In 2006, Pluto was deprived of its status as the ninth planet of the solar system thanks to the efforts of one astronomer, Michael Brown. Together with his colleagues, he discovered and then other dwarf planets far beyond the orbit of Neptune. Thus, he proved that Pluto is not remarkable and large enough to be considered a full-fledged planet. However, now Brown and our compatriot Konstantin Batygin claim that the new Planet 9 is almost discovered... and that all that remains is to see it.

Yes, yes, no one has ever seen the “almost discovered” ninth planet of the solar system! As a matter of fact, its discovery is the fruit of long observations of the orbits of other planets. According to Kepler and Newton, the place of each planet in the solar system is determined by its characteristics, mainly by mass. And if the orbit does not correspond to the parameters of the planet or is generally anomalous in nature, it means that it is influenced by some other, no less massive object. The first planet discovered by mathematical equations, rather than by live observations, was found in 1846 at a site calculated by the French mathematician Urbain Le Verrier.

Moreover, planets can influence each other very actively - in the past of the Solar System, they traveled hundreds of millions of kilometers, approaching and moving away from the Sun. The gas giants especially distinguished themselves here. In young planetary systems, they absorb all the embryos of the planets and hover close to the star - as close as Mercury. Because of this, they become very hot and unstable. Scientists call such planets “hot Jupiters” or “hot Neptunes,” depending on their mass and size.

The troubled history of the solar system

However, in the solar system, Jupiter, the largest and most influential planet, changed everything. Initially appearing at a distance of 5 to 10 from the Sun, it provoked active collisions of scattered material in the protoplanetary disk around the star. This gave impetus to the creation of other gas giants, like Saturn or Neptune, at equally close distances from the Sun.

However, the newly formed planets behaved “ungratefully”, following gravitational laws - they pushed their “parent” closer to the Sun, into the modern orbit of Mars. Thus, Jupiter invaded the inner part of the solar system. In other planetary systems, this part is the most saturated with matter and space objects. But the heavy tread of Jupiter's mass scattered the embryos of planets and asteroids there, throwing them into the nuclear furnace of the Sun or throwing them to the outskirts of the system in the zone of modern and.

If it were not for Saturn, which connected Jupiter with orbital resonance and did not bring it into its modern orbit, the gas giant could have completely devastated the Solar system, throwing out 99% of the planetary matter from it. However, his travels did not remain without a trace - so Neptune and Uranus exchanged their orbits, forming the majority of long-period comets.

Ultimately, an unusual balance reigned in the planetary system of the Sun - gas giants that form close to the star ended up on the outskirts, and “solid planets” like the Earth migrated closer to the Sun. However, some astronomers believed that to achieve such a balance, another planet was needed - and massive enough to influence the larger Neptune and Uranus. Many astronomers have been looking for it, Planet X, for a century and a half - and it seems that Brown and Batygin have finally come close to it.

History of the search for Planet X

After Le Verrier calculated Neptune from disturbances in the orbit of Uranus, astronomers discovered that even its presence did not explain the features of the ice giant’s orbit. For some time they tried to find another planet that could influence the last large objects of the solar system - however, they managed to find only Pluto, which, with its mass and direction of orbit, could not disturb larger bodies. The issue of Uranus-Neptune anomalies was finally resolved by “,” who measured the mass of Neptune in 1989 and thereby discovered that there were no contradictions in the orbits.

By that time, the power of telescopes had increased significantly, which allowed astronomers to look into the depths of the solar system. Many trans-Neptunian objects have been discovered - dwarf planets and large asteroids whose closest point in their orbit is further from the Sun than Neptune. So, in 2005, the already mentioned Eris was discovered, the second largest dwarf planet after Pluto. And back in 2003, they found an object with diameters of over 2 thousand kilometers, which moves away from the Sun at a distance of 1.4 × 10 11 km - further than any large trans-Neptunian object! It soon acquired a whole family of “sednoids,” isolated trans-Neptunian objects with similar characteristics.

Planet Nine - where and why?

While observing the newly discovered planetoids, astronomers C. Trujillo and S. Sheppard, colleagues, discovered an interesting pattern. Most of them have elongated, comet-like orbits that briefly come “close” to the Sun, at a distance of 40 to 70 astronomical units, and then move away for hundreds or even thousands of years. And the larger the object, the stronger its removal. In addition, the sednoids deviated from the Sun in the same direction.

