How Small Is Pluto Compared To Earth? Discover the size disparity between the dwarf planet Pluto and our home planet, Earth, on COMPARE.EDU.VN. Understand the scale and significance of this cosmic comparison with our comprehensive insights and data. Examine planetary dimensions and celestial body analysis.
1. Understanding Pluto: A Dwarf Planet in the Kuiper Belt
Pluto, a captivating celestial body residing in the distant Kuiper Belt, is a world of mountains, valleys, plains, craters, and glaciers. Its discovery in 1930 initially led to its classification as the ninth planet in our solar system. However, as similar worlds were found deeper within the Kuiper Belt, the International Astronomical Union (IAU) reclassified Pluto as a dwarf planet in 2006. This reclassification was based on the IAU’s definition of a dwarf planet as an object orbiting the Sun, large enough to be nearly round due to its own gravity but unable to clear its orbit of other debris. Pluto’s location in the Trans-Neptunian region, where other objects cross its path, led to this change in classification, causing some astronomical controversy.
Pluto has a diameter of only about 1,400 miles (2,380 kilometers), approximately half the width of the United States. It lies about 3.6 billion miles (5.8 billion kilometers) from the Sun and features a thin atmosphere predominantly composed of nitrogen, methane, and carbon monoxide. The average temperature on Pluto is a frigid -387°F (-232°C), making it inhospitable to life as we know it.
Pluto is accompanied by five known moons, the largest of which is Charon. Charon is about half the size of Pluto, making it the largest satellite relative to its parent body in our solar system. Because of their relative sizes, Pluto and Charon are often referred to as a “double planet.”
The NASA’s New Horizons spacecraft made history as the only spacecraft to explore Pluto up close. In 2015, it flew by Pluto and its moons, providing invaluable data and stunning images that have transformed our understanding of this distant world.
2. The Intriguing Tale of Pluto’s Naming
Pluto owes its name to an 11-year-old girl named Venetia Burney. In 1930, Venetia, residing in Oxford, England, suggested that the newly discovered celestial body be named after the Roman god of the underworld. Her grandfather, Falconer Madan, a librarian at the University of Oxford, relayed the suggestion to the Lowell Observatory, where it was ultimately selected.
In a 2006 interview with NASA, Venetia recounted offering the name Pluto during breakfast with her mother and grandfather on March 14, 1930, after her grandfather shared the news of the ninth planet’s discovery.
Alan Stern, the principal investigator for NASA’s New Horizons mission, acknowledged Venetia’s contribution: “Venetia’s interest and success in naming Pluto as a schoolgirl caught the attention of the world and earned her a place in the history of planetary astronomy that lives on.”
To clarify the mythological context of Pluto’s name, Dr. Elizabeth Vandiver, chair of the Department of Classics at Whitman College, explained: “Pluto is the name of the Roman god of the underworld, equivalent to the Greek Hades. However, the Greek name ‘Plouton’ (from which the Romans derived their name ‘Pluto’) was also occasionally used as an alternative name for Hades. But Pluto is definitely the Roman spelling.”
Venetia Burney, the girl who named Pluto, photographed in black and white, shows a young girl with a spiral bun in her hair.
3. Is There Potential for Life on Pluto?
The surface of Pluto is extremely cold, making it unlikely that life could exist there. At such low temperatures, water, which is essential for life as we know it, is essentially rock-like. However, Pluto’s interior is warmer, and some scientists believe there might even be an ocean deep inside. While the surface conditions are not conducive to life as we know it, the potential for a subsurface ocean raises intriguing questions about the possibility of microbial life existing in this hidden environment. Further research and exploration would be needed to determine the true nature of Pluto’s interior and its potential for harboring life.
4. Size Comparison: How Small is Pluto Compared to Earth?
Pluto has an equatorial diameter of about 1,477 miles (2,377 kilometers). This makes Pluto approximately 1/5th the width of Earth. To put it another way, if Earth were the size of a basketball, Pluto would be about the size of a golf ball. The dwarf planet is considerably smaller than any of the eight recognized planets in our solar system.
