New 'Planet 9' May Be Next to Join Our Solar System

Jan 20, 2016

Michael Brown doesn't care how much you love Pluto. He loves it too, but that didn't stop him from leading the charge in 2006 to strip it of its "planet" designation and bust it down to a mere dwarf planet. But now, the Caltech astronomer is making amends in a big way: along with Caltech planetary scientist Konstantin Batygin, he has just released a paper announcing the highly likely discovery of a new planet to replace Pluto—and no one's ever going to be able to demote this one.

"The existence of another planet has been spoken about 100 times before," Brown says. "But this is the first time in 150 years that we can say we have convincing evidence that the census of the solar system is incomplete."

The discovery of the world that Brown and Batygin refer to in The Astronomical Journal simply as "Planet 9" began in 2003, with the discovery of a far more modest object named Sedna. A dwarf planet even smaller than Pluto, Sedna is a Kuiper Belt object (KBO), like Pluto one of a vast band of icy, rocky objects that surround the solar system beyond the orbit of Neptune. Brown was part of the team that found Sedna too, and if anything made the new world remarkable, it was its extreme distance from the sun—one that has it completing a single orbit in 11,400 years, compared to Pluto's 248.

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But something else was strange about Sedna as well—or at least about the company it keeps. In the years that followed, astronomers discovered five other KBOs whose closest approach to the sun (or perihelion) matches Sedna's almost perfectly, both in distance and in the angle of the orbit relative to the horizon of the solar system.

This couldn't be a coincidence. The matching perihelia have only a 0.7% likelihood of occurring by chance; the matching angles have only a 1% chance. The double match among all six objects factors out to a vanishingly small .007% likelihood of being random. "It was very exciting to notice this collection of objects in this super obscure arrangement," says Brown. "The orbits are physically lined up in space."

If it wasn't chance that was behind such a tidy clustering, it had to be gravity—the influence of a passing object that herds the KBOs together, in the same way Saturn's moons influence the positioning of particles in the rings. Using mathematical modeling and computer simulations, Brown and Batygin concluded that Sedna and the other members of its flock must be herded by an as-yet-unobserved planet with about ten times the mass of Earth, circling the sun at an average distance 20 times greater than that of Neptune—making one orbit every 20,000 years. A body with different mass or a different distance simply couldn't explain the behavior of the six KBOs.

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How Planet 9 found itself in so remote a place is unclear. It's unlikely that it formed in situ, essentially coalescing out of the primordial cloud of dust and gas that formed the rest of the solar system, since there probably wouldn't have been enough raw material to form so big a world out that far. Rather, the new planet might have accreted closer in like the other planets, and then been ejected by their gravitational forces.

"Planet 9 is part of the sun's family," says Brown. "The birth cluster turned it around so it was placed in a distant orbit. It has been there all along and has witnessed the development of the solar system from afar."

Now, Brown and Batygin need earthbound witnesses to confirm that Planet 9 exists. Just as Neptune was originally inferred by wobbles spotted in Uranus's orbit, the existence of Planet 9 can be inferred by the aligned KBOs. But without a verifiable observation, it's still a theoretical discovery. The pair are hoping to crowdsource that job, getting as many telescopes looking as possible across the globe. They've made the challenge easier by mapping Planet 9's orbit; now skywatchers have to pinpoint where it is on that very long path.

