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We Are Starlight!

We are stardust; we would not be here if the stars did not exist. This is because the only atomic elements born in the wild inflation of the Big Bang birth of the Universe, almost 14 billion years ago, are hydrogen, helium, and small amounts of lithium and beryllium–while all of the heavier atomic elements that made life possible were created in the searing-hot, nuclear-fusing furnaces of the Universe’s myriad of dazzling, searing-hot stars that progressively fused heavier atoms (baryons) out of lighter ones– or, alternatively, in the brilliant blaze of supernovae blasts heralding the “death” throes of massive stars. Life exists as a wild celebration of wonderful forms–but if any organism is broken down into its components, all are made of the same star-stuff: a brew of carbon atoms attached to hydrogen, oxygen, nitrogen, and other atomic elements. But how these fundamental molecules formed in space has long been an intriguing mystery. In October 2016, astronomers announced that they have attained a better understanding of how these very important molecules, so necessary for the production of the chemicals needed for life to emerge, form in space–the ultraviolet light emitted by stars plays a necessary role in creating these molecules.

Molecules are defined as a group of atoms that are bonded together, and that represent the smallest fundamental unit of a chemical compound that has the ability to participate in a chemical reaction. Thanks to new data derived from the European Space Agency’s (ESA’s) Herschel Space Observatory, astronomers were able to make the new discovery that the ultraviolet light streaming out from fiery stars plays a central role in the creation of these important molecules–as opposed to “shock” events that create turbulence, as was suggested previously.

The scientists analyzed the ingredients that go into the complicated concoction of carbon chemistry. In order to do this, they carefully studied the Orion Nebula, which is the closest star-forming region to our planet that is in the process of giving birth to new massive baby stars. The astronomers mapped the quantity, temperature and movements of the carbon-hydrogen molecule that chemists call methylidyne (CH), the carbon-hydrogen positive ion (CH+) and their parent: the carbon ion (C+). An ion is defined as an atom or molecule possessing an imbalance of electrons and protons. This imbalance results in a net charge.

“On Earth, the Sun is the driving source of almost all the life on Earth. Now, we have learned that starlight drives the formation of chemicals that are precursors to chemicals that we need to make life,” explained Dr. Patrick Morris in an October 12, 2016 NASA Jet Propulsion Laboratory (JPL) Press Release. Dr. Morris is lead author of the paper and a researcher at the Infrared Processing and Analysis Center at the California Institute of Technology (Caltech) in Pasadena, California.

We Are Stardust

Stellar nucleosynthesis is the term used to describe how the natural abundances of the chemical elements contained within stars undergo a sea-change as a result of the nuclear-fusion reactions in their cores and their enveloping mantles. Stars, like people, change as they grow older. These changes involve the abundances of the elements that stars harbor in their nuclear-fusing hearts, and this core fusion increases the atomic weight of its elements, and reduces the number of particles. This would lead to a pressure loss, but the star’s gravitation results in contraction that, in turn, results in an increase of temperature and a balance of these two eternally warring forces–gravity and radiation pressure.

Stars are enormous balls of extremely hot, roiling, and glaring gas. The billions of stars inhabiting the observable Universe are all composed primarily of hydrogen. Hydrogen is both the lightest and most abundant of all the atomic elements, as listed in the familiar Periodic Table. In their magnificent and mysteriously secretive hearts, the stars transform their supply of hydrogen fuel into progressively heavier and heavier atomic elements. All atomic elements heavier than helium were created in the hearts of stars, and they are collectively termed metals in the jargon of astronomers. Therefore, the term metal for an astronomer does not have the same meaning that it does for a chemist.

Baby stars are nested within the secretive, billowing folds that exist deep within the undulating, giant, dark, and frigid molecular clouds that float around our Milky Way Galaxy in great abundance. These beautiful, starlit clouds are composed mostly of gas sprinkled with dust, and they serve as the strange cradles of newborn stars. Especially dense blobs, embedded within the folds of these swirling, ghostly clouds, clump together in a rich assortment of sizes, with the smaller blobs extending about one light-year across. The dense blobs eventually collapse under the weight of their own gravity to form a baby star (protostar). The entire process of star-birth takes about 10 million years.

The billions of sparkling stellar inhabitants of the Universe are all kept bouncy as a result of the energy that is produced by the nuclear-fusion taking place in their cores. The stars maintain an important, delicate equilibrium between their powerful, crushing gravity–that tries to pull everything in–and their enormous energy output, which creates radiation pressure, that tries to push everything out. This necessary, precarious balance between the ever-battling gravity and radiation pressure goes on and on and on from stellar birth to stellar death. The struggle exists throughout the entire “lifetime” of a star–which it spends on the hydrogen-burning main-sequence of the Hertzsprung-Russell Diagram of Stellar Evolution.

Alas, the inevitable must occur, and the star is doomed when it has at last consumed its entire necessary supply of hydrogen fuel in its hot nuclear-fusing heart. At this tragic point, gravity wins the war against radiation pressure, and the star’s core collapses–signifying stellar death. A star dies with either a bang or a whimper–depending on its mass. Small stars, like our own Sun, perish in relative peace–gently puffing their lovely, varicolored outer gaseous layers into the space between stars, leaving only a small, dense core behind to tell its tragic story. The dense core left behind by the star-that-was is termed a white dwarf, and its surrounding shimmering shroud of colorful and beautiful gases is called a planetary nebula.

More massive stars die with a much bigger bang than their smaller stellar siblings. The more massive stars blast themselves to pieces in the catastrophic fury of a flashy and fiery supernova explosion. Massive stars leave behind either a neutron star or a black hole of stellar mass to haunt interstellar space, telling the story of how once there was a star that is no more.

Therefore, the mass of a star determines how and when it will die. Small stars live longer lives than larger ones because they are relatively cool and burn their supply of fuel more slowly than more massive stars. The more massive stars live fast and die young–blasting themselves into the stellar cemetery at tender ages of mere millions of years. Stars like our Sun live for about ten billion years, and stars that are even smaller than our Sun (red dwarfs) can theoretically live for trillions of years. Our Universe is only about 13.8 billion years old–and so it is generally thought that there are no red dwarf relics around because none of them has had enough time to die.

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