Details

Autor(en) / Beteiligte

• Pravec, P.
• Scheirich, P.
• Kušnirák, P.
• Hornoch, K.
• Galád, A.
• Naidu, S.P.
• Pray, D.P.
• Világi, J.
• Gajdoš, Š.
• Kornoš, L.
• Krugly, Yu.N.
• Cooney, W.R.
• Gross, J.
• Terrell, D.
• Gaftonyuk, N.
• Pollock, J.
• Husárik, M.
• Chiorny, V.
• Stephens, R.D.
• Durkee, R.
• Reddy, V.
• Dyvig, R.
• Vraštil, J.
• Žižka, J.
• Mottola, S.
• Hellmich, S.
• Oey, J.
• Benishek, V.
• Kryszczyńska, A.
• Higgins, D.
• Ries, J.
• Marchis, F.
• Baek, M.
• Macomber, B.
• Inasaridze, R.
• Kvaratskhelia, O.
• Ayvazian, V.
• Rumyantsev, V.
• Masi, G.
• Colas, F.
• Lecacheux, J.
• Montaigut, R.
• Leroy, A.
• Brown, P.
• Krzeminski, Z.
• Molotov, I.
• Reichart, D.
• Haislip, J.
• LaCluyze, A.

Titel

Binary asteroid population. 3. Secondary rotations and elongations

Ist Teil von

• Icarus (New York, N.Y. 1962), 2016-03, Vol.267, p.267-295

Ort / Verlag

Elsevier Inc

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •Data on rotations of 46 binary and triple asteroid systems were collected.•An anti-correlation of secondary synchroneity with orbital eccentricity observed.•Libration angles of synchronous secondaries are less than 20° on most epochs.•A paucity of chaotic rotations among asynchronous secondaries is apparent.•An upper limit on the secondary equatorial axis ratios of 1.5 was found. We collected data on rotations and elongations of 46 secondaries of binary and triple systems among near-Earth, Mars-crossing and small main belt asteroids. 24 were found or are strongly suspected to be synchronous (in 1:1 spin–orbit resonance), and the other 22, generally on more distant and/or eccentric orbits, were found or are suggested to have asynchronous rotations. For 18 of the synchronous secondaries, we constrained their librational angles, finding that their long axes pointed to within 20° of the primary on most epochs. The observed anti-correlation of secondary synchroneity with orbital eccentricity and the limited librational angles agree with the theories by Ćuk and Nesvorný (Ćuk, M., Nesvorný, D. [2010]. Icarus 207, 732–743) and Naidu and Margot (Naidu, S.P., Margot, J.-L. [2015]. Astron. J. 149, 80). A reason for the asynchronous secondaries being on wider orbits than synchronous ones may be longer tidal circularization time scales at larger semi-major axes. The asynchronous secondaries show relatively fast spins; their rotation periods are typically <10 h. An intriguing observation is a paucity of chaotic secondary rotations; with an exception of (35107) 1991 VH, the secondary rotations are single-periodic with no signs of chaotic rotation and their periods are constant on timescales from weeks to years. The secondary equatorial elongations show an upper limit of a2/b2∼1.5. The lack of synchronous secondaries with greater elongations appears consistent, considering uncertainties of the axis ratio estimates, with the theory by Ćuk and Nesvorný that predicts large regions of chaotic rotation in the phase space for a2/b2≳2. Alternatively, secondaries may not form or stay very elongated in gravitational (tidal) field of the primary. It could be due to the secondary fission mechanism suggested by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.J. [2011]. Icarus 214, 161–178), as its efficiency is correlated with the secondary elongation. Sharma (Sharma, I. [2014]. Icarus 229, 278–294) found that rubble-pile satellites with a2/b2≲1.5 are more stable to finite structural perturbations than more elongated ones. It appears that more elongated secondaries, if they originally formed in spin fission of parent asteroid, are less likely to survive intact and they more frequently fail or fission.