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Ivana Milić Žitnik

8 papers

Sorted by publication date, newest first. New papers are marked so you can spot recent additions.

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BYORP and Dissipation in Binary Asteroids: Lessons from DART(pdf)

Matija Ćuk, Harrison Agrusa, Rachel H. Cueva et al. · 2024 · The Planetary Science Journal

At a Glance

DART data motivate weaker, size-dependent BYORP and episodic “landslide” dissipation as key drivers of small-binary evolution.

Summary

Using DART’s detailed view of Didymos–Dimorphos, the paper argues that many small-binary secondaries may be relatively smooth “debris piles,” which would make the BYORP radiation torque systematically weaker and more size-dependent than assumed from lumpy asteroid shapes. A simple synthetic-shape experiment shows BYORP strength is controlled mainly by absolute surface relief (meter-scale roughness), implying larger secondaries should have smaller dimensionless BYORP coefficients and helping reconcile the wide range of observed orbital period drifts. The authors also interpret Dimorphos’s apparent post-impact reshaping (oblate to more prolate) as evidence that dissipation may occur in short, high-mobility episodes (e.g., impact-triggered landslides) rather than steady, long-term tidal damping. If correct, binary properties like low eccentricity and near-synchronous rotation may record recent dissipative events, and Hera can test whether Dimorphos continues to relax dynamically by 2026.

Method:
Combines idealized BYORP torque calculations on randomized rough ellipsoids with order-of-magnitude energy accounting for Dimorphos’s post-DART relaxation.
Background:
Background in small-body dynamics (YORP/BYORP, tides) and rubble-pile asteroid geophysics/orbital mechanics.
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The Strength and Shapes of Contact Binary Objectcts(pdf)

Alex J. Meyer, Daniel J. Scheeres · 2024

At a Glance

Contact binary mergers can occur between rubble piles if secondaries have modest cohesion (∼1–100 Pa) or high friction, shaped by lobe geometry.

Summary

This paper quantifies when a smaller lobe can survive tidal disruption while spiraling into and merging with a larger rubble-pile body to form a contact binary. Using ellipsoidal fits to 11 radar/spacecraft shape models (asteroids, comets, and Arrokoth), it derives strength requirements showing that either a small but nonzero cohesion or a sufficiently large friction angle is typically needed, with inferred cohesive strengths broadly ∼1–100 Pa for a nominal 30° friction angle. The analysis highlights strong dependence on secondary shape: prolate (cigar-like) lobes require substantially more cohesion than oblate (disk-like) lobes, and there are regime “flips” where how cohesion scales with size or density ratio changes near modest asphericities. By comparing contact binaries to binary asteroids and asteroid pairs, the authors argue contact binaries plausibly sit on related evolutionary pathways (e.g., collapsed binaries or failed separations) rather than requiring monolithic components.

Method:
Apply a Drucker–Prager granular yield criterion to ellipsoid-fitted secondary lobes under tidal/rotational stresses at contact to map friction–cohesion survival thresholds.
Background:
Background in small-body dynamics and basic granular/continuum strength models (e.g., friction angle, cohesion, yield criteria) is needed.
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Astrometric detection of binary asteroids(pdf)

Noam Segev, Eran O Ofek, David Polishook · 2022 · Monthly Notices of the Royal Astronomical Society

At a Glance

Models Gaia astrometric center-of-light wobble to search for unresolved binary asteroids and quantifies why DR2 yields few detections.

Summary

This paper develops and tests an astrometric approach to find unresolved binary asteroids by modeling how a system’s center of light wobbles around its center of mass. The key novelty is a forward model plus an inversion/search pipeline (with bootstrap-based false-positive estimation) tailored to Gaia’s along-scan astrometry and irregular sampling, aiming to probe binary parameter space that imaging, lightcurves, and radar miss. Using Gaia DR2 Solar System residuals, the authors find no strong new detections and argue this is largely because DR2’s processing clipped “outlier” transits that may contain genuine astrophysical wobble signals; nonetheless, known binaries show a small excess in astrometric scatter compared to the overall asteroid population. A case study of (4337) Arecibo yields only a marginal (∼2.2σ) period near half the DR3-reported value, underscoring both the promise and the current catalog limitations for astrometric binary discovery.

Method:
Construct a center-of-light astrometric forward model for binary orbits, then grid-search periods and fit remaining parameters to Gaia along-scan residuals with bootstrap significance tests.
Background:
Familiarity with basic orbital mechanics, astrometric measurements (especially Gaia along-scan geometry), and statistical model fitting/hypothesis testing.
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Worth Reading
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Asteroid pairs: A complex picture

P. Pravec, P. Fatka, D. Vokrouhlický et al. · 2019 · Icarus

At a Glance

Survey of 93 asteroid pairs reveals widespread rotational-fission signatures, frequent paired binaries, and puzzling high–mass-ratio outliers.

