No evidence for interstellar planetesimals trapped in the Solar system

Morbidelli, Alessandro; Batygin, Konstantin; Brasser, R.; Raymond, Sean N.

doi:10.1093/mnrasl/slaa111

Cited by 37 publications

(27 citation statements)

References 28 publications

(25 reference statements)

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“…It is therefore a dynamically young object, not an object that has remained in its present trajectory since the formation of the solar system. For this reason, the situation described here is very different from that discussed by Morbidelli et al (2020), who showed that any interstellar planetesimals trapped during the formation of the solar system are highly unlikely to remain with us.…”

Section: Past Orbital Evolution: Possible Origincontrasting

confidence: 79%

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

Licandro¹,

León²,

Moreno

et al. 2024

Preprint

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Context. The existence of comets with heliocentric orbital periods close to that of Jupiter (i.e., co-orbitals) has been known for some time. Comet 295P/LINEAR (2002 AR 2 ) is a well-known quasi-satellite of Jupiter. However, their orbits are not long-term stable, and they may eventually experience flybys with Jupiter at very close range, close enough to trigger tidal disruptions like the one suffered by comet Shoemaker-Levy 9 in 1992. Aims. Our aim was to study the observed activity and the dynamical evolution of the Jupiter transient co-orbital comet P/2019 LD 2 (ATLAS) and its dynamical evolution. Methods. We present results of an observational study of P/2019 LD 2 carried out with the 10.4 m Gran Telescopio Canarias (GTC) that includes image analyses using a Monte Carlo dust tail fitting code to characterize its level of cometary activity, and spectroscopic studies to search for gas emission. We also present N-body simulations to explore its past, present, and future orbital evolution. Results. Images of P/2019 LD 2 obtained on 2020 May 16, show a conspicuous coma and tail, but the spectrum obtained on 2020 May 17, does not exhibit any evidence of CN, C 2 , or C 3 emission. The comet brightness in a 2.6 aperture diameter is r = 19.34±0.02 mag, with colors (g − r ) = 0.78 ± 0.03, (r − i ) = 0.31 ± 0.03, and (i − z ) = 0.26 ± 0.03. The temporal dependence of the dust loss rate of P/2019 LD 2 can be parameterized by a Gaussian function having a full width at half maximum of 350 days, with a maximum dust mass loss rate of 60 kg s −1 reached on 2019 August 15. The total dust loss rate from the beginning of activity until the GTC observation date (2020 May 16) is estimated at 1.9×10 9 kg. Comet P/2019 LD 2 is now an ephemeral co-orbital of Jupiter, following what looks like a short arc of a quasi-satellite cycle that started in 2017 and will end in 2028. On 2063 January 23, it will experience a very close encounter with Jupiter at perhaps 0.016 au; its probability of escaping the solar system during the next 0.5 Myr is estimated to be 0.53±0.03. Conclusions. Photometry and tail model results show that P/2019 LD 2 is a kilometer-sized object, in the size range of the Jupiterfamily comets, with a typical comet-like activity most likely linked to sublimation of crystalline water ice and clathrates. Its origin is still an open question. Our numerical studies give a probability of this comet having been captured from interstellar space during the last 0.5 Myr of 0.49±0.02 (average and standard deviation), 0.67±0.06 during the last 1 Myr, 0.83±0.06 over 3 Myr, and 0.91±0.09 during the last 5 Myr.