The following table illustrates this size contrast:
| Celestial Body | Equatorial Diameter (miles) | Equatorial Diameter (kilometers) |
|---|---|---|
| Earth | 7,918 | 12,742 |
| Pluto | 1,477 | 2,377 |
From an average distance of about 3.7 billion miles (5.9 billion kilometers), Pluto is about 39 times farther away than the Earth is from the Sun. At this distance, sunlight takes 5.5 hours to travel from the Sun to Pluto.
If you stood on Pluto’s surface at noon, the Sun would be 1/900th the brightness it is here on Earth, or about 300 times as bright as our full moon. There is a moment each day near sunset here on Earth when the light is the same brightness as midday on Pluto.
5. Orbit and Rotation: Pluto’s Unique Path
Pluto’s orbit around the Sun is unique compared to the planets; it is both elliptical and tilted. Pluto’s 248-year-long, oval-shaped orbit can take it as far as 49.3 astronomical units (AU) from the Sun and as close as 30 AU. (One AU is the mean distance between Earth and the Sun: about 93 million miles or 150 million kilometers.) On average, Pluto is 3.7 billion miles (5.9 billion kilometers) away from the Sun, or 39 AU.
From 1979 to 1999, Pluto was near perihelion, its closest approach to the Sun. During this time, Pluto was actually closer to the Sun than Neptune. This unusual orbit is one of the factors that led to Pluto’s reclassification as a dwarf planet, as it crosses Neptune’s orbit.
One day on Pluto lasts about 153 hours, or about 6.4 Earth days. Its axis of rotation is tilted 57 degrees with respect to the plane of its orbit around the Sun, so it spins almost on its side. Pluto also exhibits a retrograde rotation, spinning from east to west like Venus and Uranus, adding to its list of unusual characteristics.
6. Pluto’s Moons: A Diverse Family
Pluto has five known moons: Charon, Nix, Hydra, Kerberos, and Styx. This moon system might have formed by a collision between Pluto and another similarly sized body early in the history of the solar system.
Charon, the largest of Pluto’s moons, is about half the size of Pluto itself, making it the largest satellite relative to the planet it orbits in our solar system. It orbits Pluto at a distance of just 12,200 miles (19,640 kilometers). For comparison, our Moon is 20 times farther away from Earth. Pluto and Charon are often referred to as a double planet because of their relative sizes.
Charon’s orbit around Pluto takes 153 hours – the same time it takes Pluto to complete one rotation. This means Charon neither rises nor sets but hovers over the same spot on Pluto’s surface. The same side of Charon always faces Pluto, a state called tidal locking.
Pluto’s other four moons are much smaller, less than 100 miles (160 kilometers) wide. They are also irregularly shaped, not spherical like Charon. Unlike many other moons in the solar system, these moons are not tidally locked to Pluto. They all spin and don’t keep the same face towards Pluto, creating a complex and dynamic system.
Pluto’s moons are named for other mythological figures associated with the underworld. Charon is named for the river Styx boatman who ferries souls in the underworld (as well as honoring Charlene, the wife of discoverer James Christy, who was nicknamed Char). The small moon Nix is named for the goddess of darkness and night, who is also the mother of Charon. Hydra is named for the nine-headed serpent that guards the underworld. Kerberos is named after the three-headed dog of Greek mythology (known as Fluffy in the Harry Potter novels). And Styx is named for the mythological river that separates the world of the living from the realm of the dead.
7. Rings: The Absence Around Pluto
There are no known rings around Pluto. This sets it apart from other large bodies in our solar system, such as Saturn and Uranus, which have extensive ring systems. The absence of rings around Pluto may be due to its relatively small size and the gravitational influence of its moons, which could prevent ring particles from forming a stable orbit.
