Now, I hope that you remember what I talked about before,|
When I spoke at length of dying stars and such.
Well, here I am again; I'm back to give you an encore,
'Bout what happens to a star
When its behavior gets bizarre
As it dies, because it weighs so very much.
I'm talking here about those supermassive types of stars:
A dozen solar masses at the least.
What happens to them as they say their final au revoirs?
Well, they often do go nova,
But the story's not yet "ova,"
There is much to do before they are deceased.
Now these novas are exploding stars; this happens at the end,
When a massive star exhausts it nuclear fuel.
It collapses, making temperatures too high to comprehend,
Then the shell becomes so dense
It stops neutrinos cold, and hence,
It just explodes, and then its "ashes" spread and cool.
But what happens to the core that such a nova'd leave behind,
Having thrown most of its mass out into space?
Well, assuming that its mass is large enough, then you will find
That there is truth more strange than fiction
Hid in physics' jurisdiction:
The core would vanish, leaving not a trace!
Okay, that part I said about its "leaving not a trace"
Is not entirely true; I'll tell you why.
Although by merely looking, you'd see nothing in its place,
If you measured gravitation,
You would see a demonstration
Where you'd swear that something's badly gone awry.
There'd be a gravitational well that simply would not quit,
Consuming everything that happened by;
And nothing could come out that went into this bottomless pit--
Even photons can't get out,
But in steep'ning downward route,
They would vanish with a tiny, tortured cry.
See, a "black hole," as they call these things, is just exactly that:
Its escape velocity is more than c.
And, of course, this means that nothing can go past the line whereat
Even light is bound securely;
And if light is bound, then surely,
Nothing else could hope to e'er again be free.
This line beneath which light is trapped is the "event horizon"
Because whatever happens underneath
Can never be perceived, because (and this is not surprisin')
Since no signals can get out,
You can see, without a doubt,
The event horizon's just a one-way sheath.
So what happens to the star-stuff that's inside this sphere of black?
It shrinks and shrinks, 'til it's completely gone.
But how can a singularity--this spatial cul-de-sac--
Exhibit gravity like that?
Such a cosmic Cheshire cat
Goes away, but leaves a "smile" of gravitons.
Well, we're not exactly sure what astrophysics are required
To give answer to these questions; this we know.
And indeed, the more we learn, we find the more we get inspired
To learn more, for every answer,
While an intellect enhancer,
Helps us see how terribly far we've got to go.