The discovery of Chiron
Regular readers of our monthly blog will be aware of the Centaurs. Today marks the discovery of the centaur Chiron, or to give it it’s complete designation 2060 Chiron (1977UB). Aujourd’hui marque la découverte du centaure (2016)Chiron ou 2060 Chiron (1977UB).
Chiron a été découvert par l’astronome américaine Charles Kowal (8/11/1940 à 28/11/2011) à l’aide d’un télescope de 1,2m pendant qu’il travaillait à l’observatoire de Mont Palomar en Californie. L’iimportance de cette decouverte a été bientôt reconnue. Avant la découverte de Chiron, Hidalgo était considéré comme quelque chose d’exceptionnel. Mais les similarités entre l’Hidalgo et Chiron a permis l’identification d’une nouvelle classe d’objets – les Centaures.
It was discovered by Charles Kowal using a 1.2M telescope from the Mount Palomar observatory in California. The importance of the discovery was soon recognised. Whereas prior to Chiron’s detection the anomalous object Hidalgo (944 Hidalgo (1920UB) was considered as a one-off, the close orbital similarities Chiron showed brought the identification of a new class of objects, the Centaurs.
Chiron is a fascinating object. With an aphelion distance (furthest distance from the Sun) of almost 19 AU (nearly as far as the planet Uranus) it was at the time of its discovery the most remote asteroidal object detected.
It is relatively large for an asteroid and has a diameter of 166km. This has been determined by ‘stellar occultation’. An occultation is where the object being studied passes in front of a more remote object (such as a star) and eclipses the light from the remote object.
As we discussed during our Sept 2019 blog, Centaurs appear to orbit, spectroscopic, and features-wise be closer in nature to short period comets rather than asteroids. However, distinct differences from both major classes (comets and asteroids) are seen in the Centaurs. For example the size of Chiron is quite exceptional for a comet; and thus they are considered to be transition, or hybrid objects between comets and asteroids.
There has been some speculation recently that observations (Ruprecht, MIT, 2011), again using occultation, suggest that the Chiron has a ring structure – a bit like a much sparser version of the rings of the planet Saturn. Our own view is that this explanation of the observations is very unlikely. The size, and thus mass, of Chiron is insufficient to sustain a ring structure.
Our interpretation of the MIT observations is that the object exhibited a gaseous/dust outgassing (i.e. like the coma – the sublimation – of a comet).
The Education of Achilles by Bénigne Gagneraux (1785)
(Achilles riding on the back of Chiron)