The Search for Planet Nine's Whereabouts

It has been almost two decades since Pluto was demoted from being a planet to a dwarf planet by the International Astronomical Union. But still, astronomers and astrophysicists are searching for an elusive ninth planet orbiting around the sun. And so far, the places where Planet Nine could be is slowly running out, with about 78% of the sky turning up with nothing.

There were a few candidates over the years. In 2003, Sedna was discovered, although it was still considered a dwarf planet, and the distance between Sedna and the sun was about 11 billion kilometers, at its nearest, and it goes as far as 140 billion kilometers away from the sun.

For perspective, Neptune has an average distance of about 4.5 billion kilometers away from the sun. Pluto, on the other hand, was on average about 5.2 billion kilometers from the sun. So, Sedna could barely be included within the solar system. Another celestial body, 2012 VP113, was also discovered and this gave rise to the possibility that Planet Nine does exist somewhere out there.

In fact, in 2016, Caltech astronomers Konstantin Batygin and Mike Brown asserted that the alignment of the trans-Neptunian objects' orientations was far too close to be coincidental. Furthermore, they shared a similar degree of tilt with respect to Earth's orbit, so this may point to the possibility that Planet Nine does exist.

However, despite the search efforts, astronomers still have not found Planet Nine. So far, they have conducted surveys such as the Dark Energy Survey, covering about 56% of the sky and the Pan-STARRS1 survey, which looked at around 75%. Combining these two, along with their overlaps, about 78% of the sky has been searched.

After these search efforts, only 22% of the sky remains. Moreover, the part which has not yet been surveyed is perhaps the most difficult part to scour because stars are more crowded together, so it will be like finding a needle in a haystack, that is, if the needle was sure to be in the haystack. Whether Planet Nine even exists is still uncertain.

There are clues that point to the possibility of Planet Nine existing, but until the astronomers can spot an actual exoplanet orbiting around the sun, then we can only hope that it does exist. If it does exist, then that will give us more insight into our galaxy, the formation of planets, and how they transformed throughout the years.

And perhaps, apart from the fact that discovering Planet Nine would give scientists more material to analyze and study, it has been more than two centuries since the last solar system planet was discovered, and having a new one might assuage the loss some of us felt when Pluto had been demoted.

(Image credit: NASA/Unsplash)