Free Astronomy Magazine July-August 2016

SPACE CHRONICLES stored in the Oort Cloud and is now making its way back into the inner Solar System. A number of theoretical models are able to re- produce much of the structure we see in the Solar System. An important difference be- tween these models is what they predict about the ob- jects that make up the Oort Cloud. Different mod- els predict sig- nificantly dif- ferent ratios of icy to rocky objects. This first dis- covery of a rocky object from the Oort Cloud is therefore an impor- tant test of the different predic- tions of the models. The authors estimate that obser- vations of 50–100 of these Manx comets are needed to distinguish between the current models, open- ing up another rich vein in the study of the origins of the Solar Sys-tem. Co-author Olivier Hainaut (ESO, Garching, Germany), concludes: “We’ve found the first rocky comet, and we are looking for others. Depending how many we find, we will know whether the giant planets danced across the Solar System when they were young, or if they grew up quietly without moving much.” T his video shows the probable dynamic history of C/2014 S3 (PANSTARRS) in both the inner and outer Solar System, over a period of more than four billion years. [ESO/L. Calçada] T his image of C/2014 S3 (PANSTARRS) was acquired using the Canada-France-Hawai`i Telescope. [K. Meech (IfA/UH)/CFHT/ESO] known as S-type, which are usually found in the inner asteroid main belt. It does not look like a typical comet, which are believed to form in the outer Solar System and are icy, rather than rocky. It appears that the mate- rial has undergone very little processing, indi- cating that it has been deep frozen for a very long time. The very weak comet- like activity associated with C/2014 S3 (PAN- STARRS), which is consis- tent with the sublima- tion of water ice, is about a million times lower than active long- period comets at a sim- ilar distance from the Sun. The au- thors conclude that this object is probably made of fresh inner So- lar System material that has been n