Sky Scholarship

I take endless enjoyment from viewing the sky—either in the daytime, while watching patterns of the clouds, or at night, while watching patterns of the stars. Sometimes when I'm stargazing, I realize that I have not taken the time to learn the names and locations of many of the constellations. I feel quite unschooled in the celestial display above me. I know that the ancients were much more familiar with it than I am.

When I think about their sky scholarship as compared to mine, I recognize that our contemporary knowledge is fundamentally different from theirs. I know, for example, that those points of light are stars like our sun, off at distances that are hard for anyone to grasp. The science of astronomy has given me the knowledge to know certain facts that were beyond the ancients’ scholarship. They had no way of knowing what a star is, but their familiarity with the patterns and their movements far surpasses mine.

I sometimes fancy being able to transport myself back several thousand years, to sit beside an ancestor, as together we look up at the night sky, sharing our perspectives and individual scholarship on what we're viewing. I would love to tell my forebear what I know—as I struggle with attempting to describe what a star is and where it is and how it was created. Assuming we could surmount the language barrier—how might I get across the nuclear physics of star formation and their brilliance being due to all the energy being created by the fusion of hydrogen atoms? How could I even describe an atom?

But I would guess that my ancestral companion might equally struggle to help me understand the scholarship that they had built. But if we had the patience, I could benefit from their experiential understanding. I could delve deeply into the astronomical observatories that they painstakingly built—those marvels of engineering, like Stonehenge. I would learn about the knowledge accumulated over generations, as to the cyclic movement of the heavens—they did it by oral transmission, without writing anything down.

I would, with fascination, listen to how—despite their lack of astronomy—they had studied and become intimate with the comings and goings of the sun, the stars, the Moon, and the planets. They did not understand the true nature of these heavenly bodies, but they possessed a deep-seated scholarship of their behavior. And they saw meaning in those events... in the cycles. They could even forecast some heavenly happenings. They laid the foundation of their civilization and their spirituality on the predictable recurrence of those celestial sequences. My ancestor could show me a few things.

Naked-Eye Universe—Part 2

An ancient Greek astronomer, Hipparchus, became extremely familiar with the heavens. Like many of his compatriots, he was not limited by city lights and thus developed an intimate understanding of the night sky. Hipparchus was the first to classify stars according to their brightness. He had no idea of the distance between Earth and the stars (he even assumed that they were all the same distance away), but he carefully classified their relative brightness into six categories, which he labeled magnitude 1 to magnitude 6. His system has endured, so we still use it today.

Now that we know stars are at various distances away from us, it raises a few questions: When I look at a specific star—shining at its particular brightness or magnitude—am I looking at a faint star that is closer to us or a bright star that is farther away? How far away is the most distant star I can see with naked eye? Again, how big is the naked-eye universe that I can see from my tub? Just how far out can my eyes go?

A little research told me that the most distant star that we can see with the naked eye is in the constellation Cassiopeia. It's an extremely bright star—as brilliant as 100,000 suns—and it's 4,000 light years away. That's a mind-boggling distance of about 24,000,000,000,000,000 miles! It's amazing that my eyes can pick up light from a very bright star that far away. That seems to indicate a pretty big naked-eye universe. But let's put that in perspective, by comparing it to the size of the whole universe, which our most powerful telescopes and detailed scientific measurements have provided us.

Suppose I could imagine myself sitting at the center of a transparent Earth, letting the diameter of the Earth represent the size of our universe. If I looked outward from that center point, therefore, the surface of the Earth would represent the edge of the universe. What then (sitting in my tub, gazing at the stars with naked eye), would be the equivalent distance I could see in this scaled-down, Earth-sized universe? I could see as far out as about a tenth of an inch... about the size of a fat grape seed! I can't even fit inside a grape seed, but if I imagine myself at its center, my naked eye could only see as far as to the edge of the seed. Everything beyond that seed would be unknown to my naked eye.

Wow! My sense of sight (not amplified by a telescope) is but a grape seed at the center of an Earth-sized ball! It makes me realize just how small I am. I get to see but the tiniest part of this grand universe. The size of my minuscule naked-eye universe is really insignificant. Nevertheless, on a starry night I peer up from my tub and take in several hundred stars. It ain't much, compared to all that's out there, but it sure is magnificent!

