Saturday 20 October 2018

Looking for the origin of Asteroid (514107) 2015 BZ509.

The Centaurs are a population of asteroids with orbits that cross those of the Solar System’s giant planets (Jupiter, Saturn, Uranus, and Neptune). The majority of these are on somewhat chaotic pathways; they are presumed to have originated in the outer reaches of the Solar System and been knocked inwards by interaction with some other body and are now buffeted from orbit to orbit by close encounters with the giant planets. Such asteroids typically survive as Centaurs for less than a million years, and almost never survive for more than about 10 million years. Other Centaurs manage to achieve resonant orbits with one or more giant planets, finding a pathway on which they are held steady by periodic encounters with the resonant planet or planets. Such asteroids may remain in stable orbits for hundreds of millions of years, and may be in prograde or retrograde orbits (i.e. may orbit in the same direction as the planets, or in the opposite), with those in steeply inclined retrograde orbits often the most stable.

Asteroid (514107) 2015 BZ509 was discovered in January 2015 by the University of Hawaii's PANSTARRS telescope (technocally it was first captured in an image in November 2014, but not actually noticed until January 2015); the name 2015 implies that it was the 12 750th asteroid (asteroid Z509) discovered in the second half of January 2015 (period 2015 B), while the designation (514107) implies that it was the 514 107th asteroid ever discovered. (514107) 2015 BZ509 is a Jupiter-orbit crossing Centaur Asteroid with an orbit similar to those of the Jupiter Trojans (asteroids on the same orbital path as Jupiter, but within its Trojan Points, 60° ahead and behind the planet), but on a retrograde orbit inclined at 163° to the plane of the Solar System (or 17° from the plane of the Solar System, but travelling in the wrong direction).It is the first asteroid ever discovered in a 1:1 resonance with a planet, completing one orbit for every one orbit of Jupiter, and has a diameter of about 3 km.

The calculated orbit of (514107) 2015 BZ509 Minor Planet Center.

In a paper published in the journal Monthly Notices of the Royal Astronomical Society on 26 May, Fathi Namouni of the Observatoire de la Côte d’Azur at the Université Côte d’Azur and Maria Helena Morais of the Instituto de Geociências e Ciências Exatas at the Universidade Estadual Paulista, present the results of a study of (514107) 2015 BZ509, in which they attempted to use a computer model to backtrack the orbit of the asteroid, and determine its origin.

To Namouni and Morais’s surprise, the current orbit of (514107) 2015 BZ509 appears to be stable for a period of around 4.5 billion years – roughly the age of the Solar System. Based upon this they conclude that the asteroid originated outside the Solar System, and was captured during the system’s formation. This is not completely outrageous; the Solar System is thought likely to contain a number of bodies originating outside the system that have been captured, though these are by nature difficult to detect.

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