Indirect evidence for the existence of a ninth planet: a gas giant that orbits the Sun once every ten thousand years

A collaboration between an observational astronomer and a theorist has led to the discovery of indirect evidence for the possible existence of a giant planet orbiting the sun in a strange, highly elongated orbit in the outer solar system. The object that the researchers call the ninth planet and the public has earned the nickname "Planet X" has a mass 10 times that of the Earth and it orbits the Sun in an orbit from an origin 20 times more distant than that of Neptune-Rahab. It takes this planet 10,000-20,000 years to orbit the sun

Caltech researchers have found indirect evidence for the existence of a planet moving on a strange, highly elongated orbit in the outer solar system. The object, which the researchers named the ninth planet, has a mass 10 times that of Earth and orbits the Sun at an average distance 20 times greater than that of Neptune-Rahab, the most distant known planet in the Solar System. In fact, it takes this planet between 10,000 and 20,000 years to make a complete revolution around the Sun.
The researchers, Konstantin Batygin and Mike Brown, discovered the existence of the planet through mathematical models and computer simulations but have not yet observed the actual one directly. In the public, the new planet was nicknamed "Planet X" after the planet from the popular beliefs that starred in the prophecies of wrath towards December 21, 2012, when some claimed that it was on a collision course with the Earth. This is not the case, but it is a very important discovery.

"It would be a true ninth planet," says Brown, of Caltech's Department of Planetary Sciences. "Since ancient times, only two real planets have been discovered, and this will be a third. There are other significant parts of the solar system that still have more to discover and it's quite exciting.

Brown points out that the mass of the putative ninth planet is 5,000 times greater than the mass of Pluto, meaning it is large enough that there would be no discussion of whether it is a real planet. In contrast to the status of the small objects known as dwarf planets, the major planets have a large sphere of control over which their gravity acts. The ninth planet rules a larger area than any other known planet.
Batygin and Brown describe their findings in the current issue of the journal ASTRONOMY and show how the ninth planet helps explain a number of mysterious features of the field of icy and rocky objects that surround the solar system beyond Neptune - a region known as the Kuiper belt.
"Although we were initially quite skeptical that this planet could exist, as we continue to study its orbit and its impact on the outer solar system, we are becoming more and more convinced that it is out there," says Batygin, a professor of planetary sciences. "For the first time in over 150 years, there is solid evidence that the planetary commander in the solar system is incomplete."

"The road to the theoretical discovery was not easy. In 2014, Brown's former postdoctoral fellow, Chad Trujillo, and his colleague Scott Shepherd published that the orbits of the 13 most distant objects in the Kuiper Belt form a similar pattern and the only explanation for the similarity in features is the existence of a minor planet in this region.

Collaboration between an observing astronomer and a theoretician

Brown decided to partner with Batygin and the two began a six-month collaboration to study the distant objects. As a scientist and a theorist, respectively, the researchers approached the work from very different perspectives. - Brown as someone who looks at the sky and tries to anchor everything in the context of the observations and Batygin as someone who observes the dynamics and considers how things might work in terms of physics. These differences allowed researchers to challenge each other's ideas and consider new possibilities. "When I brought aspects of observation, he came back to me with arguments from the theory, and that's how we pushed each other. I don't think the discovery would have happened without this backup. This was perhaps the most enjoyable year I've had working on a problem in the solar system."

Pretty quickly the two realized that the six most distant objects in Trujillo and Shepherd's original collection follow elliptical orbits pointing in the same direction in physical space. This was particularly surprising because the outermost points of their orbits in the solar system are different in distance, and they travel at different speeds.

"It's almost like placing six hands on a clock with each one moving at a different rate and all coming out of the same place," says Brown. The chances of this happening for no reason are small, but since the orbits of the six objects are tilted in the same way - pointing at an angle of 30 degrees downward in the same direction relative to the plane of the eight known planets. The probability of this happening is 0.007 percent. "Basically it shouldn't happen randomly," says Brown. "So we thought that something else must be shaping these pathways."

The first possibility they explored was that there might be enough distant objects in the Kuiper Belt, some of them undiscovered, to exert the gravity needed to keep a subpopulation clustered together. The researchers soon discovered that such a scenario would require the Kuiper belt to have a mass 100 times heavier than its known mass.
Which left them with the idea of ​​a planet. Their first instinct was to run simulations involving a planet in a distant orbit that circled the orbits of six Kofir Belt selves and acted as a giant falsor causing them to align. It turns out that this worked but didn't solve all the oddities.

Then, by chance, the two noticed that if in the simulations the same planet is aligned in an inverted way, that is, an orbit in which the closest distance of the planet to the Sun, or the perihelion, is 180 degrees opposite the perihelion of all known objects and planets, then the same Kuiper Belt self They do align like in reality.

