"The smaller objects can lead us to the much bigger planet we think exists out there," astronomer Scott Sheppard, with the Carnegie Institute for Science in Washington DC, said in a statement.
"The more we discover, the better we will be able to understand what is going on in the outer solar system," he added.
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In 2014 Sheppard and colleague Chadwick Trujillo, with Northern Arizona University, discovered several extreme trans-Neptunian objects with similar orbital angles, raising the prospect that the bodies are being gravitationally influenced by an undiscovered, ninth planet more than 200 times farther away from the sun than Earth.
Calculations show the mystery planet would be at least several times bigger than Earth, and possibly as big as Neptune, which is about 17 times more massive than Earth.
So far, Sheppard and colleagues have scoured about 10 percent of the sky looking for objects beyond Neptune and the Kuiper Belt using the 6.5-meter Magellan Telescopes in Chile, NOAO's 4-meter Blanco telescope in Chile and the 8-meter Subaru telescope in Hawaii, among others.
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A paper about the newly found trans-Neptunian objects will be published in an upcoming edition of The Astronomical Journal.
The Minor Planet center is a NASA-funded international organization based at the Smithsonian Astrophysical Observatory in Cambridge, Mass., that is responsible for the designation of minor bodies in the solar system, including minor planets, comets and natural satellites.