Naked-Eye Universe—Part 1

Sitting in my outdoor tub, gazing at the dark (late) winter's sky, I can see hundreds of stars, even though my field of vision is significantly reduced by overhead trees and the bulk of the house behind me. Were I to be lying on my back while floating on the ocean or reposed on the flat desert sand, I would be able to count as many as 4,000 stars above me. So tonight, with my limited view, I still may be able to discern as many as a thousand stars. That's not a bad count.

But how deep a view am I looking at? How far “out there” can I see? I know that with my naked eye I can see but a tiny fraction of the number of stars that a telescope could capture. My eyes extend nowhere near as far out as telescopes go. So just how much of the whole universe can my naked eye sample?

Our ancestors were very familiar with the night sky—far more than we moderns. We may occasionally look up, but we are either limited by city lights or are so ignorant of the sky that we quickly lose interest and turn back to our electronic screens. Our ancestors did not possess telescopes (or cell phones), so they had no idea of how far away those stars were. In fact, most of the ancients believed that the stars were all about the same distance away... maybe just a little ways above the trees. So, although they were intimate with their sky, they had little idea of just how large the universe really is.

We moderns, however, know that those stars are not scattered across a hemispherical bowl immediately overhead, but are as far away as billions of light years. (A light year is really a measure of distance. It's the distance that light—the speediest thing in our universe—travels in one year; about 6,000,000,000,000 miles. That's a hell of a distance to try to wrap your head around! So we resort to light years.) So today we know something about the true size of our universe—because telescopes have told us.

But I wander. Back to my soaking in the outdoor tub: I know I can see but a tiny part of it all. How small a part? I look up and see hundreds, if not thousands of stars, and wonder what is the size of my naked-eye universe. It's ever so smaller than the whole enchilada. Astronomers tell me that there are billions of galaxies and trillions upon trillions of stars, but I can see only a wee portion... a much smaller portion of it all.

More naked-eye universe next time...

Out of Gas

Soon after the universe was created in the unique event dubbed the Big Bang, over 99% of the early universe's material was in the form of ephemeral clouds of the lightest and simplest of all elements: mostly hydrogen with a dash of helium. So where did all those blazing stars come from, and even more curious, how were all the heavier elements created, so that rocks and humans could later arrive?

The very first stars formed when those clouds of hydrogen gas began to lump together here and there, in the early universe. As gravity drew a huge glob of hydrogen tighter and tighter, the pressure became great enough that the hydrogen atoms began to fuse and ignited, the same way a hydrogen bomb does. The process emits enormous amounts of light and heat. We call it a star.

As a star's nuclear furnace cooks away, it's turning its hydrogen into helium. At the end of the star's useful life it will most likely blow up, blasting and spewing the remaining hydrogen, along with the created helium into space. We call it a nova or super nova. Of the original hydrogen that started the furnace, about 30% is left and is exploded away; the other 70% was transmuted into heavier elements—mostly helium, which is also blown away. And this process goes on in subsequent stars, forging heavier and heavier elements.

This nuclear process has continued for some 13 billion years now; stars igniting, burning for a few billion years, and blasting their remnants into space for the next generation of stars to be formed from the remains of the earlier ones. It's the universe's great recycling system.

But isn't there a limit to the number of times this recycling can occur? If every star consumes some 70% of the hydrogen that formed it, isn't the universe going to run out of hydrogen some day? Won't our great universe run out of gas? Well, yes, it will, and astronomers have recently detected that gradual depletion process. The universe isn't yet quite “running on empty,” but we certainly are slowing down. The rate of star formation has dropped off; it peaked when the universe was only a few billion years old.

The universe has only so much time left, but it needn't worry us humans too much as yet. It'll be many more billions of years before the last star is born, and billions (if not trillions) of years before they all wink out. Let our grandkids worry about it.

(On a more serious note, the fact that the universe will someday end—albeit may be trillions of years away—has significant implications to those who once thought we inhabit an eternal cosmos. That's the topic of another blog.)

Advancing Evening—Part 2

As the sun dips even farther below the western horizon, it grows ever darker. (I remind myself that the sun really stays right where it is; it's we who are rotating away from it.) I look upward, wondering how soon I'll spot the first evening's star. The sky is a medium indigo color—not quite yet ready to reveal that first pin point of starlight. 

