Fact Check: "Comets typically have eccentricities between 0.2 and 0.7."
What We Know
The eccentricity of an orbit is a measure of how much it deviates from a perfect circle, with values ranging from 0 (a perfect circle) to just below 1 (an elliptical orbit). Comets are known for having highly elliptical orbits, which can result in a wide range of eccentricities. According to COSMOS - Swinburne, "an ellipse has an eccentricity in the range 0 < e < 1," indicating that comets can indeed have eccentricities that fall within this range.
Furthermore, data from Wikipedia suggests that the eccentricities of various celestial bodies, including comets, can vary significantly. For instance, Halley's Comet has an eccentricity of approximately 0.967, which is much higher than the upper limit of 0.7 mentioned in the claim. This suggests that while some comets may have eccentricities between 0.2 and 0.7, many others have much higher values.
Analysis
The claim that "comets typically have eccentricities between 0.2 and 0.7" is somewhat misleading. While it is true that some comets fall within this range, the term "typically" implies a commonality that is not supported by the broader data on cometary orbits. The eccentricities of comets can vary widely. For example, the eccentricity of Halley's Comet is 0.967, which is significantly higher than 0.7, and many other comets also exhibit high eccentricities (Windows to the Universe).
Moreover, the source from COSMOS - Swinburne does not specify a typical range for cometary eccentricities, instead focusing on the general definition of eccentricity. This lack of specificity raises questions about the reliability of the claim. The Wikipedia entry on orbital eccentricity provides a broader context, indicating that while many comets have eccentricities that might fall within the stated range, a significant number do not.
Conclusion
Verdict: Partially True
The claim that "comets typically have eccentricities between 0.2 and 0.7" is partially true in that some comets do have eccentricities within this range. However, it is misleading as it suggests that this range is representative of all comets, ignoring the fact that many comets have much higher eccentricities. Therefore, while the statement holds for certain cases, it does not accurately reflect the diversity of cometary orbits.
