Eris -The dwarf planet That Declassified Pluto
The discovery of Eris in 2005 was one of the biggest disruptions in the scientific community.
In January 2005, the dwarf planet Eris was discovered by Michael Brown. At the time, it
was thought to be bigger than Pluto by 500 km. The discovery raised many questions, one of the most
important ones being: should Eris be added as the next planet after Pluto? Scientists had to make a
tough choice, as the discovery of Eris opened up the possibility of the existence of other large
objects of similar size in the outer solar system. On what factors would they make the choice? This
is the story of how the discovery of Eris led to the declassification of Pluto as a planet.
Eris was discovered in an ongoing survey at the Palomar Observatory by astronomers Mike Brown,
Chad Trujillo and David Rabinowitz. It is named after the ancient Greek goddess of discord and
conflict. It was discovered in 2003 as 2003 UB313 and was renamed after the television
warrior Xena by its founding team. The name is appropriate given that Eris is still at the heart
of a scientific argument about the definition of a planet. Eris has a radius of around 722
miles (1,163 kilometers), which is approximately one-fifth the radius of Earth. Eris, like Pluto,
is about the size of Earth's Moon. It would be around the size of a popcorn kernel if the Earth
were the size of a nickel. The dwarf planet is approximately 68 astronomical units distant
from the Sun at a distance of 6,289,000,000 miles (10,125,000,000 kilometers). The distance between
the Sun and Earth is measured in astronomical units (abbreviated as AU). That means, light would
take approximately nine hours to travel from the surface of the sun to Eris. This new dwarf planet
is the biggest object discovered in orbit around the sun since Neptune and its moon Triton were
discovered in 1846, and Pluto was discovered in 1930. The new dwarf planet, like Pluto,
is a part of the Kuiper belt, a ring of frozen planets beyond Neptune in orbit around the sun.
Eris was one of the solar system's first dwarf planets to be found. Though the dwarf planet Eris
on the outside of the solar system is far denser than Pluto, the two icy worlds are approximately
the same size, according to new research. Astronomers used measurements obtained in 2010,
when the dwarf planet crossed in front of a faint star to correctly determine Eris' diameter for the
first time. Using numerous telescopes in Chile, the researchers discovered that Eris and Pluto are
almost similar in size, making them "virtually perfect" twins. Its discovery resulted in the
demotion of the former eighth planet. Dysnomia, one of its moons, was found not long after the
discovery of the dwarf planet itself. The dwarf planet is the most distant object yet spotted
in orbit around the sun, much farther away than Sedna, a planetoid found nearly two years ago. It
is about 10 billion miles from the sun, more than three times as far as the next nearest planet,
Pluto, and takes more than twice as long to orbit the sun. The orbit of Eris is significantly more
eccentric than Pluto's. Over its 250-year orbit, Pluto moves from 30 to 50 times the
sun-Earth distance, whereas the new planet moves from 38 to 97 times the sun-Earth distance.
Being one of the most important discoveries of the decade, follow up observations were made about
the dwarf planet. The minor planet Eris' distance allowed astronomers to make accurate measurements
when it passed in front of a faint star in 2010, an occurrence known as an occultation.
Researchers were able to calculate Eris' form, size, and mass in addition to its size.
The findings assisted scientists in determining Eris' diameter to be 1,445
miles (2,326 kilometers), plus or minus 7 miles (12 km). It is so little smaller than Pluto.
When New Horizons arrives at Pluto, the spacecraft measured its diameter and discovered it to be
1,473 miles (2,370 km) across, roughly two-thirds the size of Earth's moon.
It is also one of the most reflective bodies in the solar system. Eris is approximately 27%
heavier than Pluto, and it is denser than Pluto as well. The surface of Eris is extremely reflective,
and it reflects 96% of the light that hits it. It is approximately the same size as Pluto,
and it has a moon called Dysnomia. Dysnomia was also discovered in 2005, and it helps to estimate
the weight and density of the dwarf planet. Researchers think Eris' surface is probably
composed of a nitrogen-rich ice mixed with frozen methane in a layer less than 1 millimeter thick.
