Cosmic Matter
From the onset of the cosmos, energy expanded and dissipated. Once matter formed, the early universe was a hot, dense plasma of emerging photons, electrons, and protons.
Depending upon the account you cotton to, it took anywhere from 10 seconds to 10’s of billions of years for the cosmos to cool enough for atoms to form: protons captivating electrons via the music of emerging electromagnetism.
Neutrons weigh 1.00137841917 that of protons; exactly the ratio needed for nucleosynthesis: the creation of atomic nuclei in stars. Further, the electrical charge of electrons neatly balances that of protons. Without these precise balances, there would be no matter in the universe.
At 3,000 Kelvin (K), electrons slowed enough to be snared by the gravitational force of atomic nuclei and set up housekeeping as atoms. Only the lightest elements – hydrogen and helium – spontaneously arose as primordial gases.
The universe was still mostly dark, though scattered with matter, and seething with energy. The slightest variations in gravitational densities acted as seeds for the distribution of what would become stars and galaxies.
Reionization is one of the major milestones in the universe’s history. ~ American astronomer Brant Robertson
A peculiar transition may have happened 13.6–12.8 BYA: reionization. Something stripped the electrons off atoms.
Radiation bursts from star formation in the 1st generations of galaxies may have caused reionization, though how it came about remains mysterious. Whether reionization even occurred is less than certain. The cosmic particle soup had thinned enough prior to reionization that photons could travel freely, turning most the universe’s matter into the glowing ionized plasma that abides to this day.
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From the appearance of primordial gas clouds it took hundreds of million years for the nascent stars to accrete. The 1st stars brought light and warmth into the cosmos, as well as melting hydrogen and helium together, forging the heavier elements, including carbon, nitrogen, and oxygen. After a few hundred million years of stars making matter, all the natural elements had emerged.
As they were the first to sup on primordial matter, the earliest stars were monstrously large. Some were the size and luminosity of 100 million suns.
The distortion of gravity was slow to make its cosmic presence felt; only with the advent of the first stars did gravity emerge in any significant way. As gravity came into play, swirls of matter coalesced into nebulas, forming galaxies ~13.2 billion years ago.
Gravity is not the only force binding cosmic matter. Magnetism was instrumental in shaping accretion disks that became stars and black holes, and in its flux begetting glue to nascent galaxies.
Metals – such as life-essential iron – are rather evenly spread throughout the cosmos. This is the legacy of an energetic episode for matter creation, when exploding stars and black holes at the hearts of young galaxies were especially vigorous.
Dust
The primordial cosmos consisted of hydrogen and helium, with slight traces of lithium. The heavier elements – needed for planets and everything else made of matter as we think of it – are manufactured via supernova explosions. Such star dust was sucked into new stars as they formed. Hence, ever-heavier elements were made.
The first supernova stars had already lived their lives and were gone 13.62 billion years ago. By 13.22 bya, the relentless progression of dust trade-up was well underway.
(There are considerable discrepancies in chronologies among the various accounts of cosmic evolution, all of which are highly speculative. On the previous page, the first stars formed 13.72–13.27 billion years ago; now, a mere page later, supernova stars had already blown their lights out 13.62 bya.)
Even now, most of the ordinary matter in the cosmos is hydrogen and helium. The most abundant molecule in the universe – H2 – primarily forms on the surfaces of dust grains. Heavier elements make up only 1% of galactic mass. Half of heavy matter is bound in dust grains which are blown into existence by the aftermath of a supernova; thus, from dust to dust.
Dust largely defines the interstellar medium. In absorbing ultraviolet radiation from stars, dust emits electrons that are the main heat source of interstellar gas. This bit of warmth from dust helps molecules survive the harshness of deep space. Hence, cold, diffuse clouds of molecular hydrogen course the vastness of space. These clouds may be as frigid as 7 K and as diffuse as 300 light-years.
Over billions of years, the persistent gentle nudge of gravity corrals the molecules in interstellar space closer to each other. They warm as they snuggle. The excitation hastens further condensation. Stars form in these regions. Dust is the subtle conductor of star formation.
Absorbing radiation imparts momentum to dust grains, driving them away from newly formed stars, or even an entire galaxy. Such winds transfer vast amounts of matter between galaxies. Large galaxies, such as the Milky Way, may have amassed half their matter from neighboring star clusters up to a million light-years away. Thus, dust plays an essential role in the evolution of galaxies.
Dust dies by shock: destroyed by shock waves that emanate from the remnants of a supernova. The shock waves are partly comprised of high-speed dust grains, traveling in excess of 1,000 km second. These fast-moving grains are also subject to shocks as they come to rest in the interstellar medium. When it comes to cosmic dust, what comes around goes around.
