Introduction / Context:
Pluto, once known as the ninth planet and now classified as a dwarf planet, has a long and eccentric orbit around the Sun. Its orbital period is a common general knowledge question in astronomy-related sections, because it highlights how far Pluto lies from the Sun compared with the inner planets. Knowing the approximate number of Earth years for Pluto's revolution helps students understand the scale of the outer Solar System.
Given Data / Assumptions:
• The question asks for the time Pluto takes to orbit the Sun, expressed in Earth years.
• Options are 76, 144, 198 and 248 years.
• We assume a basic awareness of planetary periods, especially for outer bodies.
Concept / Approach:
Kepler's third law tells us that the farther a planet is from the Sun, the longer its orbital period. Pluto orbits far beyond Neptune on an elongated path. Observations and calculations show that Pluto takes about 248 Earth years to complete one revolution around the Sun. Hence, among the given options, the correct value is 248 years, while the other numbers are significantly off from the accepted astronomical period.
Step-by-Step Solution:
1. Recall approximate orbital periods: Earth takes 1 year, Jupiter about 12 years and Neptune about 165 years.
2. Pluto lies even farther out than Neptune, so its period must be greater than 165 years.
3. Compare the options: 76 years is less than the time Neptune takes and is too small.
4. 144 and 198 years are also shorter than Pluto's well-known period in standard references.
5. 248 years closely matches the established period of approximately 247.7–248 Earth years.
6. Therefore, the correct choice is 248 years.
Verification / Alternative check:
Astronomy handbooks and reputable scientific sources list Pluto's orbital period as roughly 248 Earth years. This value is used when discussing its long year, seasonal changes and the fact that humans have not yet observed Pluto complete a full orbit since its discovery in 1930. Such cross-checks confirm that 248 years is the accepted approximate value for exam purposes.
Why Other Options Are Wrong:
Option A, 76 years, is close to the period of some comets and is far too short for a distant dwarf planet like Pluto. Options B and C, 144 and 198 years respectively, are more than Neptune's 165-year period but still significantly below Pluto's actual orbital time. These numbers serve as distractors for students who only remember that Pluto's year is ‘‘very long’’ but do not recall the precise approximate value.
Common Pitfalls:
A frequent mistake is to recall the period incorrectly as about 200 years or to confuse it with the orbital periods of Uranus or Neptune. Another pitfall is to underestimate how rapidly orbital period increases with distance from the Sun in the outer Solar System. To avoid confusion, students should memorise that Pluto's year is around 248 Earth years, making it one of the longest among known dwarf planets and classical planets.
Final Answer:
Pluto takes approximately
248 years to complete one full orbit around the Sun.
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