Discovered in 1930 by Clyde Tombaugh at Lowell Observatory, Pluto Planet initially joined the ranks of the solar system as the ninth planet, marking a significant moment in the exploration of our cosmic neighborhood. Named by 11-year-old Venetia Burney of Oxford, England, Pluto’s classification would undergo a dramatic shift. In 2006, the International Astronomical Union (IAU) rebranded Pluto as a dwarf planet, a decision that not only changed its status but also sparked widespread discussion among astronomers and the public alike. Situated in the Kuiper Belt, a realm teeming with other icy bodies beyond the orbit of Neptune, Pluto Planet and its eccentric orbit showcase the diversity and complexity of objects within our solar system.
This article navigates through pivotal moments in Pluto’s history, from its discovery and the quest for the hypothesized ‘Planet X‘ to the landmark flyby by NASA’s New Horizons spacecraft. As we traverse key dates, including Pluto’s controversial demotion and the discovery of its five moons, we gain insight into the characteristics and milestones that have cemented Pluto’s place in both the scientific community and popular imagination. Through examining these significant events, readers will uncover Pluto Planet facts, delve into the debate surrounding this celestial body’s classification, and explore what makes the Pluto planet a fascinating subject of study in our quest to understand the cosmos.
April 6, 1929: Search for Planet X Begins
The quest to identify a hypothetical ninth planet, often referred to as Planet X, was primarily motivated by anomalies observed in the orbit of Uranus, which suggested the presence of another planet exerting gravitational forces. Percival Lowell, a prominent astronomer from a distinguished Boston family, was particularly instrumental in this search. He began his quest in 1905, employing perturbation theory to predict the potential location of this elusive planet.
Despite Lowell’s dedicated search using a method involving photographic plates and a Blink Comparator to detect changes by comparing images taken at different times, his initial efforts from 1905 to 1916 were unsuccessful in discovering Planet X. Following Lowell’s death, the search experienced a hiatus until it was revitalized in 1929 by Vesto Slipher, the then director of the Lowell Observatory. Slipher appointed Clyde Tombaugh, a young and diligent astronomer, to continue the quest. Tombaugh’s approach was meticulous, involving the use of a newly constructed telescope and taking three sets of photographs spaced one to two weeks apart to increase the chances of detecting any movement against the backdrop of stars.
This renewed effort was underpinned by the construction of the 13″ Lawrence Lowell Telescope, specifically designed for the Planet X project. This telescope played a crucial role in the systematic search that eventually led to the discovery of Pluto Planet, thus continuing Lowell’s legacy and honoring his initial hypothesis and dedication to finding the ninth planet.
February 18, 1930: Pluto Planet Discovered
On February 18, 1930, a significant breakthrough occurred at the Lowell Observatory in Flagstaff, Arizona, when Clyde W. Tombaugh identified a shifting speck of light across photographic plates. This discovery, which turned out to be Pluto Planet, marked a monumental moment in the study of our solar system. Tombaugh, using a 13-inch telescope specifically designed for this purpose, conducted a meticulous and systematic search for what was then considered the ninth planet. This discovery was not only a testament to Tombaugh’s diligence but also a continuation of Percival Lowell’s earlier predictions, which hypothesized the existence of an unknown planetary body influencing the orbits of Uranus and Neptune.
The process leading to Pluto’s discovery involved the innovative use of a blink comparator, a device that allowed Tombaugh to detect changes in light between different photographic plates by rapidly switching the view from one image to another. This technique was crucial in identifying the minor changes in position that indicated the presence of a previously unknown planet. The discovery was a culmination of years of effort and the application of new astronomic techniques involving photographic plates, highlighting a significant advancement in the field of astronomy.
Pluto’s identification by Tombaugh was initially celebrated as the discovery of the Solar System’s ninth planet, a status that it held until 2006 when it was reclassified as a dwarf planet. This discovery not only expanded our knowledge of the celestial bodies within our solar system but also sparked further interest and debate about the characteristics and classification of planetary bodies beyond Neptune.
March 14, 1930: Pluto Planet Gets Its Name
On May 1, 1930, Venetia Burney, an 11-year-old schoolgirl from Oxford, England, proposed the name “Pluto” for the newly discovered celestial body. Her suggestion was submitted through her grandfather to the Lowell Observatory, where the search for the planet had been conducted. This name not only honored the classical mythology tradition of naming planets after Roman gods but also paid homage to Percival Lowell, whose initials “PL” coincidentally matched the first two letters of Pluto.
