Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Speaker 1: Lauren Vogelbaum here. Back in two thousand and six, to
Speaker 1: the puzzlement of many in the non scientific public and
Speaker 1: some astronomers as well, the International Astronomical Union decided to
Speaker 1: demote Pluto from its status as a full fledged planet. Instead,
Speaker 1: the IAU decided what had been considered the most distant
Speaker 1: of the nine planets in our Solar System actually belonged
Speaker 1: in a new category of dwarf planets. This category also
Speaker 1: includes Series, the largest object in the asteroid belt between
Speaker 1: Mars and Jupiter. The IAU's reasoning was that Pluto only
Speaker 1: had two of what they had decided were the three
Speaker 1: characteristics of a planet. That it is in orbit around
Speaker 1: the Sun, that it has sufficient mass for its self
Speaker 1: gravity to overcome rigid body forces and give it a
Speaker 1: nearly spherical shape. And that it has cleared the neighborhood
Speaker 1: around its orbit of other objects, a meaning that it's
Speaker 1: either collided with, captured, or driven away smaller objects nearby.
Speaker 1: Pluto flunked that last test because it shares its orbit
Speaker 1: with the Kuiper Belt, a sort of doughnut shaped disc
Speaker 1: of thousands of smaller icy objects beyond Neptune that Pluto
Speaker 1: has failed to clean up gravitationally speaking, the ii used decision,
Speaker 1: which was voted on by a very small percentage of
Speaker 1: the world's astronomers and planetary scientists, was a controversial one.
Speaker 1: After a debate in twenty fourteen among scientists sponsored by
Speaker 1: the Harvard Smithsonian Center for Astrophysics, the majority of the
Speaker 1: non expert audience voted for a simpler definition of planet,
Speaker 1: basically that it has to be spherical, an orbit around
Speaker 1: a star or the remnants of one. This definition included Pluto,
Speaker 1: and that audience aren't the only people who feel this way.
Speaker 1: In a paper published in the journal Icarus in February
Speaker 1: of twenty nineteen, a team of planetary scientists analyzed more
Speaker 1: than two centuries worth of scientific studies and found that,
Speaker 1: with the exception of one paper published in eighteen oh
Speaker 1: two by British astronomer Sir William Herschel, nobody talked about
Speaker 1: the non sharing of an orbit as a criterion for
Speaker 1: distinguishing planets from non planets. To the contrary, the researchers
Speaker 1: found that scientists routinely described what we now know to
Speaker 1: be asteroids as planets until the nineteen fifties, because that
Speaker 1: is when our instruments became sensitive enough to show that
Speaker 1: asteroids had geophysical differences, namely, they weren't massive enough to
Speaker 1: be rounded. The researchers wrote in the paper, We therefore
Speaker 1: conclude that the argument made during the IAU planet definition
Speaker 1: controversy that planet sized Kuiper Belt objects should be classified
Speaker 1: as non planets because they share orbits is arbit and
Speaker 1: not based on historical precedent before the article. This episode
Speaker 1: is based on how stuff Works. Spoke via email with
Speaker 1: paper co author Philip Metzger, a planetary scientist at the
Speaker 1: University of Central Florida. He explained that the ia used
Speaker 1: emotion of Pluto largely has been disregarded by planetary scientists.
Speaker 1: A quote in science, we classify objects in ways that
Speaker 1: are scientifically useful. The definition that says Pluto is not
Speaker 1: a planet is not useful because scientists are not using
Speaker 1: it in their publications. But the definition that has existed
Speaker 1: since the time of Galileo, the one that most planetary
Speaker 1: scientists actually use, is very useful, and we use it
Speaker 1: in our publications all the time. That definition from Galileo
Speaker 1: says that the planet is a geologically complex body like
Speaker 1: the Earth is. Pluto is most definitely a geologically complex body,
Speaker 1: fully worthy of the term planet, as Galileo and Planeto Harry,
Speaker 1: scientists have used the word for the past five hundred years. Moreover,
Speaker 1: Metzger argues the IAU's definition of a planet actually was
Speaker 1: a step backward toward a pre scientific view of nature.
