It may be common knowledge that the Earth is round, but scientists now say it may not always have been that way.
In fact, rather than being spherical like a Malteser, scientists believe the Earth was flatter “like a Smartie” very early in its life.
Previously, scientists assumed that ‘protoplanets’ (very young planets that have recently formed around stars) would be spheres.
To test this assumption, researchers at the University of Central Lancashire simulated how planets could form from disks of gas around stars.
This revealed that, instead of being round, the newly formed planets are actually flattened.
Researchers now believe that planets may not be spherical when they first form, but would actually have flattened shapes called “oblate spheroids.” This simulation shows a protoplanet seen from above (left) and from the side (right).
The Earth itself is not perfectly round, as it is flattened at the poles by about 0.3 percent. But researchers say protoplanets can be crushed by up to 90 percent.
This is the first time that scientists have observed the three-dimensional shape of newborn planets in their simulation.
Dr Dimitris Stamatellos, co-author of the paper, says: ‘We were very surprised that they turned out to be oblate spheroids, quite similar to Smarties!
‘We have been studying planet formation for a long time, but it had never before occurred to us to check the shape of planets as they form in simulations.
“We had always assumed they were spherical.”
Most of the planets that we can observe are spheres, or at least they are very close to being so.
Earth is flattened at its poles by about 0.3 percent, Jupiter by about 6 percent, and Saturn by a whopping 10 percent.
But scientists now believe that protoplanets are about 90 percent oblate.
The protoplanet phase is believed to last between 1 and 5 million years of a planet’s existence.
Considering the Earth is around 4.5 billion years old, it would have been Smartie-shaped for a very small fraction of its early history.
Scientists had previously assumed that the young planets would be spheres, but were surprised to discover that they are oblate spheroids like the smarties (pictured) (file image)
The researchers simulated how planets form according to the theory of disk instability. This simulation shows how the gas disk around a young star suddenly collapses, forming planets
There are currently two main theories about how protoplanets form.
The first, explained lead researcher Dr. Adam Fenton, is called the “core accretion” theory.
This theory states that planets form through the “gradual growth of dust particles that coalesce to form increasingly larger objects over long time scales.”
The second theory is the disk instability theory, which states that planets form in a relatively short time as the disk of gas rotating around a young star rapidly breaks up.
Dr Fenton says: “This theory is attractive due to the fact that large planets can form very quickly at large distances from their host star, which explains some observations of exoplanets.”
Following the predictions of this theory, the researchers simulated the formation of gaseous planets around a young star.
Dr Fenton says the calculation was extremely demanding, requiring half a million CPU hours at the UK’s DiRAC high-performance computing facility.
However, once the simulation was completed, the researchers were surprised to discover that the protoplanets were not spheres after all.
In his article, which will be published in Astronomy and Astrophysics LettersResearchers suggest that planets become flat because they form inside a rotating disk.
Like a chef spinning a ball of pizza dough, the force of its spin stretches and flattens the young planet.
Researchers believe that planets only become spherical later, when gas and other matter reaches their north and south poles more quickly than at the equator.
These results could resolve the question of how planets form. If researchers do not find spherical protoplanets like the one shown in this artist’s impression, this would be good evidence that they are forming due to disk instability.
These predictions could one day help resolve the question of how planets form.
Observations of protoplanets are still very rare and have only been possible in recent years.
However, researchers hope that the flattening of protoplanets will be observable through telescopes.
They write: “We hope that this can lead to a strong modification of the observed properties of protoplanets with the viewing angle that must be taken into account when interpreting the observations.”
But according to the central accretion theory, protoplanets would remain spherical.
This means that if researchers are able to observe flattened protoplanets, this would be good evidence for the currently disfavored disk instability theory.
The researchers are currently following up to improve the computational model to compare the results with future observations from the James Webb Space Telescope.