Such a coincidence could have been an accident, if we were talking about simple comets - over the billions of years of the history of the solar system, all the major planets, especially the already mentioned “travelers” Jupiter, Uranus and Neptune, scattered them. However, for such a coincidence in the deviations of large objects, a very large planet is needed, whose orbit would reach the Oort cloud.

This is where Brown and Batygin distinguished themselves - by comparing the orbital characteristics of the sednoids, they discovered mathematically that the probability of their random coincidence is only 0.007%. Scientists went further and compiled a computer model aimed at finding the characteristics of a planet capable of changing the orbits of bodies beyond Neptune. The data they obtained in January 2016 became the basis for the announcement of the pre-discovery of a new planet in the solar system.

Characteristics of Planet X

In his interviews, Brown claims that the probability of discovering a new planet is 90%. However, until it is actually discovered using a telescope, it is too early to talk about a final discovery. Nevertheless, the calculated characteristics of Planet 9 have been published - they will be used in future searches.

• The orbital parameters of Planet X will be mirror those of the sednoids - the planet’s orbit will still be elongated and inclined relative to the plane of the main planets of the Solar System, but directed in the other direction. Accordingly, the perihelion of the planet - the point of maximum approach to the Sun - will be 200 astronomical units at the nearest point, and aphelion - the maximum distance - will reach 1200 astronomical units. This is even more than Sedna! A year on Planet 9 will last up to 20 thousand Earth years - this is exactly how long it may take to complete the entire orbit.

A planet distant from the Sun is difficult to detect - this requires telescopes operating in the infrared spectrum, or powerful optical devices capable of capturing even the smallest solar reflections on the surface. On infrared telescopes, work will move faster, but errors are possible - but on optical telescopes, the result will be reliable, albeit at the cost of time. The WISE infrared orbiting telescope, which conducted broadband surveys in 2009, has not yet discovered Planet X, although it has provided fairly detailed images.

Therefore, Brown, Batygin and other astronomers plan to find it using the Subaru telescope in the Hawaiian Islands, which is considered one of the largest and highest quality in the world - the diameter of its main mirror exceeds 8 meters! In addition, it is capable of working in both optical and infrared light ranges. But even with such a tool, scientists will need at least 5 years to put an end to the issue of Planet X.

Astronomers Mike Brown and Konstantin Batygin from the California Institute of Technology in Pasadena about the discovery of a candidate for the ninth planet of the solar system outside the orbit of Pluto. The discovery could become one of the most sensational in the current decade, comparable to the discovery of a new continent on Earth. The authors published the results of the search for Planet X in The Astronomical Journal. Science News and Nature News talk about them briefly.

What did they discover?

Planet X is an object the size of Neptune and ten times the mass of Earth. The celestial body rotates around the Sun in a highly elongated and inclined orbit to the Earth with a period of 15 thousand years. The closest distance between the Sun and Planet X is 200 astronomical units (this is seven times the distance between Neptune and the luminary), and the maximum is estimated at 600-1200 astronomical units. This takes the object's orbit beyond the Kuiper belt, in which Pluto is located, towards the Oort cloud.

Why the ninth planet

The International Astronomical Union (IAU) definition of planet applies only to celestial bodies in the Solar System. According to it, a planet is considered to be a rounded massive body that has cleared the surroundings of its orbit from a large number of smaller bodies. The IAU officially recognizes the existence of five dwarf planets. One of them (Ceres) is located in the asteroid belt between the orbits of Mars and Jupiter, the others (Pluto, Eris, Makemake and Haumea) are further than the orbit of Neptune. The largest of them is considered to be Pluto.

In total, there are eight planets in the Solar System, according to the IAU. The largest and most massive of them is Jupiter. By decision of the IAU in 2006, Pluto ceased to be considered a planet because it does not satisfy one of the criteria that defines it (dominance in the space of its orbit). To date, astronomers have discovered more than 40 dwarf planet candidates. Scientists estimate that there may be more than two thousand dwarf planets in the Solar System, of which 200 are located within the Kuiper belt (at a distance of 30 to 55 astronomical units from the Sun). The rest are outside of it.

The definition of a planet as a dwarf is controversial among scientists. In particular, the size of the celestial body can play a decisive role. Planet X, being the fifth largest celestial body in the Solar System in terms of mass and size known to science, certainly cannot be considered a dwarf. The unusual orbit and origin of Planet X may lead to a revision of the IAU's definition of a dwarf planet.

