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Simulated structure of planet candidate 9. Courtesy of Esther Linder, Christoph Mordasini, Universität BernWhat is the enigmatic planet nine like? Is it a super-Earth, or more like its cosmic neighbors, Uranus and Neptune? How big is it? What’s its temperature?

The hypothetical planet is shrouded in mystery. However, that doesn’t stop inquisitive minds.

The aforementioned questions have been pondered by University of Bern researchers Esther Linder and Christoph Mordasini since January, when researchers announced evidence of a ninth planet.

Linder and Mordasini, in their study published in Astronomy & Astrophysics, operated under the assumption that planet nine would be a smaller version of Uranus and Neptune. With that in mind, they traced the thermodynamic evolution of such a planet since the solar system’s formation, around 4.6 billion years ago. The researchers said they believe the planet is around 700 astronomical units away.      

According to the University of Bern, the researchers concluded planet nine’s mass is equal to 10 Earth masses, has a radius that measure 3.7 Earth radii, and a temperature of 47 Kelvin (minus 226 Celsius).

“This means that the planet’s emission is dominated by the cooling of its core, otherwise the temperature would only be 10 Kelvin,” said Linder in a statement. “Its intrinsic power is about 1,000 times bigger than its absorbed power.”

The researchers’ planet nine model consisted of an iron core, which was wrapped in a silicate mantle followed by a water ice layer, and finally in a hydrogen and helium envelope.

The researchers also attempted to figure out why planet nine has evaded human detection. “They calculated the brightness of smaller and bigger planets on various orbits,” according to University of Bern. “They conclude that the sky surveys performed in the past had only a small chance to detect an object with a mass of 20 Earth masses or less, especially if it is near the farthest point of its orbit around the sun.”

However, a planet with a mass more than 50 Earth masses would be detectable by extant telescopes, such as NASA’s Wide-field Infrared Survey Explorer.  

Astronomers may be close to figuring out planet nine’s location. According to Universe Today, recent evidence shows that small perturbations in Cassini’s orbit around Saturn may be caused by the ninth planet.

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