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Section: Past Orbital Evolution: Possible Origincontrasting

confidence: 79%

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

Licandro¹,

León²,

Moreno

et al. 2024

Preprint

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show abstract

“…Therefore, we can wonder whether the chaotic divergence of trajectories during separatrix crossings could lead to some kind of time-irreversibility in our numerical solutions (see e.g. Morbidelli et al 2020), especially in the non-adiabatic regime, which has not been studied by Saillenfest et al (2021). These aspects can be investigated through a Monte Carlo search for the initial conditions of Saturn's spin axis.…”

Section: Monte Carlo Search For Initial Conditionsmentioning

confidence: 99%

The past and future obliquity of Saturn as Titan migrates

Saillenfest

Lari

Boué

et al. 2021

A&A

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Context. Giant planets are expected to form with near-zero obliquities. It has recently been shown that the fast migration of Titan could be responsible for the current 26.7°-tilt of Saturn’s spin axis. Aims. We aim to quantify the level of generality of this result by measuring the range of parameters allowing for this scenario to happen. Since Titan continues to migrate today, we also aim to determine the obliquity that Saturn will reach in the future. Methods. For a large variety of migration rates for Titan, we numerically propagated the orientation of Saturn’s spin axis both backwards and forwards in time. We explored a broad range of initial conditions after the late planetary migration, including both small and large obliquity values. Results. In the adiabatic regime, the likelihood of reproducing Saturn’s current spin-axis orientation is maximised for primordial obliquities between about 2° and 7°. For a slightly faster migration than expected from radio-science experiments, non-adiabatic effects even allow for exactly null primordial obliquities. Starting from such small tilts, Saturn’s spin axis can evolve up to its current state provided that: (i) the semi-major axis of Titan changed by more than 5% of its current value since the late planetary migration, and (ii) its migration rate does not exceed ten times the nominal measured rate. In comparison, observational data suggest that the increase in Titan’s semi-major axis exceeded 50% over 4 Gyr, and error bars imply that the current migration rate is unlikely to be larger than 1.5 times its nominal value. Conclusions. If Titan did migrate substantially before today, tilting Saturn from a small obliquity is not only possible, but it is the most likely scenario. Saturn’s obliquity is still expected to be increasing today and could exceed 65° in the future. Maximising the likelihood would also put strict constraints on Saturn’s polar moment of inertia. However, the possibility remains that Saturn’s primordial obliquity was already large, for instance as a result of a massive collision. The unambiguous distinction between these two scenarios would be given by a precise measure of Saturn’s polar moment of inertia.

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“…Another exciting possibility is to identify ISOs which have been captured by the Solar system long ago and are orbiting under our very noses. While there is currently no evidence that any known object in the Solar system is a captured ISO (Morbidelli et al 2020), this may just be because we have not been looking in the correct places, but also because these exobodies are small with low albedo. In an accompanying paper (Dehnen & Hands 2021, hereafter paper 1), we have investigated, both analytically and numerically, the cross-section 𝜎 for capturing an ISO by a planet-star binary.…”

Section: Introductionmentioning

confidence: 97%

Capture of interstellar objects – II. By the Solar system

Dehnen

Hands

Schönrich

2021

Monthly Notices of the Royal Astronomical Society

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Capture of interstellar objects (ISOs) into the Solar system is dominated by ISOs with asymptotic incoming speeds v∞ < 4 km s−1. The capture rate is proportional to the ISO phase-space density in the Solar vicinity and does not vary along the Sun’s Galactic orbit, i.e. is not enhanced during a passage through a cloud of ISOs (in contrast to previous suggestions). Most bound orbits crossing those of Jupiter and Saturn are fully mixed with unbound phase space, implying that they hold the same ISO phase-space density. Assuming an interstellar number density niso ∼ 0.1 au−3, we estimate that in 1000 years the planets capture ∼2 ISOs (while ∼17 fall into the Sun), resulting in a population of ∼8 captured ISOs within 5 au of the Sun at any time, less than the number of visiting ISOs passing through the same volume on hyperbolic orbits. In terms of phase-space volume, capture onto and ejection from the Solar system are equal, such that on average ISOs will not remain captive at a ≲ 2000 au for extensive periods.

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No evidence for interstellar planetesimals trapped in the Solar system

Cited by 37 publications

References 28 publications

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

The past and future obliquity of Saturn as Titan migrates

Capture of interstellar objects – II. By the Solar system

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