Summary

Using a greatly expanded sample of 93 genetically related asteroid pairs, this work shows that most pairs obey the predicted link between primary spin rate and pair mass ratio, strengthening rotational fission as the dominant formation path. It also uncovers a surprisingly high incidence of binaries (and even triples) among the fastest-rotating primaries, implying that pair formation often involves more complex multi-body evolution than a simple two-body split. The paper highlights four secure, high–mass-ratio pairs that fall outside existing theory, and explores (but cannot yet physically justify) an extreme scenario where a flattened parent fissions and the components reshape to enable near-equal-mass escape. Overall, it reframes asteroid pairs as a diverse population that constrains YORP-driven fission, post-fission spin/orbit evolution, and the boundary between “pairs,” “clusters,” and “paired binaries.”

Method:
Combined backward orbit integrations with Yarkovsky-enabled clone ensembles and multi-apparition photometric lightcurve analysis (plus limited TPM/WISE refinement) to derive ages, spins, poles, and mass ratios.
Background:
Comfort with asteroid dynamics (Yarkovsky/YORP, resonances), lightcurve-based rotation/shape inference, and basic binary-asteroid angular-momentum concepts.
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Dancing with Venus in the shadow of the Earth: a pair of genetically related near-Earth asteroids trapped in a mean-motion resonance(pdf)

C de la Fuente Marcos, R de la Fuente Marcos · 2018 · Monthly Notices of the Royal Astronomical Society: Letters

At a Glance

Two near-Earth asteroids form a long-lived “faux-binary” because both are trapped in Venus’s 3:5 mean-motion resonance.

Summary

This paper reports an unusually tight, dynamically coherent near-Earth asteroid pair (2017 SN16 and 2018 RY7) whose proximity persists far longer than typical NEA orbit randomization would allow. Using N-body integrations with uncertainty sampling, the authors show both objects are concurrently trapped in the 3:5 mean-motion resonance with Venus, which locks their average angular speeds and prevents secular drift in their relative mean longitude, creating a quasi-satellite-like (but non-gravitationally bound) configuration. Statistical comparison against the debiased NEOPOP steady-state model finds a significant overabundance of similar orbits relative to expectations, supporting a recent in situ origin rather than standard delivery pathways from the main belt. The most plausible formation scenarios are YORP-driven rotational fission or binary dissociation occurring while resonantly confined, suggesting resonances can preserve genetic links among NEAs long enough to be observed and tested (e.g., via spectroscopy).

Method:
Direct N-body integrations with clone orbits from covariance matrices plus statistical comparison to the NEOPOP synthetic NEA population model.
Background:
Basic celestial mechanics of near-Earth asteroid dynamics, including mean-motion resonances and Yarkovsky/YORP effects.
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Must Read★ Essential
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Asteroid Systems: Binaries, Triples, and Pairs

J.-L. Margot, P. Pravec, P. Taylor et al. · 2015 · Asteroids IV

At a Glance

A synthesis of evidence that small asteroid binaries, triples, and pairs mainly form via YORP-driven rotational fission, not impacts.

Summary

This review consolidates a decade of observations and dynamical theory showing that many small (≲20 km) asteroid systems—binaries, triples, and unbound pairs—share signatures of formation by rotational fission after YORP spin-up. It links radar, lightcurve, spectroscopy, imaging, and occultation results to a single evolutionary framework where post-fission dynamics, tides, and BYORP can yield the observed diversity of system architectures. In contrast, it argues that satellites of large (≳20 km) main-belt asteroids are best explained by collisional formation, based on their low mass ratios and angular momentum content. The synthesis matters because it elevates rotational disruption to a population-shaping process for small bodies and provides practical observational diagnostics (spin states, angular momentum, pole anisotropy, mass-ratio limits) to discriminate formation pathways.

Method:
Integrative review combining multi-technique observational constraints with analytical and numerical dynamical models of rotational fission, tides, and radiative torques.
Background:
Familiarity with asteroid physical properties and small-body dynamics (YORP/BYORP, tides, collisions, and basic orbital mechanics).
8
Worth Reading
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Rotational breakup as the origin of small binary asteroids(pdf)

Kevin J. Walsh, Derek C. Richardson, Patrick Michel · 2008 · Nature

At a Glance

Simulations show YORP spin-up can shed equatorial rubble that re-accretes into close, circular satellites matching small binary asteroids.

Summary

This paper identifies a single formation pathway that can explain why small binaries in both near-Earth and inner main-belt populations look so similar. Using rubble-pile simulations under gradual YORP-driven spin-up, the authors show that equatorial material is shed and, if collisions are sufficiently dissipative and the primary stays nearly axisymmetric, the debris efficiently accretes into a close satellite on a low-eccentricity orbit. The model naturally produces “top-shaped” primaries with equatorial ridges, consistent with detailed radar constraints for (66391) 1999 KW4, and predicts that secondaries are built mostly from the primary’s surface material. The work shifts small-binary origins away from impacts or repeated tidal encounters toward a slow, radiatively driven rotational-disruption cycle, with implications for surface refreshment and binary lifetimes via BYORP/tides.

Method:
Discrete-element (N-body) simulations of cohesionless rubble piles are slowly spun up to mimic YORP, tracking mass shedding and gravitational reaccumulation into satellites.
Background:
Basic asteroid dynamics and radiative torques (YORP), plus familiarity with rubble-pile mechanics and orbital elements.