Space Donuts: Just A Phase For Planets


Universe is mysterious. While we have learnt and understood a great deal about our universe, and our origins, there is still a lot to be known. One of those things is the origin of our planet Earth, and similar planets. Not only is the origin of the Universe itself a topic of much debate, the origin of our own home is a hot puzzle.

Till now, one of the most accepted theory to provide a solution to the puzzle is that, in the early solar system, when the sun was surrounded by hot gases and vapourised material, as time passed, this disc of material around the sun, cooled, and collected together  to form big rotating bodies of rock and metal, called protoplanets. It were these protoplanets which then collided which other to form the inner planets of the solar system. One of these protoplanets, which will later become Earth, was later collided by another wandering object (more like a bullet), named Theia. It was originally believed that Theia and the protoplanet’s collision was just a side-sweep, because of which one a broken off piece of Theia, became our Moon, and the rest of it went on its path. Later it was theorised that Theia might have actually had a head-on collision with the protoplanet, and the soaring temperatures resulting from it, melted the two of them, and Theia was eventually fused into the protoplanet, and later as it cooled, gave birth to our planet, Earth and also a part of it became our Moon. This happened around 4.5 billion years ago.

Size and shape comparision of Synestias with other possible phases of planet evolution. Image Source : ScienceDaily

“We show that rocky planets are vaporised multiple times during their formation, and are likely to form synestias.”

-Simon Lock, Harvard University, Massachusetts

Now, a new study by Sarah Stewart of University of California Davis, and Simon Lock of Harvard University, has brought to light that we might have missed somethings really important. Before condensing and cooling to the present state, Earth and moon might have been one body of vapourised rocks orbiting around a molten core, which was shaped like a donut (with a centre filling)! Planets with rings, or just spherical planets are the usual phases of planets known to us, but apparently, in the early stages of formation most of the planets might have been in a state, named “Synestia”, which was a donut in shape. Synestia comes from a mixture of two words.’syn’ meaning together and,’Hestia’, the mythical Greek  goddess of architecture. When a smaller wandering body (or the colliding body) smashes into a bigger orbiting protoplanet, the protoplanet becomes the main planet, while the small colliding body shatters into comparably tiny fragments which orbit the planet in form of rings, similar to Saturn, until they are eventually absorbed into the planet. But what happens when the two of them are of the same size and mass? Then what will be the protoplanet, and which one will be the colliding body? How can we differentiate one from other in their respective roles? When Stewart and Lock fed this data along with other parameters on a simulator, they surprisingly observed that while in some collisions the result was a spherical planet, with discs, or moons, for a majority of cases, the collision resulted in the formation of a new structure, which they named a synestia. This happened when the rate of angular rotation was higher than a certain critical value, called the corotation value. This synestia is actually a molten core with an uniform angular velocity, orbited by halos of vapourised materials, much like a donut. Synestia has a volume greater than the sum of volumes of the two colliding bodies (it has expanded due to high temperatures). The Earth had gone through a similar fate. In almost a hundred years, which is negligible in planet lifetimes, the synestia condensed and cooled. This gave rise to our present Earth and its Moon.

“We looked at the statistics of giant impacts, and we found that they can form a completely new structure.”

-Sarah Stewart, University of California Davis

If this new phase is accepted by the scientific community, it will soon become a common word in science textbooks. This also explains why the lunar rocks brought back from the Apollo mission match almost remarkably with the ones obtained from volcanic  eruptions on Earth. The oxygen isotope ratio, (the ratio of concentration of O-16 and O-17 isotopes of Oxygen) in the two group of rocks is very similar, pointing that they came from the same source. This study was published in “The Journal Of Geophysical Research: Planets”. If accepted, this can also help fill many major gaps in our understanding of the origin of our home. Who thought donuts would be the answer ?! Happy Reading.

-The Cosmogasmic Person

Paper: The structure of terrestrial bodies: Impact heating, corotation
limits, and synestias


3 Comments Add yours

  1. Amazing blog and very interesting stuff you got here! I definitely learned a lot from reading through some of your earlier posts as well and decided to drop a comment on this one!


  2. Scott Levine says:

    Another really interesting post. I think about the Moon a lot, and how it’s a really great metaphor for the entire scientific method. Scientists had an idea where it came from, they were able to disprove it or find a better answer. That became the new idea. Repeat, repeat. I love it. It’s really a great metaphor for humanity at its best. We learned something new, so we changed our stance.

    Thanks for this great post.

    Liked by 1 person

    1. Shantanu says:

      Welcome, I hope I keep you entertained. 🙂


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