The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radiation, and is the most important source of energy for life on Earth.
Or not so much? Our Sun is 4,500,000,000 years old. That's a lot of zeroes. That's four and a half billion.
In about 5.5 billion years the Sun will run out of hydrogen and begin expanding as it burns helium. It will swap from being a yellow giant to a red giant, expanding beyond the orbit of Mars and vaporizing Earth—including the atoms that make-up you.
The sunlight we see is 170 000 years and 8.5 minutes old. It is ancient!
Solar 25 Update (January 2022)
The Sun is in the rising part of its 11-year cycle of activity. NOAA recently confirmed that Cycle 25 is outperforming the official forecast. As of January 2022, actual sunspot counts to date are stronger than predicted. Credit: NOAA.
Solar flares and eruptions will likely increase from now until 2025, as we reach “solar maximum,” writes Nicola Fox, the director of NASA's heliophysics division. “During the Sun's natural 11-year cycle, the Sun shifts from relatively calm to stormy, then back again,” says Fox.
The sun is no different, and when the sun dies, the Earth goes with it. But our planet won't go quietly into the night. Rather, when the sun expands into a red giant during the throes of death, it will vaporize the Earth.
The Sun survives by burning hydrogen atoms into helium atoms in its core. In fact, it burns through 600 million tons of hydrogen every second. And as the Sun's core becomes saturated with this helium, it shrinks, causing nuclear fusion reactions to speed up - which means that the Sun spits out more energy.
They made observations via the European Space Agency's (ESA) (opens in new tab) Hipparcos satellite and estimated that HD140283 — or Methuselah as it's commonly known — was a staggering 16 billion years old.
At the current rate of solar brightening—just over 1% every 100 million years—Earth would suffer this "runaway greenhouse" in 600 million to 700 million years. Earth will suffer some preliminary effects leading up to that, too.
It will not grow by much more than another factor of a few for the next 6 billion years, but at that distant time, it will make a rapid transition to a red giant phase and its outer surface will expand by several hundred times to perhaps the orbit of Venus.
The study pushes back the clock on the origin of Earth's water by hundreds of millions of years, to around 4.6 billion years ago, when all the worlds of the inner solar system were still forming.
Astronomers believe that our own Milky Way galaxy is approximately 13.6 billion years old.
After spending about 1 billion years as a red giant, our own sun will become a white dwarf, packing most of its initial mass into a sphere roughly the size of Earth. This fate awaits many other stars as well — all of them that are less than about eight times more massive than the sun, in fact.
The Sun could not harbor life as we know it because of its extreme temperatures and radiation. Yet life on Earth is only possible because of the Sun's light and energy.
If derived from Latin, the moon is feminine and the sun masculine. If Germanic, it's the other way round.
Our Sun May Have Been Born With a Trouble-Making Twin Called 'Nemesis' A recent model on how stars are formed adds weight to the hypothesis that most – if not all – stars are born in a litter with at least one sibling.
A star called 18 Scorpii is a mirror image of our own sun
This "solar twin," a faint star in the constellation Scorpio, mirrors the sun's physical properties in every measurable respect, according to a report here 6 January at a meeting of the American Astronomical Society.
Fires can't start in space itself because there is no oxygen – or indeed anything else – in a vacuum. Yet inside the confines of spacecraft, and freed from gravity, flames behave in strange and beautiful ways. They burn at cooler temperatures, in unfamiliar shapes and are powered by unusual chemistry.
Air is made-up of about 21% oxygen, 78% nitrogen and less than 1% other gases including carbon dioxide and water vapor. Fire only needs about 16% oxygen to burn. Without oxygen, fires won't burn. Water vapor in the air, or high relative humidity values, help to keep fuel sources moist.
So what happens to the sun when it runs out of its hydrogen fuel? JOSHUA: Right, so the sun is about four and a half billion years old, and in about five billion years, it's going to start to run out of its fuel. And then it will expand into what's known as a red giant.
Warmth: not too much and not too little
And we get the amount of warmth needed for humans, animals and plants to live. If the sun would go out, no life could survive on most of earth's surface within a few weeks. Water and air would freeze over into sheets of ice.
Our Sun is just one of about 200 billion stars in our galaxy.
Without the Moon stabilising our tilt, it is possible that the Earth's tilt could vary wildly. It would move from no tilt (which means no seasons) to a large tilt (which means extreme weather and even ice ages).