The Sun is about 4.6 billion years old. That puts it roughly halfway through its main-sequence life of around 10 billion years, so our star is essentially middle-aged. It was born from a collapsing cloud of gas and dust, and it has been steadily fusing hydrogen into helium ever since.
How we know its age
We do not read the age off the Sun directly. The most reliable number comes from dating the oldest solid bits of the solar system, like meteorites, which formed at essentially the same time as the Sun.
Those rocks date to about 4.6 billion years, and since the whole system condensed together from the same cloud, the Sun shares that birthday. Models of how stars like ours burn through their fuel confirm the figure fits neatly.
It is a rare case where chemistry, physics, and astronomy all point to the same answer. That agreement is why scientists are confident in the 4.6-billion-year mark.
Born from a collapsing cloud
The Sun started as part of a giant cloud of gas and dust. Something nudged a dense pocket of it to collapse under its own gravity, and as it fell inward it spun faster and heated up.
When the core got hot and dense enough, hydrogen fusion ignited and the Sun switched on. That moment marked the birth of the star as we know it.
The leftover material in the spinning disk went on to form the planets, including Earth. So the Sun and everything orbiting it are siblings, all born from the same collapsing cloud at roughly the same time.
Middle-aged, not old
At 4.6 billion years into a roughly 10-billion-year run, the Sun has plenty of fuel left. It is burning through its hydrogen at a stable, steady pace.
That stability is why Earth has had billions of years of fairly consistent sunlight, long enough for life to appear and stick around. A wildly fluctuating star would have made that far harder.
In human terms, the Sun is in the calm, productive middle of its life, far from any dramatic changes.
Our star is about 4.6 billion years old and only halfway done. The Sun is in no hurry.
What happens at the end
In about 5 billion years, the Sun will run low on core hydrogen and start to swell. It will balloon into a red giant, likely large enough to scorch or even swallow the inner planets.
After shedding its outer layers, what remains will shrink into a white dwarf: a dense, slowly cooling ember about the size of Earth. That faint cinder is the Sun's final form, and it will simply fade over an enormous stretch of time.
- Current age: about 4.6 billion years
- Total main-sequence life: about 10 billion years
- Stage now: roughly halfway, middle-aged
- Next phase (~5 billion years): red giant
- Final form: white dwarf
Young by cosmic standards
For all its 4.6 billion years, the Sun is not an especially old star. The universe itself is about 13.8 billion years old, so plenty of stars formed long before ours and many will outlive it by far.
The Sun is a fairly ordinary middle-sized star, which is part of what makes it so steady. The most massive stars burn through their fuel in just a few million years and die violently, while small red dwarfs can keep going for trillions of years.
Our Sun lands comfortably in between, with a long enough life and a calm enough temperament to give a planet like Earth the stability it needed. That balance is a big reason we are here to ask how old it is at all.
Knowing the Sun is only halfway through its life is also strangely reassuring. Whatever happens to it next is so far off that it has no bearing on anything we will ever experience, billions of years removed from any human concern.
Try It Yourself
Want to mess around with the ideas above? On whatifs.fun, Solar System, Size of Space and Galaxy Map all let you do exactly that — free, in your browser, no download.
Keep reading: how old the universe is and how old the Earth is. Both go deeper on the same rabbit hole.