288 research outputs found
Colliding with G2 near the Galactic Centre: a geometrical approach
The object G2 will pass within nearly 100 au from Sgr A* in 2014. Due to its
very short periapse, the study of the dynamical evolution of this object in the
short-term future may offer some insight into the region surrounding the
supermassive black hole at the centre of the Galaxy. With this scenario in
mind, it has recently been proposed by Bartos et al. (arXiv:1302.3220) that,
prior to its perinigricon, G2 will likely experience multiple encounters with
members of the black hole and neutron-star populations believed to orbit near
the Galactic Centre. Here, we further explore this possibility and study the
general case for collisions with the G2 object using the latest orbital
solutions provided by Phifer et al. (arXiv:1304.5280) and Gillessen et al.,
(arXiv:1306.1374) and a Monte Carlo approach to estimate the minimum orbit
intersection distance (MOID) with G2 as a function of the orbital parameters of
the incoming body. Our results indicate that encounters at distances closer
than 100 au started to become statistically significant only during the last
few years or so. MOIDs under 100 au are statistically more probable for the
most dynamically cold orbits. If there is a population of objects moving in
low-inclination, low-eccentricity orbits around the central black hole, the
highest probability for a close encounter with G2 is found to be in the period
2014 January-March but enhanced activity due to encounters may start as early
as 2013 July-August.Comment: 5 pages, 4 figures. Revised to reflect final version published in
MNRAS Letter
Recent multi-kiloton impact events: are they truly random?
It is customarily assumed that Earth-striking meteoroids are completely
random, and that all the impacts must be interpreted as uncorrelated events
distributed according to Poisson statistics. If this is correct, their impact
dates must be uniformly spread throughout the year and their impact coordinates
must be evenly scattered on the surface of our planet. Here, we use a time- and
yield-limited sample of Earth-impacting superbolides detected since 2000 to
explore statistically this critical though frequently overlooked topic. We show
that the cadence of these multi-kiloton impact events is incompatible with a
random fall pattern at the 0.05 significance level or better. This result is
statistically robust and consistent with the observed distribution of the
longitudes of the ascending nodes of near-Earth objects (NEOs). This lack of
randomness is induced by planetary perturbations, in particular Jupiter's, and
suggests that some of the recent, most powerful Earth impacts may be associated
with resonant groups of NEOs and/or very young meteoroid streams. An intriguing
consequence of this scenario is that the impact hazard of Chelyabinsk-like
objects should peak at certain times in the year.Comment: 5+1 pages, 2 figures, 1 table. Thrice revised to reflect final
version published in MNRAS: Letter
Asteroid 2014 OL339: yet another Earth quasi-satellite
Our planet has one permanently bound satellite -the Moon-, a likely large
number of mini-moons or transient irregular natural satellites, and three
temporary natural retrograde satellites or quasi-satellites. These quasi-moons
-(164207) 2004 GU9, (277810) 2006 FV35 and 2013 LX28- are unbound companions to
the Earth. The orbital evolution of quasi-satellites may transform them into
temporarily bound satellites of our planet. Here, we study the dynamical
evolution of the recently discovered Aten asteroid 2014 OL339 to show that it
is currently following a quasi-satellite orbit with respect to the Earth. This
episode started at least about 775 yr ago and it will end 165 yr from now. The
orbit of this object is quite chaotic and together with 164207 are the most
unstable of the known Earth quasi-satellites. This group of minor bodies is,
dynamically speaking, very heterogeneous but three of them exhibit Kozai-like
dynamics: the argument of perihelion of 164207 oscillates around -90 degrees,
the one of 277810 librates around 180 degrees and that of 2013 LX28 remains
around 0 degrees. Asteroid 2014 OL339 is not currently engaged in any
Kozai-like dynamics.Comment: 10 pages, 7 figures, 1 table. Revised to reflect final version
published in MNRAS. arXiv admin note: text overlap with arXiv:1401.501
Finding Planet Nine: apsidal anti-alignment Monte Carlo results
