The search for planet X takes a new impetus with the discovery of a super-distant object

A new discovery reinforces the idea that a large and mysterious planet – known as Planet 9 or Planet X – could hide from the invisible at the edge of the solar system. Astronomers claim to have found a tiny object in orbit away from the Sun that corresponds to the theory of Planet X. In fact, the object may have even been pushed on the path it now takes by the gravity of this planet hidden.

The tiny rock – aptly named TG387 and nicknamed "The Goblin" – was spotted by astronomers from the Carnegie Institution of Science with the help of a giant Japanese observatory in Hawaii called Subaru. The Carnegie team first spotted the object in 2015, then followed it for four years around the Sun. These observations revealed an incredibly distant target. TG387 takes 40,000 years to achieve a single orbit around the Sun. And it's on a very elliptical trajectory, far from the internal solar system; The closest possible to the Sun is 65 astronomical units (AU), which is 65 times the distance between the Sun and the Earth. For reference, Pluto only reaches 49 AU from the Sun.

This orbit is particularly attractive in that it places TG387 in a small group of distant solar system objects that all suggest the possible existence of the planet X. At present, there are 14 distant space rocks that all share similar orbit patterns, the planet is there. Their paths are all super long and they all gather in the same area when they approach the Sun. Moreover, their orbits are all inclined in the same way, and they indicate the same general direction, as if something big had pushed them into similar places. These objects are the strongest evidence available to astronomers for Planet X, and finding a new one that fits this model reinforces the idea that this planet is more than just a theory.

In addition, each new discovery helps astronomers pinpoint where to search for planet X. "Every time we find another of these smaller objects, it will lead us to determine where the largest planet could be," Scott Sheppard, astronomer at Carnegie Science and the main author of a study The astronomical journal detailing the discovery, tells The edge. "They are all in very similar orbits, but their orbits are all slightly different, which [limits] where the planet could be. "

The idea that a giant planet is hiding behind Neptune is an idea that astronomers have speculated for the last century. However, the hunt for this planet became much more serious in 2012, when Sheppard and his team discovered a distant object that was truly unique. It was an object called VP113, and it currently holds the record for the farthest object in orbit around the Sun. As close as possible to the star is 80 AU, or 80 times the Earth-Sun distance. Sheppard noticed that this object also followed a path similar to that of some other distant space rocks, as well as to a distant dwarf planet called Sedna. "They all have this grouping, which suggests that something was pushing them into similar orbits," says Sheppard.

Then, in 2016, two Caltech researchers, Mike Brown and Konstantin Batygin, did the math. Based on the orbits of six of these objects, they estimated that a planet about ten times greater than Earth's mass gravitating around Neptune. Their calculations showed that it would probably take 10,000 to 20,000 years to orbit the Sun. Brown and Batygin have dubbed the ghost planet "Planet 9," while others called it Planet X years ago.

Since then, more and more objects have been found that fit this model of orbit. The idea is that these objects are in the good orbits necessary for the survival of the gravitational anger of planet X. If they followed another path, they would probably collide with the big planet or the gravity of the planet would send them out of the solar system. However, all these extreme far-away objects orbit in such a way that they never get close to the planet X when it passes on their orbit. "Whenever the planet goes through the orbit of one of these objects, these objects are on the other side of the solar system. They never get close, "says Sheppard.

But all these objects are not narrators as reliable as they could be. "Of these 14 objects, some tell a story more accurate than others," says Batygin, who did not participate in today's study. The edge. On the one hand, some objects cross Neptune's orbit and the gravity of this planet could have an influence on the objects and distort their routes. "Neptune has the effect of blurring things, even if you have an orbit carefully carved by planet 9." It is therefore difficult to know if the object is actually pushed by this invisible planet.

Image: Scott Sheppard

But this new discovery, TG387, is special because its orbit is so far away. Further from the Sun, the rock will be at an extreme distance of 2300 AU. In fact, it is remarkable that astronomers have found all this because it is about seven times smaller than Pluto and so far. But because of its extreme distance, TG387 is in no way influenced by the large objects of the internal solar system. Jupiter, Saturn, Uranus and Neptune have no effect on its orbit. This means that if this object was actually bypassed by Planet X, it could contain more information about the planet's orbit than other objects. And when they simulated the solar system with a planet X, the team found that the orbit of this object could not be changed. "This joins an elite group of six stable objects," says Batygin.

Of course, Planet X is not close to being concluded. There are only 14 objects that can support his existence. This is an extremely low number in terms of statistical standards. "We do not have dozens of these objects," says Michele Bannister, an astronomer studying small distant bodies at Queen's University in Belfast, who did not participate in this research. The edge. "I would be very happy if we had dozens, but we have barely a handful." In addition, Bannister says it's important to remember that astronomers still do not have a complete snapshot of the distant solar system. The time of year, the weather conditions and the part of the sky observed by a telescope have an influence on the type of objects discovered, which adds a bias to the sample.

In addition, the objects we find are usually at the nearest approach to the Sun in their ultra-distant orbit, which biases our findings a little bit. For example, TG387 was found when it was about 80 AU, not thousands of AU. This means that we may not have a good idea of ​​everything that happens, because we can not see objects that are very distant in their orbit. "Each of these objects we detect is the tip of an iceberg for a larger population," says Bannister. For every new discovery, there must be hundreds of thousands of objects that astronomers can not see. And these objects could tell a story different from that of planet X.

However, Bannister, who predicted the existence of an object such as TG387 in the solar system, says this discovery is instrumental in helping us shape our understanding of the remote solar system. We still do not understand why some objects like this one are completely detached from the rest of the planets. "They made a big discovery," she says. "These are exactly the objects we need to find to understand the formation and history of our solar system."

Meanwhile, our best hope in the search for Planet X is to find more objects that corroborate its existence. "We do not expect all the objects we find to fit this model, although that's what's happening right now," says Sheppard. Better yet, finding Planet X would also be pretty compelling. The problem is that there is a lot of sky to go and that our telescopes do not cover a lot of ground at a time. The Subaru Telescope in Hawaii is perhaps the best tool as it can observe about six full moons at a time. But it is always difficult to determine the exact location of such a distant and weak planet. "It's like looking for your target with a sniper rifle," says Batygin. "You must know where to look."

But TG387 Is help astronomers point in a slightly better direction. Before this discovery, Sheppard and his team thought that Planet X could be about 30 orbits. Now there are only 25 or so, he says. And astronomers will return to Subaru in mid-October to resume research. "We have covered about 30% of the field of choice, and we hope that by the end of the year, we will have covered 60 to 70% of this area," Sheppard said.

If planet X is found, a new set of questions will arise. Perhaps the most important of all is where it comes from? Most do not think that it is possible that this planet was formed where it is now. He probably formed in the inner solar system and was projected outward, perhaps by Jupiter or Saturn. "It would suggest a lot of great things formed in our solar system, and it was a very chaotic place at the time of training," Sheppard says.

But before we can answer these questions, planet X must be found. And those who are hunting are certain that this will happen. "I'm really confident, with a 99% confidence level, that Planet 9 is really there," says Batygin. "It may take about a decade or so to find, but I am quite convinced that it is there."