Star birth, star death
The night sky reminds us that we inhabit but a small portion of space and time, a tiny fragment of our vast galaxy, a brief moment in a universe vast beyond human comprehension.
These days, humans live a century or so if they are lucky. Stars last 100 million centuries. A recent walk in the Zaleski State Forest reminded me that we humans can still see the long life of a star from beginning to ending.
This time of the year, the acorns fall like rain. It’s hard not to get bonked on the head at least once. My bonk produced a revelation. I saw the acorns fall. I saw the tiny seedlings with their huge leaves. I saw the mighty, mature oak. And I saw its rotting remnants on the ground.
The universe is the ultimate forest. Look around, and you will see stars at every stage of their development.
They are born in huge clouds of hydrogen gas and dust called emission nebulae. One of the best of them can be seen in the summer sky as the season wanes.
Look almost straight overhead in the early evening for the constellation Cygnus. It looks like a large cross lying on its side. Just down and to the left of the north-most star (the top star in the cross) is a large, faint patch of light. It is just visible in binoculars on a crystal-clear night from dark, rural skies.
You are looking at the North American Nebula, so named because of its striking resemblance to our continent. In a telescope, use the lowest power available. The part by the “Gulf of Mexico” is easiest to see.
Enmeshed in the North American Nebula are hot, new baby stars that will last perhaps 10 billion years.
At the western end of the same constellation, the situation is reversed. Down and to the right from the west-most star in the cross is a faint star. That star is embedded in a faint arc of light that is just visible with large binoculars away from city lights.
Nearby to the north is another faint arc. The two wisps of light, called the Veil Nebula, seem to form a broken circle.
In a large amateur telescope, they have the subtle look of smoke rising from a dying ember. Their detailed filaments, undulations, and cataracts of light are played out against the velvet blackness of space behind and intertwined within them.
I spent over a thousand bucks building my telescope. When I saw the Veil for the first time, I knew it was worth it. That, my friends, is a thousand-dollar view.
During their lives, stars combine hydrogen into helium in a stupendous hydrogen-bomb explosion that lasts 10 billion years.
But this seething thermonuclear reaction is nothing compared to what happens to some stars when they reach the end of their life cycles. Having used up their supply of hydrogen, they self destruct, sending their substance back out into space, perhaps to form the building blocks of new stars.
As stars like our sun use up the hydrogen in their hot centers, they expand to gigantic sizes and turn red. The normal evolution of a large star is from the relatively stable yellow star like our sun to a bloated red giant, over 500 times the diameter of our sun.
Often these red giants collapse into very dense balls, called white dwarfs, which are only a few thousand miles in diameter. Imagine most of the substance of our sun, which is over 850,000 miles in diameter, condensed into a sphere only half the diameter of Earth, about 4,000 miles across.
A small portion of the star’s substance is blown into space, forming a rapidly expanding shell of gas made up mostly of hydrogen.
Some stars end their lives in a much more violent expansion. They explode with brilliance hundreds of millions of times greater than their original brightness. Such explosions, or supernovas, are commonly observed in other galaxies. They briefly shine brighter than the their galaxy, which is made up of billions of stars.
The Veil Nebula is the remnant of such a cataclysm.
Forged in the inferno of such an explosion are the heavier elements found on rocky planets like our Earth. Metals like copper and iron can be formed in no other way than in the belly of a supernova. The gold you wear around your neck and in the ring around your finger is the beautiful artifact of the spectacular death of a star billions of years ago.
The cloud of dust and gas surrounding the Veil was expelled at about 1,000 miles per second. The supernova that caused it happened a long time ago, perhaps 40,000 years.
The expansion of these arcs of light has decreased to only 45 miles per second, slowed by the other dust and gas that inhabit the interstellar medium in the area. In a few tens of thousands of years, they will no longer be visible. They will have blended into the gas and dust between the stars.
Perhaps their hydrogen will form new stars. Perhaps their metals will make up the substance of new planets, their gold to adorn the forms of new races.
Human life is short, a candle in the wind compared to the blazing conflagration we call a star. But with the investment of a few hundred dollars and a sleepless night or two, we can in the short expanse of our brief candles the full range of stellar evolution.
Tom Burns is the director of Ohio Wesleyan University’s Perkins Observatory. He can be reached at email@example.com.