Questions and Answers
Match the parts of a comet to their approximate sizes:
Nucleus = 10 km Gas and dust tails = 100 million km Coma = 100,000 km Hydrogen envelope = 10 million km
How would a comet nucleus be best described?
As a dirty snowball, loosely packed.
A comet loses material that forms its tail each time it passes by the Sun.
True
Where would you find a comet that has a long tail?
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The Sun has no role in creating the tails of a comet.
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What is the process of fluorescence?
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As a comet approaches the Sun, its ices turn directly into gas.
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What is the source of materials for a comet's tail?
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Ion tails of comets glow through fluorescence.
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What is the Kuiper belt?
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How long might a typical short-period comet take to return to the inner Solar System?
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What is significant about the object Oumuamua?
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Study Notes
Comet Structure and Characteristics
- The nucleus of a comet is about 10 km, characterized as a "dirty snowball" with a density of less than 1 kg/L.
- The coma measures approximately 100,000 km in diameter, surrounded by a hydrogen envelope up to 10 million km.
- Gas and dust tails can extend up to 100 million km.
Behavior Near the Sun
- Comets lose material with each approach to the Sun, leading to outbursts, explosions, and melting of the nucleus.
- As comets get closer to the Sun, solar radiation causes their surface ices to sublimate, transitioning directly into gas.
Tails of Comets
- The dust tail forms from particles pushed out of the coma by radiation pressure from sunlight, while the ion tail is influenced by the solar wind.
- Ion tails glow due to fluorescence as ultraviolet photons excite electrons in gas atoms, leading to the emission of visible light.
Sources of Cometary Materials
- The tail of a comet is primarily formed from sublimated material from the nucleus, originating from ices turning into gas as it approaches the Sun.
Fluorescence and Visibility
- The glowing effect of comet tails, particularly ion tails, occurs through fluorescence, similar to brightening of fluorescent paint under specific light conditions.
Kuiper Belt and Comet Origins
- The Kuiper belt is the source of short-period comets, containing significantly more mass than the asteroid belt and featuring objects with varied orbital inclinations.
- Short-period comets typically have orbital periods of less than 200 years, with a typical return interval of about 150 years to the inner Solar System.
Notable Observations
- The interstellar object Oumuamua passed within the orbit of Mercury in September 2017, showing accelerated motion and variations in brightness, suggesting it could be a comet from outside the Solar System.
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Description
Explore essential facts about comets with these flashcards. Each card provides crucial details such as the sizes of different comet parts and characteristics of comet nuclei. Perfect for quick revision or enhancing your understanding of comets.