"The natural reaction is to say that the geometry of this track cannot be correct. This is an unstable trajectory over time, because it will cause the planet and these objects to collide in the end," says Batygin. "There is a mechanism known as average motion resonance. The retrogradely aligned orbit of the ninth planet actually prevents those Kuiper Belt selves from colliding with it and keeps them aligned. Because they seem to reach the same point once in a while, like a parent pushing his child's swing every time it gets close to him, the ninth planet periodically nudges the orbits of these objects so that their configuration relative to the planet is maintained. "Still, I was very skeptical," Batygin says. "I have never seen anything like this in the mechanics of the planets."

But little by little, when the researchers explored additional features and implications of the model, they were convinced. "A good theory should not only explain things we know but explain observations and predict how to test them." Batygin said.

The existence of the ninth planet explains the observations

Indeed the existence of the ninth planet helps to explain more than just the alignment of the distant Kuiper Belt self. It also provides an explanation for the mysterious routes the two followed. The first – the dwarf planet Sedna discovered by Brown in 2003. Unlike the other Kuiper belt bodies, Sedna appears to have been kicked out of the inner solar system by Neptune and although it is coming back in it will never come close to Neptune. Another object is VP113 discovered in 2012 and declared by Trujillo and Shepherd in 2014 as a dwarf planet. The two found that the presence of a ninth planet in the proposed orbit naturally causes objects such as a workshop to be less attracted to Neptune's orbit.

But the real incentive for the researchers was the fact that their simulations also predicted the existence of Kuiper belt objects that are in orbits inclined perpendicular to the plane of the planets. Batygin continued to investigate this in simulations and showed it to Brown. "Suddenly I realized that there are objects similar to these," Brown recalled. In the last three years, observational astronomers have identified four Kuiper belt objects whose orbits are perpendicular to that of Neptune and one object at a different angle. I checked the location of the objects and their trajectories and they matched the simulations exactly," says Brown. "When we found out, my jaw hit the floor."

"When the same simulation caused the distant Kuiper Belt to self-align and create workshop-like objects, it looked amazing. – You're killing two birds with one stone," says Batygin. "But when the existence of this planet also explains these perpendicular orbits, not only do you kill two birds, you also catch an uncomprehending bird that was sitting in a nearby tree."

Where is the ninth planet and what does the outer solar system look like? Many scientists believed that the early solar system began with four planetary cores that continued to capture all the gas around them, creating the four gas planets - Jupiter, Saturn, Uranus, and Neptune. Over time, collisions and emissions shaped them and moved them to their current orbits. "But there's no reason why there can't be five cores and not four," says Brown. The ninth planet may represent the fifth core and if it got too close to Jupiter and Saturn it could be ejected into its far, eccentric orbit.
Batygin and Brown continue to refine their simulations and learn more about the planet's orbit and its effect on the outer solar system. Meanwhile, Brown and other observational colleagues have begun scanning the skies for the ninth planet. Its orbit is only roughly known, and it is not clear where it is along its elliptical path. If it happens to be close to its perihelion, Brown says, astronomers should be able to spot it in images taken by previous surveys. If it is in the most distant part of its orbit, the world's largest telescopes – such as the twin 10-meter telescopes at the Keck Observatory and the Subaru Telescope – all atop Mauna Kea in Hawaii – will be required to observe it. If it is in the middle of the road, many telescopes can be pointed at it to observe it.

"I would love to find him," says Brown. "But I'll be just as happy if someone else finds it. This is why we are publishing this article. We hope other people will be inspired and start looking.

In broader terms of the context of the solar system in the universe, Batygin says that in several ways, this ninth planet that seems strange to us actually makes our solar system more similar to the other solar systems that astronomers discover around other stars. Some planets are very close to their host star, and others are distant. The common mass of such planets ranges from 1 to 10 times the mass of the Earth, that is, between the mass of the Earth and the mass of Neptune. Until now we thought that the solar system was missing the most common type of planets, maybe we are more normal after all."

Brown, who had a significant role in relegating Pluto to dwarf planet status, adds, "All those people who are upset that Pluto is no longer a planet can be happy to know that there is a real planet out there that can still be found," he says. "Now we can go and find that planet and return the solar system to its previous size - nine planets."

to the notice of the researchers

For the scientific article "Evidence for a giant planet far away in the solar system."

More of the topic in Hayadan:

• NASA - Despite an extensive scan, the Wise telescope failed to locate Planet X
• Pluto and beyond
• The twenty frequently asked questions that NASA answered in response to messages published on the Internet in preparation for 2012