According to Kepler , planets move in

Options

A. Circular orbits around the sun
B. Eliptical orbits around the sun with sun at exact centre .
C. Straight lines with constant velocity
D. Eliptical orbits around the sun with sun at one of its foci

Answer

**Step-by-Step Solution:**

1. **Understanding Kepler's Laws**: Kepler formulated three laws of planetary motion. The first law, known as the Law of Ellipses, states that planets move in elliptical orbits around the Sun.

2. **Identifying the Shape of the Orbit**: According to Kepler's first law, the orbits of the planets are not circular but elliptical. An ellipse has two focal points (foci), and in the case of planetary motion, the Sun is located at one of these foci.

3. **Defining Key Terms**:
- **Perihelion**: This is the point in the orbit where the planet is closest to the Sun.
- **Aphelion**: This is the point in the orbit where the planet is farthest from the Sun.

4. **Evaluating the Options**:
- **Option 1**: "Circular orbits around the Sun" - This is incorrect as Kepler's first law specifies elliptical orbits.
- **Option 2**: "Elliptical orbits around the Sun with the Sun at the exact center" - This is also incorrect because the Sun is at one of the foci, not at the center.
- **Option 3**: "Straight lines with constant velocity" - This is incorrect as planets do not move in straight lines; they follow elliptical paths.
- **Option 4**: "Elliptical orbit around the Sun with the Sun at one of its foci" - This is correct according to Kepler's first law.

5. **Conclusion**: The correct answer is that planets move in elliptical orbits around the Sun with the Sun at one of its foci.

**Final Answer**: Elliptical orbit around the Sun with the Sun at one of its foci.

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