible spectrum of Pallas is significantly
different from that of its 9 family members, while the one of Phaethon
matches strikingly well. We propose differences in asteroid sizes as
the most likely explanation for these differences we have found. While
Pallas is a large asteroid (
km), the 9 family members and also Phaethon have diameters of the order of tens of kilometers. Smaller asteroids are probably covered by a coarser regolith, and so their surfaces get bluer and darker. This is consistent with the findings of Delbo et al. (2007), where smaller asteroids have higher thermal inertia, which is indicative of a coarser regolith.
- 3.
- Our numerical simulations show the existence of a robust dynamical pathway, connecting the orbital neighborhood of Pallas with that of Phaethon. In this respect, the Pallas family may constitute a source of primitive NEAs. Spectral comparison with other main belt asteroids classfied as B-type objects has confirmed the uniqueness of Pallas as the most likely parent body of Phaethon and, consequently, of the Geminids meteor shower.
J.deL. and J.L. gratefully acknowledge support from the Spanish ``Ministerio de Ciencia e Innovación'' projects AYA2005-07808-C03-02 and AYA2008-06202-C03-02. H.C. acknowledges support from NASA's Planetary Astronomy program. H.C. was a visiting Fullbright Scholar at the ``Instituto de Astrofísica de Canarias'' in Tenerife, Spain. H.C. was a visiting astronomer at the Observatoire de la Cte d'Azur, Nice, France. Part of the data utilized in this publication were obtained and made available by the MIT-UH-IRTF Joint Campaign for NEO Reconnaissance. The IRTF is operated by the University of Hawaii under Cooperative Agreement No. NCC 5-538 with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program. The MIT component of this work is supported by the National Science Foundation under Grant No. 0506716.
References
- Asphaug, E. 1997, Meteor. Planet. Sci., 32, 965 [NASA ADS] [CrossRef] [Google Scholar]
- Binzel, R. P., Harris, A., Bus, S. J., & Burbine, T. 2001, Icarus, 151, 139 [NASA ADS] [CrossRef] [Google Scholar]
- Binzel, R. P., Rivkin, A. S., Stuart, J. S., et al. 2004, Icarus, 170, 259 [NASA ADS] [CrossRef] [Google Scholar]
- Binzel, R. P., et al. 2008, The MIT-UH-IRTF Joint Campaign for NEO Spectral Reconnaissance, http://smass.mit.edu/minus.html [Google Scholar]
- Bottke, W. F., Jedicke, R., Morbidelli, A., et al. 2000, Science, 288, 2190 [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
- Bottke, W. F., Morbidelli, A., Jedicke, R., et al. 2002, Icarus, 156, 399 [NASA ADS] [CrossRef] [Google Scholar]
- Bus, S. J., & Binzel, R. 2002a, Icarus, 158, 106 [CrossRef] [Google Scholar]
- Bus, S. J., & Binzel, R. 2002b, Icarus, 158, 146 [NASA ADS] [CrossRef] [Google Scholar]
- Chapman, C. R., & Salisbury, J. W. 1973, Icarus 19, 507 [NASA ADS] [CrossRef] [Google Scholar]
- Clark, B. E., Ziffer, J., Nesvorny, D., et al. 2009, Icarus, submitted [Google Scholar]
- Delbo, M., Harris, A. W., Binzel, R. P., et al. 2003, Icarus, 166, 116 [NASA ADS] [CrossRef] [Google Scholar]
- Delbo, M., dell'Oro, A., Harris, A. W., et al. 2007, Icarus, 190, 236 [NASA ADS] [CrossRef] [Google Scholar]
- de León, J., Licandro, J., Serra-Ricart, M., et al. 2010, A&A, accepted [Google Scholar]
- DeMeo, F. E., Binzel, R. P., Slivan, S. M., & Schelte, J. B. 2009, Icarus, 202, 160 [NASA ADS] [CrossRef] [Google Scholar]
- Emery, J. P., Lim, L. F., Marchis, F., & Cruikshank, D. P. 2008, LPI Contributions, 1405, 8345 [NASA ADS] [Google Scholar]
- Fowler, J. W., & Chillemi, J. R. 1992, The IRAS Minor Planet Survey, Technical report [Google Scholar]
- Gil-Hutton, R. 2006, Icarus, 183, 93 [NASA ADS] [CrossRef] [Google Scholar]
- Harris, A. W. 1998, Icarus, 131, 291 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
- Hsieh, H. H., & Jewitt, D. 2006, Science, 312, 561 [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
- Johnson, T. V, & Fanale, F. 1973, JGR, 78, 8507 [NASA ADS] [CrossRef] [Google Scholar]
- Johnson, T. V., & Matson, D. L. 1975, ApJ, 197, 527 [NASA ADS] [CrossRef] [Google Scholar]