8. Formation: How Pluto Came to Be
Dwarf planet Pluto is a member of a group of objects that orbit in a disc-like zone beyond the orbit of Neptune called the Kuiper Belt. This distant realm is populated with thousands of miniature icy worlds, which formed early in the history of our solar system about 4.5 billion years ago. These icy, rocky bodies are called Kuiper Belt objects, transneptunian objects, or plutoids. Pluto is believed to have formed from the accretion of these smaller objects in the Kuiper Belt, gradually growing in size through collisions and gravitational attraction.
9. Structure: Unveiling Pluto’s Interior
Pluto is about two-thirds the diameter of Earth’s Moon and likely has a rocky core surrounded by a mantle of water ice. Interesting ices like methane and nitrogen frost coat the surface. Due to its lower density, Pluto’s mass is about one-sixth that of Earth’s Moon.
The following table provides a structural comparison:
| Feature | Pluto | Earth’s Moon |
|---|---|---|
| Diameter | ~2/3 of Earth’s Moon | N/A |
| Core | Rocky | Iron |
| Mantle | Water ice | Partially molten |
| Surface | Ices (methane, nitrogen) | Regolith |
| Relative Mass | ~1/6 of Earth’s Moon | N/A |
10. Surface Features: A World of Diversity
Pluto’s surface features mountains, valleys, plains, and craters. The temperature on Pluto can be as cold as -375 to -400 degrees Fahrenheit (-226 to -240 degrees Celsius).
Pluto’s tallest mountains are 6,500 to 9,800 feet (2 to 3 kilometers) in height. The mountains are big blocks of water ice, sometimes with a coating of frozen gases like methane. Long troughs and valleys as long as 370 miles (600 kilometers) add to the interesting features of this faraway dwarf planet.
Craters as large as 162 miles (260 kilometers) in diameter dot some of the landscape on Pluto, with some showing signs of erosion and filling. This suggests tectonic forces are slowly resurfacing Pluto.
The most prominent plains observed on Pluto appear to be made of frozen nitrogen gas and show no craters. These plains do show structures suggesting convection (blobs of material circulating up and down). The diverse surface features of Pluto provide evidence of a complex geological history, with ongoing processes shaping its landscape.
11. Atmosphere: A Transient Veil
Pluto has a thin, tenuous atmosphere that expands when it comes closer to the Sun and collapses as it moves farther away – similar to a comet. The main constituent is molecular nitrogen, though molecules of methane and carbon monoxide have also been detected.
When Pluto is close to the Sun, its surface ices sublimate (changing directly from solid to gas) and rise to temporarily form a thin atmosphere. Pluto’s low gravity (about 6% of Earth’s) causes the atmosphere to be much more extended in altitude than our planet’s atmosphere. Pluto becomes much colder during the part of each year when it is traveling far away from the Sun. During this time, the bulk of the planet’s atmosphere may freeze and fall as snow to the surface. This dynamic atmospheric cycle is unique in our solar system and is a result of Pluto’s eccentric orbit and low gravity.
12. Magnetosphere: The Unknown Shield
It isn’t known whether Pluto has a magnetic field, but its small size and slow rotation suggest little or none. Without a magnetic field, Pluto’s atmosphere is directly exposed to the solar wind, a stream of charged particles emanating from the Sun. This interaction can cause the atmosphere to be gradually stripped away over time.
13. Why Pluto Lost Its Planetary Status: The IAU Definition
The International Astronomical Union (IAU) established three criteria for a celestial body to be considered a planet:
- The object must orbit the Sun.
- The object must be massive enough for its own gravity to pull it into a nearly round shape.
- The object must have “cleared the neighborhood” around its orbit, meaning it has gravitationally dominated its orbital zone, clearing away other objects.
Pluto meets the first two criteria but fails to meet the third. Its orbit is shared with other Kuiper Belt objects, and it has not cleared its orbital path. This led the IAU to reclassify Pluto as a dwarf planet in 2006, sparking debate and discussion among astronomers and the public alike. Despite the reclassification, Pluto remains a fascinating and important object of study in our solar system.