Image: NASA/JPL-CALTECH

How they opened it

The existence of Planet X was suspected in 2014. Then Chadwick Trujillo from the Gemini Observatory in Hawaii and Scott Sheppard from the Carnegie Institution in Washington published an article in Nature where they reported the discovery of a trans-Neptunian object 2012 VP113 at a distance of 80 astronomical units (Pluto is 48 astronomical units from the Sun) from the Sun. In their work, astronomers also suggested that at a distance of 250 astronomical units from the star there is a planet larger than Earth.

Observer astronomer Brown and astronomy computing expert Batygin decided to refute the data of Trujillo and Sheppard. But it turned out differently. Scientists discovered the new planet by analyzing data on the gravitational effect it exerts on other celestial bodies beyond the orbit of Neptune. Among them, in particular, is the candidate dwarf planet Sedna, discovered in 2003 by Brown, Trujillo and David Rabinowitz. Computer modeling and theoretical calculations carried out by Brown and Batygin explain the observational results with the existence of Planet X. Astronomers estimate the probability of error in their conclusions at 0.007 percent.

How did Planet X come into being?

Astronomers cannot yet give an exact answer to the question of the origin of Planet X. They are inclined to the following hypothesis. At the dawn of the solar system, there were five large protoplanets, four of which formed modern Jupiter, Saturn, Uranus and Neptune. However, approximately three million years after their birth, the gravity of the first two celestial bodies threw Protoplanet X beyond the orbit of Neptune.

Structure and composition of Planet X

The origins of Planet X suggest that it was originally similar to the ice giants Uranus and Neptune. The latter is 17 times heavier than Earth, and its diameter is four times larger than that of the Blue Planet. Uranus and Neptune are classified as ice giants. Their atmosphere consists of gases (hydrogen, helium and hydrocarbons) and ice particles (water, ammonia and methane). Under the atmosphere of the giants there is a mantle of water, ammonia and methane ice, under which lies a solid core of metals, silicates and ice. Planet X may have a similar core and mantle without a dense atmosphere.

Criticism

The reviewer of the scientists' work in The Astronomical Journal was the celestial mechanic Alessandro Morbidelli from Nice. He was optimistic about the chances of the discovery of Planet X by astronomers Brown and Batygin. Last but not least, thanks to the authority of scientists. Planetary scientist Hal Levison from Colorado was skeptical of his colleagues’ work, citing the hasty conclusions drawn by Brown and Batygin and the need for further verification. As the discoverers of Planet X themselves note, astronomers will believe in their find only when they can observe the planet through a telescope.

What's next

To discover Planet X, astronomers have reserved time at Japan's Subaru Observatory in Hawaii. Scientists will compete with Trujillo and Sheppard in their search for the planet. Confirming the existence of a celestial body can take up to five years. If discovered, the object could become the ninth planet in the solar system. Previously, the search for Planet X in the Solar System led scientists to the discovery of Neptune (in 1864) and Pluto (in 1930). There is little doubt that the existence of Planet Nine will be confirmed.

The discovery was announced by scientists at the California Institute of Technology. No one has yet seen the new object through a telescope. As Michael Brown and Konstantin Batygin assure, the planet was discovered by analyzing data on the gravitational disturbance it exerts on other celestial bodies. It has not yet been given a name, but scientists have been able to determine various parameters. It weighs 10 times more than Earth. The chemical composition of the new planet resembles two gas giants - Uranus and Neptune. By the way, it is similar to Neptune in size, and is located even further from the sun than Pluto, which, due to its modest dimensions, lost its planetary status. Confirming the existence of a celestial body will take five years. Scientists have reserved time at a Japanese observatory in Hawaii. The probability that their discovery is wrong is 0.007 percent. The new planet, if the discovery is recognized, will become the ninth in the solar system.

The solar system appears to have a new ninth planet. Today, two scientists announced evidence that a body nearly the size of Neptune-but as yet unseen-orbits the sun every 15,000 years. During the solar system’s infancy 4.5 billion years ago, they say, the giant planet was knocked out of the planet-forming region near the sun. Slowed down by gas, the planet settled into a distant elliptical orbit, where it still lurks today.

The claim is the strongest yet in the centuries-long search for a “Planet X” beyond Neptune. The quest has been plagued by far-fetched claims and even outright quackery. But the new evidence comes from a pair of respected planetary scientists, Konstantin Batygin and Mike Brown of the California Institute of Technology (Caltech) in Pasadena, who prepared for the inevitable skepticism with detailed analyzes of the orbits of other distant objects and months of computer simulations. “If you say, ‘We have evidence for Planet X,’ almost any astronomer will say, ‘This again? These guys are clearly crazy.’ I would, too,” Brown says. “Why is this different? This is different because this time we’re right.”

