Question

Why is the sun also a star?

Answer 1

Hint: Planets do not twinkle or shine. They remain constant in their brightness and their overall appearance in the night sky due to some other brightness. If viewed through a telescope, planets may appear to "wiggle" along the edges. Any object that blinks, twinkles, or shimmers is a star. Stars have their own brightness. Sun also has its own sunshine and it shines like other stars.

Complete answer:
As sun fulfils the requirements to be called a star, i.e.
Stars are space objects that produce their own energy through fusion reactions of gasses. They are like round, gas burning, energy producing luminous orbs.
Sun- the star of our solar system is a star because it produces energy by the fusion reaction of Helium turning into Hydrogen.
Our Sun is an average-sized star: there are smaller stars and larger stars, even up to 100 times larger. The Sun is composed almost entirely of hydrogen and helium gas. Multimillion-degree temperatures in its dense core sustain nuclear fusion, providing the energy source for sunlight. The Sun usually displays a few dark splotches. These sunspots are regions of concentrated magnetic fields. It is often said that the Sun is an ‘ordinary’ star. The outer layers of the Sun exhibit differential rotation: at the equator, the surface rotates once every 25.4 days; near the poles, it is as much as 36 days.
In addition to its role as the central object of our solar system, the Sun also is a star in a universe of stars. The Sun is sometimes referred to as a “typical” or “average” star. Perhaps if we were to average together in some mathematically appropriate way the properties of the most massive and hottest stars with those of the least massive and coolest stars, we would have the basic properties of the Sun. But stars that are closely like the Sun constitute only about 5% of the stars in our Milky Way galaxy! More than 80% of the stars in our galaxy are cool, less massive “red dwarf” stars. The Sun is by no means typical in the sense of common!
The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are ‘cool’ regions, only 3800 K (they look dark only by comparison with the surrounding regions). The Sun is about 4.5 billion years old. Since its birth, it has used up about half of the hydrogen in its core. There are eight planets and many smaller objects orbiting the Sun.
So, we can say that the Sun is also a star.

Note:
Just remember the fact that the sun fulfils all the criteria to be a star and proceed. As here the answer is noticeably big but do not confuse just read out all the points and paragraphs you will get a complete overview about the sun.