It hits me that I am watching a game of “photon competition.” As the sun's profuse outpouring of photons (call it bright light) gets intercepted by yonder ridge, it lowers the light level surrounding me. As the sun’s photons decrease, the much fewer photons I receive from distant stars will begin to get a chance to be noticed. Those stars scattered out their abundant allotment of photons millions of years ago—a scant few of them finally reaching my eye. They will become visible only when the arriving nighttime reduces the sun's photons to near nonexistence.

The opposite of the rising ridge-shadow phenomenon visits in the morning, as the sun's first rays illuminate the very tips of trees. The shadows then retreat down the tree trunks—slowly yielding to the new day's light. 

I am reminded of a time a decade ago, when I meandered through Glacier National Park in Montana, and then across the border into Canada's Waterton Lakes National Park—the other half of that gorgeous Waterton-Glacier International Peace Park. Camped on the Canadian side, I arose before dawn to watch the morning's light slowly grow. I was greeted by the stunning sight of a distant, tall Rocky Mountain peak bathed in a golden spotlight, as the sun lit up the top of the mountain. I was riveted by the view, watching the brilliant yellow creep down the mountain. Then I noticed a dark, horizontal line etched across the mountain’s face. Curious! It didn't seem as if it could be a rock formation, so what could it be? Then it seemed to grow a wee bit larger and even appeared to undulate. Curioser! 

Perplexed, I stared at this wavering black line, and then noticed that it took on the appearance of a string of black pearls on a quivering necklace. Finally, I watched as the black pearls transformed into tiny Canada geese. Their wide V-formation grew larger, bore down upon me, and eventually flew overhead. By then, the mountain was half bathed in light, and I was still standing, unmoving, stunned.

When you take the time to register the sun's slow creep, as shadows steal sluggishly across the landscape, like the minute hand of a clock, another world exposes itself to you...a world that our rushed pace usually keeps hidden from us. It's great to step away from that bustle and become aware of a more measured world—one that lights up those serene places in our consciousness.

Senescent Cosmos

Most of us know that the universe is old…very old. In fact, only in the last few years has science been able to nail down the birth date of the universe with any accuracy. We now know it all began 13.7 billion years ago. In fact, cosmologists are certain enough that they’re confident it wasn't 13.6 or 13.8 billion years ago, but quite exactly 13.7. Just a few years ago, cosmologists weren't sure but what the Big Bang's birthday could have been as little as eight billion years or more than 20 billion years ago. Progress occurs. Isn't it comforting to know just how long this universe has been around? Don't we all want to know our true age?

Science is always refining its knowledge. That's why it appeals to me. We humans think that we are the smartest kid on the planetary block—and maybe we are, but we need to stay humble enough to acknowledge that's there's always room for improvement in our understanding. That's what science is all about: constantly working to improve our limited understanding...realizing that if we keep our minds open and our questioning active, our knowledge will certainly grow.

A British team of cosmologists recently expanded our knowledge of star birth across the universe—and the news can be a little depressing, if we let it. Their bottom-line result: as of this date in the life of our universe, 95% of all the stars that will ever come alive have already been born. Forget how old the cosmos is or how much longer it has to go, it'll only see another measly 5% of its stars come into existence.

Just think if we were to say the same for the human race. We've been around as a unique species for only about 200,000 years. Of all the billions of people who have existed, if we were to have only another 5% to go, that's frightening! Terrifying! It says that we only have just another couple of hundred years to go, and that's the end of humans. Senescence has caught up with us and we are done!

Well, the same is true of the cosmos. What can ease our propensity to panic is that the stars live so incredibly much longer than we do. While Homo sapiens might last a few score years, your average star will hang around for billions of years. Time is relative.

Although cosmologists have nailed down the birth date of the universe, they have yet to get a handle on how long before it winks out. They are sure we have at least 100 billion years to go, and maybe trillions, before that last star dies. Well, that's a time span we flash-in-the-pan humans cannot begin to comprehend—let alone fret about.

Still, it's a sobering thought. Those British cosmologists determined that peak star formation in the universe was about 10 billion years ago, when the cosmos was just a 3.7 billion-year-old baby. At that point, half of all the stars that would ever be formed were burning. It's been downhill ever since. Go out and take a gander at the starry sky soon. In a few billion years it'll be a lot more sparse.

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…