| Autor: |
Micheli M; ESA SSA-NEO Coordination Centre, Frascati, Italy. marco.micheli@esa.int.; INAF-Osservatorio Astronomico di Roma, Monte Porzio Catone, Italy. marco.micheli@esa.int., Farnocchia D; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA., Meech KJ; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Buie MW; Southwest Research Institute, Boulder, CO, USA., Hainaut OR; European Southern Observatory, Garching bei München, Germany., Prialnik D; School of Geosciences, Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Israel., Schörghofer N; Planetary Science Institute, Tucson, AZ, USA., Weaver HA; The Johns Hopkins University Applied Physics Laboratory, Space Exploration Sector, Laurel, MD, USA., Chodas PW; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA., Kleyna JT; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Weryk R; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Wainscoat RJ; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Ebeling H; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Keane JV; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Chambers KC; Institute for Astronomy, University of Hawai'i, Honolulu, HI, USA., Koschny D; ESA SSA-NEO Coordination Centre, Frascati, Italy.; ESTEC, European Space Agency, Noordwijk, The Netherlands.; Chair of Astronautics, Technical University of Munich, Garching bei München, Germany., Petropoulos AE; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. |
| Abstrakt: |
'Oumuamua (1I/2017 U1) is the first known object of interstellar origin to have entered the Solar System on an unbound and hyperbolic trajectory with respect to the Sun 1 . Various physical observations collected during its visit to the Solar System showed that it has an unusually elongated shape and a tumbling rotation state 1-4 and that the physical properties of its surface resemble those of cometary nuclei 5,6 , even though it showed no evidence of cometary activity 1,5,7 . The motion of all celestial bodies is governed mostly by gravity, but the trajectories of comets can also be affected by non-gravitational forces due to cometary outgassing 8 . Because non-gravitational accelerations are at least three to four orders of magnitude weaker than gravitational acceleration, the detection of any deviation from a purely gravity-driven trajectory requires high-quality astrometry over a long arc. As a result, non-gravitational effects have been measured on only a limited subset of the small-body population 9 . Here we report the detection, at 30σ significance, of non-gravitational acceleration in the motion of 'Oumuamua. We analyse imaging data from extensive observations by ground-based and orbiting facilities. This analysis rules out systematic biases and shows that all astrometric data can be described once a non-gravitational component representing a heliocentric radial acceleration proportional to r -2 or r -1 (where r is the heliocentric distance) is included in the model. After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects originating from 'Oumuamua potentially being composed of several spatially separated bodies or having a pronounced offset between its photocentre and centre of mass, we find comet-like outgassing to be a physically viable explanation, provided that 'Oumuamua has thermal properties similar to comets. |
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