Thursday, 27 March 2014
In a surprise discovery two rings have been found around the remote asteroid Chariklo, which lies more than a billion kilometres from Earth.
This is the first time rings have been discovered around an asteroid and makes it only the fifth object in our solar system to have rings – after Jupiter, Saturn, Uranus and Neptune.
Not only were the rings detected but amazing detail is now known about them, with the results published in the journal Nature today.
Not really looking for rings
The discovery was made by a team of researchers using a plethora of instruments and telescopes, including a new high-resolution camera on the Danish telescope at European Southern Observatory’s La Silla Observatory in Chile.
The camera is actually designed to help in the search for exoplanets – planets that orbit other stars.
The special camera was designed to observe exoplanets in other star systems but has also shown its usefulness for observing objects in our own solar system. Jesper Skottfelt, Niels Bohr Institute.
Click to enlarge
Chariklo is 250 kilometres across and is the largest of the Centaurs, objects that have unstable orbits between Jupiter and Neptune.
There are about 250 Centaurs currently known about and, just like the mythical Centaurs that are half-man, half-horse, these objects share a mix of characteristics from both icy comets and rocky asteroids.
From Earth, Chariklo appears as a mere dot, even when it is viewed with powerful telescopes.
But when an asteroid passes in front of a star, the star’s light is blocked. Such events are known as occultations and happen remarkably often. Several asteroid occultations will be visible from different parts of Australia tonight.
Astronomers can use multiple telescopes scattered across hundreds of kilometres to map the size and shape of an asteroid during an occultation.
A coordinated effort
Last June Chariklo was to pass in front of an obscure star (UCAC4 248-108672). But the occultation could only be seen from South America so an observing campaign was coordinated across seven observatories including two telescopes operated by the European Southern Observatory in Chile.
Usually the star just fades for a few seconds as the asteroid passes by. Astronomers were expecting the star to fade for about five seconds while Chariklo blocked its light.
But surprisingly, a few seconds before and after the asteroid moved by, there was additional dimming of the starlight. Rings surrounding Chariklo were blocking star light too.
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