As we gaze up at the night sky, while standing far from the interfering glare of bright city lights, we can see our Milky Way Galaxy stretching from horizon to horizon like a sparkling starlit grin –telling us that we are only a small part of something vast, ancient, and mysterious. Astronomers have long believed that our Galaxy is extremely old. Indeed, scientists have proposed that it may be almost as old as the Universe itself. In November 2018, astronomers with the Gemini Observatory announced they have discovered a tiny tattle-tale star that is likely the oldest known star dwelling in the disk of our Milky Way. Despite its unimpressive size, this diminutive star could play a significant role in our scientific knowledge of the true history and age of our Galaxy. The early star also sheds fresh light on the mysterious conditions that existed in the newborn Universe soon after its arrival in the Big Bang almost 14 billion years ago.
The Gemini Observatory is composed of twin 8.1-meter diameter optical/infrared telescopes that can together scan the entire sky. Gemini North and Gemini South are situated at two different locations in Hawaii and Chile, respectively.
The little tattle-tale celebrity has a very interesting story to tell. It’s old, small, and most importantly composed of components very similar to those that formed from the Big Bang. In order to host a star like this, the disk of our Milky Way might well be up to three billion years older than previously thought. Our Galaxy’s age was calculated to be roughly 13.51 billion years, while our Universe is believed to be roughly 13.8 billion years old.
“Our Sun likely descended from thousands of generations of short-lived massive stars that have lived and died since the Big Bang. However, what’s most interesting about this star is that it’d perhaps just one ancestor separating it and the beginnings of everything,” commented Dr. Kevin Schlaufman in a November 5, 2018 Gemini Observatory Press Release. Dr. Schlaufman is of Johns Hopkins University in Maryland, and lead author of this study published in the November 5, 2018 dilemma of The Astrophysical Journal.
The Big Bang theory suggests that the first generation of stars were composed almost entirely of hydrogen and helium. The Big Bang birth of the Universe formed only the lightest of nuclear elements–hydrogen, helium, and small quantities of lithium (Big Bang Nucleosynthesis). All nuclear elements heavier than helium–termed metals by astronomers–were made by the stars in their nuclear-fusing furnaces (Stellar Nucleosynthesis). Alternatively, in the event of the heaviest atomic components of –such as gold and uranium–in the powerful and fiery supernovae blasts that heralded the explosive demise of massive stars (Supernova Nucleosynthess).
When celebrities perish, their leading material is recycled to be utilised in the creation of new baby stars. Newborn stars receive–as their heritage from earlier generations of stars–all the elder stars newly forged heavier atomic elements. The oxygen you breathe, the iron in your blood, the calcium in your bones, the sand beneath your feet, the water that you drink, were all formed in the nuclear-fusing hearts of the Universe’s myriad stars.
Astronomers refer to stars which are depleted of nuclear elements heavier than helium as low metallicity stars. “However, this one has such low metallicity it’s known as an ultra metal poor star–this star could be one in ten million,” Dr. Schlaufman continued to explain in the Gemini Observatory Press Release.
The birth of the first generation of stars is among the most fascinating mysteries haunting cosmologists. However, the first stars to form in the Universe were unlike the celebrities we know today. This is because they formed directly from the pristine primordial gases churned out in the Big Bang itself. These primordial gases were mostly hydrogen and helium, and these two lightest of atomic components are believed to have gravitationally pulled themselves together to form ever tighter and tighter knots. The cores of the first generation of protostars to emerge from our ancient Universe first caught fire within the mysterious dark and frigid hearts of these exceptionally cold dense knots of pristine ancient gases–that finally collapsed under their own relentless, heavy gravitational pull. The very first stars did not form the same manner or even from the same elements as celebrities do now. The first stars are known as Population III stars. Our own Sun is a part of the youngest stellar generation, and is classified as a Population I star. Sandwiched between the youngest and oldest stellar generations are the Population II stars.
It’s been proposed that the massive primordial Population III stars were brilliant, and their existence is regarded as responsible for causing the Universe to change from what it once was to what it now is. These cryptic, dazzling first celebrities altered the dynamics of the Universe by heating it up and ionizing the present gases.
The metallicity of a star refers to the fraction of its substance that’s made up of atomic elements–metals–which are heavier than hydrogen and helium. Stars account for nearly all of the nuclear (visible) thing in the Cosmos, being composed primarily of hydrogen and helium. A star, regardless of which of the three leading generations it belongs to, will be a gigantic roiling, searing-hot sphere composed mostly of hydrogen gas. The term metallic in astronomical jargon doesn’t mean the same thing that it does in chemistry. Metallic bonds cannot exist at the extremely hot cores of stars, and the strongest of chemical bonds are only possible from the outer layers of cool”failed stars” called brown dwarfs. Brown dwarfs might be born the same manner as true stars, but they never quite manage to attain the necessary mass to light their nuclear-fusing stellar fires.
The metallicity of a celebrity offers an important tool that astronomers use to ascertain a specific celebrity’s true age. When the Universe was born, its”ordinary” atomic matter was mostly hydrogen which, by way of the process of primordial nucleosynthesis, proceeded to create a large amount of helium along with much smaller quantities of beryllium and lithium–but nothing thicker. The expression nucleosynthesis itself is defined as the process by which heavier atomic elements are made out of lighter ones, as the result of nuclear fusion (the combination of atomic nuclei.
