The sun is important to Earth because it helps regulate the climate, is the main source of energy for producers in the ecosystems and it keeps the oceans from freezing, along with providing light. If just one of these factors changed dramatically, it would impact all life on Earth. Without the sun, the planet's oceans would freeze, temperatures would drop and all life would die off without light or food.
The sun is important to every single aspect of life on the planet. Human life could not exist without it because it would cause all of the water and food sources to cease to exist. The sun is in no danger of disappearing any time soon. Scientists estimate the sun has at least another 5 billion years before it turns into a red giant and swallows up Mercury and Venus. It will also destroy all life on Earth because it will be close to the planet once that change occurs. The temperature of the sun will also increase tenfold from 18 million to 180 million degrees Fahrenheit. The increase in the sun's size when it finally begins to change will be due to the heat increase causing expansion.