This year the summer solstice happens on June 21. If you were standing on the Arctic Circle with a clear view to the north, you would see the sun just touch the northern horizon at midnight. Farther north, the sun would not set at all.
Here in the Northwest, the solstice brings us our longest day and shortest night of the year. It also marks the northern most point in the sky our sun reaches in the northern hemisphere.
So what is our sun exactly? How did it come to be? Will it always be there for us?
Our sun, like most stars, is a gigantic thermonuclear explosion. It has been happening for billions of years and will continue for more billions of years. Deep in the core of our sun where pressures are extreme and temperatures reach millions of degrees, hydrogen atoms are being crammed together into helium atoms. This process releases photons, which create almost all the light we see by here on Earth.
Interestingly, after a photon is born in the core of the sun, it takes tens of thousands of years to reach the surface because it bounces around in there so much. Once clear of the sun, that photon zooms to the earth at 186, 282 miles per second in 8 minutes. Our sun produces and emits the equivalent energy of 6 trillion Hiroshima-sized atomic bombs every second. Wow! That’s a lot of energy!
Why are we not blasted off the surface of our little planet by all those atomic bombs? Luckily, we reside a comfortable 93 million miles away.
Billions of years ago before our sun was even a twinkle in the Milky Way’s eye, a large dark cloud of hydrogen gas was drifting through our galaxy just minding its own business. Suddenly, not too far away a star exploded. Shock waves rippled through that cloud causing it to collapse and compress in places. When a gas compresses it heats up, and when the temperature reaches millions of degrees, nuclear fusion starts. A star is born.
Astronomers think this is more or less how our sun came to be. They also believe that we once had a few hundred siblings with us to boot. Huge gravitational forces of the Milky Way galaxy have ripped our sun apart from its brothers and sisters, and we now travel alone through the cosmos.
All things grow old, and stars are no exception. Our sun is slowly and inexorably advancing towards the red giant phase of its life, which will spell doom for all things living on earth. Our sun is a balance between the explosive outward pressure of nuclear fusion and the crushing inward force of gravity.
As the sun runs out of gas, hydrogen gas, that balance is upset. The sun will get bigger and hotter. Scientists give it about another 800 million years until things get critical. At that point the oceans will be boiling away, leaving our planet with an atmosphere of oppressive, hot steam and making it impossible for us or much of anything else to live here.
If anything is left of humanity at that point, they will have to move. One of Jupiter’s moons would be a good choice, but even there it will be only a temporary respite as things get worse and worse for our sun.
Eight-hundred million years sounds like a very long time, but remember that life has been evolving here on earth for three and a half billion years. The Earth has only one shot at creating advanced life here, and this is it. There is simply not enough time for a second chance.
The planets are all in a line in the east before dawn. Jupiter and Venus are the two bright ones, but Mars and Saturn are there too. Never look at the sun through a telescope, binoculars or the unaided eye. Not even with dark glasses. Severe eye damage could occur. The sun is just too bright.
Do not worry too much about all the doom and gloom happening to our sun. Your social security will run out long before you have to start breathing steam.