arXiv subjects

Dušan Marčeta

Publications and source records attributed to Dušan Marčeta.

6 recordsLinked to original sources

arXiv2025

The Distribution of Earth-Impacting Interstellar Objects

In this paper we calculate the expected orbital elements, radiants, and velocities of Earth-impacting interstellar objects. We generate a synthetic population of $\sim10^{10}$ interstellar objects with M-star kinematics in order to obtain $\sim10^4$ Earth-impactors. The relative flux of impactors arriving from the direction of the solar apex and the galactic plane is enhanced by a factor of $\sim2$ relative to the mean. The fastest impactors also arrive from these directions, although Earth-impactors are generally slower than objects in the overall population. This is because the Earth-impacting subset contains a higher fraction of low-eccentricity hyperbolic objects which are more strongly affected by gravitational focusing. Earth-impacting interstellar objects are more likely to have retrograde orbits close to the ecliptic plane. A selection effect makes the distribution of inclination of Earth-impacting interstellar objects uniform/sinusoidal at low/high perihelion distances. In turn, low perihelion impactors have higher impact probability towards the ecliptic plane. The overall impactor population therefore exhibits an intermediate inclination distribution between uniform and sinusoidal. The highest velocity impacts are most likely to occur in the spring when the Earth is moving towards the solar apex. However, impacts in general are more likely to occur during the winter when the Earth is located in the direction of the antapex. Interstellar objects are more likely to impact the Earth at low latitudes close to the equator, with a slight preference for the Northern hemisphere due to the location of the apex. These distributions are independent of the assumed interstellar object number density, albedos, and size-frequency distribution and are publicly available.

astro-ph.EP↗

arXiv2025

Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS

We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of $e\sim6.1$, perihelion of $q\sim 1.36$ au, inclination of $\sim175^\circ$, and hyperbolic velocity of $V_\infty\sim 58$ km s$^{-1}$. We report deep stacked images obtained using the Canada-France-Hawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light curve variation for the object over a $\sim4$ day time span. The visible/near-infrared spectral slope of the object is 17.1$\pm$0.2 %/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). 3I/ATLAS will be observable through early September 2025, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late November 2025. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time.

astro-ph.EP↗

arXiv2023

ASTERIA -- Asteroid Thermal Inertia Analyzer

Thermal inertia estimates are available for a limited number of a few hundred objects, and the results are practically solely based on thermophysical modeling (TPM). We present a novel thermal inertia estimation method, Asteroid Thermal Inertia Analyzer (ASTERIA). The core of the ASTERIA model is the Monte Carlo approach, based on the Yarkovsky drift detection. We validate our model on asteroid Bennu plus ten well-characterized near-Earth asteroids (NEAs) for which a good estimation of the thermal inertia from the TPM exists. The tests show that the ASTERIA provides reliable results consistent with the literature values. The new method is independent from the TPM, allowing an independent verification of the results. As the Yarkovsky effect is more pronounced in small asteroids, the noteworthy advantage of the ASTERIA compared to the TPM is the ability to work with smaller asteroids for which TPM typically lacks the input data. We used the ASTERIA to estimate the thermal inertia of 38 NEAs, with 31 of them being sub-km asteroids. Twenty-nine objects in our sample are characterized as Potentially Hazardous Asteroids. On the limitation side, the ASTERIA is somewhat less accurate than the TPM. The applicability of our model is limited to NEAs, as the Yarkovsky effect is yet to be detected in main-belt asteroids. However, we can expect a significant increase in high-quality measurements of the input parameters relevant to the ASTERIA with upcoming surveys. This will surely increase the reliability of the results generated by the ASTERIA and widen the model's applicability.

astro-ph.EP↗

arXiv2023

Synthetic Detections of Interstellar Objects with The Rubin Observatory Legacy Survey of Space and Time

