Out of the Blue, Into the Black

Transition from the light and certainty, into the dark and uncertainty. This is the story of mass’s endpoint, at least within the context of relativity. Still, it’s beyond explanation, a mystery.

Once mass goes beyond 20 solar masses it can happen but there is no magic predictive number. The endpoint is determined by the leftover stellar remnant’s mass.

Out of the blue – beyond the mass of a neutron star, from the light. Into the black – beyond the event horizon, into the dark uncertainty of matter collapsing into a singularity. A black hole.

Over the past several weeks I have illustrated how the universe is a continuum by describing how stellar evolution depends on mass. It’s a scale. A star’s evolutionary endpoint depends where it exists on this scale. I began with yellow dwarf stars, like our Sun and I am ending with extra massive stars, beyond 20 times the mass of our Sun.  I did not include red dwarf stars; their evolution is so protracted it’s almost not measurable.

Looking at the mass scale, stellar evolution is mostly predicable. As mass increases for young stars their end evolutionary products decrease in size, from Earth size White Dwarfs  to Canyon Lake size Neutron Stars, to the enigmatic singularity. Let’s look at the singularity – oh, sorry can’t do that. I’ll just talk about it.

How does it happen? We think we have an idea. The star will have greater than 20 solar masses.  The critical condition is what happens when this star evolves, when its outward fusion pressure cannot counteract gravity. One of three things can result. It just blows itself to smithereens, it ends up with a remnant 1.5-2 solar masses, or it ends up with a remnant greater than 2 solar masses. In all cases there will be significant mass shed, speeding away rapidly. With the 1.5-2 solar mass remnant neutron degeneracy pressure plus nuclear forces holds it up and it’s a neutron star. Beyond 2 solar masses however (the Tolman-Oppenheimer-Volkoff limit), all its mass collapses into a singularity – a point or ring with no known volume and infinite density.

Is it black? We do not know. It could be brilliant on the inside for all we know, with photons whizzing and bouncing everywhere, unable to escape the singularity’s gravity. It has what we call an event horizon. That’s the border where its gravity can capture objects, including photons, and not let go.

Into the black – maybe, maybe not. It’s uncertain.

What’s in the Sky?

Tye Preston Memorial Library in Canyon Lake is hosting its last Astronomy Night of the season tonight, April 30. Start time is 8:30 PM in the library.  We will be having a Sun Party next month, May 21st, at 2PM.

Comet C/2021 03 (PanSTARRS) is lurking in the western sky after sunset. Use binoculars. It will be just west and then moving northwest of the Pleiades (M45) star cluster, low in the west-northwest.