im for the Center

The Milky Way is 13 BILLION years old. Some of our Galaxy’s oldest stars were born near the beginning of the Universe itself. During all these eons of time, we know at least one technological civilization has been born – US!

But if the Galaxy is so ancient, and we know it can create life, why haven’t we heard from anybody else? If another civilization was just 0.1% of the Galaxy’s age older than we are, they would be millions of years further along than us and presumably more advanced. If we are already on the cusp of sending life to other worlds, shouldn’t the Milky Way be teeming with alien ships and colonies by now?

Maybe. But it’s also possible that we’ve been looking in the wrong place. Recent computer simulations by Jason T. Wright et al suggest that the best place to look for ancient space-faring civilizations might be the core of the Galaxy, a relatively unexplored target in the search for extra terrestrial intelligence.

Animation showing the settlement of the galaxy. White points are unsettled stars, magenta spheres are settled stars, and white cubes represent a settlement ship in transit. The spiral structure formed is due to galactic shear as the settlement wave expands. Once the Galaxy’s center is reached, the rate of colonization increases dramatically. Credit: Wright et al

The Churn

Older mathematical models of space colonization have tried to determine the time required for a civilization to spread throughout the Milky Way. Given the size of the Milky Way, wide-scale galactic colonization could take longer than the age of the Galaxy itself. However, a unique feature of this new simulation is its accounting for the motion of the Galaxy’s stars. The Milky Way is not static, as assumed in prior models, rather it is a churning swirling mass. Colonization vessels or probes would be flying among stars that are themselves in motion. The new simulation reveals that stellar motion aids in colonization contributing a diffusing effect to the spread of a civilization.

The simulation is based previous research by Jonathan Carroll-Nellenback et al which proposed that a hypothetical civilization could spread at sub-light speeds through a moving Galaxy. The simulation assumes a civilization using ships travelling at velocities comparable to our own spacecraft (about 30km/s). When a ship arrives at a virtual habitable world in the simulation, the world is considered a colony and can itself launch another craft every 100,000 years if another uninhabited world is in range. Simulated space craft range is 10 light years with maximum travel duration of 300,000 years. Technology from a virtual colony was set to last 100 million years before dying out with the opportunity to be resettled should another colony drift into range by galactic motion.

The results are dramatic. The Galaxy’s rotation generates a wave or “front” of colonization. Once the front reaches the Galactic core, the core’s density catalyzes a rapid increase in the rate of colonization. Even with very conservative limits placed on the speed of the space craft, a majority of the Galaxy could be colonized in less than a billion years – a fraction of its total age.

Line of Sight

The simulation’s results reaffirm past proposals by Vishal Gajjar et al. to search the Galactic center for signs of life. Not only can the center of the Galaxy be rapidly colonized, but also efficiently scanned for technology. We have a direct line of sight to the Galaxy’s center which encompasses the densest region of space relative to us. And since the Galaxy formed from the inside out, the center is filled with older planets which provide more time for life to evolve.

The center also serves as a logical place to “talk” to and from – a central focal point of the Galaxy. If you wanted to get a signal out to the rest of the Galaxy, you could do so from the center to blanket the disk of the Milky Way. Likewise, if you wanted to find a signal, you might look to that same center. Gajjar et al. also hypothesize that an advanced civilization may be capable of tapping into the energy of the Milky Way’s central supermassive black hole to power a galaxy-wide signal beacon. Talk about a powerful “hello!”