14. Pluto vs. Earth: A Comprehensive Comparison Table
To summarize the key differences between Pluto and Earth, consider the following comparison table:
| Feature | Pluto | Earth |
|---|---|---|
| Diameter | ~1,477 miles (2,377 km) | ~7,918 miles (12,742 km) |
| Distance from Sun | ~3.7 billion miles (5.9 billion km) | ~93 million miles (150 million km) |
| Orbital Period | 248 Earth years | 1 Earth year |
| Rotational Period | 153 hours | 24 hours |
| Atmosphere | Thin, nitrogen-based | Dense, nitrogen- and oxygen-based |
| Temperature | -375 to -400°F (-226 to -240°C) | -129 to 136°F (-89 to 58°C) |
| Moons | 5 (Charon, Nix, Hydra, Kerberos, Styx) | 1 |
| Rings | None | None |
| Planetary Status | Dwarf planet | Planet |
| Potential for Life | Low | High |
| Surface Composition | Ices (nitrogen, methane) | Rock, water, and vegetation |
| Geological Activity | Evidence of tectonic activity | Active volcanism and plate tectonics |
| Magnetic Field | Unknown | Present |
15. How Does Pluto Compare to Other Dwarf Planets?
Pluto is one of several dwarf planets in our solar system. Here’s a brief comparison:
- Eris: Slightly smaller than Pluto, Eris is another Kuiper Belt object with a highly eccentric orbit.
- Makemake: Another large Kuiper Belt object, Makemake is known for its reddish color and lack of a substantial atmosphere.
- Haumea: This dwarf planet is unique due to its elongated shape and rapid rotation.
- Ceres: Located in the asteroid belt, Ceres is the smallest dwarf planet and the only one in the inner solar system.
These dwarf planets share some similarities with Pluto, such as their small size and icy composition, but they also have unique characteristics that make them fascinating objects of study.
16. Exploring the Significance of Pluto’s Size
The small size of Pluto has significant implications for its geology, atmosphere, and potential for life. Its low gravity means that it has a tenuous atmosphere that is easily lost to space. Its small size also means that it cools down more quickly than larger planets, which can affect its internal geological activity.
Despite its small size, Pluto has proven to be a dynamic and complex world, with a diverse range of surface features and a fascinating atmospheric cycle. The New Horizons mission revealed that Pluto is far from being a dead, frozen world; it is an active and evolving body that continues to surprise and intrigue scientists.
17. The Future of Pluto Exploration: What’s Next?
While the New Horizons mission provided a wealth of information about Pluto, there is still much to learn about this distant world. Future missions could focus on:
- Atmospheric Studies: Detailed analysis of Pluto’s atmosphere to understand its composition, dynamics, and interaction with the solar wind.
- Surface Mapping: High-resolution mapping of Pluto’s surface to identify new geological features and study the processes shaping its landscape.
- Subsurface Ocean Exploration: Investigating the possibility of a subsurface ocean and its potential for harboring life.
- Kuiper Belt Object Studies: Studying other Kuiper Belt objects to understand the formation and evolution of Pluto and its neighbors.
These future missions will undoubtedly provide new insights into Pluto and the distant reaches of our solar system.
18. Key Discoveries from the New Horizons Mission
The New Horizons mission, which flew by Pluto in July 2015, revolutionized our understanding of this distant dwarf planet. Some of the key discoveries from the mission include:
- Geological Activity: Evidence of recent geological activity on Pluto, including smooth plains, mountains, and valleys.
- Atmospheric Complexity: A complex and dynamic atmosphere with layers, haze, and evidence of nitrogen snow.
- Icy Composition: Confirmation of the icy composition of Pluto’s surface, with a mix of nitrogen, methane, and water ice.
- Charon’s Surface: Detailed images of Charon’s surface, revealing a diverse landscape with canyons, mountains, and a reddish polar region.
- Absence of New Moons: No new moons were discovered during the flyby, confirming the presence of five known moons.
These discoveries have transformed Pluto from a distant, blurry dot into a dynamic and complex world that continues to intrigue scientists and the public alike.