This ice layer could be the result of the dwarf planet's atmosphere condensing as frost on the
surface as it moves away from the sun, they said. Astronomers estimated that the side of the dwarf
planet facing the sun likely gets no warmer than minus 396 degrees Fahrenheit (minus 238 degrees
Celsius), while temperatures on the night side would be even lower. This extreme cold makes
Eris an unlikely candidate for hosting life as we know it, but it still provides an important window
into the ways that planets can form and change over time. Eris is bright and uniform because
the atmosphere that it once had (280 years ago at its height) has now frozen solid to the ground,
providing a brilliant gleaming covering to whatever sort of variegated surface was formerly
present. The entire atmosphere is probably barely a few inches thick presently. With the dwarf
planet's orbital period of 580 years, this entire process is repeated indefinitely. In comparison,
the relative temperature change on the new planet is equivalent to the Earth's average temperature
fluctuating between 60 and 360 degrees Fahrenheit every six months. No other planet in the solar
system, dwarf or otherwise, experiences temperature swings as extreme as this one!
The planet and its characteristics were already on everyone’s mind but an even bigger thing was
a question that was worrying the scientific community. Now that a new planet-like object
was discovered, scientists had to make the decision of classifying Eris as a planet.
But then there might be even more similar sized objects in the outer solar system and
scientists would have to classify them all as planets. That would have been a wild journey!
However, the concept that Pluto was a planet was ingrained in our culture and society in
a million different ways, from plastic placemats representing the solar system
with the nine planets, to official NASA web pages, to mnemonics that all schoolchildren
learned to keep the nine planets straight, to U.S. postage stamps. Our civilization had
thoroughly accepted the concept that Pluto is a planet, as well as the belief that big asteroids
and Kuiper band objects are not planets. But the discovery of Eris challenged everything.
Pluto was assumed to be the size of terrestrial planets like Earth following its discovery in
1930, however it weighs just 0.24% of our planet and has a diameter of 2300 km, making it even
smaller than the Moon (3400 km in diameter)! Furthermore, nearly a thousand huge frozen
asteroids have been detected in this distant part of the solar system since 1992. They are known
as Trans-Neptunian Objects (TNO) because they are located beyond Neptune's orbit in the Kuiper Belt.
The discovery of Eris raised the prospect of the existence of other large objects
of this size in the far reaches of the solar system, necessitating an immediate response.
To reach a conclusion a special astronomical committee was constituted. A special committee
of the International Astronomical Union (IAU) was charged with determining "what is a planet?"
During the summer of 2006, the IAU formed a new committee that convened
in Paris for two days and developed the "anything round is a planet" definition.
At the IAU General Assembly in Prague, the concept was received with vehement criticism. They defined
a "planet" as an entity large enough to be spherical (gravity having conquered internal
cohesive forces) but also having cleared its orbit of other potential entities. Pluto has been barred
from the category of "planet" due to the fact that it has not cleared its orbit, which it shares
with other TNOs, much to the chagrin of some Americans, who took to the streets to protest.
But the die had already been thrown. Our solar system currently contains just eight planets,
as a result of IAU study group recommendations and a plenary session decision. Pluto lost its
designation as a "planet," ushering in the new category of "dwarf planets." At the same time,
Eris was elevated from the rank of a simple trans-Neptunian asteroid (TNO) to that of a dwarf
planet, similar to Ceres, the largest object in the main asteroid belt between Mars and Jupiter.
Two more "dwarf planets" have joined them since then: Makemake and Haumea, two TNOs found in 2005
and 2003, respectively. And there are a dozen more on the waiting list! The International
Astronomical Union votes to modify the definition of a planet after months of discussion about how
to categorize Eris. Pluto has been reclassified as a dwarf planet, reducing the number of planets
in the solar system to eight. Eris and Ceres were now classified as dwarf planets. That
judgment is still debated today, leaving behind Eris as the culprit of the decision.
Eris' vast distance, along with its small size, makes it impossible to see without
strong telescopes and modern technology. While no spacecraft are scheduled to sail by Eris in the
foreseeable future, the James Webb Space Telescope will provide astronomers with a clearer look at
the dwarf planet. The JWST website lists Eris explicitly as a focus of study and says that the
telescope will look at tiny objects in the solar system to better identify what their landscapes
are composed of. Not only that, who knows what new planet-like objects we might discover in the
outer solar system in the coming future. There is already a hunt for Planet 9 going on. So,
what do you think about the dwarf planet Eris? Was it the right decision to demote Pluto as a planet?
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