Pluto photo from four images from New Horizons' Long Range Reconnaissance Imager (LORRI) combined with color data from the Ralph instrument
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This photo of Pluto was made during the New Horizons spacecraft's historic flyby of the dwarf planet in July 2015. New Horizons is now sailing into the Kuiper Belt for a rendezvous with another small world.NASA/Reuters
Pluto photo from four images from New Horizons' Long Range Reconnaissance Imager (LORRI) combined with color data from the Ralph instrument
This nebula named "Thor's Helmet" is powered by a central "Wolf Rayet" star whose explosive tantrums blow huge bubbles of gas and make them glow like neon. This star is easily 20 times the mass of the Sun and located 15,000 light years away. Eventually the star's instability will lead it to explode as a supernova. The photo was captured at the Mount Lemmon SkyCenter in Arizona and released on Jan. 3, 2015.
Space Station Flies Over Super Typhoon Maysak: Typhoon Maysak strengthened into a super typhoon on March 31, reaching Category 5 hurricane status on the Saffir-Simpson Wind Scale. NASA Astronaut Terry Virts captured this image while flying over the weather system on board the International Space Station. Commenting on the storm, Virts wrote, "The eye of #Maysak typhoon really stands out early in the morning with the shadow being cast deep into the vortex." His ESA crewmate on station also viewed the storm and wrote, "Commands respect even from #space: we just flew over typhoon #Maysak."
The total solar eclipse at Svalbard, Norway, on March 20, 2015. A partial solar eclipse was seen in Europe, northern and eastern Asia and northern and western Africa.
Pluto's haze layer shows its blue color in this picture taken by the New Horizons Ralph/Multispectral Visible Imaging Camera (MVIC). The high-altitude haze is thought to be similar in nature to that seen at Saturn’s moon Titan. The source of both hazes likely involves sunlight-initiated chemical reactions of nitrogen and methane, leading to relatively small, soot-like particles (called tholins) that grow as they settle toward the surface. This image was generated by software that combines information from blue, red and near-infrared images to replicate the color a human eye would perceive as closely as possible.More: New Horizons Finds Blue Skies and Water Ice on PlutoImage Credit: NASA/JHUAPL/SwRILast Updated: Oct. 8, 2015Editor: Sarah Loff
A NASA camera on the Deep Space Climate Observatory (DSCOVR) satellite captures the entire sunlit side of Earth from one million miles away on July 6, 2015.
Orbital Sciences Antares Launch
The stark transition between radiating sand dunes and an old volcanic flow on the surface of Earth was captured by astronaut Kjell Lindgren aboard the International Space Station, on Dec. 5 2015.
The Lagoon Nebula, a bright cloud of dust and gas 4,000 light years away and 40 light years across, glows brilliantly due to hot energetic young stars forming within. It can even be glimpsed with the unaided eye under dark skies away from city lights. The photo was captured at the Mount Lemmon SkyCenter in Arizona and released on July 15, 2015.
Circinus X-1 is an X-ray binary star known for its erratic variability can be seen in this photo released on June 23, 2015. Within the system, a dense neutron star, the collapsed remnant of a supernova explosion, orbits with a more ordinary stellar companion Circinus X-1 30,700 light-years away.
The spectacular cosmic pairing of the star Hen 2-427 and the nebula M1-67 was captured by the Hubble Space Telescope, released on Aug. 21, 2015. The twin formation is located in the constellation of Sagittarius, 15,000 light-years away. The star shines brightly at the very center of the image. Surrounding it are hot clumps of gas being ejected into space at over 93,000 mph.
A meteor from the Perseid Meteor shower can be seen in the upper left corner in this long exposure image taken as a wildfire burned in Lake and Napa Counties near the town of Clearlake, Calif. on Aug. 12, 2015.
The once in a generation supermoon total lunar eclipse viewed from Glastonbury, England, on Sept. 28, 2015.
This composite image made from five frames shows the International Space Station, with a crew of nine onboard, in silhouette as it transits the sun at roughly five miles per second, Sunday, Sept. 6, 2015, Shenandoah National Park, Front Royal, VA. Onboard are; NASA astronauts Scott Kelly and Kjell Lindgren: Russian Cosmonauts Gennady Padalka, Mikhail Kornienko, Oleg Kononenko, Sergey Volkov, Japanese astronaut Kimiya Yui, Danish Astronaut Andreas Mogensen, and Kazakhstan Cosmonaut Aidyn Aimbetov. Photo Credit: (NASA/Bill Ingalls)
The Soyuz TMA-14M spacecraft is seen as it lands with Expedition 42 commander Barry Wilmore of NASA, Alexander Samokutyaev of the Russian Federal Space Agency (Roscosmos) and Elena Serova of Roscosmos near the town of Zhezkazgan, Kazakhstan on Thursday, March 12, 2015. NASA Astronaut Wilmore, Russian Cosmonauts Samokutyaev and Serova are returning after almost six months onboard the International Space Station where they served as members of the Expedition 41 and 42 crews. Photo Credit: (NASA/Bill Ingalls)