19. Understanding Astronomical Units (AU) and Their Importance
An astronomical unit (AU) is the average distance between the Earth and the Sun, approximately 93 million miles (150 million kilometers). This unit of measurement is used to describe distances within our solar system. For example, Pluto is about 39 AU from the Sun, meaning it is 39 times farther away from the Sun than the Earth is. Using AU makes it easier to compare distances between objects in our solar system and to understand their relative positions.
20. Tidal Locking: The Unique Relationship Between Pluto and Charon
Tidal locking is a phenomenon where one celestial body always faces the same side to another celestial body due to gravitational forces. In the case of Pluto and Charon, Charon is tidally locked to Pluto, meaning that the same side of Charon always faces Pluto. This is because Charon is relatively large compared to Pluto, and its gravitational influence has slowed Pluto’s rotation until it matches Charon’s orbital period. Tidal locking is a common phenomenon in our solar system, and it has important implications for the geology and atmosphere of the bodies involved.
21. Convection: What It Means for Pluto’s Surface
Convection is a process where heat is transferred through a fluid (liquid or gas) by the movement of the fluid itself. On Pluto, evidence of convection has been observed in the smooth plains of frozen nitrogen gas. This suggests that heat from Pluto’s interior is causing the nitrogen ice to circulate, with warmer ice rising and cooler ice sinking. This process can create patterns on the surface, such as the cellular structures observed in Pluto’s nitrogen plains. Convection is an important mechanism for heat transfer and can play a significant role in shaping the surface of icy bodies like Pluto.
22. Sublimation: Pluto’s Atmospheric Cycle Explained
Sublimation is the process where a solid changes directly into a gas without passing through a liquid phase. On Pluto, sublimation occurs when the dwarf planet is closest to the Sun, causing its surface ices (primarily nitrogen, methane, and carbon monoxide) to turn into gas and form a thin atmosphere. As Pluto moves farther away from the Sun, the atmosphere freezes and falls back to the surface as snow. This sublimation cycle is responsible for Pluto’s dynamic atmosphere, which changes with its distance from the Sun.
23. The Kuiper Belt: Pluto’s Neighborhood and Its Significance
The Kuiper Belt is a region of the solar system beyond Neptune, extending from about 30 to 55 astronomical units (AU) from the Sun. It is populated by thousands of small, icy bodies, including Pluto and other dwarf planets. The Kuiper Belt is believed to be a remnant of the early solar system, containing materials that never coalesced into larger planets. Studying the Kuiper Belt and its objects can provide valuable insights into the formation and evolution of our solar system.
24. Exploring Trans-Neptunian Objects (TNOs) and Plutoids
Trans-Neptunian Objects (TNOs) are any objects in the solar system that orbit the Sun at a greater average distance than Neptune. This includes objects in the Kuiper Belt and the more distant scattered disc. Plutoids are a subclass of TNOs that are also dwarf planets. This includes Pluto, Eris, Makemake, and Haumea. Studying TNOs and plutoids helps us understand the diversity of objects in the outer solar system and the processes that shaped them.
25. Impact Craters: Clues to Pluto’s Past
Impact craters are bowl-shaped depressions on the surface of a celestial body, formed when an asteroid or comet collides with the surface. On Pluto, craters have been observed in some regions, while others appear to be relatively crater-free. The presence of craters can provide information about the age of the surface, with heavily cratered areas being older than smoother areas. The size, shape, and distribution of craters can also provide insights into the impact history of Pluto and the types of objects that have collided with its surface.
26. Tectonic Forces: Shaping Pluto’s Landscape
Tectonic forces are the forces that cause the Earth’s (and other celestial bodies’) crust to move and deform. On Pluto, evidence of tectonic activity has been observed in the form of long troughs, valleys, and ridges on the surface. These features suggest that Pluto’s crust has been subjected to stresses and strains, possibly due to internal processes or external forces such as tidal interactions with Charon. Tectonic forces can play a significant role in shaping the landscape of icy bodies like Pluto, creating diverse and complex geological features.
