Meet synestia, a new type of planetary object

Posted Jun 10, 2017 by Tim Sandle
Astrophysicists are proposing a new type of planetary object which they’ve named a 'synestia'. By this they are referring to a large, rotating, donut-shaped mass of hot, vaporized rock.
This artist’s concept illustrates the two Saturn-sized planets discovered by NASA’s Kepler missi...
This artist’s concept illustrates the two Saturn-sized planets discovered by NASA’s Kepler mission. The star system is oriented edge-on, as seen by Kepler, such that both planets cross in front, or transit, their star, named Kepler-9. This is the first star system found to have multiple transiting planets.
Image credit: NASA/Ames/JPL-Caltech
The research and the naming of the object remains theoretical, for a synestia has never been observed. What has been put forwards is based on a model: here a synestia is composed of two parts. The first is an inner region that behaves like a planet (rotating at one pace); the second is an outer region resembling a ‘donut’ of vaporized space debris resembling a gigantic cloud of superheated matter. The term "synestia," derives from "syn-," which means ‘together’ and "Hestia," who was the Greek goddess of architecture and structures.
A synestia is formed as planet-sized objects smash into each other. The object relates to the formation of rocky planets, which are thought to arise from giant impacts between planet-size bodies. When impacts occur these are of high energy. It is possible that the impacts also lead to the formation of synestia, if the angular motion of the colliding bodies is sufficiently high.
The resultant object – the synestia - is a rotating mass of vaporized rock. The outermost layers of the structure appear in orbit around the remainder of the body. University of California - Davis researchers say that synestias are important for study since they provide new insights into how planets and moons form. Such study may also provide clues about how our planet formed for it is possible that the Earth emerged from a completely new structure after a planetary collision, with outer layers of vaporized rock rotating in orbit around the rest of the body. If this did occur with the Earth, then the synestia generated would have been short lasting in astronomical terms: a few hundred years. Following this, heat would have been lost and the vapor would condense back into a solid object, helping to form the planet as we understand it. The same model may also account for the formation of Mars and Venus, and even the Earth’s Moon.
Lead researcher Dr. Sarah Stewart uses the analogy of the ice skaters to account for the formation. She presents the scenario whereby ‘ice skaters’ are like Earth-sized rocky planets. When these objects collide with other large objects, with both high energy and high angular momentum, then new structures can be formed.
Based on the theoretical model, the researchers are now attempting to find real examples in the cosmos to prove their theory to be correct.
The proposal for naming the planetary object has been put forward in the Journal of Geophysical Research: Planets. The research is titled “The structure of terrestrial bodies: Impact heating, corotation limits, and synestias.”