Pluto Day Quiz: How Much You Know About Pluto Day?

Pluto is a relatively small dwarf planet in our solar system, and its diameter is approximately 2,376 kilometers (1,476 miles). This measurement makes Pluto significantly smaller than the eight recognized planets, including Earth. In fact, Pluto is even smaller than some of the larger moons in our solar system. The size of Pluto was a subject of interest and debate in the scientific community, and its status as the ninth planet in our solar system was challenged. In 2006, the International Astronomical Union (IAU) reclassified Pluto as a "dwarf planet," highlighting its smaller size and distinctive characteristics compared to the eight classical planets. Despite being smaller than Earth's moon, Pluto has a complex and dynamic atmosphere, a variety of surface features, and a moon of its own called Charon. The New Horizons spacecraft, which conducted a flyby of Pluto in 2015, provided valuable data and images that enhanced our understanding of this distant world.

New Horizons is a NASA spacecraft designed to explore the outer regions of our solar system. Launched on January 19, 2006, the primary objective of New Horizons was to study Pluto, its moon Charon, and other objects in the Kuiper Belt, which is a region of the solar system beyond the orbit of Neptune. After a nine-and-a-half-year journey covering a distance of over three billion miles, New Horizons conducted its historic flyby of Pluto on July 14, 2015. During the flyby, the spacecraft collected a wealth of data, including detailed images of Pluto's surface, information about its atmosphere, and measurements of its various characteristics. This mission provided scientists with the first close-up views of Pluto and significantly expanded our knowledge of this distant world. New Horizons continued its mission into the Kuiper Belt, where it conducted a flyby of another Kuiper Belt Object (KBO) named Arrokoth (previously known as Ultima Thule) on January 1, 2019. The spacecraft continues to transmit valuable data back to Earth as it ventures deeper into the outer reaches of our solar system. The New Horizons mission has been instrumental in advancing our understanding of the outer solar system and the objects that inhabit it.

The extremely cold temperatures on Pluto's surface can be attributed to its significant distance from the Sun and its thin atmosphere. Pluto is located in the outer regions of the solar system, where sunlight is much weaker compared to the inner planets. Additionally, Pluto has a highly elliptical orbit, which means its distance from the Sun varies considerably during its orbital journey. At its farthest point from the Sun (aphelion), Pluto is over 7 billion miles away, and at its closest point (perihelion), it is still more than 4.4 billion miles away. This vast distance results in a very weak and distant sunlight, leading to extremely cold conditions. Furthermore, Pluto's thin atmosphere, primarily composed of nitrogen, methane, and carbon monoxide, is not sufficient to retain and trap heat effectively. As a result, the surface temperature drops to remarkably low levels. The average temperature of -230 degrees Celsius (-382 degrees Fahrenheit) makes Pluto one of the coldest objects in our solar system. The challenging environmental conditions on Pluto's surface contribute to the unique and inhospitable nature of this distant dwarf planet.

Pluto's atmosphere is primarily composed of nitrogen, making up the majority of its thin envelope of gases. Nitrogen is the dominant component, constituting about 98% of Pluto's atmosphere. Additionally, there are trace amounts of other gases, including methane and carbon monoxide. The thinness of Pluto's atmosphere is a result of its small size and low surface gravity, which makes it challenging for the planet to retain a substantial atmosphere. When Pluto is closer to the Sun in its elliptical orbit, the increase in solar radiation causes some of the ices on its surface, such as nitrogen, methane, and carbon monoxide, to sublimate and temporarily form a thin atmosphere. However, as Pluto moves farther from the Sun, these gases freeze back onto the surface. While nitrogen is the primary component, the presence of other trace gases contributes to the complex chemistry of Pluto's atmosphere. Studying the composition and behavior of Pluto's atmosphere provides valuable insights into the characteristics and dynamics of this distant dwarf planet. The New Horizons spacecraft, which conducted a flyby of Pluto in 2015, provided crucial data to enhance our understanding of Pluto's atmosphere and surface features.

Pluto is known to have five moons. Here is a brief explanation of each:Charon: Charon is the largest and closest moon to Pluto. It is so large in comparison to Pluto that the two bodies are often considered a binary system rather than a planet and a moon. Charon's diameter is about half that of Pluto.Styx, Nix, Kerberos, and Hydra: These four smaller moons were discovered using the Hubble Space Telescope. Styx, Nix, Kerberos, and Hydra are much smaller than Charon and have irregular shapes. They were named after mythological figures associated with the underworld, in keeping with the theme of naming Pluto's moons after characters related to the god Pluto (the Roman equivalent of the Greek god Hades).The study of Pluto's moons provides valuable insights into the formation and evolution of the Pluto system. These moons are believed to be remnants of a collision or capture events in Pluto's history.

