Rotational lightcurves of Dimorphos and constraints on its post-DART impact spin state

Pravec, P.; Meyer, A.J.; Scheirich, P.; Scheeres, D.J.; Benson, C.J.; Agrusa, H.F.

doi:10.1016/j.icarus.2024.116138

Cited by 5 publications

(7 citation statements)

References 44 publications

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“…Thus, we suspect that the rule of the Yarkovsky effect would still be valid for tumbling components in a binary system, while a more thorough investigation is required for confirmation in the future. There is some observational evidence indicating that Dimorphos may be in some excited tumbling state (Pravec et al 2024), where the satellite's longest axis is approximately tidally locked to the direction toward the primary. Given its on average synchronous rotation, the Yarkovsky effect could be weak or even shut off in this case, but a more detailed analysis of this interesting system is needed.…”

Section: Kyrmentioning

confidence: 99%

The Yarkovsky Effect on the Long-term Evolution of Binary Asteroids

Zhou 周,

Vokrouhlický,

Kanamaru

et al. 2024

ApJL

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We explore the Yarkovsky effect on small binary asteroids. While significant attention has been given to the binary YORP effect, the Yarkovsky effect is often overlooked. We develop an analytical model for the binary Yarkovsky effect, considering both the Yarkovsky–Schach and planetary Yarkovsky components, and verify it against thermophysical numerical simulations. We find that the Yarkovsky force could change the mutual orbit when the asteroid’s spin period is unequal to the orbital period. Our analysis predicts new evolutionary paths for binaries. For a prograde asynchronous secondary, the Yarkovsky force will migrate the satellite toward the location of the synchronous orbit on ∼100 kyr timescales, which could be faster than other synchronization processes such as YORP and tides. For retrograde secondaries, the Yarkovsky force always migrates the secondary outward, which could produce asteroid pairs with opposite spin poles. Satellites spinning faster than the Roche limit orbit period (e.g., from ∼4 hr to ∼10 hr) will migrate inward until they disrupt, reshape, or form a contact binary. We also predict a short-lived equilibrium state for asynchronous secondaries where the Yarkovsky force is balanced by tides. We provide calculations of the Yarkovsky-induced drift rate for known asynchronous binaries. If the NASA DART impact broke Dimorphos from synchronous rotation, we predict that Dimorphos’s orbit will shrink by a ̇ ∼ 7 cm yr−1, which can be measured by the Hera mission. We also speculate that the Yarkovsky force may have synchronized the Dinkinesh–Selam system after a possible merger of Selam’s two lobes.

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Section: Kyrmentioning

confidence: 99%

The Yarkovsky Effect on the Long-term Evolution of Binary Asteroids

Zhou 周,

Vokrouhlický,

Kanamaru

et al. 2024

ApJL

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“…The Didymos system has arguably been better characterized after the DART impact than before, at least in terms of the secondary's lightcurve, which was not detected preimpact. Lightcurve and other observations have enabled measurements of orbital precession (Naidu et al 2024;Pravec et al 2024;Scheirich et al 2024). While an oblate shape of the components leads to prograde precession of the pericenter of the orbit, a prolate shape of a synchronously rotating component would lead to a retrograde contribution to the orbital precession (Borderies & Yoder 1990;Ćuk & Nesvorný 2010).…”

Section: Dissipation In Dimorphos After the Dart Impactmentioning

confidence: 99%

“…While an oblate shape of the components leads to prograde precession of the pericenter of the orbit, a prolate shape of a synchronously rotating component would lead to a retrograde contribution to the orbital precession (Borderies & Yoder 1990;Ćuk & Nesvorný 2010). Fitting of Dimorphos's post-DART orbit indicates that there is a substantial contribution to the orbital precession from the figure of Dimorphos (Pravec et al 2024;Scheirich et al 2024), requiring some degree of alignment of the secondary's long axis with the line between components. Pravec et al (2024) interpret the post-DART lightcurve data as implying moderate librations of Dimorphos around a synchronous state and find that an axis ratio of a/b = 1.1-1.4 for Dimorphos is consistent with the observations.…”

