Eris, the unremembered planet When Michael Brown reported on February 28, 2004, the discovery of Sedna, an object believed to be almost 2,000 km in diameter and circling between the Kuiper belt and the inner section of the Oort Cloud. It appeared to everyone that the solar system had found its tenth planet. But it lasted only a short time.
The diameter of the planetoid Sedna was quickly lowered, and the number of planets restored to their original number. On July 29, 2005, after only 517 days had gone, Mike Brown announced the identification of a second big object, provisionally dubbed 2003 UB313.
The first one discovered beyond Pluto’s orbit
The outcome of the situation was subsequently revealed. Not only was Eris, as it was subsequently firmly referred to, never regarded a “planet,” but Pluto also lost its planetary status, reducing the number of planets from nine to eight. Pluto, despite its demotion, remained on everyone’s lips and in their hearts, whereas Eris, having missed the train that would have brought it fame, was soon almost forgotten.
Most likely because it was considered merely one of the many planetoids that would continue to be discovered in the Kuiper belt in the future. In fact, nothing nearly equivalent has been discovered in these isolated places since 2005. Eris is the largest object known since Triton, Neptune’s huge moon, was discovered in 1847.
Eris, on the other hand, merits considerably more attention than it has thus far received. To locate something much larger, we may have to travel as far as the Oort Cloud, and even then we may not find something more deserving of the name “planet.” Let’s keep its memories alive and become more familiar with it, shall we?
“Roll intro” Eris was discovered on January 5, 2005, by astronomer Michael Brown and his collaborators Chad Trujillo and David Rabinowitz using photos captured on October 21, 2003.
Why the extended delay?
The explanation is straightforward. The crew had systematically scanned the sky for the largest trans-Neptunian objects for several years and had discovered a number of them, including Quaoar, Orcus, and Sedna, using automatic search algorithms that processed all the photographs obtained. This drastically sped the object discovery process and allowed them to search a larger portion of the sky.
However, the researchers opted to exclude from the software those objects moving at an angular velocity greater than 1.5 arcseconds per hour, as their presumed distance was incompatible. Consider that the angular diameter of the Moon is approximately 1800 arc seconds to get a sense of how modest this change is. After manually discovering Sedna, a very slow-moving item, Brown and his colleagues knew that the software would miss its presence.
Hence, they chose to inspect and reanalyze all the photographs they had acquired in the preceding months. Only in this manner were they able to locate the object that would eventually become Eris. A transneptunian whose motion relative to the background stars was so sluggish that it had been overlooked during the initial round of investigation.
The announcement was made on July 29, 2005, the same day as Makemake and just two days after Haumea. The preliminary orbit of Eris was then determined through more observations, and on September 10, 2005, a subsequent investigation with the 10-meter Keck telescope in Hawaii confirmed the presence of a satellite that was eventually designated Dysnomia.
Dysnomia has a diameter of around 700 kilometers, making it the second-largest dwarf planet moon after Pluto’s Charon. It orbits Eris in approximately 16 days at a distance of 37,000 kilometers. At that time, Brown was carrying a gigantic item that was even accompanied by a large moon. It seems nothing could prevent Eris from obtaining the status of “tenth planet”.
However, chaos ensued, and Pluto’s discovery essentially signalled the beginning of the end for the planet. In 2006, Pluto and Eris were awarded the consolation label of “dwarf planet”. This category now includes Ceres, Haumea, and Makemake as well. Eris orbits the Sun in a tremendously elliptical orbit with a period of 559 years.
This orbit is extremely eccentric and tilted. In reality, during aphelion, its maximum distance from the Sun is 98 AU, whereas at perihelion, it is just 38 AU. The planet completes one rotation every 25.9 hours as it orbits the Sun. Eris reached perihelion in the year 1699 and aphelion in the year 1977; it will return to perihelion in December 2257.
In contrast to the orbits of the other eight planets, which lay nearly in the same plane as Earth’s, Eris’ orbit is steeply inclined by around 44 degrees. In fact, searches for massive objects in the outer Solar System tend to concentrate on the ecliptic plane, where the majority of celestial bodies reside. Eris is now the most distant known object in our Solar System, excluding long-period comets.
The detached object Sedna, which we encountered while discussing transneptunian objects, is theoretically farther from the Sun, with a semi-major axis of approximately 524 AU. Nevertheless, Sedna is currently travelling along a portion of its orbit closer to the Sun, around 84 AU, and will reach perihelion between 2075 and 2076.