The orbital period of a celestial object refers to the time it takes to complete one orbit around its parent body—in the case of Pluto, its orbit around the Sun. Pluto has a highly elliptical and elongated orbit compared to the more circular orbits of the eight classical planets in our solar system. Pluto's average distance from the Sun is much greater than that of the inner planets. This, coupled with its elliptical orbit, results in a longer orbital period. The average orbital period for Pluto is approximately 248 Earth years. This means that it takes about 248 Earth years for Pluto to complete one full orbit around the Sun. During its long journey around the Sun, Pluto undergoes significant changes in its distance from the Sun, temperature, and other environmental factors. The elongated orbit contributes to Pluto's unique characteristics and places it in a region of the solar system known as the Kuiper Belt, which is populated with other icy objects. The study of Pluto's orbit and its interactions with the solar environment has been a subject of interest in planetary science and astronomy.

The New Horizons spacecraft was launched by NASA on January 19, 2006, with the primary mission of exploring the outer regions of our solar system and studying Pluto, its moons, and other objects in the Kuiper Belt. The spacecraft was equipped with various scientific instruments, including cameras, spectrometers, and other sensors, to capture high-resolution images and collect data about Pluto's composition, atmosphere, and surface features. After a journey of over nine years, covering a distance of more than three billion miles, New Horizons made its historic flyby of Pluto on July 14, 2015. During the flyby, the spacecraft came within about 7,800 miles (12,500 kilometers) of Pluto's surface, providing scientists with unprecedented views and valuable scientific measurements. The data collected by New Horizons revealed a diverse and dynamic world, with a complex atmosphere, distinct surface features, and surprising geological processes. The mission significantly expanded our understanding of Pluto and its moons, challenging some earlier assumptions and leading to new insights into the outer reaches of our solar system. New Horizons continued its mission beyond Pluto, conducting a flyby of the Kuiper Belt Object (KBO) Arrokoth (previously known as Ultima Thule) on January 1, 2019. The spacecraft is now on its way out of the solar system, continuing to transmit valuable data about the space environment as it ventures into the unexplored regions beyond.

In 2006, the International Astronomical Union (IAU) introduced a formal definition for the term "planet," which led to the reclassification of Pluto. According to the IAU definition, for a celestial body to be considered a planet, it must meet three criteria:1. Orbiting the Sun: The object must orbit the Sun.2. Sufficient mass for a nearly round shape: The object must have sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape (in other words, it has to be spherical or nearly spherical).3. Clearing its orbit: The object must have cleared its orbit of other debris.Pluto meets the first two criteria but fails the third one. Its orbit is not entirely cleared of other debris, as it shares its orbital neighborhood with other objects in the Kuiper Belt. Therefore, Pluto was reclassified as a "dwarf planet."A dwarf planet is a distinct category of celestial bodies that, while similar to planets in some aspects, does not satisfy the "clearing its orbit" criterion. Other notable dwarf planets include Eris, Haumea, and Makemake, all located in the Kuiper Belt beyond Neptune. While Pluto's status as a dwarf planet has been established within the scientific community, it remains a fascinating object of study and exploration. The New Horizons mission, which conducted a flyby of Pluto in 2015, provided valuable data about this distant world.

Clyde Tombaugh discovered Pluto through a systematic search for a ninth planet in our solar system. The discovery process involved using a technique called "blink comparison," which was developed by astronomer Vesto Melvin Slipher. Tombaugh took pairs of photographic plates of the same region of the sky at different times and carefully compared them using a device called a blink comparator.The blink comparator allowed Tombaugh to switch rapidly between the two photographic plates. Stars would appear stationary, but anything that moved, such as a planet or a distant object within our solar system, would show a slight shift in position. After months of careful examination, Tombaugh noticed a small, faint point of light that changed position between the plates.On February 18, 1930, Tombaugh announced the discovery of Pluto. The discovery was particularly significant because it represented the first detection of a new planet in our solar system since the discovery of Neptune in 1846. Pluto remained classified as the ninth planet until 2006 when the International Astronomical Union (IAU) redefined the criteria for what constitutes a planet, leading to Pluto's reclassification as a dwarf planet.Clyde Tombaugh's work not only marked a historic moment in astronomy but also opened up new avenues for understanding the outer regions of our solar system. His discovery expanded our knowledge of the celestial bodies beyond the known planets at that time.