Archive for April 6th, 2016

Astronomy Domine

April 6, 2016

Astronomy domine is a song much played in philosophy, not just by Pink Floyd, ever since there are men, and they observe. (Homo Erectus probably observed the last fabulous Galactic Core Eruption, two million years ago.)

Before feeding the pocketbooks of the greedy, science feeds the imagination of poets.

Astronomy has been at the forefront of physics, at least since Buridan (14th Century). Buridan applied his notion of impetus to explain that planets went around in circles from what we now call inertia. In Greek Antiquity, a large, wagon sized meteorite landed in Northern Greece, and was visited for centuries (it may have been a piece of Halley’s comet, which whizzed by spectacularly close in 466 BCE).

A Place Of Great Eruptions, Past & Future. Eta Carinae Nebula, At Least A Couple of Giant Stars, The Lightest One At Least 30 Sun Masses, the Largest Maybe As Much As 220 Solar Masses, 7,500 Light Years Away. Five Million Times The Luminosity Of the Sun. Stellar Natures & Explosions Are Far From Fully Understood!

A Place Of Great Eruptions, Past & Future. Eta Carinae Nebula, At Least A Couple of Giant Stars, The Lightest One At Least 30 Sun Masses, the Largest Maybe As Much As 220 Solar Masses, 7,500 Light Years Away. Five Million Times The Luminosity Of the Sun. Stellar Natures & Explosions Are Far From Fully Understood!

Supernova explosions are awesome: the most luminous one ever detected had a peak luminosity 570 BILLION times the luminosity of the Sun (yes, (570) 10^9 Suns; that was seen in 2015).

Supernovae are us. Supernovae create most of chemistry: the extremely high temperatures of their explosions enable light nuclei to smash into each other, and fuse, making most elements of the periodic table.

There are two main types of stars which explode as supernovae: white dwarfs and massive giant stars. In the so-called Type Ia supernovae, gases falling onto a white dwarf raise its mass until it nears a critical level, the Chandrasekhar limit, resulting in an explosion when the mass approaches exactly 1.44 Solar Mass. In Type Ib/c and Type II supernovae, the progenitor star is a massive star which runs out of fuel to power its nuclear fusion reactions and collapses in on itself, reaching astounding temperatures as it implodes, and then explodes.

Supernova science is very far from finished knowledge. Even the nature of the Crab Nebula supernova, which was seen to explode in 1054 CE, is not clear (it is known it was a big star, more than 8 Solar Masses; it left a pulsar).

Even the Crab was philosophically interesting in devious ways: the explosion was duly recorded by Europeans and Chinese. However the Muslims tried very hard not to see it (a mention was recently found). Indeed, the heavens, for desert savages, are supposed to be messages from God, and God playing games with stars was apparently not kosher…

Type Ia supernovae have completely changed our idea of the universe in the last two decades. (According to your modest servant, other types of supernovae may change our view of the universe even more dramatically. See the conclusion!)

Eta Carinae is the only star known to produce ultraviolet laser emission!

There is some philosophy to be extracted from Eta Carinae: if a star, or a system of gravitationally bound stars, can be that exotic, how sure are we from the astrophysics we think we know?

I am not the only one who thought of this. The teams who determined the accelerating acceleration of the universe (“Dark Energy”), had to exclude weird, sort-of Type Ia Supernovae… from their statistics (pre-selecting the population of explosions they would apply statistics on…). There are now other ways to detect Dark Energy (and they give the same results as the pre-selected Type Ia supernovae studies). So the results have been confirmed.

However my position is more subtle, and general. How sure are we of the astrophysics we have, to the point that we can claim that stars are unable to create all the known elements? In the proportion observed?

I am no specialist of astrophysics. But, as a philosopher, I have seen the science evolve considerably, so I think we cannot be sure that we absolutely need the hellish temperatures of the Big Bang to generate all observed elements.

Very large stars (600 Solar masses) have now been observed. They don’t live very long. I don’t see why stars thousands of Solar Masses, living only for a few hundred years, before exploding, are not possible. During these so-far-unconceived apocalypses, nucleogenesis could well follow unexpected ways.

And that could well remove one of the main arguments for the Big Bang.

Patrice Ayme’