LANCE HAYASHIDA/CALTECH

Outside scientists say their calculations stack up and express a mixture of caution and excitement about the result. “I could not imagine a bigger deal if—and of course that’s a boldface ‘if’—if it turns out to be right,” says Gregory Laughlin, a planetary scientist at the University of California (UC), Santa Cruz. "What's thrilling about it is detectable."

Batygin and Brown inferred its presence from the peculiar clustering of six previously known objects that orbit beyond Neptune. They say there’s only a 0.007% chance, or about one in 15,000, that the clustering could be a coincidence. Instead, they say, a planet with the mass of 10 Earths has shepherded the six objects into their strange elliptical orbits, tilted out of the plane of the solar system.

The orbit of the inferred planet is similarly tilted, as well as stretched to distances that will explode previous conceptions of the solar system. Its closest approach to the sun is seven times farther than Neptune, or 200 astronomical units (AUs). (An AU is the distance between Earth and the sun, about 150 million kilometers.) And Planet X could roam as far as 600 to 1200 AU, well beyond the Kuiper belt, the region of small icy worlds that begins at Neptune's edge about 30 AU.

If Planet X is out there, Brown and Batygin say, astronomers ought to find more objects in telltale orbits, shaped by the pull of the hidden giant. But Brown knows that no one will really believe in the discovery until Planet X itself appears within a telescope viewfinder. “Until there’s a direct detection, it’s a hypothesis—even a potentially very good hypothesis,” he says. The team has time on the one large telescope in Hawaii that is suited for the search, and they hope other astronomers will join in the hunt.

Batygin and Brown published the result today in The Astronomical Journal. Alessandro Morbidelli, a planetary dynamicist at the Nice Observatory in France, performed the peer review for the paper. In a statement, he says Batygin and Brown made a “very solid argument” and that he is “quite convinced by the existence of a distant planet.”

Championing a new ninth planet is an ironic role for Brown; he is better known as a planet slayer. His 2005 discovery of Eris, a remote icy world nearly the same size as Pluto, revealed that what was seen as the outermost planet was just one of many worlds in the Kuiper belt. Astronomers promptly reclassified Pluto as a dwarf planet-a saga Brown recounted in his book How I Killed Pluto.

Now, he has joined the centuries-old search for new planets. His method-inferring the existence of Planet X from its ghostly gravitational effects-has a respectable track record. In 1846, for example, the French mathematician Urbain Le Verrier predicted the existence of a giant planet from irregularities in the orbit of Uranus. Astronomers at the Berlin Observatory found the new planet, Neptune, where it was supposed to be, sparking a media sensation.

Remaining hiccups in Uranus’s orbit led scientists to think that there might yet be one more planet, and in 1906 Percival Lowell, a wealthy tycoon, began the search for what he called “Planet X” at his new observatory in Flagstaff, Arizona. In 1930, Pluto turned up-but it was far too small to tug meaningfully on Uranus. More than half a century later, new calculations based on measurements by the Voyager spacecraft revealed that the orbits of Uranus and Neptune were just fine on their own: No Planet X was needed.

Yet the allure of Planet X persisted. In the 1980s, for example, researchers proposed that an unseen brown dwarf star could cause periodic extinctions on Earth by triggering fusillades of comets. In the 1990s, scientists invoked a Jupiter-sized planet at the solar system’s edge to explain the origin of certain oddball comets. Just last month, researchers claimed to have detected the faint microwave glow of an outsized rocky planet some 300 AU away, using an array of telescope dishes in Chile called the Atacama Large Millimeter Array (ALMA). (Brown was one of many skeptics, noting that ALMA’s narrow field of view made the chances of finding such an object vanishingly slim.)

Brown got his first inkling of his current quarry in 2003, when he led a team that found Sedna, an object a bit smaller than both Eris and Pluto. Sedna’s odd, far-flung orbit made it the most distant known object in the solar system at the time. Its perihelion, or closest point to the sun, lay at 76 AU, beyond the Kuiper belt and far outside the influence of Neptune’s gravity. The implication was clear: Something massive, well beyond Neptune, must have pulled Sedna into its distant orbit.

(DATA)JPL; BATYGIN AND BROWN/CALTECH; (DIAGRAM) A. CUADRA/ SCIENCE

That something didn’t have to be a planet. Sedna’s gravitational nudge could have come from a passing star, or from one of the many other stellar nurses that surrounded the nascent sun at the time of the solar system’s formation.

