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A contact binary satellite of the asteroid (152830) Dinkinesh

2024; Nature Portfolio; Volume: 629; Issue: 8014 Linguagem: Inglês

10.1038/s41586-024-07378-0

1476-4687

Harold F. Levison, S. Marchi, Keith Noll, J. R. Spencer, Thomas S. Statler, J. F. Bell, E. B. Bierhaus, Richard P. Binzel, W. F. Bottke, D. T. Britt, Michael E. Brown, M. W. Buie, P. R. Christensen, N. Dello Russo, Joshua P. Emery, W. M. Grundy, M. Hahn, V. E. Hamilton, C. J. A. Howett, H. H. Kaplan, Katherine A. Kretke, Tod R. Lauer, C. Manzoni, Raphael Marschall, A. Martin, B. May, S. Mottola, C. B. Olkin, M. Pätzold, J. W. Parker, Simon Porter, Frank Preusker, S. Protopapa, Dennis C. Reuter, S. J. Robbins, Julien Salmon, A. A. Simon, S. A. Stern, J. M. Sunshine, Ian Wong, H. A. Weaver, Coralie D. Adam, Shanti Ancheta, John P. Andrews, Saadat Anwar, O. S. Barnouin, Matthew Beasley, Kevin Berry, Emma Birath, Bryce Bolin, Mark Booco, Rich Burns, P. S. Campbell, Russell Carpenter, Katherine Crombie, Mark Effertz, Emily Eifert, C. Ellis, Preston Faiks, Joel T. Fischetti, Paul J. Fleming, Kristen Francis, Ray Franco, Sandy Freund, Claire Gallagher, J. Geeraert, Caden Gobat, Donovan Gorgas, Chris Granat, Sheila Gray, P. Haas, A. Harch, Katie Hegedus, Chris Isabelle, Bill Jackson, Taylor Jacob, S. H. M. Jennings, D. E. Kaufmann, Brian A. Keeney, T. Kennedy, Karl Lauffer, Erik J. Lessac‐Chenen, Rob Leonard, Andrew H. Levine, Allen Lunsford, Tim Martin, Jim McAdams, G. Mehall, Trevor F. Merkley, Graham Miller, Matthew Montanaro, Anna B. Montgomery, G. A. Murphy, Maxwell Myers, Derek Nelson, Adriana Ocampo, Ryan Olds, John Pelgrift, Trevor Perkins, Jon P. Pineau, D. Poland, Vaishnavi Ramanan, D. Rose, Eric Sahr, Owen G. Short, Ishita Solanki, Dale Stanbridge, Brian Sutter, Zachary Talpas, Howard E. Taylor, Bo Treiu, Nate Vermeer, Michael A. Vincent, Mike Wallace, Gerald Weigle, Daniel R. Wibben, Zach Wiens, John P. Wilson, Yifan Zhao,

Stellar, planetary, and galactic studies

Asteroids with diameters less than about 5 km have complex histories because they are small enough for radiative torques, YORP, to be a notable factor in their evolution. (152830) Dinkinesh is a small asteroid orbiting the Sun near the inner edge of the Main Asteroid Belt with a heliocentric semimajor axis of 2.19 AU; its S type spectrum is typical of bodies in this part of the Main Belt. Here we report observations by the Lucy spacecraft as it passed within 431 km of Dinkinesh. Lucy revealed Dinkinesh, which has an effective diameter of only $\sim$720 m, to be unexpectedly complex. Of particular note is the presence of a prominent longitudinal trough overlain by a substantial equatorial ridge, and the discovery of the first confirmed contact binary satellite, now named (152830) Dinkinesh I Selam. Selam consists of two near-equal sized lobes with diameters of $\sim$210 m and $\sim$230 m. It orbits Dinkinesh at a distance of 3.1 km with an orbital period of about 52.7 hr, and is tidally locked. The dynamical state, angular momentum, and geomorphologic observations of the system lead us to infer that the ridge and trough of Dinkinesh are probably the result of mass failure resulting from spin-up by YORP followed by the partial reaccretion of the shed material. Selam probably accreted from material shed by this event.