The Lowell Observatory received a flood of suggestions from around the world, totaling approximately 1,000 names. Among these, Pluto was suggested over 150 times. The staff at Lowell faced a challenging decision process, tallying the most popular names from a diverse group of proposers including students, teachers, attorneys, and even a U.S. senator. Despite the popularity of other names like Minerva and Cronus, Pluto was ultimately selected. This choice was influenced by the fact that Minerva was already assigned to an asteroid, and Pluto fittingly represented the god of the underworld, aligning with the planet’s distant, mysterious nature.
This naming process highlighted the public’s keen interest in astronomy and the symbolic significance of names in the exploration of our solar system. Pluto’s name reflects its position in the outer reaches, akin to the dark and remote underworld its namesake ruled. This decision not only resonated with the astronomical community but also with the general public, further embedding Pluto into popular culture and scientific discourse.
June 22, 1978: Discovery of Charon
On June 22, 1978, James W. Christy of the U.S. Naval Observatory made a groundbreaking discovery while reviewing photographic plates taken at the observatory’s Flagstaff Station in Arizona. He noticed an unusual bulge on images of Pluto Planet, indicating the presence of what would later be confirmed as Pluto’s largest moon, Charon. This discovery was facilitated by the use of a 61-inch telescope, which captured detailed images showing Pluto’s elongated appearance, a hint at Charon’s presence.
Christy, along with astronomer Robert S. Harrington, analyzed images dating back to 1965, which led them to conclude that this bulge was indeed a separate celestial body orbiting Pluto at a distance of approximately 12,200 miles. The official announcement of Charon’s discovery was made on July 7 through the International Astronomical Union (IAU), marking a significant addition to our understanding of the celestial dynamics within the solar system.
The naming of Charon was influenced by both personal and mythological considerations. Christy chose the name in part because it resembled his wife Charlene’s nickname, “Char,” and also because Charon is the mythological ferryman who transports souls across the river Acheron in the underworld, ruled by Hades—known as Pluto in Roman mythology. This name aptly reflects the moon’s connection to its parent planet, Pluto, enhancing the mythological coherence within our solar system’s nomenclature.
February 7, 1979: Pluto Planet Crosses Neptune’s Orbit
On February 7, 1979, a significant astronomical event occurred when Pluto Planet’s orbit brought it closer to the Sun than Neptune, marking one of the few times this celestial phenomenon takes place. Due to the highly elliptical shape of Pluto Planet’s orbit, it crosses inside Neptune’s more circular path every 248 years. This event is a result of Pluto Planet’s eccentric and inclined orbit, which ranges from a perihelion of 29.7 AU (closest point to the sun) to an aphelion of 49.5 AU (farthest point from the sun).
Pluto Planet’s orbit is inclined at an angle of 17 degrees relative to the plane of the solar system, which is believed to be influenced by Neptune’s gravitational pull. This inclination combined with its elliptical orbit path allows Pluto, at its closest approach, to swoop inside Neptune’s orbit, which ranges between 30.4 AU and 29.8 AU. This orbital characteristic categorizes Pluto as having the most elliptical and tilted orbit among known planets.
The next occurrence of Pluto crossing Neptune’s orbit is projected to happen in the year(https://www.discovery.com/science/pluto-and-neptune-swap-places-every-248-years), marking another noteworthy event in the long orbital dance between these two distant bodies in our solar system. This pattern underscores the dynamic and ever-changing nature of planetary orbits within our solar system, influenced by gravitational interactions and other celestial mechanics.
May 15, 2005: Nix and Hydra Discovered
On May 15, 2005, NASA’s Hubble Space Telescope captured images that led to the discovery of two previously unknown moons orbiting Pluto Planet, named Nix and Hydra. These moons are significantly fainter and farther from Pluto compared to its larger moon, Charon, making them intriguing subjects of study due to their remote and elusive characteristics. The discovery was pivotal for the upcoming New Horizons mission, aimed at exploring Pluto and the broader Kuiper Belt.
Key Characteristics of Nix and Hydra
Nix and Hydra are not only distant and faint but also possess unique physical and orbital properties. Nix, measuring approximately 42 km in length and 36 km in width, follows a nearly circular orbit around Pluto, showing minimal eccentricity and a low inclination, aligning closely with Charon’s orbital plane. It is in a 3:2 orbital resonance with Hydra and a 9:11 resonance with another of Pluto’s moons, Styx, completing an orbit every 24.9 days. Interestingly, Nix rotates chaotically due to its oblong shape, a dynamic that adds complexity to its orbital behavior.