Since then, a handful of other icy objects have turned up in similar orbits. By combining Sedna with five other weirdos, Brown says he has ruled out stars as the unseen influence: Only a planet could explain such strange orbits. Of his three major discoveries-Eris, Sedna, and now, potentially, Planet X-Brown says the last is the most sensational. “Killing Pluto was fun. Finding Sedna was scientifically interesting,” he says. “But this one, this is head and shoulders above everything else.”

Brown and Batygin were nearly beaten to the punch. For years, Sedna was a lone clue to a perturbation from beyond Neptune. Then, in 2014, Scott Sheppard and Chad Trujillo (a former graduate student of Brown’s) published a paper describing the discovery of VP113, another object that never comes close to the sun. Sheppard, of the Carnegie Institution for Science in Washington, D.C., and Trujillo, of the Gemini Observatory in Hawaii, were well aware of the implications. They began to examine the orbits of the two objects along with 10 other oddballs. They noticed that, at perihelion, all came very near the plane of solar system in which Earth orbits, called the ecliptic. In a paper, Sheppard and Trujillo pointed out the peculiar clumping and raised the possibility that a distant large planet had herded the objects near the ecliptic. But they didn’t press the result any further.

Later that year, at Caltech, Batygin and Brown began discussing the results. Plotting the orbits of the distant objects, Batygin says, they realized that the pattern that Sheppard and Trujillo had noticed “was only half of the story.” Not only were the objects near the ecliptic at perihelia, but their perihelia were physically clustered in space (see diagram, above).

For the next year, the duo secretly discussed the pattern and what it meant. It was an easy relationship, and their skills complemented each other. Batygin, a 29-year-old whiz kid computer modeler, went to college at UC Santa Cruz for the beach and the chance to play in a rock band. But he made his mark there by modeling the fate of the solar system over billions of years, showing that, in rare cases, it was unstable: Mercury may plunge into the sun or collide with Venus. “It was an amazing achievement for an undergraduate,” says Laughlin, who worked with him at the time.

Brown, 50, is the observational astronomer, with a flair for dramatic discoveries and the confidence to match. He wears shorts and sandals to work, puts his feet up on his desk, and has a breeziness that masks intensity and ambition. He has a program all set to sift for Planet X in data from a major telescope the moment they become publicly available later this year.

Their offices are a few doors down from each other. “My couch is nicer, so we tend to talk more in my office,” Batygin says. "We tend to look more at data in Mike's." They even became exercise buddies, and discussed their ideas while waiting to get in the water at a Los Angeles, California, triathlon in the spring of 2015.

First, they won the dozen objects studied by Sheppard and Trujillo to the six most distant-discovered by six different surveys on six different telescopes. That made it less likely that the clumping might be due to an observation bias such as pointing a telescope at a particular part of the sky.

Batygin began seeding his solar system models with Planet X’s of various sizes and orbits, to see which version best explained the objects’ paths. Some of the computer runs took months. A favored size for Planet X emerged-between five and 15 Earth masses-as well as a preferred orbit: antialigned in space from the six small objects, so that its perihelion is in the same direction as the six objects' aphelion, or farthest point from the sun. The orbits of the six cross that of Planet X, but not when the big bully is nearby and could disrupt them. The final epiphany came 2 months ago, when Batygin’s simulations showed that Planet X should also sculpt the orbits of objects that swoop into the solar system from above and below, nearly orthogonal to the ecliptic. "It sparked this memory," Brown says. "I had seen these objects before." It turns out that, since 2002, five of these highly inclined Kuiper belt objects have been discovered, and their origins are largely unexplained. “Not only are they there, but they are in exactly the places we predicted,” Brown says. “That is when I realized that this is not just an interesting and good idea—this is actually real.”

Sheppard, who with Trujillo had also suspected an unseen planet, says Batygin and Brown “took our result to the next level. …They got deep into the dynamics, something that Chad and I aren’t really good with. That’s why I think this is exciting.”

Others, like planetary scientist Dave Jewitt, who discovered the Kuiper belt, are more cautious. The 0.007% chance that the clustering of the six objects is coincidental gives the planet claim a statistical significance of 3.8 sigma-beyond the 3-sigma threshold typically required to be taken seriously, but short of the 5 sigma that is sometimes used in fields like particle physics That worries Jewitt, who has seen plenty of 3-sigma results disappear before. By reducing the dozen objects examined by Sheppard and Trujillo to six for their analysis, Batygin and Brown weakened their claim, he says. “I worry that the finding of a single new object that is not in the group would destroy the whole edifice,” says Jewitt, who is at UC Los Angeles. "It's a game of sticks with only six sticks."

