Strive for the Center13 BILLION YEARS old is the Milky Way. Some of our Galaxy's oldest stars were created near the beginnings of the Universe. We know of at least one technological civilization that has been founded in the US during all these eons.We know that the Galaxy is ancient and can produce life. So why haven't we heard anything else? Even if another civilization were only 0.1% older than ours, they would be millions of year ahead of us and likely more advanced. Shouldn't the Milky Way already be full of alien colonies and ships, if we are on the brink of sending life to other planets?Perhaps. It's also possible that we have been looking in the wrong places. Jason T. Wright and colleagues have recently shown that the Galaxy's core is a good place to search for ancient spacefaring civilizations. This galaxy is a target relatively unknown in the hunt for extra terrestrial intelligence.Animation depicting the settlement of the galaxy. Magenta spheres and unsettled star magenta points represent settled stars. White cubes signify a settlement ship in transit. Galactic shear is responsible for the formation of the spiral structure. The rate of colonization increases dramatically once the Galaxy's center has been reached. Credit: Wright et.alThe ChurnAn older mathematical model of space colonization attempted to predict the time it would take for a civilization spread across the Milky Way. Due to the size of our Milky Way, galactic colonization on a large scale could take more time than the Galaxy's age. This simulation's unique feature is that it accounts for the motions of the Galaxy stars. The Milky Way isn't static as previously assumed. It is a churning, swirling mass. A colonization vessel or probe would fly among stars in motion. New simulations reveal that stellar motion helps in colonization and contributes to the spreading of civilization.Jonathan Carroll-Nellenback and colleagues have previously conducted research that suggested that a hypothetical civilization could spread at sublight speeds through a moving Galaxy. Simulation assumes that a civilization uses ships traveling at speeds comparable to those of our spacecraft (30km/s). If a ship arrives on a virtual world that is habitable, it is considered a colony. It can launch another craft every 100,000 year if there is another world within its range. The range of simulated spacecraft is 10 light-years with a maximum travel time of 300,000. Technology from a virtual colony was designed to last 100,000,000 years before it dies. However, there is the possibility to be resettled in case another colony moves into range via galactic motion.These are the dramatic results. The Galaxy's rotation creates a front of colonization. The speed of colonization increases dramatically when the front reaches Galactic Core. Even with the most conservative speed limits, the majority of the Galaxy could still be colonized in less that a billion years. This is a fraction of its total time.Line of sightThese simulations confirm previous proposals made by Vishal Gajjar and co. To search the Galactic Center for signs of life. The center of the Galaxy can be colonized quickly and efficiently. The Galaxy's center is within our direct sight, and it covers the most dense area of space. The Galaxy was formed from the inside out. This means that the center of the Galaxy is filled with older planets, which gives life more time to develop.It also functions as a place where you can talk to or from a central point in the Galaxy. To transmit a signal to the rest, you can use the center to cover the Milky Way. You might also look at that center if you want to locate a signal. Gajjar and colleagues. The idea that an advanced civilization could tap into the energy from the Milky Way's central supermassive dark hole to power a galaxie-wide signal beacon is also supported by Gajjar et al. This is a powerful hello!The Mojave Desert captures a view towards the Galaxy's Center from Earth. Credit: Photo by AuthorThen, why so quiet?None of this will answer the question, "Where are they?" The speed at which the Galaxy could become colonized is a reason why we haven't heard from anyone. Caroll-Nellenback and co. Caroll-Nellenback et al. also noted that colonization might have an impact on the spread of advanced technology, reducing the spread time. However, radio scans of Galactic Core so far have not revealed any signals. Maybe the silence is the answer. Because the Galaxy is so old and has so much time for life to spread, some believe silence will endanger any chance of ever meeting anyone.There is still hope. It is possible, however, that parts of the Galaxy may never be settled even after eons of time. It's all about efficiency. You want to colonize within the shortest range possible. Some colonies will die as time goes by, possibly due to resource exhaustion or a cataclysmic incident. Instead of reaching further into space, colonies decide to re-habitate a dying colony closer to home. Uninhabited planets are often surrounded by clusters of inhabited colonies. It is possible to maintain a steady state in regions where it is too difficult to colonize habitable planets.Other explanations for the silence could exist. Long-lived civilizations may be governed by sustainability, which means they grow slower than expected. Multiple colonizing civilizations may be competing for resources, or keeping a distance. Like Star Trek's Prime Directive, civilizations may be careful not to interfere with other inhabited worlds. These possibilities could explain why we have not met anyone, unless we know otherwise.The Buried PastCarroll-Nellenback and al. Carroll-Nellenback et al. Imagine, for instance, that a galactic alien civilization arrived on Earth billions years ago and lived thousands of years before dying off. There would be virtually no evidence of their existence after all these years. We have not met an alien civilization. But, it is possible that we have.Simulation shows that there is an 89% chance that the Galaxy will remain empty for at least one million years without interstellar visits. It is important to note that the simulation shows that the Galaxy can either be completely colonized or completely empty. However, there are middle ground valid responses that still leave room for technological extraterrestrial