Superstar—Part 2

Picking back up on the post of a few days ago...

If a star is much larger than our sun (at least twice the size), it will terminate itself with an even larger spectacular ending. It goes on beyond a red giant to become a supergiant, after which it explodes into a supernova. The core can then collapse into an unimaginably dense ball the size of a small city, called a neutron star.

Let’s go up to the next size star—at least four times our sun—the biggest stars until recently that were thought to exist. When these guys go supernova and then collapse, what’s left is called a black hole… the most dense object we know of in the universe.

Going down from our sun in star size, we find red dwarf stars. These are anywhere from about half the size of our sun, to less than a tenth. Being so small, they don’t have that much gravity to squeeze them, so they burn very slowly. Whereas a star like our sun will last for 5-10 billion years, a red dwarf will keep going for many billions of years… maybe even a trillion.

That, until a few years ago, was the full range of star sizes thought possible. But now comes along the superstars found by Gal-Yam and his cohorts. These stars may be 100-200 times the size of our sun! Any star this big was thought either to be impossible to form or, if it could exist, was too big to explode. They, like old soldiers, were believed to just fade away. Astronomers now have to rethink the stellar process, however.

These newly-discovered superstars end in more than just a supernova; so maybe we have to come up with a new moniker and maybe call them super supernova? And we have to expand our understanding of star formation and death. One of the more fascinating results of the regular old supernova is that they have previously been thought to be the only way heavy elements were formed in the early universe. Just after the Big Bang, something like 99.99% of the material in the baby universe was hydrogen—no oxygen, carbon, silicon, iron, or any of the other many elements that compose our Earth and us human-like critters. (By the way, the other 0.01%? Mostly a wee bit of helium.) Only in the wake of the massive early supernova explosions were the heavier elements formed; only after these early stars burned and blew up, could planets, people, and fireflies be formed.

But now we find that there’s a new chapter to the story. We have gone beyond mere supernovae to super supernovae. Our limited human knowledge once again expands. No one yet knows quite what these superstars mean. Maybe we have yet to discover super superstars, with their super super supernovae? This is getting a little clumsy. Will we have to come up with even more superlative names? Megastars? Meganovae? Mega megastars?

The universe still refuses to accede to our limited definitions and comprehension. It remains bigger than we can wrap our heads around. We’re just beginning to pry open its secrets. (Actually, they are not secrets at all, but knowledge just waiting for us to wake up to.) I wish I could live another couple of hundred years, if only to learn a few more of these mysteries.

Superstar—Part 1

Back in 1971 Andrew Lloyd Weber and Tim Rice—two very talented Brits—conceived of the rock opera “Jesus Christ Superstar” and ushered in a new kind of entertainment, as well as provoked a lot of people to rethink the story of Jesus. I recently watched the 1973 movie once again—an inspired production filmed in the beautiful Israeli desert. I love the music!

What Sir Andrew and Sir Tim couldn’t anticipate was that decades after their opera, another type of superstar would be discovered—this time not by a couple of talented Brits, but by a skilled Israeli astronomer. Avishay Gal-Yam has an article in the June 2012 issue of Scientific American magazine, titled “Super Supernovae,” that describes how he and associates came upon these superstars. (Maybe super superstars?)

Prior to this discovery, the accepted wisdom in the astronomical world was that the largest a star could get was maybe as much as 100 times the size of our sun. There are many kinds of stars in our majestic universe—with a wide range of size, temperature, color, brightness, age, and number (single, double, or even triple stars). Each kind has its own type of life history. Every star winks into existence when a cloud of interstellar gas (almost completely hydrogen) collapses on itself and ignites under tremendous gravitational pressure, kicking off a nuclear fusion process. The star emits its shine for millions or billions of years, as the hydrogen fuel becomes slowly fused into helium.

When the hydrogen begins to run out is when stars get interesting. Their next act is a dying one—sometimes far more dramatic than what Shakespeare conjured up in “Romeo and Juliet.” The nature of that swan song depends mostly on the size of the star. Every star begins to collapse into itself, when its fuel diminishes. Some (like our sun) will then swell into red giants, and what’s left after that will then shrink back to a white dwarf. If the dwarf has a partner (part of a double star system) that’s still burning, the dwarf may steal some of its partner’s fuel and later explode into a nova. They are called that because, to the ancients (who were very familiar with the night sky), the explosion suddenly became very visible to the naked eye and seemed to them to be a new star appearing in the heavens.

More superstars next time…