Al Stahler: Birthing stars
Before there were clocks or calendars or compasses, there was the sky. Stars and sun and moon tell time and date and direction.
Stars in the pre-dawn southeastern sky remind us that the rainy season is coming.
Missing for months, the constellation Orion has now re-entered the night sky, rising before the sun, in the southeast. A major constellation of the rainy season, Orion not only announces the coming end of the hot, dry summer, but also allows us to look back – way back – into the past.
First thing to catch the eye, when hunting the Hunter, is the Hunter’s belt –a line of three, medium-bright stars. Hanging from the belt is another line of three stars, not quite so bright: The Hunter’s knife.
Binoculars reveal the middle “star” of the knife as an imposter. All the other stars in the glass are twinkling points, but the middle “star” of the knife is a fuzzball.
A small telescope reveals the fuzzball to be a ginormous ball of gas and dust. And within the fuzzy ball of gas and dust, the binocs reveal true stars.
The knife’s ginormous ball of gas and dust is cosmic womb. The stars within are babes, born in regions where dust and gas fell in on itself, squeezing the gas and dust hot enough, first, to glow, then hot enough to glue the nuclei of hydrogen atoms together to make helium nuclei. The process – fusion – releases energy: Starlight.
Events taking place in that ball of gas and dust in Orion are repeating events that took place in another ball of gas and dust, four-and-a-half billion years ago.
Long ago, moving among the star of our galaxy, this ball of gas and dust would slowly approach, then abandon, one star after another. Not much happened … until the ball of gas and dust drifted close to a massive star nearing the end of its life.
A massive stars dies in a humongous explosion: a supernova.
(A smaller star may experience an occasional, non-fatal outburst. Previously invisible, the exploding star would suddenly burst into naked eye visibility. Early observers, thinking something new had been born, called this a “stella nova” – a “new star,” soon shortened to “nova.” A supernova is way more powerful than a nova.).
Four-and-a-half billion years ago, before the ball of gas and dust could drift away, the massive star went supernova. The shockwave from the explosion squeezed gas and dust together. Then gravity took over, pulling gas and dust toward the center, squeezing it yet harder. The ball collapsed. In the center, a star was born: our sun. From some of the gas and dust remaining, planets formed.
Prior to collapse, the ball of gas and dust had been spinning.
A pizza chef takes a round ball of dough, and spins it. Even as the edges of the dough ball stretch outward, the top and bottom pull inward. The ball flattens into a pizza-shaped disc.
Our spinning ball of gas and dust did the same – it flattened into a disk. The solar system is flat as a pancake … flat as a pizza. All the planets lie inside that pancake.
Looking down on the spinning ball of gas and dust, prior to collapse … looking down from above its north pole … we would have seen the gas and dust spinning counterclockwise. We know this, because planets circle the sun counterclockwise; planets spin, giving us night and day, counterclockwise. Even the sun spins – over some weeks – counterclockwise.
We live in a carousel: The solar system – sun and planets – is a merry-go-round. Each planet is a horse on the carousel. We ride the horse called Earth.
But … something odd. The horses (planets) themselves are spinning.
When the sun sets, our horse is facing backwards – facing back, in the direction from which we’ve come. The stars that come out as the sun goes down are the stars of the previous season.
By midnight, though, our horse has turned enough to look outward …To look at the stars of the present season.
And then – by dawn – our horse has turned enough to look straight ahead – to look in the direction toward which the carousel is carrying us. Now we can see the constellations of the season ahead. And thus, before dawn, Orion climbs high in the southeastern sky … telling us the rainy season is coming.
Astronomers recognize close to a hundred constellations. But, moving in their flat pancake, planets and moon can pass before only a dozen or so of those constellations – the constellations of the zodiac.
Constrained to the same, narrow part of the sky, planets and moon often pass one another.
Our moon will pass planet Venus tonight (Thursday), right after sunset. Venus and moon have already passed each other several times this year, but so close to the horizon, I’ve held off mentioning them. Now, where I live, they’re just high enough to get briefly above the trees. So if you’ve got a decent view of the western sky – someplace from which you can watch the sunset – Venus and the moon will be a treat, just after the sun goes down, before the sky grows dark – 7:30 or 8 o’clock. (There will be more, easier ops to see Venus and moon together, later this year.).
Another planet has been shining in the early-evening sky for some time: Jupiter shining brightly in the east, after sunset.
Al Stahler enjoys sharing science and nature with friends and neighbors in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and can be reached at firstname.lastname@example.org
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