27. The Importance of Studying Pluto for Understanding Our Solar System
Studying Pluto, despite its reclassification as a dwarf planet, is crucial for understanding the broader context of our solar system. Pluto provides valuable insights into:
- The Formation of the Solar System: Pluto, as a Kuiper Belt object, offers clues about the materials and processes that were present in the early solar system.
- The Diversity of Planetary Bodies: Pluto’s unique characteristics challenge our assumptions about what a “planet” should be and highlight the diversity of objects in our solar system.
- The Processes Shaping Icy Worlds: Studying Pluto’s geology, atmosphere, and interactions with its moons can help us understand the processes that shape other icy bodies in our solar system and beyond.
- The Potential for Life Beyond Earth: While Pluto’s surface conditions are not conducive to life, the possibility of a subsurface ocean raises intriguing questions about the potential for life in unexpected environments.
By studying Pluto, we can gain a deeper understanding of the history, evolution, and potential of our solar system and the universe beyond.
28. Addressing Common Misconceptions About Pluto
There are several common misconceptions about Pluto, including:
- Pluto is no longer a planet: While Pluto is no longer classified as a “planet,” it is still considered a dwarf planet and an important object of study.
- Pluto is a cold, dead world: The New Horizons mission revealed that Pluto is a dynamic and geologically active world with a diverse range of surface features.
- Pluto is too small to be interesting: Pluto’s small size is precisely what makes it interesting, as it challenges our assumptions about what a planetary body should be like.
- Pluto is too far away to study: While Pluto is far away, missions like New Horizons have shown that it is possible to study these distant worlds and gain valuable insights.
By addressing these misconceptions, we can help the public appreciate the importance and fascination of Pluto and the ongoing exploration of our solar system.
29. The Role of NASA and Other Space Agencies in Pluto Exploration
NASA’s New Horizons mission was a landmark achievement in Pluto exploration, providing unprecedented images and data that have transformed our understanding of this distant world. Other space agencies, such as the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), have also contributed to our knowledge of the outer solar system through various missions and research programs. The ongoing collaboration between space agencies and researchers around the world is essential for advancing our understanding of Pluto and the solar system as a whole.
30. Pluto in Popular Culture: From Mythology to Modern Media
Pluto has captured the imagination of people around the world, appearing in numerous works of fiction, art, and popular culture. From its namesake, the Roman god of the underworld, to its appearance in science fiction novels and films, Pluto has become a symbol of the mysterious and unexplored reaches of our solar system. Its reclassification as a dwarf planet has also sparked public debate and discussion about the nature of planets and the process of scientific discovery.
31. FAQ About How Small Is Pluto Compared to Earth
-
How much smaller is Pluto compared to Earth?
Pluto is approximately 1/5th the width of Earth. -
If Earth were a basketball, how big would Pluto be?
If Earth were the size of a basketball, Pluto would be about the size of a golf ball. -
Why is Pluto so small compared to other planets?
Pluto is a dwarf planet in the Kuiper Belt, a region containing many small, icy bodies. -
Has the size of Pluto changed over time?
No, the size of Pluto has remained relatively constant over time. -
How does Pluto’s small size affect its atmosphere?
Pluto’s small size and low gravity result in a thin, tenuous atmosphere. -
What are the implications of Pluto’s size for potential life?
Pluto’s cold surface and thin atmosphere make it unlikely to support life as we know it. -
How does Pluto’s size compare to other dwarf planets?
Pluto is one of the larger dwarf planets, but smaller than Eris. -
Is there any benefit to Pluto being small?
Pluto’s small size allows scientists to study the composition of an icy body in the outer solar system. -
How has our understanding of Pluto’s size changed over time?
Our understanding of Pluto’s size has become more precise with advanced telescopes and space missions. -
Why does Pluto’s size matter in astronomical studies?
Pluto’s size is a key factor in understanding its geology, atmosphere, and potential for life.
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