How old is the sun and how long will it really last?
It is about 4.6 billion years old, and halfway through its main sequence. In about 5 billion years it will expand to a red giant. We won’t be here to worry about it though. It will be heating up gradually before that and will become too hot for human habitation in about 2 – 3 billion years. “1.1 billion years from now – The Sun becomes 10% brighter than today. The Earth’s atmosphere dries out. 3 billion years from now – The Andromeda Galaxy collides with our galaxy. Many solar systems are destroyed. 3.5 billion years from now – The Sun becomes 40% brighter than today. If the Earth is still orbiting the sun, its oceans evaporate. 5.4 billion years from now – The Sun’s core runs out of hydrogen, and it enters its first red giant phase, becoming 1.6 times bigger and 2.2 times brighter than today. 6.5 billion years from now – The Sun becomes a full-fledged red giant, 170 times bigger and 2400 times brighter than today. 6.7 billion years from now – The Sun starts fusing helium and shrinks b