Hydra, along with Nix, was officially named by the International Astronomical Union in 2006, drawing from rich mythological origins. Nix is named after the Greek goddess of darkness and night, while Hydra is named after the Lernaean Hydra, the formidable, many-headed serpent. These names not only reflect their mythological ties but also their mysterious and enigmatic natures as distant celestial bodies in the solar system.
The discovery of these moons has significantly expanded our understanding of the Pluto Planet system, increasing the count of its known moons to three at the time, alongside Charon. This finding also supports theories suggesting that Nix and Hydra may have formed from the same collision that created Charon. However, their precise origins and the reasons behind their specific orbital resonances remain subjects of ongoing research and fascination within the astronomical community.
January 19, 2006: New Horizons Mission Launch
On January 19, 2006, the New Horizons spacecraft embarked on its pioneering journey to Pluto Planet and beyond, launched by an Atlas V 551 rocket at 19:00 UTC. This marked the beginning of a historic mission under NASA’s New Frontiers program, orchestrated by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI). The spacecraft was propelled directly into an Earth-and-solar escape trajectory, reaching a speed of about 16.26 km/s, which is equivalent to 58,500 km/h.
Specifications and Mission Objectives
The New Horizons spacecraft, weighing 478 kg at launch, was equipped with a suite of scientific instruments designed to conduct detailed studies of Pluto and its moons. Its power source, a radioisotope thermoelectric generator, provided 245 watts of power at launch, essential for its long journey through the solar system. The spacecraft’s payload included sophisticated instruments such as Alice, LORRI, SWAP, PEPSSI, REX, Ralph, and VBSDC, all crucial for the exploration of Pluto and the Kuiper Belt.
Journey and Achievements
New Horizons’ trajectory towards Pluto involved several corrections and a vital gravity assist from Jupiter in February 2007, which was pivotal in achieving the necessary velocity and trajectory towards its primary target. The mission’s primary objective was to perform a flyby study of the Pluto system, with a secondary mission to explore other Kuiper Belt Objects (KBOs). This ambitious journey culminated in a historic flyby in 2015, providing humanity with the first detailed images and extensive data about the dwarf planet Pluto.
August 24, 2006: Pluto Demoted to Dwarf Planet
On August 24, 2006, the International Astronomical Union (IAU) made a significant decision that altered the status of Pluto within the solar system. During a conference in Prague, the IAU voted to redefine the criteria for planetary classification, which resulted in the demotion of Pluto to a dwarf planet. This decision was based on three criteria that a celestial body must meet to be classified as a planet: it must orbit the sun, be spherical in shape, and have cleared its orbit of other similar-sized objects. Pluto, sharing its orbital neighborhood with other objects in the Kuiper Belt, such as plutinos, failed to meet the third criterion.
The reclassification of Pluto sparked a global debate and had a significant cultural impact. In response to the IAU’s decision, some state legislatures in the United States declared March 13 as “Pluto Day,” challenging the demotion. The term “plutoed” was even selected as the American Dialect Society’s Word of the Year in 2006, defined as “to demote or devalue someone or something,” reflecting the public’s reaction to the decision. This controversy highlighted the attachment and significance that the public and some astronomers held for Pluto, with many questioning the logic behind the IAU’s final proposal, especially given the low turnout of voters at the conference.
Pluto’s new classification includes several categories: it is not only a dwarf planet but also a trans-Neptunian object, a Kuiper belt object, and a plutino. This reclassification does not diminish the scientific interest in Pluto but rather highlights the dynamic and ever-evolving nature of astronomical classification as our understanding of the universe expands.
July 14, 2015: New Horizons’ Historic Flyby
On July 14, 2015, the New Horizons spacecraft made its closest approach to Pluto, passing at a mere distance of 12,500 kilometers (7,800 miles). This historic event marked the first-ever flyby of the dwarf planet, providing unprecedented close-up images and a wealth of scientific data. During this encounter, the spacecraft’s Long Range Reconnaissance Imager (LORRI) and the LEISA instrument, an infrared imaging spectrometer, captured detailed movies and images. These observations revealed fascinating surface features and compositions, including the discovery of water ice on Pluto and ammonia ice within Charon’s Organa crater.
