US scientists say they have evidence of a ninth planet lurking in the outskirts of the solar system. The researchers have only calculated its existence theoretically and physical proof is still needed.
Image: Reuters/R. Hurt/Caltech/IPAC/Handout via Reuters
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Researchers Konstantin Batygin and Mike Brown of the California Institute of Technology (Caltech) said they calculated the planet's presence through mathematical modeling and computer simulation.
A 'true' planet
"The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of the earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun," Caltech said on its website.
Mike Brown said only two true planets had been discovered since ancient times and this would be the third. "It's a pretty substantial chunk of our solar system that's still out there to be found," he added.
The quest for Planet Nine
Batygin and Brown revealed their findings in the latest issue of the "Astronomical Journal" and showed how Planet Nine helped explain mysterious features of the Kuiper belt- icy objects and debris beyond Neptune. Planet Nine's existence could also mean that the early solar system was made of five planetary cores instead of four.
"Nature" correspondent Alexandra Witze tweeted this explanatory diagram:
"Scientists have long believed that the early solar system began with four planetary cores that went on to grab all of the gas around them, forming the four gas planets - Jupiter, Saturn, Uranus and Neptune," Caltech's website explained. But for astronomer Mike Brown, "Planet Nine could represent that fifth core, and if it got too close to Jupiter or Saturn, it could have been ejected into its distant eccentric orbit."
Batygin and Brown were now refining their simulations, while Brown and his other colleagues would scout the skies for Planet Nine. If the planet were in the farthest part of its orbit, the world's largest telescopes - at the W.M. Keck Observatory and the Subaru Telescope in Mauna Kea in Hawaii would be needed to find it. If Planet Nine were anywhere in between, many telescopes could spot it, Brown said.
All's well with the solar system
For Batygin, one of the most exciting things about the finding was that Planet Nine "has been the most common type of planet out there." Its existence in the solar system makes us more "normal" in the universe, he said.
Astronomer Mike Brown, best known for demoting Pluto from a planet to the status of a dwarf planet said Planet Nine was an opportunity to rejoice again. Brown - who aptly calls himself "Pluto Killer" on Twitter - posted this message:
"All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found…Now we can go and find this planet and make the solar system have nine planets once again," he said.
Meet the planets
The first close-ups of Pluto awed the world this week. A couple of decades ago, photos of Venus or Saturn taken from space had a similar effect on scientists. Join DW on an interplanetary photo safari!
Image: Reuters/NASA/APL/SwRI/Handout
Our solar system
Depending on who you ask, there are eight or nine planets in our solar system - some experts still count Pluto, while the International Astronomical Union (IAU) took away its planetary status in 2006. People were still excited when NASA presented the first high-res images of Pluto this week. Its neighbors all had their portrait taken as early as the 1960s.
Mercury
The spacecraft Mariner 10 left for the planet closest to the Sun in 1973. It took this picture of Mercury's moon-like surface in March 1974. The planet's distance to the Sun varies between 28.5 million miles (46 kilometers) and 43.5 million miles (70 kilometers), because its orbit isn't a perfect circle. Scientists were surprised to discover that Mercury had a small magnetic field.
Image: picture-alliance/dpa/Nasa
Venus
Mariner 10 took this first close-up of Mercury's direct neighbor on February 5, 1974. The picture was color-enhanced by NASA to bring out Venus' cloudy atmosphere - the planet is perpetually blanketed by a thick veil of clouds rich in carbon dioxide. Mariner 10's journey to Venus was a rocky one: the spacecraft's high-gain antenna developed problems and a mechanical issue caused a large fuel-loss.
Image: picture-alliance/dpa/Nasa
Earth
The first full-on photo of our planet as seen from outer space was taken by Lunar Orbiter 1 in August 1966. That was three years before a human being had ever set foot on the Moon, which can be seen in the foreground of this picture as a shadow. The now-iconic photo was one of a series of pictures taken in preparation for the Apollo missions that would eventually put a human on the Moon.
Image: picture-alliance/dpa/Nasa/Loirp
Mars
This close-up of Earth's neighbor is the first picture ever taken of another planet by a spacecraft. Mariner 4 snapped it on July 15, 1965. Scientists who had expected to see lakes, valleys and mountains were disappointed - instead of an Earth-like planet, they were treated to craters similar to those on the Moon. The New York Times wrote: "Mars is probably a dead planet."
Image: picture-alliance/dpa
Jupiter
Spacecraft Pioneer 10 took the planet's first close-up from roughly 80,780 miles (130,000 kilometers) away on November 19, 1973. Jupiter is our solar system's largest planet. At its equator, Jupiter's diameter is a whopping 88,846 miles (142,984 kilometers). Its mass is two-and-a-half times larger than the masses of all other planets combined.
Image: picture-alliance/dpa/UPI
Saturn
This first shot of the ringed planet was taken on Pioneer 10's follow-up mission, Pioneer 11, on August 31, 1979. It was a perilous adventure: as the spacecraft flew through Saturn's outer rings, it almost crashed into one of two new moons it discovered. Visible at the upper left-hand corner in this photo is Saturn's moon Titan.
One of the first glimpses scientists got of Uranus was of its rings. Voyager 2 took this shot of them in 1986. Scientists had to remote-fix the spacecraft's camera for it to be able to photograph the planet with the coldest atmosphere in our solar system (as low as -366 degrees Fahrenheit or -221 degrees Celsius). The device had malfunctioned while Voyager 2 was passing Saturn.
Image: picture-alliance/dpa/Consolidated
Neptune
Voyager 2 also took the first picture of Neptune in August 1989. The planet has four cloud features that scientists know about. For those who don't count Pluto, Neptune is the planet in our solar system that's furthest away from the sun: at an average of 2.8 billion miles (4.5 billion kilometers), that distance is 30 times greater than the one between the Sun and Earth.
Image: picture-alliance/dpa
Pluto
The fact that Pluto is not officially a planet anymore didn't detract from the excitement scientists and lay-people all over the world experienced when NASA released this first close-up of the copper-colored (dwarf-) planet taken by New Horizons on July 13, 2015. The spacecraft traveled 3 billion miles (4.88 billion kilometers) to the solar system's farthest reaches for this shot.
