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From UPSC perspective, the following things are important :
Prelims level: Sun’s Rotation
Why in the News?
Indian astronomers at the Kodaikanal Solar Observatory (KSO) have achieved a groundbreaking feat by mapping, for the first time, the variation in the Sun’s rotation speed from its equator to its poles.
Sun’s Rotation: Key Facts
- Unlike a solid body, the Sun exhibits differential rotation, meaning different parts of the Sun rotate at different speeds.
- The rotation speed varies depending on latitude, with faster rotation near the equator and slower rotation toward the poles.
- This variation is primarily due to the Sun’s composition of gaseous plasma rather than solid material.
Rotation Period Variation by Latitude:
- Equatorial Regions: The rotation period at the equator is the fastest, around 24.47 days (sidereal rotation).
- Sunspot Zones (about 16 degrees latitude): Rotation slows slightly, with a period of about 27.3 days.
- Higher Latitudes (up to 75 degrees): Rotation slows significantly; for example, at 75 degrees latitude, the rotation period is about 33.4 days.
- Poles: The slowest rotation occurs at the poles, with a period around 31.1 days.
Sidereal vs. Synodic Rotation Periods:
- Sidereal Rotation Period: The time taken for the Sun to complete one full rotation relative to distant stars. It varies by latitude, from 24.47 days at the equator to around 33.4 days at higher latitudes.
- Synodic Rotation Period: This is the time for a fixed feature on the Sun to appear in the same position when observed from Earth. It is longer than the sidereal period due to Earth’s own movement around the Sun, averaging around 26.24 days.
Why Differential Rotation Occur?
- Gaseous Plasma Composition: The Sun is composed of plasma—a hot, ionized state of matter—which allows its different regions to rotate at different speeds.
- Convective Zone Dynamics: The outer convective layer of the Sun contributes to differential rotation. Plasma circulates, rising and sinking, which influences the rotational speed at different latitudes.
Scientific Implications
- Solar Dynamo Theory: The differential rotation of the Sun is central to theories about the solar dynamo—the process that generates the Sun’s magnetic field.
- Mystery of Differential Rotation: Despite extensive research, the exact mechanism behind the Sun’s differential rotation remains an active area of investigation in solar physics.
PYQ:[2013] Consider the following phenomena 1. Size of the sun at dusk 2. Colure of the sun at dawn 3. Moon being visible at dawn 4. Twinkle of stars in the sky 5. Polestar being visible in the sky Which of the above are optical illusions? (a) 1, 2 and 3 (b) 3, 4 and 5 (c) 1, 2 and 4 (d) 2, 3 and 5 |
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