Pluto: A Planet Or Not Debate Re-emerges

After years of knowing that our solar system consists of 9 planetary bodies,its been disconcerting that the iciest planet Pluto is no longer deemed as a planet but one of the icy bodies floating around the universe.

The planet Pluto was declassified from full-pledged planet to “dwarf planet,” back in 2006,just as astronomers discovered the existence of another heavenly body Eris, another icy body from Pluto’s neighborhood,a year earlier. Eris was originally thought to be bigger than Pluto until Nov. 6, when astronomers got a chance to recalculate Eris’ size.

The latest Eris findings renewed astronomers’ attention top the forgotten planet.It appears that Pluto is bigger than Eris reigns with slimmest of margins (the numbers are so close as to be nearly indistinguishable, when uncertainties are taken into account).

With this findings prompted the science world to reconsider their controversial decision to strip the frigid world of its planet status.

Should Pluto be a planet? Should Eris, and many other objects circling the sun beyond Neptune’s orbit?

Pluto’s demotion

The International Astronomical Union,in 2006,had came up with the following official definition of “planet:” A body that circles the sun without being some other object’s satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has “cleared its neighborhood” of most other orbiting bodies.

In Pluto’s case,scientists discovered that the “icy planet” shares orbital space with other objects in the Kuiper Belt.

Kuiper Belt is the icy ring that is found beyond planet Neptune.

With this discovery,Pluto,can not be actually considered as a planetary body thus, the IAU recategorized Pluto, and Eris, as “dwarf planets.”

Dwarf planets are not officially full-fledged planets.

Pluto,since its discovery in 1930 has been branded as the ninth planet was stripped of from planet status after 75 years. Eight planets officially remain: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The scientist who discovered Eris-which is about 9 billion miles (15 billion kilometers) from the sun at its farthest orbital point, making it about twice as distant as Pluto, Caltech astronomer Mike Brown, thinks Pluto’s re-classification was the right move.

“Pluto, Eris and the many other Kuiper Belt objects are far too different to be lumped in with the eight official planets,” he said.

“For one thing, they’re much smaller. Pluto is about 1,455 miles (2,342 km) wide. The smallest official planet, Mercury, is more than twice as big at 3,032 miles (4,880 km) across.

“The dwarfs’ orbits tend to be very different, too — much more elliptical and more inclined, relative to the plane of the solar system. And they’re made of different stuff, with ices comprising more of their mass.”

“It just makes no sense from a classification standpoint to take these objects that clearly belong together and pick one — or two, or a dozen — and say, ‘Oh, these belong with the very different, large, planet-like things,” Brown said.

Brown reinstated that the only explanation why early astronomers deemed Pluto as planet just because it was “first detected so long ago, before people realized that it was just one of a vast flotilla of objects beyond Neptune’s orbit.”

The Kuiper Belt ,who was seen to embody more than 1,000 icy bodies or more,wasn’t even discovered until 1992.

“It’s just a funny historical accident that we found Pluto so early, and that it was the only thing known out there for so long,” Brown told “No one in their right mind would not have called it a planet back then, because we didn’t know any better.”

“We have progressed so much further in our understanding of what the solar system is that it’s pretty obvious,” he said. “We can go back and reassess the mistakes of our ancestors.”

Some astronomers think that Pluto should take its rightful place alongside other Kuiper Belt objects rather than being classified as a planet.

Director of New York City’s Hayden Planetarium,Neil deGrasse state,”I group Pluto with the other icy bodies in the Kuiper Belt I think it’s happier there, actually. Pluto has family in the outer solar system.”

However,some unconvinced astronomers are not fully convinced with the re-classification of Pluto and the reorganization of the solar system.
Rather,they say,that the IAU’s planet definition is fundamentally flawed.

“If you take the IAU’s definition strictly, no object in the solar system is a planet,” said Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colo. “No object in the solar system has entirely cleared its zone.”

“The definition also sets different standards for planethood at different distances from the sun,” according to Stern, who is principal investigator of NASA’s New Horizons mission, which is sending a spacecraft to Pluto.

“The farther away a planet is from the sun, the bigger it needs to be in order to clear its zone. If Earth circled the sun in Uranus’ orbit, it wouldn’t be able to clean out its neighborhood and would thus not qualify as a planet, Stern said.

“It’s literally laughable,” he told

So Pluto should be a planet, as should Eris and the dwarf planet Ceres (the largest body in the asteroid belt between Mars and Jupiter), as well as many other objects.

Such a definition would greatly expand the list of planets in the solar system.

“Many people think it’s special to be a planet,” Stern said.

“But adding a bunch of names to the list wouldn’t cheapen the ones that had been there forever,” he added.

“It would simply reflect astronomers’ increasing understanding of the solar system. In that understanding, small, icy planets far outnumber big gassy or rocky ones.”

“There are a large number of planets, and most of them are small,” Stern said. “It’s the Earth-like planets and the giant planets that are freakish.”

Tyson said he tries not to use the word “planet” in its generic sense, since it does not hold very much meaningful information.

“The word ‘planet’ has far outlived its usefulness,” Tyson told “It doesn’t celebrate the scientific richness of the solar system.”

So Tyson thinks in categories such as gas giants (Jupiter, Saturn, Uranus and Neptune) and terrestrial planets (Mercury, Venus, Earth and Mars) as well as asteroids and Kuiper Belt objects (Pluto, Eris and many others).

For his part, Brown thinks stripping Pluto of its planethood doesn’t make the icy body any less interesting or important.

“I think that Pluto as an example of a large Kuiper Belt object is so much more interesting than Pluto as this very weird planet at the outer edge of the solar system unlike anything else,” Brown said. “We are going to learn so much more about the solar system with our new understanding of what Pluto is.”

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