existence even without contact.Globular Life?The Galaxy's center is a great place to conduct SETI research. However, there are other areas of the Galaxy that have similar conditions to the Galaxy's center Globular Clusters.Globular Clusters (GC) are massive, ancient collections of stars that orbit around the Galaxy's center at distances of tens to thousands of light-years. One hundred and fifty-five GCs are known to exist in the Milky Way. They date back to a time of intense star formation, which was catalyzed through galaxy mergers.3D Model of Globular Clusters Known and Their Position in Relation to the Milky Way Credit: Galax 3DThe GCs are extremely dense, with stars that are closer together than in the Milky Way disk. Interstellar communication and travel are often referred to in terms of millennia. A civilization located within a GC could experience travel times between stars of the order of a few years, with communication times of weeks or months. The problem is that GCs can negatively impact the formation of planets and their orbital stability.A. Ray and R. Di Stefano calculate what they call a GC Habitable Zone. Habitable zone is the distance that a planet must orbit a star in order to sustain liquid water temperatures. The habitable zone of our Sun is where Earth lives (which is a good thing). A GC habitable area is not a two-dimensional radius, as the orbit of a satellite. It's a three-dimensional shell orbiting around its center. The outer shell thickness starts at the point where the GC density drops below the limit where solar systems are able to survive the gravitational interference from nearby stars. A nearby star's gravity might cause planetary dust rings to break apart, thereby preventing the creation of new planets. A star that passes near a system might also be able to eject a satellite from its parent star.The outer edge of the shells thickness can be defined as the point at which the density is so low that it is more than 10,000 AU. These are Astronomical Units, which represent the Earth's distance from the Sun at approximately 150,000 km. 10,000 AU equals approximately 2 light months. The benefits of the cluster, namely the shorter travel times and faster communication with neighbouring stars, diminish after this point. Ray and Di Stefano call this the GC sweet spot, which is close to colonization star system. It allows for quick communication and travel.Fraser Cain of Universe is joined by Dr. Jason Wright, a Penn State University exoplanet researcher. Jason Wright was a lead on the Galaxy Colonization SimulationWe want the GC sweetspot to include mainly low mass stars that live longer. It is not by chance that low mass stars have the smallest radius of solar habitable zones. The less likely a planet is to be sucked away by another star, the closer it orbits its parent star. Mass Segregation is another phenomenon that GCs experience. This occurs when the largest stars, and therefore most favorable for habitability in the cluster, gravitationally draw toward the center. This segregation naturally sorts the cluster, from core to periphery, from the least to most desirable choice systems.These results are positive. The sweet spot for a hypothetical GC with 100,000 solar masses is 40% of G stars (yellow dwarfs similar to our Sun) and 15% K and M stars (orange-red dwarfs) within the cluster. This is a lot of stars. Even if the civilization is able to capture solar energy, it is possible that planets that have been ejected could host a civilization. Free floating world made up of space aliens.Ray and Di Stefano suggest that at most one communication civilization could exist in each GC of the Milky Way, even if 10% of GC stars are home to habitable planets. One communicating civilization would be possible if the Milky Way had a lower stellar density. If the percentages were slightly more conservative, it would allow for more civilizations to exist in the diffuse disc but they would be separated by huge distances exceeding 300 light years.You might try to contact the distant Milky Way disk if you are located in a GC. Unfortunately, we have not been able to locate any evidence that planets exist in GCs. The distance from and densities of the GCs hinder our ability to find exoplanets. However, this doesn't mean that there is no possibility. Ray and Di Stefano believe that if a civilization exists in a GC with instant access to thousands upon thousands of stars, it would be essentially immortal.Globular Cluster M13 Credit to Howard Trottier, SFU Trottier ObservatoryWe have actually sent a message to GC about the M13 Hercules Globular Cluster. The cluster, which is located in the constellation Hercules is approximately 22,000 light-years away and 145 light-years in diameter, is made up of around 100,000 stars. A message was sent from the Arecibo radiotelescope (RIP) to M13 in 1974. The message contained the numbers 1-10, chemical compounds of DNA, a graphic figure representing a human and a graphic showing the radio telescope. The broadcast lasted 3 minutes. It still has several thousand years to go.It is likely that the low resolution message will not be detectable by M13. Perhaps we will eventually make contact with another galaxy-spanning civilization. Perhaps WE will be a civilization that spans the galaxy. I'm eagerly anticipating the screen adaptation of Asimovs Foundation!The Arecibo Message was transmitted to the M13 Globular Cluster. Creative CommonsFeature Image: A composite image of the Milky Ways core, created by Hubble and Spitzer telescopes. Credit Xray: NASA/CXC/UMass/D. Wang et.al. ; Optical : NASA/ESA/STScI/D.Wang ; IR : NASA/JPL–Caltech/SSC/S.StolovyFollow Matthew on Instagram, Twitter and Facebook for more stories from SPAAAACEThere's more to explore:The Dynamics of the Transition From Kardashev Type II To Type III Galaxies Favor Technosignature Researches in the Central Regions of Galaxies IOPscience.The Fermi Paradox, the Aurora Effect: Exocivilization Settlement, Expansion and Steady State IOPscience (Open Access).The Breakthrough Listen Search for Intelligent Life Near the Galactic Center (Harvard.edu/ADS) (Open Access).GLOBULAR CLUSTERS - CRADLES OF LIFE & ADVANCED CIVILISATIONS (Open Access)Extraterrestrial Civilizations Transmit Information. NASA/ADS (harvard.edu), (Open Access).
