Skywatching 3 – Watching the Stars Go By

proper motion

Watching the Stars Go By

Looking up on these dark clear nights
Gets me thinking –
Are these stars ever-burning lights ?
I doubt it – some are already blinking –
Variables, never the same through the year,
Though the diff’rence is pretty small beer.

And the way the heavens have always wheeled,
The polar axis shifting round,
Till some low stars will be concealed,
Below the horizon, gone to ground.
Others are still up there, still shine,
But the pyramids no longer align.

And of course, they’re all in orbit through the galaxy,
Just like the Sun,
Drifting in the gravity waves of the sea,
Closer and further as round they run
Changing the brightness that each appears,
Over the hundreds of thousands of years.

On even longer timeframes are the giants,
Stars which simply swell and swell,
And brighten as they do, in strict compliance
With their enlarged shell.
And after that, they slowly fade from view –
At least, without a lens or two.

And then there’s the stars that go boom –
The supernovas, blazes of glory,
The superstars that meet their doom
In one almighty furore.
But how many of these tonight
Will ever get to burn so bright ?

Well, first of all, forget the Type 1a’s,
We’ll never see them coming –
But the Type 2s, before they end their days,
They warn us first by humming –
Blowing off mass in dimming clouds
Whose nebulas we see as shrouds.

And we know they must be massive beasts
To begin with, these monster stars
But weighing one is a movable feast
With ridiculous error bars.
But we reckon they need eight Sun’s-worth of matter –
Though birth-weight or death-weight ?  Surely the latter …?

Yet finding a list of stars by mass is illusive,
Given their many uncertainties –
Perhaps their spectrums will prove more conclusive
In trying to determine these –
We know all O’s and B’s 1-to-4
Are massive enough to fatally roar.

Well, technic’ly the white dwarfs can be
As super-hot and white,
But all such dwarfs are too dim to see
On even the clearest night –
Take Sirius B – closer and larger than average dwarfs,
Yet still into the black of the sky he morphs.

But what about the other extreme,
The supergiants, too big to fade ?
The I’s, and maybe some II’s, by the Yerkes scheme,
Ought to make the grade.
But what percentage of all these stars comply ?
Who knows ?, but I doubt it’s very high

Still, however scant are these,
There’s some already shining bright –
Like Spica, Deneb and Antares,
Quite oblivious to their plight.
And Betelgeuse and Rigel bold –
Indeed, half of Orion, all told.

The sky is a restless place,
Forever shifting its paradigm,
It’s just that the eyes of the human race
Are merely a blink in time.
So if you ask me why I stare up ev’ry night,
It’s just to check the stars are all alright.

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