J/AJ/151/11 Taxonomy of potentially hazardous asteroids (Perna+, 2016)
Grasping the nature of potentially hazardous asteroids.
Perna D., Dotto E., Ieva S., Barucci M.A., Bernardi F., Fornasier S.,
De Luise F., Perozzi E., Rossi A., Epifani E.M., Micheli M.,
Deshapriya J.D.P.
<Astron. J., 151, 11 (2016)>
=2016AJ....151...11P 2016AJ....151...11P (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Spectroscopy
Keywords: minor planets, asteroids: general - techniques: spectroscopic
Abstract:
Through their delivery of water and organics, near-Earth objects
(NEOs) played an important role in the emergence of life on our
planet. However, they also pose a hazard to the Earth, as asteroid
impacts could significantly affect our civilization. Potentially
hazardous asteroids (PHAs) are those that, in principle, could
possibly impact the Earth within the next century, producing major
damage. About 1600 PHAs are currently known, from an estimated
population of 4700±1450. However, a comprehensive characterization
of the PHA physical properties is still missing. Here we present
spectroscopic observations of 14 PHAs, which we have used to derive
their taxonomy, meteorite analogs, and mineralogy. Combining our
results with the literature, we investigated how PHAs are distributed
as a function of their dynamical and physical properties. In general,
the ''carbonaceous'' PHAs seem to be particularly threatening, because
of their high porosity (limiting the effectiveness of the main
deflection techniques that could be used in space) and low inclination
and minimum orbit intersection distance (MOID) with the Earth
(favoring more frequent close approaches). V-type PHAs also present
low MOID values, which can produce frequent close approaches (as
confirmed by the recent discovery of a limited space weathering on
their surfaces). We also identified those specific objects that
deserve particular attention because of their extreme rotational
properties, internal strength, or possible cometary nature. For PHAs
and NEOs in general, we identified a possible anti-correlation between
the elongation and the rotational period, in the range of
Prot∼5-80hr. This would be compatible with the behavior of
gravity-dominated aggregates in rotational equilibrium. For periods
≳80-90hr, such a trend stops, possibly under the influence of the
YORP effect and collisions. However, the statistics is very low, and
further observational and theoretical work is required to characterize
such slow rotators.
Description:
Observations of 14 Potentially Hazardous Asteroids (PHAs) were carried
out at the 3.6-m Telescopio Nazionale Galileo (TNG, La Palma, Spain),
the ESO 3.6-m New Technology Telescope (NTT, La Silla, Chile), and the
NASA 3.0-m Infrared Telescope Facility (IRTF, Mauna Kea, USA). The
observational circumstances, as well as the instrumentation used are
given in Table1.
According to the population model by Mainzer et al.
(2012ApJ...752..110M 2012ApJ...752..110M), ∼4700±1450 PHAs are expected to exist. To
further investigate the PHA population as a whole, and in particular
to verify how the different taxonomic types are distributed with
respect to other physical and dynamical properties, we combined our
results with the available literature.
We started retrieving the European Asteroid Research Node (EARN;
http://earn.dlr.de/; retrieved on 2015 April 28) database of
Near-Earth Object (NEO) physical properties, selecting those 255
Potentially Hazardous Asteroids (PHAs) with published taxonomic
classifications. Of our 14 targets, 7 are classified in the present
work for the first time, for a total sample of 262 targets to be
considered in our analysis (see Table4). The results for our remaining
seven targets are in agreement with the literature.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 107 17 Observational circumstances
table4.dat 82 261 Physical and dynamical properties of Potentially
Hazardous Asteroids (PHAs)
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See also:
B/astorb : Orbits of Minor Planets (Bowell+ 2014)
J/ApJ/784/110 : NEOWISE observations of 105 near-Earth objects (Mainzer+, 2014)
J/ApJ/743/156 : WISE observations of NEOs: preliminary results (Mainzer+, 2011)
http://earn.dlr.de/ : European Asteroid Research Node (EARN)
http://minorplanetcenter.net/iau/lists/PHAs.html : List of the PHAs
http://www.oa-roma.inaf.it/planet/NEOSurface.html : NEO-SURFACE
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Planet [4450/350751]? Asteroid number
8- 17 A10 --- Name Asteroid name
19- 22 A4 --- Tel Telescope designation (IRTF, NTT, or TNG) (1)
24- 30 A7 --- Inst Instrument (DOLORES, EMMI, NICS, SofI, or
SpeX) (2)
32- 59 A28 --- Slit Grism/Prism slit
61- 71 A11 "Y:M:D" Obs.date Starting date of observation
73- 77 A5 "h:m" Obs.time UT start time
79- 82 I4 s Exp [5/3600] Exposure time
84- 86 I3 --- Nexp [120]? Number of exposures
88- 91 F4.2 --- AirM1 [1.02/1.71] Airmass
93-102 A10 --- Analog Solar analog
104-107 F4.2 --- AirM2 [1.02/1.43] Solar analog airmass
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Note (1): Telescope code defined as below:
IRTF = The NASA 3.0-m InfraRed Telescope Facility (IRTF; Mauna Kea, USA);
NTT = The ESO 3.6-m New Technology Telescope (NTT; La Silla, Chile);
TNG = The 3.6-m Telescopio Nazionale Galileo (TNG; La Palma, Spain).
Note (2): DOLORES and EMMI for the visible wavelength range, NICS, SofI, and
SpeX for the Near-InfraRed (NIR).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Asteroid name
12- 13 A2 --- Type Taxonomic classification (A, B, C, Ch, D, K, L,
O, P, Q, S, Sa, Sk, Sq, Sr, T, V, X, Xc, Xe,
or Xk) (1)
15- 18 F4.1 mag HMag [13.9/22] Absolute visual magnitude
20- 24 F5.3 --- Alb [0.018/0.75]? Albedo
26- 34 F9.5 h Per [0.1/176]? Rotational period
36- 39 F4.2 mag Amp [0.04/2]? Light curve amplitude
41- 45 F5.3 AU a [0.64/3.21] Semimajor axis
47- 51 F5.3 --- e [0.072/0.93] Orbital eccentricity
53- 56 F4.1 deg i [0.3/64] Inclination
58- 62 F5.3 AU q [0.1/1.05] Perihelion distance
64- 68 F5.3 AU Q [1/5.46] Aphelion distance
70- 74 F5.3 --- Tj [2.4/8.51] Tisserand parameter with respect to
Jupiter
76- 82 F7.5 AU MOID [0/0.05] Minimum Orbit Intersection Distance (2)
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Note (1): Based on DeMeo et al. (2009Icar..202..160D 2009Icar..202..160D) and on our Sections 3 and
5, we defined four "groupings" of potentially hazardous asteroids:
* The "silicaceous" (types S, Q, A, and O);
* The "basaltic" (V-types);
* The "carbonaceous" (types B, C, D, P, T, and Xc);
* The "miscellaneous" (types X, Xe, Xk, K, and L).
Note (2): This is the minimum distance between the orbit of the earth and the
minor planet. See more details at
http://www2.lowell.edu/users/elgb/moid.html
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 11-Jul-2016