TY - JOUR
T1 - Non-gravitational acceleration in the trajectory of 1I/2017 U1 ('Oumuamua)
AU - Micheli, Marco
AU - Farnocchia, Davide
AU - Meech, Karen J.
AU - Buie, Marc W.
AU - Hainaut, Olivier R.
AU - Prialnik, Dina
AU - Schörghofer, Norbert
AU - Weaver, Harold A.
AU - Chodas, Paul W.
AU - Kleyna, Jan T.
AU - Weryk, Robert
AU - Wainscoat, Richard J.
AU - Ebeling, Harald
AU - Keane, Jacqueline V.
AU - Chambers, Kenneth C.
AU - Koschny, Detlef
AU - Petropoulos, Anastassios E.
N1 - Publisher Copyright:
© 2018 Macmillan Publishers Ltd., part of Springer Nature.
PY - 2018/7/12
Y1 - 2018/7/12
N2 - '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.
AB - '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.
UR - http://www.scopus.com/inward/record.url?scp=85049793859&partnerID=8YFLogxK
U2 - 10.1038/s41586-018-0254-4
DO - 10.1038/s41586-018-0254-4
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AN - SCOPUS:85049793859
SN - 0028-0836
VL - 559
SP - 223
EP - 226
JO - Nature
JF - Nature
IS - 7713
ER -