A star which appears blue will be

Options

A. very cold
B. colder than the Sun
C. a black hole
D. hotter than the Sun

Answer

To determine whether a star that appears blue is hotter or colder compared to the Sun, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Color and Temperature Relationship**:
- The color of a star is related to its temperature. Stars emit light at different wavelengths, and these wavelengths correspond to different colors. The visible spectrum ranges from red (longer wavelengths) to blue (shorter wavelengths).

2. **Identifying the Color of the Sun**:
- The Sun appears to emit light in the yellow-orange range, which corresponds to a temperature of about 5,500 degrees Celsius.

3. **Applying Wien's Displacement Law**:
- According to Wien's Law, the wavelength of light emitted by a black body is inversely proportional to its temperature. This can be expressed as:
\[ \lambda_{max} \cdot T = b \]
where \( \lambda_{max} \) is the wavelength of maximum emission, \( T \) is the temperature in Kelvin, and \( b \) is a constant.

4. **Comparing Wavelengths**:
- Blue light has a shorter wavelength compared to red light. Since the Sun emits light in the yellow-orange range, we can conclude that a blue star has a shorter wavelength than the Sun.

5. **Inferring Temperature**:
- Since shorter wavelengths correspond to higher temperatures (as per Wien's Law), a star that appears blue must be hotter than the Sun.

6. **Conclusion**:
- Therefore, a star that appears blue will be hotter than the Sun.

### Final Answer:
A star which appears blue will be **hotter** than the Sun.

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