New evidence suggests a ninth planet lurking at the edge of the solar system
Astronomers say they have evidence of a ninth planet in our solar system. Here's what they say they know about it. (Joel Achenbach,Gillian Brockell/The Washington Post)
By Joel Achenbach and Rachel Feltman-January 20
Astronomers at the California Institute of Technology announced Wednesdaythat they have found new evidence of a giant icy planet lurking in the darkness of our solar system far beyond the orbit of Pluto.
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Astronomers say they have evidence of a ninth planet in our solar system. Here's what they say they know about it. (Joel Achenbach,Gillian Brockell/The Washington Post)
By Joel Achenbach and Rachel Feltman-January 20
Astronomers at the California Institute of Technology announced Wednesdaythat they have found new evidence of a giant icy planet lurking in the darkness of our solar system far beyond the orbit of Pluto.
They are calling it "Planet Nine."
Their paper, published in the Astronomical Journal, describes the planet as about five to 10 times as massive as the Earth. But the authors, astronomersMichael Brown and Konstantin Batygin, have not observed the planet directly.
Instead, they have inferred its existence from the motion of recently discovered dwarf planets and other small objects in the outer solar system. Those smaller bodies have orbits that appear to be influenced by the gravity of a hidden planet – a "massive perturber." The astronomers suggest it might have been flung into deep space long ago by the gravitational force of Jupiter or Saturn.
Telescopes on at least two continents are searching for the object, which on average is 20 times farther away than the eighth planet, Neptune. If "Planet Nine" exists, it's big. Its estimated mass would make it about two to four times the diameter of the Earth, distinguishing it as the fifth-largest planet after Jupiter, Saturn, Uranus and Neptune. But at such extreme distances, it would reflect so little sunlight that it could evade even the most powerful telescopes.
Confirmation of its existence would reconfigure the models of the solar system. Pluto, discovered in 1930, spent three-quarters of a century as the iconic ninth planet. Then, a decade ago, Pluto received a controversial demotion, in large part because of Brown.
His observations of the outer solar system identified many small worlds there – some close to the size of Pluto –and prompted the International Astronomical Union to reconsider the definition of a planet. The IAU voted to change Pluto's classification to "dwarf planet," a decision mocked repeatedly last summer when NASA's New Horizons probe flew past Plutoand revealed a world with an atmosphere, weather and a volatile and dynamically reworked surface.
