Question

Why does the sun appear to be bigger and brighter as compared to other stars?

Answer 1

Hint: Comparison of apparent size of objects is the comparison of angular sizes. This means that a close 10 cm sized object will be apparently smaller if it was kept far.

Complete step-by-step answer:
Apparent size can be said to be given as the ratio of the actual size of the object to the distance of the object from the observer. Brightness is given as the total intensity over squared of the distance from the source.
Size of the sun is \[ \sim {10^{10}}\] m and is \[ \sim {10^{15}}\] m away from us. Hence the apparent size is \[ \sim {10^{ - 5}}\]. However, others stars are \[ \sim {10^{20}}\] m away, which means that their apparent sizes are \[ \sim {10^{ - 10}}\], Which is five orders smaller. Similar is the case of the Sun’s brightness.
So basically, the sun is closer to the Earth as compared to the other stars and that’s why it appears bigger and brighter to us.

Note: All the stars do not shine equally; there are stars which glow brighter than others. There are two major things that astronomers look at while determining how bright a star is. They are: a star’s true brightness and its apparent brightness.
Additional information: Astronomers sometimes refer to a star’s true brightness as its luminosity. Luminosity is a measure of how much energy or light a star shines from its surface. Assume stars as a light bulb; light bulbs with higher wattages or more power glow brighter. The same thing happens with starts. The more luminous or powerful a star is the brighter it glows. While measuring the luminosity astronomers are considering how bright the star is as if they were standing in space right in front of it. That’s why they call it its true brightness. It’s how bright the star really is and not how bright a star might look depending on where you are.