The distribution of the orbital elements of the known extreme trans-Neptunian
objects or ETNOs has been found to be statistically incompatible with that of
an unperturbed asteroid population following heliocentric or, better,
barycentric orbits. Such trends, if confirmed by future discoveries of ETNOs,
strongly suggest that one or more massive perturbers could be located well
beyond Pluto. Within the trans-Plutonian planets paradigm, the Planet Nine
hypothesis has received much attention as a robust scenario to explain the
observed clustering in physical space of the perihelia of seven ETNOs which
also exhibit clustering in orbital pole position. Here, we revisit the subject
of clustering in perihelia and poles of the known ETNOs using barycentric
orbits, and study the visibility of the latest incarnation of the orbit of
Planet Nine applying Monte Carlo techniques and focusing on the effects of the
apsidal anti-alignment constraint. We provide visibility maps indicating the
most likely location of this putative planet if it is near aphelion. We also
show that the available data suggest that at least two massive perturbers are
present beyond Pluto.Comment: 7 pages, 4 figures, 3 tables. Revised to match version published in
MNRA
A trio of horseshoes: past, present and future dynamical evolution of Earth co-orbital asteroids 2015 XX169, 2015 YA and 2015 YQ1
It is widely accepted that a quasi-steady-state flux of minor bodies moving
in and out of the co-orbital state with the Earth may exist. Some of these
objects are very good candidates for future in situ study due to their
favourable dynamical properties. In this paper, we show that the recently
discovered near-Earth asteroids 2015 XX169, 2015 YA and 2015 YQ1 are small
transient Earth co-orbitals. These new findings increase the tally of known
Earth co-orbitals to 17. The three of them currently exhibit asymmetric
horseshoe behaviour subjected to a Kozai resonance and their short-term orbital
evolution is rather unstable. Both 2015 YA and 2015 YQ1 may leave Earth's
co-orbital zone in the near future as they experience close encounters with
Venus, the Earth-Moon system and Mars. Asteroid 2015 XX169 may have remained in
the vicinity of, or trapped inside, the 1:1 mean motion resonance with our
planet for many thousands of years and may continue in that region for a
significant amount of time into the future.Comment: 15 pages, 9 figures, 1 table, accepted for publication in
Astrophysics and Space Science. arXiv admin note: text overlap with
arXiv:1511.0836
Reconstructing the Chelyabinsk event: pre-impact orbital evolution
The Chelyabinsk superbolide was the largest known natural object to enter the
Earth's atmosphere since the Tunguska event in 1908 and it has become a
template to understand, manage and mitigate future impacts. Although the event
has been documented in great detail, the actual pre-impact orbit of the parent
body is still controversial. Here, we revisit this topic using an improved
Monte Carlo approach that includes the coordinates of the impact point to
compute the most probable solution for the pre-impact orbit (a = 1.62 au, e =
0.53, i = 3.97 degrees, \Omega; = 326.45 and \omega; = 109.71). We also check
all the published solutions using a simple yet robust statistical test to show
that many of them have problems to cause an impact at the right time. We use
the improved orbit and N-body simulations to revisit the dynamical status of a
putative Chelyabinsk asteroid family and confirm that it could be linked to
resonant asteroids 2007 BD7 and 2011 EO40. In addition, and as the
classification of Chelyabinsk meteorites is well established, a search for
meteorite falls of the same chondrite group and petrologic type gives some
evidence for the existence of an associated LL5 chondrite cluster.Comment: 5+4 pages, 5+1 figures, 1+4 tables, accepted for publication in MNRAS
Letters. Revised to reflect final version published in MNRA
Transient Co-orbitals of Venus: An Update
Venus has no known satellites, but has four known co-orbitals: (322756) 2001
CK32, 2002 VE68, 2012 XE133, and 2013 ND15. Here, we present numerical evidence
suggesting that 2015 WZ12 is a possible Venus co-orbital; it might have been
until recently a transient Trojan. Follow-up observations of this target in the
near future will be difficult, though.Comment: 4 pages, 1 figur
Evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects: avoiding a trans-Plutonian planet or just plain bias?