Therefore, the leading Populations I, II, and III, display an increasing metal content with decreasing age. Population I stars, such as our Sun, have the maximum metal content, while Population III stars are depleted of metals. Population II stars have only trace quantities of metals.
A Big Starlit Smile
Galaxies like our Milky Way, are gravitationally bound systems composed of stars, interstellar gas, dust, stellar relics, and dark matter. Dark matter is regarded as composed of exotic non-atomic particles that do not interact with light or any other form of electromagnetic radiation, which makes it invisible. However, most astronomers believe that it really exists in the Universe since it does interact gravitationally with objects which can be observed. Dark matter is a far more abundant form of matter compared to”ordinary” atomic matter that composes the Universe that we’re most familiar with.
The word galaxy itself is taken from the Greek galaxias, translated literally as “milky”. Galaxies can range in size from dwarfs that sponsor just a couple hundred million stars to galactic behemoths that contain an astounding one hundred trillion stellar inhabitants, each orbiting around its galaxy’s center of mass.
Relatively small, spherical, and closely bound collections of celebrities termed globular clusters are one of the most ancient objects in our Milky Way. The ages of individual stars in our Galaxy could be estimated by measuring the abundance of long-lived radioactive elements such as thorium-232 and uranium-238. Astronomers can then compare the results to estimates of their original abundance, by means of a technique termed nucleocosmochronology.
Several individual stars have been discovered in our Galaxy’s halo with ages measured very close to the 13.80-billion-year-old Universe. As the most ancient known item inhabiting our Milky Way at the moment, this dimension put a lower limit on our Galaxy’s age.
The era of stars dwelling from the Galactic thin disk was also estimated by astronomers with nucleocosmochronology. Measurements of stars inhabiting the thin disk indicate they were created roughly 8.8 billion years ago–give or take about 1.7 billion years. These measurements indicate that there was an interval of nearly 5 billion years between the creation of the Galactic halo and the thin disk. More recent studies of the chemical signatures of thousands of stars indicate that starbirth might have plummeted by an order of magnitude at the time of disc formation, 8 to 10 billion years ago, when interstellar gas was much too hot to give birth to new baby stars at precisely the same rate as before. Even though it seems counterintuitive, things have to get really cold for a fiery new stellar baby to be born.
Satellite galaxies surrounding our Milky Way aren’t dispersed randomly. Indeed, they appear to be the result of an early break-up of some larger system that produced a ring arrangement about 500,000 light-years in diameter and 50,000 light-years wide. Close and catastrophic encounters between galaxies tear off enormous tails of gas which, over time, can coalesce to make dwarf galaxies.
In November 2018, astronomers reported the discovery of the small tattle-tale star that’s one of the oldest inhabiting the Universe. This tiny star may also be one of the very first stars to be born in the Cosmos, and it is categorized as an ultra-metal-poor (UMP) star composed almost entirely of matter formed in the Big Bang. Astronomers refer to these stars that are depleted of heavy metals as low metallicity stars. “But this one has such low metallicity, its known as an ultra metal poor star–this star could be one in ten thousand,” Dr. Schlaufman commented in the November 5, 2018 Gemini Observatory Press Release.
2MASS J18082002-5104378 B
Really, this star’s location within our Milky Way’s disc –that is usually both crowded and extremely active–is a surprise.
2MASS J18082002-5104378 B is a member of a binary stellar system. It is the smaller companion of a low-metallicity celebrity observed in 2014 and 2015 from the European Southern Observatory’s (ESO’s) Very Large Telescope UT2. Before the discovery of the tiny tattle-tale star, astronomers had wrongly assumed that the binary system could host a stellar mass black hole or a neutron star. Stellar mass black holes and neutron stars are the relics that massive stars leave behind once they’ve gone supernova. From April 2016 to July 2017, Dr. Schlaufman and his colleagues used the Gemini Multi Object Spectrograph (GMOS) on the Gemini South telescope in Chile and the Magellan Clay Telescope located at Las Campanas Observatory, so as to study the stellar system’s light and measure its relative motions, like this discovering the small UMP by spotting its gravitational pull on its stellar partner.
“Gemini was critical for this discovery, as the elastic observing modes allowed weekly check-ins on the system over six months,” Dr. Schlaufman commented in the November 5, 2018 Gemini Observatory Press Release.
“Understanding the history of our own Galaxy is critical for humanity to comprehend the wider history of the whole Universe,” noted Dr. Chris Davis at the same Press Release. NSF Offers financing for the Gemini Observatory on behalf of the USA.
2MASS J18082002-5104378 B comprises approximately a mere 14 percent of the mass of our Sun which makes it a red dwarf star. Red dwarfs are also the most numerous stars inhabiting our Galaxy.
“Diminutive stars like these tend to shine for a very long time. This star has aged well. It looks precisely the same now as it did when it formed 13.5 billion years back,” Dr. Schlaufman stated in the November 5, 2018 Gemini Observatory Press Release.
The discovery of 2MASS J18082002-5104378 B is important since it provides astronomers with new hope for discovering more of those ancient stars which shed new light on what happened in the primordial Universe. Just about 30 UMPs have been identified so far. However, as Dr. Schlaufman concluded,”Observations such as these are paving the way to possibly one day finding that elusive first generation star.”
Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various magazines, journals, and papers. Although she has written on a variety of topics, she especially loves writing about astronomy as it gives her the opportunity to communicate to others some of the numerous wonders of her field. Her first book,”Wisps, Ashes, and Smoke,” will be released soon.