As new data continues to support the existence of "Planet Nine," astronomers are now trying to determine what it looks like.
Konstantin Batygin and Mike Brown, the California Institute of Technology astronomers who originally proposed the existence of an undetected planet in the outer reaches of the solar system, never actually caught a glimpse of the hypothetical planet. Instead, they inferred its existence based on the orbit of objects in the Kuiper Belt, a ring of icy interstellar objects that lies beyond Neptune.
The data from this research suggests that Planet Nine is approximately 10 times bigger than Earth and probably circles the sun at a distance of 600 astronomical units (AU).
Now, a new study is modeling what Planet Nine might look like based on the parameters revealed by Batygin and Brown's data.
The team calculated that if it exists, Planet Nine would be 3.7 times wider than our planet, with a surface temperature of minus 375 degrees Fahrenheit.
"This means that the planet's emission is dominated by the cooling of its core; otherwise, the temperature would only be 10 Kelvin," said Esther Linder, co-author of the study and student from the University of Bern in Switzerland.
Furthermore, since reflected sunlight would not increase the total radiation emitted by the planet by a significant amount, it would likely be brighter in infrared light than in visual wavelengths.
"With our study, candidate Planet Nine is now more than a simple point mass; it takes shape, having physical properties," said Christoph Mordasini, co-author of the study and astrophysics professor at the University of Bern.
Mordasini and Linder also calculated the brightness of both small and big planets on various orbits and, using this data, concluded that Planet Nine is likely too faint to have been detected by past astronomical surveys, suggesting a reason for why telescopes have failed to pick up the planet thus far.
The team believes that NASA's Wide-Field Infrared Survey Explorer (WISE) space telescope might be able to get the job done.
"This puts forward an interesting upper mass limit for the planet," Linder said.
In terms of its formation, the team believes that Planet Nine originated from the same disk of dust and gas as the other planets in our solar system, although some astronomers are suggest that other more exotic origins are possible.
The findings will be published in the journal Astronomy & Astrophysics.
