August 21, 2011
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 an even vaster universe.
Humans live a century or so. Stars last 100-million centuries. 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 west 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. These two wisps of light, called the Bridal 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 a couple of hundred bucks building my telescope. When I saw the Veil for the first time, I knew it was worth it. This, 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.
Some stars 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 their entire galaxy, which is made up of hundreds of billions of stars.
The Veil Nebula is the remnant of such a cataclysm. Forged in the inferno of that 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. In fact, so are you. The iron in your blood and the calcium in your bones could have been made in only one place — the hot, dense, bubbling, boiling cauldron of a dying star.
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 of life.
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 lives experience the full range of stellar birth and death.
As I shifted my telescope from the North American to the Bridal Veil Nebula for the first time so long ago, I remembered these lines by an anonymous amateur astronomer:
I have seen the birth
and death of suns
A hint, a wisp of light,
Seen but dimly from afar
The beginning and the ending
The morning and the evening star
Tom Burns is the Director of Ohio Wesleyan University’s Perkins Observatory. Contact him at email@example.com.