A galactic Goliath haunts the ancient universe
When we look up into the sky on a clear midnight, we see a expanse of darkness dotted with the distant fires of myriad stars. The stars of the Cosmos inhabit the billions of galaxies that exist in the visible Universe, which is that relatively small region of the entire incomprehensibly vast Cosmos that we are capable of observing. This is due to the finite speed of light and the accelerating expansion of space-time. The light that travels to us from regions beyond our cosmological horizon it hasn’t had enough time to reach us since the Big Bang birth of the Universe nearly 14 billion years ago. One of the biggest mysteries facing astronomers today is understanding how galaxies form. According to the prevailing theory of galaxy formation, small galaxies were born first and eventually merged in the ancient Universe to form the large, majestic galaxies seen in today’s Universe. However, large galaxies have been observed to lurk in the very old Cosmos, and they shouldn’t be there according to this bottom up galaxy formation theory.
In October 2019, a team of astronomers reported that, by chance, they discovered faint traces of a huge, never-before-seen “monster” galaxy, dating from the early Universe. Making a playful comparison of his galactic discovery to photograph the tracks of the mythical monster yeti–the “abominable snowman” of the Himalayan people–astronomers commented that the scientific community once believed that such galactic giants were just folklore. This is because there was no evidence of its true existence in nature, until now.
The team of astronomers, led by postdoctoral fellow Dr. Christina Williams of the University of Arizona (Tucson), say their discovery provides new insights into the first baby steps of some of the largest galaxies in the Universe. The research paper appears in the The Astrophysical Journal.
Dr. Kate Whitaker, an assistant professor at the University of Massachusetts Amherst and a member of the team, is an expert on the early evolution of galaxies. She noted on a October 22, 2019 Amherst press release that “These otherwise hidden galaxies are really intriguing; it makes you wonder if this is just the tip of the iceberg, with a whole new kind of galaxy population waiting to be discovered.”
the birth of galaxies
There are currently two leading theories that seek to explain how the first galaxies were born in the ancient Cosmos. However, some astronomers propose that the truth may actually involve both ideas.
One of the prevailing theories proposes that the first galaxies formed when huge clouds composed of gas and dust collapsed under their own gravitational pull, allowing stars to be born. This is sometimes referred to as the From top to bottom theory.
The second theory, bottom up theory, has gained considerable credibility in recent years. According to this idea, the young Universe contained numerous relatively small droplets of matter. These little amorphous spots (protogalaxies) they met and merged, eventually becoming the large galaxies we observe in the Universe today. Tea Hubble Space Telescope (HST) has imaged many of these clumps of material, which may be the “seeds” that eventually became modern galaxies. According to this theory, most of the great ancient galaxies were spirals. However, as time passed, many of the spirals collided and merged to create elliptical galaxies elliptical they are very large egg-shaped galaxies that host mostly old red stars. The stars that live inside elliptical galaxies travel in chaotic orbits, which are unlike the stellar populations of the neater, more elegant spirals that host stars of all ages, like our own Milky Way.
But the galactic birthing process has not come to an end. The Universe continues to evolve in time. Small galaxies are frequently devoured by larger ones. Our own Milky Way galaxy may contain the tragic remnants of previous parties, having devoured many of its smaller galactic relatives, much as big fish devour their smaller neighbors. Our Galaxy is currently digesting at least one duo of small, unlucky galaxies, and may well rise up into others in the next few billion years. Such mergers are common because the Cosmos is crowded on the galactic distance scale.
In fact, there is a massive merger in the far future of our galaxy. The nearest major galaxy, the Great Andromeda Spiral, which is slightly larger than our Milky Way, is currently at a safe distance of 2.5 million light-years. This means that the distance between this duo of large galaxies is only about 25 times greater than the size of the galaxies themselves. Like our own galaxy, Andromeda is home to stars of various ages and contains a rich supply of gas. Gravity pulls Andromeda towards us at about 100 kilometers per second. In about 4.5 billion years, the Andromeda Galaxy and our Milky Way galaxy will collide and form a single, vast galaxy. elliptical galaxy that astronomers have already dubbed the great Milkomeda Galaxy. The future Milkomeda galaxy will be twice as big as the duo of unlucky spirals that collided with each other to create it. Supermassive black holes, lurking in the dark hearts of the two ancient spirals, will also merge and become twice as massive as the two black holes that collided to form a single entity. Technically though, the Andromeda galaxy will eat our Milky Way. This is because Andromeda is a slightly larger galactic “fish.”