- Lazzaro, D., Angeli, C. A., Carvano, J. M., et al. 2004, Icarus, 172, 179 [CrossRef] [Google Scholar]
- Lebofsky, L. A. 1980, AJ, 85, 573 [NASA ADS] [CrossRef] [Google Scholar]
- Lemaitre, A., & Morbidelli, A. 1994, Cel. Mech. Dyn. Astron., 60, 29 [Google Scholar]
- Licandro, J., Campins, H., Mothé-Diniz, T., et al. 2007, A&A, 461, 751 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
- Luu, J., & Jewitt, D. 1990, AJ, 99, 1985 [NASA ADS] [CrossRef] [Google Scholar]
- Mothé-Diniz, T., Roig, F., & Carvano, J. M. 2005, Icarus, 174, 54 [NASA ADS] [CrossRef] [Google Scholar]
- Rivkin, A. S., Howell, E. S., Vilas, F., et al. 2002, in Asteroids III, ed. W. F. Bottke Jr., A. Cellino, P. Paolicchi, & R. P. Binzel (Tucson: University of Arizona Press), 235 [Google Scholar]
- Schmidt, B. E., Thomas, P. C., Bauer, J. M., et al. 2009, Science, 326, 275 [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
- Shepard, M., Clark, B. E., Nolan, M. C., et al. 2008, Icarus, 193, 20 [NASA ADS] [CrossRef] [Google Scholar]
- Tedesco, E. F. 1992, The IRAS Minor Planet Survey, Tech. Rep. PLTR-92-2049, Phillips Laboratory, Hanscom Air Force Base, MA [Google Scholar]
- Tholen, D. J. 1984, Ph.D. Thesis, AA (Tucson: Arizona University) [Google Scholar]
- Whipple, F. L., IAU Circ., 3881 [Google Scholar]
- Zappala, V., Bendjoya, Ph., Cellino, A., et al. 1995, Icarus, 116, 291 [NASA ADS] [CrossRef] [Google Scholar]
Footnotes
- ... bars
- Uncertainties in the diameter estimated with thermal modelling
usually exceed the formal errors, and are typically 10-15% (e.g. Delbo
et al. 2003), which translated to albedo means uncertainties of 20-30%. For
that means errors of 0.03-0.05, larger than the nominal errors included in the IRAS database.
- ... family
- We already demonstrated in Fig. 1b that Pallas family members of the size of Phaethon should have been trapped into these resonances.
All Tables
Table 1: Proper orbital elements and physical parameters for Pallas and 9 Pallas family members classified as B-types.
All Figures
![]() |
Figure 1:
Determination of asteroids that belong to the Pallas family.
a) Number of asteroids against the velocity cut-off
|
Open with DEXTER | |
In the text |
![]() |
Figure 2:
Spectral comparison between asteroid Phaethon, Pallas and Pallas family members. a)
The visible and near-infrared reflectance spectrum of asteroid Phaethon
is shown in blue. This composite spectrum results from averaging the
spectra taken from two different databases (Binzel et al. 2008;
Licandro et al. 2007), after interpolating with a step of 0.005 |
Open with DEXTER | |
In the text |
![]() |
Figure 3:
Dynamical evolution of a fictitious Pallas fragment towards a Phaethon-like orbit. The time evolution of its semi-major axis (top), eccentricity (middle) and inclination (bottom)
are shown. The particle was initially injected in the 8:3 MMR with
Jupiter. The horizontal dotted lines superimposed on each graph
correspond to |
Open with DEXTER | |
In the text |
![]() |
Figure 4:
Long-term orbital evolution in the NEA space. In the top panels ( a) and b)) the (a,e) and the (q,i) projections are shown, where
q = a (1-e) is the perihelion distance. The
quantity plotted in grey-scale is the logarithm of the mean time (in
years) that our Pallas-fugitives spend in different regions of the NEA
space. Thus, black regions correspond to residence times TR
> 10 5.5 yrs, while white regions correspond to TR < 104 yrs. Bottom panels ( c) and d))
are the same but only particles spending more than 30 My as NEAs
are taken into account. The fact that the present positions of Phaethon
and Rudra are in better agreement with the residence time distributions
of panels c,d than a,b, suggests that the distribution of B-types in
the NEA space is not kept in steady state by a continuous flux of
Pallas fragments. The mean values of the respective orbital parameters
of Phaethon (resp. Rudra) are indicated by a red (resp. green) solid
circle. The red (resp. green) error-bars correspond to |
Open with DEXTER | |
In the text |
Copyright ESO 2010
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