Astronaut Scott Kelly, re-entering the International Space Station after his spacewalk on Oct. 29, 2015.
Kjell Lindgren captures on last stunning view of the milkway before his return to Earth on Dec. 10, 2015.
A handout photo of the lift off of a 'Vega' rocket carrying the European Space Agency ESA's 'LISA Pathfinder' spacecraft, in Kourou, French Guiana on Dec. 3 2015.
A perigee full moon, or supermoon, is seen above the Washington Monument during a total lunar eclipse on Sunday, September 27, 2015, in Washington, DC. The combination of a supermoon and total lunar eclipse last occurred in 1982 and will not happen again until 2033. Photo Credit: (NASA/Aubrey Gemignani)
Charon, the largest moon of Pluto, captured by the New Horizons spacecraft on July 13, 2015 from a distance of 290,000 miles.
The Soyuz TMA-15M spacecraft is seen as it lands with Expedition 43 commander Terry Virts of NASA, cosmonaut Anton Shkaplerov of the Russian Federal Space Agency (Roscosmos), and Italian astronaut Samantha Cristoforetti from European Space Agency (ESA) near the town of Zhezkazgan, Kazakhstan on June 11, 2015.
Volunteers using the web-based Milky Way Project brought star-forming features nicknamed "yellowballs" to the attention of researchers, who later showed that they are a phase of massive star formation.
New Horizons scientists made this false color image of Pluto using a technique called principal component analysis to highlight the many subtle color differences between Pluto's distinct regions. The image data were collected by the spacecraft’s Ralph/MVIC color camera on July 14 at 11:11 AM UTC, from a range of 22,000 miles (35,000 kilometers). This image was presented by Will Grundy of the New Horizons’ surface composition team on Nov. 9 at the Division for Planetary Sciences (DPS) meeting of the American Astronomical Society (AAS) in National Harbor, Maryland.Image Credit: NASA/JHUAPL/SwRILast Updated: Nov. 12, 2015Editor: Tricia Talbert
The Twin Jet Nebula, or PN M2-9, is a striking example of a bipolar planetary nebula, formed when the central object is not a single star, but a binary system. An earlier image of the Twin Jet Nebula using data gathered by Hubble’s Wide Field Planetary Camera 2 was released in 1997. This newer version released on Aug. 26, 2015 incorporates more recent observations from the telescope’s Space Telescope Imaging Spectrograph.
The brilliant palette of Africa captured by astronaut Scott Kelly aboard the International Space Station on July 22, 2015.
Aurora Borealis seen over the Brecon Beacons, Wales, Britain - 17 Mar 2015
Blood moon over Pike Peak Colorado Springs
NASA's Curiosity Mars rover recorded this view of the sun setting at the close of the mission's 956th Martian day, or sol (April 15, 2015), from the rover's location in Gale Crater.This was the first sunset observed in color by Curiosity. The image comes from the left-eye camera of the rover's Mast Camera (Mastcam). The color has been calibrated and white-balanced to remove camera artifacts. Mastcam sees color very similarly to what human eyes see, although it is actually a little less sensitive to blue than people are.Dust in the Martian atmosphere has fine particles that permit blue light to penetrate the atmosphere more efficiently than longer-wavelength colors. That causes the blue colors in the mixed light coming from the sun to stay closer to sun's part of the sky, compared to the wider scattering of yellow and red colors. The effect is most pronounced near sunset, when light from the sun passes through a longer path in the atmosphere than it does at mid-day.Malin Space Science Systems, San Diego, built and operates the rover's Mastcam. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover.
The rippled surface of the first Martian sand dune ever studied up close can been seen is this photo taken on Nov. 27, 2015 by NASA Mars Rover Curiosity. The dunes close to Curiosity's current location are part of "Bagnold Dunes," a band along the northwestern flank of Mount Sharp inside the Gale Crater.
A 3-D computer model (a digital terrain map) of Hale Crater on Mars based on stereo information from two HiRISE observations showing dark, narrow streaks on the Martian slopes that are inferred to be formed by seasonal flow of water on contemporary Mars was released on Sept. 28, 2015.
Astronaut Scott Kelly captured this image of the Bahamas from the International Space Station on July 19, 2015.
An image of the wildfires in the Northwest taken from the International Space Station released on Aug. 17, 2015.
Sand dunes sculpted by wind, captured by astronaut Kjell Lindgren, aboard the International Space Station on Dec. 8 2015.
This photo shows the new mountain range discovered by NASA’s New Horizons spacecraft on July 14, 2015 on Pluto, in a heart-shaped region named Tombaugh Regio.
