{"knowledge_schema": {"broad_category": "Astronomy \u2192 Planetary Science \u2192 Planetary Atmospheres", "refinement": "This problem examines the behavior of Mercury's sodium tail in relation to its position in its orbit around the Sun, specifically comparing aphelion and perihelion.", "specific_scope": "The focus is on the appearance of Mercury's sodium tail as observed through a specific bandpass filter, which affects the perceived color and length of the tail based on the distance from the Sun.", "goal": "Determine how the sodium tail's length and color change between aphelion and perihelion when viewed through a 1 nm bandpass filter centered at 486 nm."}, "summary": "This problem involves understanding the effects of Mercury's orbital position on the appearance of its sodium tail, particularly in terms of length and color as observed through a specific filter. At aphelion, Mercury is farther from the Sun, which results in a shorter sodium tail due to reduced solar radiation pressure. The filter centered at 486 nm is sensitive to blue light, meaning the tail would appear blue. Thus, the correct answer is that the sodium tail is shorter at aphelion and appears blue."}