Speaker 1: He said, scientists discovered the solar system is messy, that
Speaker 1: planets don't all orbit the Sun, that they kick each
Speaker 1: other around and share orbits with other objects. The IAU
Speaker 1: definition tries to emphasize the organization of a solar system,
Speaker 1: saying planets are the small number of objects that rule
Speaker 1: in their orbits. It communicates the wrong idea that organization
Speaker 1: is the central truth about solar systems. In fact, for
Speaker 1: a planet to clear its orbit, the process is contingent, incomplete,
Speaker 1: and often temporary. A broadening or rebroadening the definition of
Speaker 1: planets would lead the way to including other objects like Aris,
Speaker 1: an object in the Kuiper Belt that's twenty five percent
Speaker 1: larger than Pluto. It was discovered in two thousand in
Speaker 1: five and prompted the debate that led to the IAU's redefinition.
Speaker 1: A Metzker said a problem with the two thousand and
Speaker 1: six definition is that people have lost interest in the
Speaker 1: discovery of planets. People think, well, they are just leftover
Speaker 1: junk like asteroids, though they're not important. As a result,
Speaker 1: the excitement is not taught in the classroom and the
Speaker 1: public doesn't pay attention. But they are actually amazing planets
Speaker 1: like Pluto and Shareon, and there are over one hundred
Speaker 1: and fifty of them, and there is plenty that's interesting
Speaker 1: about Pluto. How stuffworks also spoke via email with paper
Speaker 1: co author Kirby Runyan, a planetary geomorphologist at the Planetary
Speaker 1: Science Institute. He said Pluto has glaciers sliding down from
Speaker 1: the mountains. It has a multi layered atmosphere with climate cycles.
Speaker 1: It has mountains as big as the Rocky Mountains and
Speaker 1: they are currently being built up. It has an ancient
Speaker 1: ice lake with a shoreline. It has sublimation pits in
Speaker 1: the ice with fantastical patterns that suggest convection is happening
Speaker 1: under the ice. There's evidence of an underground ocean. There
Speaker 1: must be a heat source to keep that ocean liquid.
Speaker 1: There's even a possibility that life could exist in that ocean.
Speaker 1: There's still much to be learned about Pluto. The probe
Speaker 1: New Horizons did a fly by in twenty fifteen, but
Speaker 1: most of Pluto's southern hemisphere was shrouded in winter darkness
Speaker 1: at the time, and other regions were in low resolution,
Speaker 1: and the probe didn't include every possible piece of equipment.
Speaker 1: For example, if there is or was a subsurface liquid ocean,
Speaker 1: discovering a magnetic field around the planet would provide a
Speaker 1: solid clue, but would need to send a magnetometer on
Speaker 1: our next spacecraft to head that way. Beyond that, it's
Speaker 1: not known whether Pluto's features are unusual or representative of
Speaker 1: other small planets, Iranian said. For instance, are our most
Speaker 1: Huper Belt planets simple with just craters and fractures like
Speaker 1: the moons of Uranus or share On, or are they
Speaker 1: dynamic planets. Triton, we think, used to be a Kuiper
Speaker 1: Belt planet and is now a satellite planet orbiting Neptune.
Speaker 1: It also has rich and varied act of geology, like geysers,
Speaker 1: but of a different nature than Pluto. However, Metzger is
Speaker 1: not hopeful that the IAU will reconsider its decision. He
Speaker 1: said many of its members have become stubborn about it.
Speaker 1: This is why we aren't supposed to vote in science.
Speaker 1: Voting creates biases. Taxonomical classification is a part of science,
Speaker 1: so we should not allow biases to enter in. That
Speaker 1: is why it was a mistake to vote on the
Speaker 1: definition of a planet. It should have never happened. Today's
Speaker 1: episode is based on article Pluto is it a planet?
Speaker 1: After all? On how stuffworks dot Com? Written by Patrick J. Kiger.
Speaker 1: And Stuff is production of iHeartRadio in partnership with how
Speaker 1: stuffworks dot Com and is produced by Tyler Klang. Four
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