Billions of miles from the Sun’s warmth, the outer Solar System holds icy secrets. In the Kuiper Belt’s dark expanse, a small orb traces a wildly elliptical path, dancing to its rhythm. Cold and mysterious Pluto eluded discovery for centuries, lurking in plain sight. But when was Pluto discovered? How did Pluto get its name?
Join us as we navigate through decades of astronomical search, culminating in a surprising revelation. We uncover the intricate astronomical detective story that led to Pluto’s debut on the cosmic stage, revealing when, how, and by whom our understanding of the Solar System was forever transformed.
When Was Pluto Discovered?
American astronomer Clyde Tombaugh discovered Pluto on February 18, 1930, at Lowell Observatory in Flagstaff, Arizona. Initially considered the ninth planet in our Solar System, Pluto’s classification changed in 2006 when it was redefined as a dwarf planet by the International Astronomical Union.
Despite this reclassification, Pluto remains a fascinating object of study. It continues to provide insights into the outer reaches of our Solar System and our evolving understanding of celestial bodies.
Tombaugh and his discovery of Pluto
How was Pluto discovered? Tombaugh looked at stars from his family’s farm as a boy using homemade telescopes. Local astronomers noticed his skills and passion, the early traits leading to Pluto’s discovery. Lowell Observatory hired the teen Tombaugh to photograph the skies.
He had to check thousands of photos to spot a moving point of light showing Planet X. After 3 tough years, Tombaugh finally saw a faint dot moving near where Planet X was expected. But who named Pluto?
More observations confirmed Tombaugh’s sighting of a new planet. His discovery would need a name, eventually dubbed Pluto after the Roman god of the underworld, explaining how Pluto got its name. The finding made Tombaugh famous overnight.
Appearances between photographs that confirmed a new planet
Using a blink comparator, Tombaugh quickly switched between two-star field photographs to uncover Planet X. Any object changing positions would blink through this device.
As he compared images, Tombaugh noticed a faint point of light shifting, suggesting an object with an orbit beyond Neptune. The movement revealed linear travel and an orbit around the Sun, ruling out possibilities like asteroids or comets.
Furthermore, its distance ruled out being a star or nebula in the Milky Way, pointing only to the likelihood of a very remote, massive object. Observing the dot’s movement repeatedly over several nights through the blink comparator, Tombaugh concluded that the pattern indicated a body over 4 billion miles from the Sun.
This compelling data convinced astronomers in Flagstaff that they had discovered something significant. The shifting light provided definitive proof of a previously unknown outer Solar System planet.
Confirmatory photographs to prove Pluto’s existence
Tombaugh noticed a small dot moving across the sky. So, he took more pictures of the same area to confirm his observation. He wanted to ensure no temporary issues affected his vision or the photographic plates. After developing the new images, Tombaugh examined them using a blink comparator.
The faint dot of light was still changing its position compared to earlier images. This confirmed that it was moving in orbit. With this clear evidence, doubts about it being a trans-Neptunian object vanished.
Tombaugh wrote a short announcement about discovering a new member of the Solar System. He sent it to other astronomers via telegraph to ensure they were informed first. Over the following year, Tombaugh meticulously tracked Pluto’s movement against the stars.
Using Lowell Observatory’s advanced telescopes, he made precise measurements of its position. By plotting these positions over time, Tombaugh determined Pluto’s orbit parameters beyond Neptune. Its orbit around the Sun took approximately 365 days, confirming its status as a new planet.
What Was Known About Pluto Before Its Discovery?
Astronomers suspected the presence of a hidden large planet beyond Neptune’s orbit, believing its gravity influenced Neptune’s position. To determine its potential mass and orbit, scientists performed calculations.
Percival Lowell proposed the existence of a sizable Planet X and actively sought it, but he passed away without discovering it. However, he left projected coordinates to guide future searches. The term “Planet X” lingered in people’s minds, causing confusion when the much smaller Pluto was eventually found, deviating from the predicted giant.
Contrary to expectations of a distant giant, Pluto turned out to be significantly smaller and closer. It boasts only about 0.2% of Earth’s mass and orbits the Sun at a distance merely 39 times that of Earth. The revelation of this tiny frozen world lurking far beyond what was anticipated surprised everyone.
Aftermath: Reclassification as a Dwarf Planet
Decades after the discovery of Pluto, astronomers found other objects in the distant Kuiper Belt, some nearly the size of Pluto, such as Eris. These findings sparked questions about how to classify Pluto and the similar icy, rocky bodies in the Kuiper Belt.
In 2006, the International Astronomical Union (IAU) introduced a planet definition, requiring objects to clear and dominate their orbital path. Pluto fell short of meeting this criterion, creating a new class called “dwarf planets” to encompass Pluto, Eris, and other large Kuiper Belt objects.
Pluto was then reclassified as the first dwarf planet. Despite its change in status, Pluto continues to provide valuable insights. Its intricate interactions with its five moons offer clues about the history and composition of the distant Kuiper Belt.
The Status Debate: Is Pluto a Planet or Not?
Pluto lost its planetary status because it didn’t follow the new criteria set by the IAU in 2006. Instead of having a cleared orbital path, Pluto orbits amid icy debris, leading to its reclassification as a dwarf planet.
The discovery of larger Kuiper Belt objects like Eris raised questions about Pluto’s uniqueness. It became apparent that Pluto was just one of many small icy bodies.
To address concerns about the increasing number of planets, especially with the discovery of larger KBOs, a new category for dwarf planets was introduced. This category grouped Pluto with similar icy objects.
Despite the reclassification, Pluto remains a beloved planet in the public’s eyes, with a deep cultural attachment that is hard to shake. However, studying dwarf planets provides crucial insights into the makeup and history of the Solar System.
Conclusion
When was Pluto discovered? Pluto’s discovery occurred after years of meticulous photographic analysis by young astronomer Clyde Tombaugh in 1930.
The revelation of Pluto’s discovery marked an astonishing feat, considering this remote world’s diminutive size and distant location. Percival Lowell’s predictions of Planet X shaped early conceptions of what defines a planet, evolving over time.
Pluto, with its status as the prototype for dwarf planets and the gateway to the Kuiper Belt, remains firmly cemented in astronomical significance. Its identification represented an unprecedented leap in our understanding of the boundaries and expanse of the Solar System.
We hope you have a better appreciation for the winding path that led to the recognition of this tiny, icy orb. Moreover, we trust you better understand the enduring impact of unveiling Pluto’s movements across night skies, far from our home. This discovery proves that Planet X awaited recognition, lingering unseen amid the stars.