It is a well-known fact that the presence of a massive perturber interacting
with a population of minor bodies following very eccentric orbits can strongly
affect the distribution of their nodal distances. The details of this process
have been explored numerically and its outcome confirmed observationally in the
case of Jupiter, where a bimodal distribution of nodal distances of comets has
been found. Here, we show evidence for a possible bimodal distribution of the
nodal distances of the extreme trans-Neptunian objects (ETNOs) in the form of a
previously unnoticed correlation between nodal distance and orbital
inclination. This proposed correlation is unlikely to be the result of
observational bias as data for both large semimajor axis Centaurs and comets
fit well into the pattern found for the ETNOs, and all these populations are
subjected to similar background perturbations when moving well away from the
influence of the giant planets. The correlation found is better understood if
these objects tend to avoid a putative planet with semimajor axis in the range
300-400 au.Comment: 5 pages, 5 figures, 2 tables. Revised to match version published in
MNRAS: Letters --MNRAS 471, L61-L65 (2017
Asteroid 2017 FZ2 et al.: signs of recent mass-shedding from YORP?
The first direct detection of the asteroidal YORP effect, a phenomenon that
changes the spin states of small bodies due to thermal reemission of sunlight
from their surfaces, was obtained for (54509) YORP 2000 PH5. Such an alteration
can slowly increase the rotation rate of asteroids, driving them to reach their
fission limit and causing their disruption. This process can produce binaries
and unbound asteroid pairs. Secondary fission opens the door to the eventual
formation of transient but genetically-related groupings. Here, we show that
the small near-Earth asteroid (NEA) 2017 FZ2 was a co-orbital of our planet of
the quasi-satellite type prior to their close encounter on 2017 March 23.
Because of this flyby with the Earth, 2017 FZ2 has become a non-resonant NEA.
Our N-body simulations indicate that this object may have experienced
quasi-satellite engagements with our planet in the past and it may return as a
co-orbital in the future. We identify a number of NEAs that follow similar
paths, the largest named being YORP, which is also an Earth's co-orbital. An
apparent excess of NEAs moving in these peculiar orbits is studied within the
framework of two orbit population models. A possibility that emerges from this
analysis is that such an excess, if real, could be the result of mass shedding
from YORP itself or a putative larger object that produced YORP. Future
spectroscopic observations of 2017 FZ2 during its next visit in 2018 (and of
related objects when feasible) may be able to confirm or reject this
interpretation.Comment: 20 pages, 23 figures, 2 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Society Main Journa
Plutino 15810 (1994 JR1), an accidental quasi-satellite of Pluto
In the solar system, quasi-satellites move in a 1:1 mean motion resonance
going around their host body like a retrograde satellite but their mutual
separation is well beyond the Hill radius and the trajectory is not closed as
they orbit the Sun not the host body. So far, minor bodies temporarily trapped
in the quasi-satellite dynamical state have been identified around Venus,
Earth, the dwarf planet (1) Ceres, the large asteroid (4) Vesta, Jupiter,
Saturn and Neptune. Using computer simulations, Tiscareno and Malhotra have
predicted the existence of a small but significant population of minor bodies
moving in a 1:1 mean motion resonance with Pluto. Here we show using N-body
calculations that the Plutino 15810 (1994 JR1) is currently an accidental
quasi-satellite of Pluto and it will remain as such for nearly 350,000 yr. By
accidental we mean that the quasi-satellite phase is triggered (or terminated)
not by a direct gravitational influence in the form of a discrete close
encounter but as a result of a resonance. The relative mean longitude of the
Plutino circulates with a superimposed libration resulting from the oscillation
of the orbital period induced by the 2:3 mean motion resonance with Neptune.
These quasi-satellite episodes are recurrent with a periodicity of nearly 2
Myr. This makes 15810 the first minor body moving in a 1:1 mean motion
resonance with Pluto. It also makes Pluto the second dwarf planet, besides
Ceres, to host a quasi-satellite. Our finding confirms that the quasi-satellite
resonant phase is not restricted to small bodies orbiting major planets but is
possible for dwarf planets/asteroids too. Moreover, 15810 could be considered
as a possible secondary target for NASA's Pluto-Kuiper Belt Mission New
Horizons after the main Pluto flyby in 2015.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letters (the
abstract has been shortened
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