Scientists may have discovered the solar system's 10th planet, more than 3 billion kilometers farther away from the sun than Pluto.
NASA is set to make an official announcement later Monday U.S. time.
The object -- about 10 billion kilometers from Earth -- has been given the provisional name of Sedna after the Inuit goddess of the sea.
Dr. Michael Brown of the California Institute of Technology and his team of astronomers, using the recently launched high power Spitzer Space Telescope, found Sedna during an ongoing three-year outer solar system project.
The Tenagra Observatory in Arizona was used to provide a verifying second set of measurements for the object.
Sedna is the largest object to be found circling the sun since Pluto was discovered in 1930.
The discovery has also sparked debate over what constitutes a planet.
Initial details indicated Sedna to be made of ice and rock and to be of a smaller size than Pluto, with a diameter of almost 2,000 km.
Many astronomers say Pluto, with a diameter of 2,300 km, is too small to be a termed a planet and is actually just one of many minor objects in the outer reaches of the solar system.
But those who argue Pluto is a planet are likely to push the claim for Sedna to become the 10th planet in the solar system.
Dr. Brown will present the discovery during a NASA briefing on Monday at 1:00 p.m. EST (1800 GMT).
The Spitzer Space Telescope was launched in August last year and is the fourth of NASA's Great Observatories. The program also includes the Hubble Space Telescope.