The discovery of two interstellar objects passing through the Solar System, 1I/`Oumuamua and 2I/Borisov, implies that a galactic population exists with a spatial number density of order $\sim0.1$ au$^{-3}$. The forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) has been predicted to detect more asteroidal interstellar objects like 1I/`Oumuamua. We apply recently developed methods to simulate a suite of galactic populations of interstellar objects with a range of assumed kinematics, albedos and size-frequency distributions (SFD). We incorporate these populations into the objectsInField (OIF) algorithm, which simulates detections of moving objects by an arbitrary survey. We find that the LSST should detect between $\sim 0-70$ asteroidal interstellar objects every year (assuming the implied number density), with sensitive dependence on the SFD slope and characteristic albedo of the host population. The apparent rate of motion on the sky -- along with the associated trailing loss -- appears to be the largest barrier to detecting interstellar objects. Specifically, a relatively large number of synthetic objects would be detectable by the LSST if not for their rapid sky-motion ($>0.5^\circ$ d$^{-1}$). Therefore, algorithms that could successfully link and detect rapidly moving objects would significantly increase the number of interstellar object discoveries with the LSST (and in general). The mean diameter of detectable, inactive interstellar objects ranges from $\sim50 - 600$ m and depends sensitively on the SFD slope and albedo.

astro-ph.EP↗

arXiv2023

The low surface thermal inertia of the rapidly rotating near-Earth asteroid 2016 GE1

Asteroids smaller than about 100 meters are observed to rotate very fast, with periods often much shorter than the critical limit of 2.2 h. Some of these super-fast rotators can also achieve a very large semi-major axis drift induced by the Yarkovsky effect, that in turn, is determined by internal and surface physical properties. We consider the small super-fast rotating near-Earth asteroid 2016 GE1. This object rotates in just 34 seconds, and a large Yarkovsky effect has been determined from astrometry. Here we aim to constrain the thermal inertia of the surface of this extreme object. We used a recently developed statistical method to determine the thermal properties of near-Earth asteroids. The method is based on the comparison between the observed and the modelled Yarkovsky effect, and the thermal conductivity (inertia) is determined by a Monte Carlo approach. Parameters of the Yarkovsky effect model are either fixed if their uncertainty is negligible, modelled with a Gaussian distribution of the errors if they are measured, or deduced from general properties of the population of near-Earth asteroids when they are unknown. Using a well-established orbit determination procedure, we determined the Yarkovsky effect on 2016 GE1, and verified a significant semi-major axis drift rate. Using a statistical method, we showed that this semi-major axis drift rate could be explained only by low thermal inertia values below 100 J m$^{-2}$ K$^{-1}$ s$^{-1/2}$: namely, 90\% of the probability density function of the model outcomes is contained at values smaller than 100 J m$^{-2}$ K$^{-1}$ s$^{-1/2}$. We propose two possible interpretations for the extremely low values: a high porosity or a cracked surface, or a thin layer of fine regolith on the surface. Though this seems unexpected in either case, it opens up the possibility of a subclass of low thermal inertia, super-fast rotating asteroids.

astro-ph.EP↗

arXiv2023

Synthetic Population of Interstellar Objects in the Solar System

The discovery of the first two macroscopic interstellar objects (ISOs) passing through the Solar System has opened entirely new perspectives in planetary science. The exploration of these objects offers a qualitatively new insight into the processes related to the origin, structure and evolution of planetary systems throughout the Galaxy. Knowledge about these phenomena will greatly advance if current and future sky surveys discover more ISOs. On the other hand, the surveys require better characterization of this population in order to improve their discovery algorithms. However, despite their scientific significance, there is still no comprehensive orbital model of ISOs in the Solar System and computationally efficient algorithm for generating their synthetic representations that would respond to these increasing needs. Currently available method for generating synthetic populations cannot fully take into account important phenomena, such as gravitational focusing and the shielding effect of the Sun. On the other hand, this method is also computationally far too demanding to be used for systematic exploration of the ISO population. This paper presents an analytical method for determining the distributions of the orbital elements of ISOs, as well as computationally efficient algorithm for generating their synthetic populations, based on the multivariate inverse transform sampling method. The developed method is several orders of magnitudes more efficient than the available method, depending on the size of the synthetic population. A Python implementation of the method is freely available and can be used to generate synthetic populations of ISOs with user-defined input parameters.

astro-ph.EP↗