Due to the steep inclination of its orbit, Eris traverses only a few traditional Zodiac constellations and is currently in Cetus. “
Size matters
Eris’ diameter has been gradually refined and lowered since its discovery. Using photos from the Hubble Space Telescope, the diameter of Eris was determined to be 2,397 kilometers in 2003. For this, the traditional method of using Eris’s distance, albedo, and apparent brightness was employed. Albedo is the astronomical name for the surface reflectivity of a celestial body. Albedo reaches its maximum value of 1 when all incident light is reflected.
The minimal albedo value is zero when no light is reflected. The first scenario involves a flawlessly white object, whereas the second involves a fully black one. Eris has an estimated albedo of 0.96, which is greater than any other major bodies in the Solar System with the exception of Saturn’s sixth-largest moon, Enceladus.
It is speculated that Eris’s high reflectivity is owing to its increasing surface ices, which are on the rise due to its current orbital position far from the Sun. Comparing the diameter of Eris to Pluto’s diameter, which was calculated at 2,370 km at the time, Eris appeared to be slightly larger than Pluto in the best-case scenario. It is exceedingly difficult to say whether Pluto or Eris is larger.
This evaluation is further complicated by Pluto’s atmosphere, which interferes with observations of the planet’s solid surface. In 2007, the Spitzer Space Telescope was used to refine the dwarf planet’s diameter, and the resulting measurements showed a size of 2,600 kilometers.
In 2010, a rare phenomenon known as a stellar occultation occurred. Never before has such a remote object in our solar system been detected to occulated. The results cast considerable doubt on prior observations, particularly the Spitzer Space Telescope’s measurements. Eris has a diameter of only 2,326 kilometers, according to data derived from its occultation in front of a star.
In comparison, the New Horizons spacecraft assessed Pluto’s diameter to be 2,376 kilometers in 2015. Pluto is currently verified to be the largest dwarf planet, albeit by a very narrow margin compared to Eris, barring other changes that are always possible.
Mass is equally important
Obtaining an approximation of the mass of a solitary object like Eris is unquestionably challenging. Thankfully, the identification of Dysnomia has resolved the underlying issue. In astronomy, it is sufficient to know the orbital period of a satellite and its distance from its home planet in order to calculate the mass of the parent planet using Kepler’s third law.
Then, a straightforward calculation revealed that Eris’s mass is 27 percent bigger than Pluto’s. Therefore, Eris’s density must be larger than that of Pluto. Eris has a density of 2.5 grams per cubic centimeter, which is considerably greater than Pluto’s density of 1.75 grams per cubic centimeter (for comparison, the density of water is 1, while the average density of our planet is 5.5).
Therefore, since Pluto and Eris appeared to have comparable diameters but distinct densities, their composition must have been considerably different. Eris is likely made of significantly more rocky and dense material than Pluto. Some astronomers propose a composition of approximately 70% rock and 30% ice. However, they are simply speculations.
The atmosphere and the surface
As a result of the planet’s variable distance from the Sun, the surface temperature ranges between -240° and -216°C. No surface features may be directly detected from Earth, regardless of the location of the telescopes. In order to learn more, it is important to do indirect measurements, such as spectrum analysis.
On January 25, 2005, spectra were collected from the 8-meter Gemini North Telescope in Hawaii, and infrared spectrum analysis confirmed the presence of methane near the surface. Additional investigation revealed high concentrations of carbon monoxide and nitrogen. It is comparable to Pluto.
As Eris approaches its perihelion, sublimation processes will be activated, causing surface gases to escape and create a thin atmosphere. Then, when Eris departs from its perihelion, the surface temperature will gradually decline until it reaches its lowest point at the aphelion. The dropping temperatures will enable re-sublimation, wherein atmospheric gases will refreeze and return to the surface.
At these temperatures, sublimation processes may be possible since methane is highly volatile. Nonetheless, this poses another question. How can the observed abundances of methane be explained if it is so volatile and sublimation is possible? Two scenarios are feasible. Eris has always remained at such great distances from the Sun as to prevent sublimation from occurring. Second, the methane that escapes the surface may be replenished by an internal source.
Eris’ surface has no further details known
We can only determine that its hue is distinct from those of Pluto and Triton. In contrast to Pluto and Triton, which have a reddish hue, Eris seems to be gray like many other Kuiper Belt objects. Eris is the largest object that has never been visited by a spacecraft, and its immense distance and small size make it difficult to see the dwarf planet without sophisticated telescopes and technology.
