Isolated, shapeless, and small for a galaxy, WLM provides a precious gift to curious astronomers because it allows for a rare insight into the primordial nature of galaxies that have been left peacefully undisturbed by their environment.
WLM was discovered by the German astronomer Max Wolf in 1909, and was designated a galaxy a decade-and-a-half later by astronomers Knut Lundmark of Sweden and Philibert Jacques Melotte of Great Britain. The secluded galaxy was named in honor of all three astronomers. The faint galaxy is situated in the constellation Cetus (The Sea Monster), and it resides approximately three million light-years from our Galaxy. Our Milky Way is one of a trio of dominant spiral galaxies in the Local Group.
Our Milky Way's Place In Space
The Magellanic Clouds--the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC)--are the closest galactic neighbors to our Milky Way. Both the LMC and the SMC may be considered satellite galaxies to our own large spiral Galaxy, where they reside at a distance of only a little less than 200,000 light-years--which puts them right in our Milky Way's backyard. The Magellanic Clouds can only be seen in the Southern Hemisphere, but can easily be observed with the naked-eye--and their most brilliant stellar constituents can be observed with binoculars. Both the LMC and the SMC are irregular galaxies that are considerably smaller than our Milky Way.
There are two galaxies visible to the unaided human eye in the Northern Hemisphere. The Andromeda Galaxy (M31) is a large spiral galaxy very similar to our own, and it is situated at a distance of about 3 million light-years away--at least, for now. In about 4 billion years, the Andromeda Galaxy and our Milky Way will collide and merge to form a single enormous football-shaped elliptical galaxy. To the naked eye, the Andromeda Galaxy is a dim and fuzzy patch that appears, with the aid of binoculars, to be a lens-shaped celestial object. It possesses a duo of dwarf elliptical satellite galaxies that are visible to Earthly observers using a small telescope.
The second galactic constituent of our Local Group, that can be seen with the naked eye, is dubbed M33 in Triangulum. M33 resides at a distance similar to that of Andromeda, and it too is a spiral galaxy. However, M33 is much smaller than Andromeda, and for this reason it is much more difficult to observe.
The Birth Of Galaxies
The visible Universe is that relatively small part of the entire Universe that we are able to observe. Most of our unimaginably vast Cosmos is so very far away that the light flowing out from these distant regions has not had sufficient time to travel to us since the Big Bang, as a result of the expansion of the Universe. The great majority of galaxies are situated in groups or clusters, with clusters being considerably larger than groups. Clusters and superclusters of galaxies are the largest structures known to inhabit the visible Universe, and they are usually populated by hundreds to thousands of separate starlit galaxies living close together because of their gravitational ties that bind, creating the densest portion of the large-scale structure of the Universe.
The Local Group of galaxies is situated near the outer fringes of the Virgo Cluster of galaxies, whose heart is 50 million light-years from Earth. The starlit galaxies of our Cosmos trace out the gigantic and mysterious web-like filaments of the weird Cosmic Web. The enormous Cosmic Web is composed of the transparent dark matter--whose composition is still unknown. However, scientists believe that the dark matter is made up of some as yet undiscovered exotic non-atomic particles that cannot interact with light, which is why the dark matter is transparent--and invisible. The sparkling starry galaxies, that dance around together in groups and clusters, light up this transparent Cosmic Web like billions of candle flames, outlining with their lovely light that which otherwise could not be observed.
The prevailing theory of galaxy formation is casually referred to as the bottom-up theory. This theory suggests that large galaxies, such as our own Milky Way, were rare denizens inhabiting the ancient Cosmos, and they only eventually reached their more mature sizes when they collided, and then merged, with other smaller, similar protogalactic blobs. The most ancient galaxies were only approximately one-tenth the size of our Galaxy, but they were just as brilliant with sparkling stellar light because they were fiercely churning out an incredibly large number of bright, fiery, and very, very hot baby stars. These extremely brilliant, relatively tiny ancient galactic structures served as the "seeds" of the large and mature galaxies seen today in the Universe--such as our own Milky Way.
