September 22, 2023

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Tayna: A Faint Little Galaxy Lights Up

The star-splattered galaxies of the Cosmos ignited very long ago, and their sparkling stellar inhabitants lit up–with their fabulous, fierce fires–the strange swath of darkness that had previously existed throughout Space and Time. The earliest galaxies were only about one-tenth the size of our own majestic, large spiral Milky Way Galaxy, but they were just as brilliant. This is because they were rapidly giving birth to a host of very hot, very bright new baby stars. These extremely brilliant, though relatively small, primordial galactic structures served as the “seeds” of the mature galaxies that dwell in today’s Universe–such as our own Milky Way. In December 2015, astronomers using the combined power of NASA’s Hubble (HST) and Spitzer (SST) Space Telescopes, announced that they had discovered the dimmest object ever observed in the ancient Universe–and this little galaxy, that existed so long ago and far away, was already there only about 400 million years after the Big Bang, that marks the birth of our Universe almost 14 billion years ago.

The team has nicknamed this little and very ancient amorphous galaxy Tayna, which translates into “first-born” in Aymara, the language spoken by the people of the Andes and Altiplano regions in South America.

Even though both HST and SST have spotted other galaxies that are record-holders for distance, this little, faint galaxy is an example of a smaller, dimmer class of new-born galaxies that until this study usually slipped by undetected.

“Thanks to this detection, the team has been able to study for the first time the properties of extremely faint objects formed not long after the Big Bang,” commented study lead author Dr. Leopoldo Infante in a December 3, 2015 HubbleSITE Press Release. Dr. Infante is an astronomer at Pontifical Catholic University of Chile (Pontificia Universidad Catholica de Chile). The very distant object is part of a discovery that spotted 22 youthful galaxies inhabiting our very ancient Universe, and it is situated almost at the observable horizon of the visible, or observable, Universe.

The visible Universe is that relatively small domain of the entire unimaginably immense Cosmos that we are able to observe. Anything that may exist beyond this horizon is forever beyond the reach of our visibility. This is because the light traveling to us from those very remote objects has not had enough time to reach us since the Big Bang birth of our Universe due to the expansion of Space. No known signal in the Universe can travel faster than light in a vacuum, and the light traveling towards us from remote and ancient celestial objects situated beyond our cosmological horizon can travel towards us no faster than this universal speed limit. Time is the fourth dimension. The three spatial dimensions of our familiar world are up-and-down, back-and-forth, and side-to-side. It is impossible to locate an object in Space without also locating it in Time. Hence, the term Spacetime. The farther away a shining celestial object is in Space, the more ancient it is in Time. In astronomy, long ago is the same as far away.

The Cosmos that we observe today is dancing with the furious, brilliant fires of billions and billions of glittering stars, that dwell within the more than 100 billion galaxies situated within that relatively small region we are able to observe–the visible Universe.

Soon after the Big Bang birth of our Universe, about 13.8 billion years ago, there was a dark, mysterious era without light. The Universe was a strange expanse of incredible, featureless blackness. This very ancient era is termed the Cosmic Dark Ages, and it came to a magnificent, dramatic end when the first generations of dazzling baby stars were born to toss their fabulous light out into this universal swath of perpetual, bizarre darkness. The very first galaxies were opaque, dark clouds of pristine gas, pooling in the centers of dark matter halos, and they pulled in the first nurseries of roiling, glaring, huge and hungry baby stars. The dark matter is a mysterious substance. It is likely composed of some as yet unidentified exotic non-atomic particles that do not interact with light, or any other form of electromagnetic radiation, and are therefore invisible. The transparent dark matter is much more abundant than the badly misnamed so-called “ordinary” atomic matter that makes up our familiar world, and that we can see. In fact, the “ordinary” atomic matter, or baryonic matter, composes a mere 4% of the mass-energy of the Cosmos. But “good things come in small packages.” So called “ordinary” atomic matter is the precious stuff of planets, stars, moons, and people, and it accounts for literally all of the elements listed in the familiar Periodic Table. Atomic matter is the material that brought life to our Universe.

The Universe was a witch’s broth of seething-hot plasma for about three hundred thousand years after its Big Bang beginning. At long last, protons (which, along with neutrons, form the nuclei of atoms) and electrons (which encircle the nuclei of atoms in a cloud) merged together to form hydrogen–the lightest and most abundant atomic element in the Universe. About 700 million years after the birth of the first brilliant baby stars and new-born galaxies, the Universe was reionized. That is, something tore the existing atoms apart, and converted hydrogen back to its constituent protons and neutrons.

Scientists know very little about that mysterious, ancient era when the first galaxies were born. However, it is generally thought that opaque clouds of primarily hydrogen, collected along heavy filaments of the transparent, invisible dark matter. The dense portions of the dark matter snatched up clouds of primordial, pristine hydrogen gas with powerful gravitational tugs.