The flyby also allowed for a series of other significant scientific experiments and observations. The Student Dust Counter (SDC) recorded the dust density distribution in the space environment from Earth to Pluto and beyond, making it the farthest-reaching dust impact detector in history. Additionally, the radioscience experiment (REX) onboard conducted crucial experiments, including radio occultation and thermal scans of Pluto and Charon, providing insights into their atmospheric compositions and thermal profiles.
New Horizons’ Alice UV spectrograph played a critical role during the flyby by detecting molecular ‘fingerprints’ on Pluto. This instrument identified a variety of molecules, including nitrogen and various hydrocarbons like methane, which are crucial for understanding the dwarf planet’s atmosphere and surface conditions. This successful mission not only brought Pluto into clearer focus but also continued its journey towards the Kuiper Belt, aiming to explore more distant and mysterious celestial bodies.
March 23, 2178: One Plutonian Year Since Discovery
Pluto, despite its demotion to a dwarf planet, continues to fascinate scientists and astronomers due to its unique orbital characteristics and distant position in the solar system. One Plutonian year, equivalent to about 248 Earth years, represents the time it takes for Pluto to complete one full orbit around the sun. This extraordinary duration underscores the slow and elongated trajectory Pluto follows, which averages nearly four billion miles from the sun.
The Plutonian year that began on July 4, 1776, an iconic date marking the adoption of the Declaration of Independence in the United States, will conclude on June 12, 2024. This marks one full orbit of Pluto since that historic Earth date, providing a cosmic perspective on time and the slow dance of celestial bodies in our solar system.
Pluto’s surface temperature, estimated at around -360 degrees Fahrenheit, adds another layer of intrigue to its already mysterious nature. The extreme cold and vast distance from the sun create an environment that is challenging yet intriguing for scientific study and exploration. These characteristics not only highlight the resilience required for space exploration but also the ongoing curiosity that drives our understanding of the universe.
Conclusion
Throughout this journey across the pivotal moments that have shaped the history of Pluto, we have revisited the fascinating narrative of a celestial body that captures the imagination of both the scientific community and the public. From its discovery in 1930, inspired by the quest for a hypothesized Planet X, to its recent demotion to a dwarf planet, Pluto continues to be a source of intrigue and debate. The exploration of Pluto, including the landmark flyby by NASA’s New Horizons spacecraft, has enriched our understanding of the outer reaches of our solar system, underscoring the dynamic nature of space discovery and the continuous evolution of astronomical classifications.
The story of Pluto is far from concluded, with each discovery prompting new questions and avenues for further investigation. As we move forward, the ongoing study of Pluto and its moons promises to yield more insights into the Kuiper Belt and the myriad of celestial phenomena beyond the familiar confines of our terrestrial viewpoint. The significance of these findings extends beyond mere academic curiosity, offering a deeper appreciation for the vast, intricate tapestry of our universe. As we stand on the cusp of further explorations, Pluto remains a compelling emblem of the boundless quest for knowledge that drives humanity to look upward and beyond.
FAQs
What are some notable facts about Pluto?
Pluto is recognized as a dwarf planet and was previously classified as the ninth planet until 2006. It is located in the Kuiper Belt and occasionally orbits closer to the Sun than Neptune. Compared to Earth’s Moon, Pluto is smaller. The surface of Pluto features white mountains, and it takes 248 Earth years for Pluto to complete one orbit around the Sun.
Can you explain the historical significance of Pluto?
Pluto was discovered in 1930 and was considered the ninth planet in our solar system until 2006. Following the discovery of other similar objects in the Kuiper Belt, the International Astronomical Union redefined Pluto as a dwarf planet. Despite its small size of approximately 1,400 miles in diameter, Pluto remains an object of significant scientific interest.
What occurred with Pluto’s planetary status in 2006?
On August 24, 2006, the International Astronomical Union implemented a new definition for planets. This new classification led to the reassignment of Pluto from being the ninth planet to a dwarf planet. This decision sparked debates and discussions both within the scientific community and in popular culture.
How was Pluto first discovered?
Pluto’s discovery dates back to February 18, 1930, when Clyde Tombaugh noticed a moving object in photographs of the night sky that were taken six days apart. This object, which appeared as a small, dim point moving against the backdrop of stars, was later identified as Pluto, marking it as a distant member of our solar system.