Section: Dissipation In Dimorphos After the Dart Impactmentioning

confidence: 99%

“…Fitting of Dimorphos's post-DART orbit indicates that there is a substantial contribution to the orbital precession from the figure of Dimorphos (Pravec et al 2024;Scheirich et al 2024), requiring some degree of alignment of the secondary's long axis with the line between components. Pravec et al (2024) interpret the post-DART lightcurve data as implying moderate librations of Dimorphos around a synchronous state and find that an axis ratio of a/b = 1.1-1.4 for Dimorphos is consistent with the observations.…”

Section: Dissipation In Dimorphos After the Dart Impactmentioning

confidence: 99%

“…Using the above-stated values for different diameters, we find that E E 0.985 pre sphere = (since both energies are negative, a sphere is a lower energy state). Postimpact, we will assume that Dimorphos has the same volume and is now a prolate ellipsoid with axis ratios a = 1.3b and c = b (a value in the middle of the region allowed by Pravec et al 2024). The expression for the self-gravitating energy of a prolate ellipsoid is (Danby 1962 2024) model very likely also has a lower self-gravitating energy than the preimpact figure.…”

Section: )mentioning

confidence: 99%

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BYORP and Dissipation in Binary Asteroids: Lessons from DART

Ćuk,

Agrusa,

Cueva

et al. 2024

Planet. Sci. J.

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The near-Earth binary asteroid Didymos was the target of the planetary defense demonstration mission DART in 2022 September. The smaller binary component, Dimorphos, was impacted by the spacecraft in order to measure momentum transfer in kinetic impacts into rubble piles. DART and associated Earth-based observation campaigns have provided a wealth of scientific data on the Didymos–Dimorphos binary. DART revealed the largely oblate and ellipsoidal shape of Dimorphos before the impact, while the postimpact observations suggest that Dimorphos now has a prolate shape. Here we add those data points to the known properties of small binary asteroids and propose new paradigms of the radiative binary Yarkovsky–O’Keefe–Radzievskii–Paddack (BYORP) effect as well as tidal dissipation in small binaries. We find that relatively spheroidal bodies like Dimorphos made of small debris may experience a weaker and more size-dependent BYORP effect than previously thought. This could explain the observed values of period drift in several well-characterized binaries. We also propose that energy dissipation in small binaries is dominated by relatively brief episodes of large-scale movement of (likely surface) materials, rather than long-term steady-state tidal dissipation. We propose that one such episode was triggered on Dimorphos by the DART impact. Depending on the longevity of this high-dissipation regime, it is possible that Dimorphos will be more dynamically relaxed in time for the Hera mission than it was in the weeks following the impact.

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The Dynamical State of the Didymos System before and after the DART Impact

Richardson,

Agrusa,

Barbee

et al. 2024

Planet. Sci. J.

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NASA’s Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the natural satellite of (65803) Didymos, on 2022 September 26, as a first successful test of kinetic impactor technology for deflecting a potentially hazardous object in space. The experiment resulted in a small change to the dynamical state of the Didymos system consistent with expectations and Level 1 mission requirements. In the preencounter paper, predictions were put forward regarding the pre- and postimpact dynamical state of the Didymos system. Here we assess these predictions, update preliminary findings published after the impact, report on new findings related to dynamics, and provide implications for ESA’s Hera mission to Didymos, scheduled for launch in 2024 October with arrival in 2026 December. Preencounter predictions tested to date are largely in line with observations, despite the unexpected, flattened appearance of Didymos compared to the radar model and the apparent preimpact oblate shape of Dimorphos (with implications for the origin of the system that remain under investigation). New findings include that Dimorphos likely became prolate due to the impact and may have entered a tumbling rotation state. A possible detection of a postimpact transient secular decrease in the binary orbital period suggests possible dynamical coupling with persistent ejecta. Timescales for damping of any tumbling and clearing of any debris are uncertain. The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the Hera mission.

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Rotational lightcurves of Dimorphos and constraints on its post-DART impact spin state

Cited by 5 publications

References 44 publications

The Yarkovsky Effect on the Long-term Evolution of Binary Asteroids

The Yarkovsky Effect on the Long-term Evolution of Binary Asteroids

BYORP and Dissipation in Binary Asteroids: Lessons from DART

The Dynamical State of the Didymos System before and after the DART Impact

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