First Asteroid With Rings Discovered

In a paper published today in Nature, astronomers report the discovery of two icy rings around a small object named Chariklo that orbits between Saturn and Uranus. Chariklo is only 154 miles (248 kilometers) across. (Related: “Asteroids and Comets.”)

Well, I certainly didn’t see this one coming.

It should be called a “centaur” rather than an asteroid, because, residing between Saturn and Uranus, it is made largely of ices rather than rocks. Asteroids are mostly made of rocks and comets of ices.

The discovery was made by seeing Chariklo occult a star from 8 different locations on Earth. The man body of Chariklo occulted the star in three of those observations, but five of the eight observed occultation by the ring system. There’s absolutely no question about this being anything other than a genuine ring system about a minor planet. The distance of the ring system from the surface of Chariklo is very similar to the diameter of Chariklo.

> The discovery was made by seeing Chariklo occult a star from 8 different locations on Earth

I was wondering how anyone knew to look for a ring around the centaur Chariklo and that took me to a couple of interesting websites:

On http://www.eclipsetours.com/paul-maley/occultations/ we find:
“If, as an amateur astronomer or telescope owner, you are thirsting to feel relevant, to do something meaningful in your life and to see sights that few have every witnessed, then occultations are the thing for you. The occultation process offers discovery and research. It is possible for amateur astronomers to discover new companions of stars, help to improve the polar diameter of the sun and moon, identify the existence of possible satellites orbiting asteroids, to improve knowledge of heights of lunar mountain peaks and depths of valleys in the polar regions, determine corrections to ephemeris errors and assess star position errors, improve knowledge of the shape and sizes of asteroids, and more through occultation science. It does not matter where you live in the world. If you have access to a computer and possess a telescope of at least 4-6 inches, know your geodetic position either from GPS or a good topographic map, have a source of time signals and tape recorder, you can make your own observations of these rare and critical events.”

From timing it is possible to find the detailed shape of asteroids, eg. of Atiope:

Asteroid occultations are remarkably common. For example http://www.asteroidoccultation.com/ lists, among many others, six different asteroid occultations that will all occur on the 31 Mar 2014. The following is the path of occultation on 30 Mar 2014 of asteroid Maritima over Australia.

And here’s one for two days later, April fool’s day.

And another from 3 Apr 2014.