How Old Is The Sun?
QUICK ANSWER
The Sun is about 4.5 billion years old, formed at roughly the same time as the rest of our solar system. It's a middle-aged star, currently in the main sequence stage of its life, and has about 5 billion more years before it expands into a red giant and eventually dies.
The Sun is about 4.5 billion years old, which makes it middle-aged for a star like itself. It formed at the same time as Earth and the rest of the solar system, when a dense cloud of gas and dust collapsed under its own gravity. The Sun has roughly 5 billion more years before it starts its dramatic final phase.
How do we know the Sun's age?
From dating the oldest material in the solar system. According to NASA, the Sun's age is estimated at about 4.5 billion years, based on radiometric dating of the oldest known meteorites and lunar samples. These objects formed at essentially the same time as the Sun, condensing from the same nebula. Radiometric dating uses the decay of radioactive isotopes to measure how long ago a rock formed. The oldest meteorites date to about 4.57 billion years.
How did the Sun form?
From a collapsing cloud of gas and dust. About 4.5 billion years ago, a region of a giant molecular cloud became dense enough to collapse under its own gravity. As the cloud collapsed, it spun faster and flattened into a disk. The center of the disk grew hotter and denser, eventually reaching temperatures and pressures high enough to ignite nuclear fusion. The hydrogen-helium fusion lit up the young Sun, while the leftover material in the surrounding disk gradually formed into planets, moons, and other smaller bodies.
What stage of life is the Sun in?
Main sequence, the longest and most stable stage. Stars spend the majority of their lifetimes in the main sequence, fusing hydrogen into helium in their cores at a steady, predictable rate. The Sun is roughly halfway through its main sequence lifetime, which lasts about 10 billion years total for a star its size. After exhausting its core hydrogen, the Sun will leave the main sequence and start a more dramatic phase. Until then, the Sun will continue much as we see it today, slowly brightening but not changing much.
How much time does the Sun have left?
About 5 billion more years before significant changes. The Sun has been gradually getting brighter throughout its lifetime and will continue to do so as it ages. Long before it ends its main sequence phase, the Sun's brightness will make Earth uninhabitable, probably within a billion years. In about 5 billion years, the Sun will expand into a red giant. After the red giant phase, the Sun will shed its outer layers and shrink to a white dwarf, fading slowly over billions more years.
The Sun is about 4.5 billion years old, roughly the same age as Earth and the rest of our solar system. It formed from a collapsing nebula and is currently in its stable main sequence phase, fusing hydrogen in its core. The Sun has about 5 billion more years before it expands into a red giant, then shrinks down to a white dwarf at the end of its long life.
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