Pluto’s planet status is being debated based on new astronomical data, since its demotion in 2006 to a “dwarf planet” after the 2005 discovery of Eris, an icy body believed to be bigger.
The calculations show Pluto could in fact be the largest object in the outer solar system. But the measurements are close, according to National Geographic, with Eris coming in at 1,454 miles (2,340 km) across and Pluto at 1,456 miles (2,344 km) across.
However, the measurements were taken via ground-based and Earth-orbiting telescopes, which introduce a wide range of uncertainties due to the sheer distance of Pluto and Eris from Earth. Pluto is 39 times farther from the sun than the Earth, and Eris is more than twice as far away.
“The reports that Pluto is bigger than Eris all take the largest possible size of Pluto and the smallest size of Eris,” Caltech scientist Mike Brown, who discovered Eris but wasn’t involved in the new research, told National Geographic.
Brown says “we really don’t know” which of the two is bigger. He adds that Pluto remains a dwarf planet because there are similar large bodies in its vicinity—the Kuiper Belt—a flotilla of objects beyond Neptune’s orbit that includes Eris.
In 2006, the International Astronomical Union (IAU) provided the official definition of a planet: “A body that circles the sun without being some other object’s satellite, is large enough to be rounded by its own gravity ... and has ’cleared its neighborhood’ of most other orbiting bodies.”
But some astronomers believe this definition is fundamentally flawed.
“If you take the IAU’s definition strictly, no object in the solar system is a planet,” Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colo., told SPACE.com. “No object in the solar system has entirely cleared its zone.”
In Stern’s and some other astronomers’ opinion, a planet is any body that meets the IAU definition’s first two criteria, regardless of other bodies in the vicinity. This viewpoint defines Pluto as a planet and vindicates the swaths of Pluto enthusiasts who maintain it’s number nine.
The calculations show Pluto could in fact be the largest object in the outer solar system. But the measurements are close, according to National Geographic, with Eris coming in at 1,454 miles (2,340 km) across and Pluto at 1,456 miles (2,344 km) across.
However, the measurements were taken via ground-based and Earth-orbiting telescopes, which introduce a wide range of uncertainties due to the sheer distance of Pluto and Eris from Earth. Pluto is 39 times farther from the sun than the Earth, and Eris is more than twice as far away.
“The reports that Pluto is bigger than Eris all take the largest possible size of Pluto and the smallest size of Eris,” Caltech scientist Mike Brown, who discovered Eris but wasn’t involved in the new research, told National Geographic.
Brown says “we really don’t know” which of the two is bigger. He adds that Pluto remains a dwarf planet because there are similar large bodies in its vicinity—the Kuiper Belt—a flotilla of objects beyond Neptune’s orbit that includes Eris.
In 2006, the International Astronomical Union (IAU) provided the official definition of a planet: “A body that circles the sun without being some other object’s satellite, is large enough to be rounded by its own gravity ... and has ’cleared its neighborhood’ of most other orbiting bodies.”
But some astronomers believe this definition is fundamentally flawed.
“If you take the IAU’s definition strictly, no object in the solar system is a planet,” Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colo., told SPACE.com. “No object in the solar system has entirely cleared its zone.”
In Stern’s and some other astronomers’ opinion, a planet is any body that meets the IAU definition’s first two criteria, regardless of other bodies in the vicinity. This viewpoint defines Pluto as a planet and vindicates the swaths of Pluto enthusiasts who maintain it’s number nine.