(IMAGES) WIKIMEDIA COMMONS; NASA/JPL-CALTECH; A. CUADRA/ SCIENCE ; NASA/JHUAPL/SWRI; (DIAGRAM) A. CUADRA/ SCIENCE

At first blush, another potential problem comes from NASA’s Widefield Infrared Survey Explorer (WISE), a satellite that completed an all-sky survey looking for the heat of brown dwarfs-or giant planets. It ruled out the existence of a Saturn-or-larger planet as far out as 10,000 AU, according to a 2013 study by Kevin Luhman, an astronomer at Pennsylvania State University, University Park. But Luhman notes that if Planet X is Neptune-sized or smaller, as Batygin and Brown say, WISE would have missed it. He says there is a slim chance of detection in another WISE data set at longer wavelengths-sensitive to cooler radiation-which was collected for 20% of the sky. Luhman is now analyzing those data.

Even if Batygin and Brown can convince other astronomers that Planet X exists, they face another challenge: explaining how it ended up so far from the sun. At such distances, the protoplanetary disk of dust and gas was likely to have been too thin to fuel planet growth. And even if Planet X did get a foothold as a planetesimal, it would have moved too slowly in its vast, lazy orbit to hoover up enough material to become a giant.

Instead, Batygin and Brown propose that Planet X formed much closer to the sun, alongside Jupiter, Saturn, Uranus, and Neptune. Computer models have shown that the early solar system was a tumultuous billiards table, with dozens or even hundreds of planetary building blocks the size of Earth bouncing around. Another embryonic giant planet could easily have formed there, only to be booted outward by a gravitational kick from another gas giant.

It’s harder to explain why Planet X didn’t either loop back around to where it started or leave the solar system entirely. But Batygin says that residual gas in the protoplanetary disk might have exerted enough drag to slow the planet just enough for it to settle into a distant orbit and remain in the solar system. That could have happened if the ejection took place when the solar system was between 3 million and 10 million years old, he says, before all the gas in the disk was lost into space.

Hal Levison, a planetary dynamicist at the Southwest Research Institute in Boulder, Colorado, agrees that something has to be creating the orbital alignment Batygin and Brown have detected. But he says the origin story they have developed for Planet X and their special pleading for a gas-slowed ejection add up to “a low-probability event.” Other researchers are more positive. The proposed scenario is plausible, Laughlin says. “Usually things like this are wrong, but I’m really excited about this one,” he says. "It's better than a coin flip."

All this means that Planet X will remain in limbo until it is actually found.

Astronomers have some good ideas about where to look, but spotting the new planet won’t be easy. Because objects in highly elliptical orbits move fastest when they are close to the sun, Planet X spends very little time at 200 AU. And if it were there right now, Brown says, it would be so bright that astronomers would probably have already spotted it.

Instead, Planet X is likely to spend most of its time near aphelion, slowly trotting along at distances between 600 and 1200 AU. Most telescopes are capable of seeing a dim object at such distances, such as the Hubble Space Telescope or the 10-meter Keck telescopes in Hawaii, have extremely tiny fields of view. It would be like looking for a needle in a haystack by peering through a drinking straw.

One telescope can help: Subaru, an 8-meter telescope in Hawaii that is owned by Japan. It has enough light-gathering area to detect such a faint object, coupled with a huge field of view-75 times larger than that of a Keck telescope. That allows astronomers to scan large swaths of the sky each night. Batygin and Brown are using Subaru to look for Planet X-and they are coordinating their efforts with their early competitors, Sheppard and Trujillo, who have also joined the hunt with Subaru. Brown says it will take about 5 years for the two teams to search most of the area where Planet X could be lurking.

Subaru Telescope, NAOJ

If the search pans out, what should the new member of the sun’s family be called? Brown says it’s too early to worry about that and scrupulously avoids offering up suggestions. For now, he and Batygin are calling it Planet Nine (and, for the past year, informally, Planet Phattie-1990s slang for “cool”). Brown notes that neither Uranus nor Neptune-the two planets discovered in modern times-ended up being named by their discoverers, and he thinks that that’s probably a good thing. It’s bigger than any one person, he says: “It’s kind of like finding a new continent on Earth.”

He is sure, however, that Planet X-unlike Pluto-deserves to be called a planet. Something the size of Neptune in the solar system? Don't even ask. “No one would argue this one, not even me.”