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 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 tlburns@owu.edu.

Posted by Tom Burns on Aug 21 2011. You can follow any responses to this entry through the RSS Feed. Comments can be made below.