In the primordial Universe, clouds of gas collided with one another and merged together along the enormous and heavy dark matter filaments of the bizarre Cosmic Web. Try to envision that very ancient era long before the first generation of stars started to ignite, when opaque clouds composed primarily of hydrogen gas, gathered together along the filaments of the transparent dark matter. Dark matter does not interact with "ordinary" atomic (baryonic) matter or electromagnetic radiation except through the force of gravity. But because it does interact with baryonic matter gravitationally, and it does warp and bend light (gravitational lensing), scientists know that it is really there. Gravitational lensing is a phenomenon predicted by Albert Einstein when he realized that gravity could warp light, and because of this have lens-like effects.
The transparent dark matter snatched up the clouds of pristine hydrogen gas, and these pools of ancient gas became the strange nurseries of the first generation of stars to light up the Cosmos. The gravity of the great Cosmic Web snatched at its atomic prey until the imprisoned clouds of gas formed blobs as black as onyx within the transparent halos of the dark matter. The blobs of gas tumbled down into the very hearts of these transparent halos, that strung themselves out on this strange cosmic spider's web.
It is generally thought that the first galaxies were dark and opaque blobs of pristine hydrogen gas, pooling in the hearts of dark matter halos, and that they pulled in the first generation of fiery baby stars with their powerful gravitational grip. The luminous stars and hot glowing gas lit up what was previously a swath of featureless, barren Space devoid of light.
Gradually, but relentlessly, the swirling pristine primeval gases and the weird, ghostly non-atomic dark matter wandered throughout the ancient Universe, mixing themselves up together to form the familiar and distinct structures that exist today. Regions of higher than average density within the filaments of the Cosmic Web filled the ancient Cosmos, and served as the precious seeds from which the galaxies eventually were born--and then grew. If the seed was small, a small protogalaxy formed, but if the seed was large, a large protogalaxy formed. These ancient galactic blobs began to dance around together gravitationally and then cluster together. The protogalaxies, both large and small, swarmed around together like honeybees around a discarded piece of candy. They were the ancient galactic building blocks that took shape when the dark matter halos collapsed under their own weight. The protogalaxies did a gravitational jitter bug together, merging and then forming ever larger and larger amorphous masses. The primordial Universe was much smaller and crowded than it is today. The shapeless protogalaxies bumped into one another frequently, and then stuck together, creating larger galactic structures.
A Lonely Little Galaxy Lost In The Wilderness
WLM is very small and devoid of structure, which is why it has been classified as a dwarf irregular galaxy. WLM spans approximately 8,000 light-years at its greatest extent. This measurement includes a halo of very elderly stars that were discovered back in 1996.
Many astronomers believe that WLM is akin to the shapeless primordial protogalaxies that long ago gravitationally interacted with one another, and frequently merged together in the relatively small and crowded ancient Universe. This would mean that WLM could shed new light on the nature of the early protogalaxies that eventually built themselves up to become the large and majestic galaxies that we see today. Over billions of years, small protogalaxies similar to WLM bumped into one another and ultimately assembled into the large spiral and elliptical galaxies that are now common in the modern Universe.
Poor little WLM, isolated and alone without the companionship of others of its kind, never experienced the familial influence of other galaxies and their sparkling stellar populations. Alas, the secluded little galaxy apparently only had very limited contact with its galactic cousins. Therefore, WLM represents a relatively unchanged, and lingering relic of the past, because it has spent its entire "lifetime" largely independent of activity going on elsewhere.
Nevertheless, this lonely little galaxy provides a precious gift to astronomers. Showing off an extended halo composed of a host of very faint, red stars, that reaches far out into the frigid, dark wilderness of surrounding Space, WLM is poised to reveal many long-lost secrets about the ancient Universe. The reddish hue of its population of dim stars suggests that they are elderly. It is probable that WLM's halo dates all the way back to the original primeval formation of the lonely little galaxy itself.
In contrast, the stars that inhabit the center of WLM appear to be in their flaming youth, boasting a young tattle-tale blue hue. Images of WLM show where the powerful and brilliant light rushing out from the baby blue stars has ionized the ambient hydrogen--making it glow warmly in a characteristic shade of red.
This discovery will provide important clues about the mysterious mechanisms that formed the first galaxies to inhabit the Universe.
Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various journals, magazines, and newspapers. Although she has written on a variety of topics, she particularly loves writing about astronomy because it gives her the opportunity to communicate to others the many wonders of her field. Her first book, "Wisps, Ashes, and Smoke," will be published soon.
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