Galaxy mergers were more common in the early Cosmos than they are today because during that ancient time the Universe was smaller and considerably more populated than it is now. Therefore, the small galactic “spots” were more likely to collide with each other and merge. It is generally thought that ancient galaxies were different from the ones we see today. The first galaxies showed a much greater diversity, and there was a much larger population of unequal galaxies, which are usually small galaxies that have low masses and do not have a specific shape.
Which brings us to the strange existence of the “monstrous” galaxy that shouldn’t exist in the early Universe, where it was once thought that only the smallest protogalaxies it could exist–and perform its fire dance in the newborn light of the Cosmos.
The good news is that galactic collisions rarely result in head-on collisions between individual constituent stars that inhabit the colliding duo. Even when two galaxies collide with each other, the distance between their stars is so great that they rarely suffer the consequences of the catastrophe. However, there are stars that can suffer as a result of the shipwreck. Some stars may be flung into new orbits, or even howled from their parent galaxies, doomed to wander lost and alone in the dark wasteland of intergalactic space.
Although galactic collisions do not usually destroy stars, they frequently result in star birth. As the huge clouds made up of gas and dust inside the merging galaxies collide with each other, they can give birth to millions of sizzling bright new baby stars.
A galactic Goliath that shouldn’t be There
Dr. Williams and her team used the Atacama Large Millimeter Array (ALMA) collection of 66 radio telescopes, located high in the mountains of Chile, to make their discovery. In new observations made with extremely sensitive detection limits, Dr. Williams detected a very faint spot of light. “It was very mysterious, but the light seemed not to be linked to any known galaxy. When I saw that this galaxy was invisible at any other wavelength, I got very excited, because it meant that it was probably very far away and hidden by dust clouds” Dr. Williams commented on October 22, 2019 Amherst press release.
Astronomers estimate that the faint signal originated from so far away that it took 12.5 billion years to reach Earth. At that time, the Universe was still in its infancy. Scientists believe that the observed emission is the result of the warm glow of dust particles (effectively obscuring all light) that have been heated by fiery stars being born deep within a young galaxy.
Study co-author Dr. Ivo Labbe noted in the Amherst press release that “We found that the galaxy is actually a massive monster galaxy with as many stars as our Milky Way but teeming with activity, forming new stars at a rate 100 times that of our own galaxy.” Dr. Labbe is from Swinburne University of Technology in Melbourne, Australia.
The new discovery is important because it can potentially solve a long-standing puzzle in astronomy. Some of the largest galaxies inhabiting the early Universe appear to have grown and matured very rapidly, which conflicts with theoretical predictions of science. bottom up galaxy formation theory. Even more mysterious, these large, mature galaxies appear to have sprung up out of nowhere when the Universe was comparatively young: just 10% of its current age, astronomers say.
Also, astronomers never seem to catch them at the point where they are first forming, Dr. Williams continued to explain to the press. Smaller galaxies have been observed in the early Universe with the hubble space telescope, but they are not growing fast enough. Other monster galaxies have also been previously reported. However, such sightings are too rare to provide a satisfactory explanation for what was happening at that ancient time. “Our hidden monster galaxy has just the right ingredients to be that missing link, because they are probably much more common,” Dr Williams continued in the Amherst press release.
The unsolved mystery today, astronomers point out, is exactly how many of these gigantic galaxies there are. The current study was conducted over a small region of the sky, less than 1/100 the size of the full Moon. It could mean that finding “yeti footprints” in a small swath of desert means it was a lucky find or that they are cloaked in layers of dust but hidden everywhere.
Dr. Williams added that “Right now we are looking forward to the James Webb Space Telescope (JWST) to take a look at these things. JWST will be able to peer through the veil of dust so we can learn how big these agalaxies really are and how fast they’re growing, to better understand why models fail to explain them.”
Tea JWST is a revolutionary new telescope due to launch in March 2021.