Eris could be viewed by the James Webb Space Telescope, which is slated to reach its operational phase in the next days. This is a potential that could become a reality in the near future. Regarding probe investigation, numerous studies were conducted in the 2010s for follow-up missions to investigate the Kuiper belt, among which Eris was considered.
Based on launch dates of April 3, 2032, or April 7, 2044, it was determined that a flyby mission to Eris would require 25 years using Jupiter’s gravity assist. Eris’ distance from the Sun would be 92 or 90 AU when the probe arrives. However, these are currently merely projects. Eris is still a faraway fantasy for us now.
FAQ
Why is Eris not a planet anymore?
Eris was formerly thought to be a possible tenth planet in our solar system, but the International Astronomical Union (IAU) changed its definitions and standards, forcing a reclassification. Similar to Pluto, Eris was first noticed for its size upon discovery in 2005, which led to a reevaluation of what qualifies as a planet. But in 2006, the IAU updated the standards for planetary status, which resulted in Pluto and Eris being reclassified. The revised definition states that in order for a celestial body to be considered a planet, it must orbit the Sun, have a spherical form, and be free of other debris. Similar to Pluto, Eris failed not satisfy the final requirement since it orbits near other objects in the Kuiper Belt. As such, Eris is no longer considered a full-fledged planet in our solar system, but rather a “dwarf planet”. This reclassification emphasizes how definitions are always being improved as our awareness of the universe expands and how dynamic scientific understanding is.
Which is bigger Pluto or Eris?
Although Eris is marginally smaller than Pluto, the two celestial planets are thought to be roughly equal in size. Eris is roughly 2,326 kilometers (1,445 miles) in diameter, while Pluto is around 2,377 kilometers (1,477 miles) in diameter. Both objects are found in the Kuiper Belt, an area of space beyond Neptune that is home to a large number of tiny, ice bodies. The International Astronomical Union (IAU) reclassified Pluto and Eris as dwarf planets in 2006 as a result of a review of the solar system’s planet classifications prompted by the discovery of Eris in 2005. Pluto and Eris are nevertheless important objects in the study of the outer solar system and continue to pique scientific curiosity despite their lesser size than the regular planets.
Can we live in Eris?
There are too many obstacles for humans to live on Eris, a far-off minor planet in our solar system, making human life currently impracticable. The Kuiper Belt, where Eris is located, is known for its extremely frigid temperatures. Surface temperatures there often reach -240 degrees Celsius (-400 degrees Fahrenheit). Eris also possesses a thin, fragile atmosphere that is mostly made up of trace gases like nitrogen and methane. There isn’t enough breathable air to sustain human life because there isn’t a considerable atmosphere. Since Eris is so far from Earth and its climate is so harsh, it is extremely improbable that humans will ever dwell there with present technology. For now, astronomers and planetary scientists find Eris to be an interesting object of research, but the notion of residing on this tiny planet is still firmly in the realm of science fiction.
Is Eris bigger than Earth’s moon?
Yes, Eris is substantially bigger than the moon of Earth. Eris is a minor planet with a diameter of roughly 2,326 kilometers (1,445 miles), whereas the moon has a diameter of about 3,474 kilometers (2,159 miles). The moon is a major player in Earth’s tidal and gravitational dynamics, despite being smaller than Earth and quite huge in comparison to many other moons in our solar system. On the other hand, Eris was first found in 2005 and is situated in the Kuiper Belt, which is an area beyond Neptune. Even though Eris is a unique object in the outer regions of our solar system due to its size and composition—a combination of rock and ice—it is still smaller than the moon of Earth.
How is Eris different from Pluto?
Both Eris and Pluto, which are found in the Kuiper Belt beyond Neptune, have important distinctions in addition to a number of commonalities. Their sizes are one obvious difference: Eris is slightly smaller than Pluto, measuring around 2,326 kilometers (1,445 miles) in diameter, whereas Pluto has a diameter of roughly 2,377 kilometers (1,477 miles). Their orbital properties represent yet another significant distinction. Pluto’s orbit is comparatively more circular, but Eris’s is more eccentric and inclined. Eris is also more massive than Pluto. The International Astronomical Union (IAU) reclassified both objects as planets in 2006 as a result of the controversy surrounding them. They are now categorized as dwarf planets, which are objects that don’t satisfy all the requirements to be called planets in the traditional sense. Notwithstanding these distinctions, Eris and Pluto both add significantly to our knowledge of the outer solar system by providing insightful observations into the complex population of objects in the Kuiper Belt.