Long ago and far away, invisible dark matter pulled at the clouds of pristine gas. These pools of gas became the nurseries of the first generation of baby stars to light up the Cosmos. The gravity of the filaments of this dark and mysterious stuff, that weaves a Cosmic Web throughout Space and Time, tugged on its atomic prey until the imprisoned clouds of gas created blobs like onyx beads within the transparent halos of the dark matter. The black onyx-like clouds of ancient gas floated down, down, down into the dark hearts of these invisible halos, strung out like lovely black beads on this magnificent and bizarre cosmic spider’s web.

Slowly, relentlessly, the swirling primordial gases and the transparent, bizarre dark matter spread out through the entire ancient Universe, mixing themselves up together to ultimately give rise to the structures that we see today.

Nature’s Magnifying Glasses

Astronomers know little about that ancient era when the first galaxies formed. However, nature supplied a valuable gift in the form of gravitational lenses. Gravitational lensing is a phenomenon proposed by Albert Einstein when he realized that gravity had the ability to warp, distort, and bend light–and therefore possess lens-like attributes.

Einstein’s first theory of Relativity, the Special Theory of Relativity (1905), describes a Space that has often been compared to an artist’s canvas. The artist takes her paint brush and draws lines and points on this marvelous canvas, which represents the stage where the universal drama is being played out–rather than the drama itself. The great achievement finally uniting the stage with the drama was proposed by Einstein a decade later in his Theory of General Relativity (1915). According to General Relativity, Space becomes one of the starring players in this greatest of all dramas. Space tells mass how to move, and mass tells Space how to curve. Spacetime is as flexible as a rubber sheet. Toss a heavy object, such as a bowling ball, onto the surface of this fantastic sheet, and it causes a dimple to form in the fabric–in a way similar to how the gravity of a massive object influences Space. If a handful of eight little marbles are then tossed onto the rubber sheet, where the bowling ball has created a dimple, they will travel curved paths around the bowling ball. Imagine that the bowling ball is a massive object, like our own Sun, and the marbles are the eight major planets of our Solar System. If the bowling ball is then removed, the marbles will take straight paths. Without the heavy bowling ball, there is no gravitational well–no dimple in the fabric that can mimic the way gravity behaves in the Universe. The planets travel according to the more massive Sun’s gravitational warpage of the stretchy fabric that represents Spacetime.

In astrophysics, a gravitational well (gravity well) is a gravitational potential field surrounding a massive body. The more massive the body, the deeper and more extensive the well that is associated with it.

Therefore, General Relativity predicts that dense collections of mass in the Universe will warp traveling light like a lens, magnifying objects lurking behind the mass when observed from our planet. The first gravitational lens was seen in 1979, and today lensing enables astronomers to observe extremely faint objects in the ancient Universe soon after its birth so many billions of years ago.

When the path that wandering light takes is far away from the foreground lensing mass or, alternatively, if the mass is not especially great, weak lensing occurs. Weak lensing only slightly distorts the background lensed object that is emitting the traveling light. However, when the lensed object is located almost exactly behind the lensing mass, strong lensing can occur. Strong lensing smears out extended objects–such as galaxies–into what is called an Einstein ring that surrounds the lensing galaxy or cluster of galaxies. However, strong lensing of point-like, small celestial objects frequently produces multiple images–an Einstein cross–emitting glittering light around the lens.

Tayna: A Faint Little Galaxy Lights Up

The newly discovered very faint object, dwelling in the ancient and distant Cosmos, is about the same size as the Large Magellanic Cloud (LMC), an amorphous, small satellite galaxy of our own Milky Way. The newly-detected, very faint little galaxy is giving birth to searing-hot, brilliant, and sparkling baby stars at a frenetic rate that is ten times faster than that of the LMC. Indeed, this remote object, that dazzled the Cosmos so long ago, might be forming a growing core of what will probably evolve into a large, full-sized galaxy–such as our own.

The faint, ancient galaxy was observed as a result of gravitational lensing–Nature’s own “magnifying glass” in space. As part of its Frontiers Field program, HST kept a close eye in the sky on a massive cluster of galaxies, dubbed MACS J0416.1-2403, which is located about 4 billion light-years away and weighs about the same as a million billion suns. This enormous galaxy cluster takes on the role of a powerful natural lens by bending and magnifying the light of much-more-remote objects located behind it. In a way that has been compared to a “zoom lens” on a camera, the huge cluster’s gravity intensifies the light of the remote faint protogalaxy, making it appear to be 20 times brighter than it actually is.

The ancient, faint galaxy’s distance was estimated by astronomers who built a color profile from combined HST and SST images. The expansion of the Universe causes the light traveling from remote galaxies to be stretched, or redshifted, with increasing distance. Even though a large number of the galaxy’s neonatal stars are intrinsically blue-white, their wandering light has been shifted into infrared wavelengths that are measurable by HST and SST. Absorption by cool, intervening intergalactic hydrogen also causes the galaxies to appear redder.

This research is published in the December 3, 2015 issue of The Astrophysical Journal, and it indicates that the ancient Universe will be heavily populated by galaxies that can be targeted by the upcoming James Webb Space Telescope (JWST). Astronomers expect JWST to help them observe the embryonic stages of galactic birth soon after the Big Bang.