NASA's Cassini spacecraft captured this parting view showing the rough and icy crescent of Saturn's moon Dione following the spacecraft's last close flyby of the moon on Aug. 17, 2015. Five visible light, narrow-angle camera images were combined to create this mosaic view. The view was acquired at distances ranging from approximately 37,000 miles to 47,000 miles from Dione and at a sun-Dione-spacecraft angle of 145 degrees.
Comet 67P, photographed by the Rosetta Orbiter from a distance of 79 miles on Nov. 22, 2015.
Saturn's icy moon Enceladus and a small stretch of Saturn's rings, as seen by the Cassini spacecraft on July 29, 2015.
This image released on April 6, 2015, shows the centre of the globular cluster Messier 22, also known as M22, as observed by the Hubble Space Telescope. Globular clusters are spherical collections of densely packed stars, relics of the early years of the Universe, with ages of typically 12 to 13 billion years.
New view of the Pillars of Creation — infrared
Moonlight over Italy, as captured by astronaut Scott Kelly aboard the International Space Station on Sept. 23, 2015.
New view of the Pillars of Creation — visible
A Total Lunar Eclipse Spawns Blood Supermoon
Three of Saturn’s moons (Titan, Mimas, and Rhea) captured in a single photo
Spiral galaxies are delicate and subtle things. Even when captured in large telescopes- more striking than their beauty is the concept that they are so large and so far away. NGC 488 in particular is around 90 MILLION light years away and certainly looks better than its name might suggest.
This high-resolution image captured by NASA’s New Horizons spacecraft combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). Pluto’s surface shows a remarkable range of subtle colors, enhanced in this view to a rainbow of pale blues, yellows, oranges, and deep reds. The bright expanse is the western lobe of the “heart,” informally known as Tombaugh Regio. The lobe, informally called Sputnik Planum, has been found to be rich in nitrogen, carbon monoxide, and methane ices.Credit: NASA/JHUAPL/SwRIView Image FeatureLast Updated: Oct. 15, 2015Editor: Tricia Talbert
A brilliant aurora as seen from the International Space Station on June 27, 2015.
Brief Outburst The Sun blew out a coronal mass ejection along with part of a solar filament over a three-hour period (Feb. 24, 2015). While some of the strands fell back into the Sun, a substantial part raced into space in a bright cloud of particles (as observed by the SOHO spacecraft). The activity was captured in a wavelength of extreme ultraviolet light. Because this occurred way over near the edge of the Sun, it was unlikely to have any effect on Earth.https://www.flickr.com/photos/gsfc/16760026566/
Astronaut Scott Kelly captures this striking view of earth on Asteroid Day on June 30, 2015.
There seems to be more green in the #African desert lately. This is a good thing. #YearInSpace
An image captured on Halloween, Oct. 31, 2015, from the International Space Station by astronaut Scott Kelly, who described what he saw as "ghostly and dark but beautiful too."
The artificial Palm and World Islands off the coast of Dubai as photographed by astronaut Kjell Lindgren aboard the International Space Station on Nov. 20, 2015.
This image taken by NASA's Mars Reconnaissance Orbiter in May 2015 shows Acidalia Planitia, a location on the red planet that was recreated in the film "The Martian."
The Saturnian moon Dione hangs in front of Saturn and its icy rings in this view, captured during the Cassini spacecraft's final close flyby of the icy moon on Aug. 17, 2015.
The Saturnian moon Tethys, dwarfed by Saturn itself and its rings, appears as an elegant crescent in this image taken by NASA's Cassini Spacecraft on on Aug. 18, 2015.
The moon shines during the Spanish league football match FC Barcelona vs. Malaga CF at the Camp Nou stadium in Barcelona on Aug. 29, 2015.
This photo of Pluto was made during the New Horizons spacecraft's historic flyby of the dwarf planet in July 2015. New Horizons is now sailing into the Kuiper Belt for a rendezvous
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The name of the planet will be crowd-sourced too, if the researchers get their way — as opposed to being proposed by the discoverer and then approved by the International Astronomical Union (IAU), which is the usual way of doing things. Brown's and Batygin's personal name preference is "George," a hat-tip to British astronomer William Herschel, who discovered Uranus and wanted to name it Georgium Sidus (the Georgian Planet) after King George III. That might be a hard sell to the IAU—to say nothing of nearly all other stargazers, who tend to like a little more lyricism in their cosmos.

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Whatever the planet is eventually called, its very existence will do more than simply add to the population of the solar system. It will also add to its mystery. Even in our tiny corner of the universe, it seems, there can still be big surprises lurking.

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