In the end, the Sun would die if the Sun was smaller than Earth

Here is what will happen if the Sun is smaller than Earth.

It takes 1.3 million Earth to fill the volume of the Sun. The sun is so big that it accounts for 99% of the system's mass.

Viewed from Earth, the Sun is very small because it is 150 million kilometers away from us. Assuming the Sun is smaller than Earth, Earth will become an uninhabitable place and the Sun may no longer be a star.

In the universe, size is important and distance is equally important. The Earth is close to the Sun just enough to not freeze like Mars. It was also far enough away, so as not to be heated like Venus.

We are fortunate to be in the habitable area around the Sun. This means that our planet's size, the size of the Sun and the distance between them, are the conditions that allow life to evolve on Earth.

What will happen if the Sun is smaller than our Earth?

No matter what scenario, life on Earth will be destroyed.

The mass of a star determines its color and temperature. Larger stars are hotter and blue, while smaller stars are colder and red.

The sun is a white star, not as big as a giant superstar and not as small as a red dwarf. You may think that when the size of the Sun is smaller, it will turn into a red dwarf with a smaller habitable region. But that's not true.

By definition, a star regardless of whether it is a giant superstar or a red dwarf is just a star when there is a thermonuclear fusion reaction at its core. How small can stars be? Currently, we have not measured many red dwarfs, but the smallest star we have ever detected has a mass of 10 Earths. That level is close to the theoretical size needed for a star to maintain its reaction. If it is less than 10 Earth, it is no longer a star, but only a cold and dark star.

If for any reason the Sun shrinks smaller than Earth, the Sun will not have a mass to produce a reaction and will burn completely. Our solar system will lose a single star.

Because the sun is a source of gravity that keeps planets in orbit, every planet, including the Earth, will drift into space in search of other anchors. Life on Earth will not have a good outcome.

Let's assume again. This time, let the Earth be bigger than the Sun, while the size of the Sun stays the same.

The mass of the Earth will be at least 333,000 times larger now. Such a large planet will produce enough heat and core pressure to become a star itself. Of course, life will no longer exist on this hot star, but there is an interesting thing. Our star system will not only have one but two suns. It will become a binary star system, with two stars revolving around each other and the planets orbiting both.

No matter what scenario, life on Earth will be destroyed. But life can evolve on other planets, or even the Moon.

About a third of the star systems that we find are binary stars or more stars. Some of them have areas that can live sustainably.