The Search for Extragalactic Aliens in 2015

Are we alone in our universe or not? Answering this question seems to be purely science fiction. Yet, for several decades, since the birth of the radio humanity has been probing the sky for messages from ET’s (Extraterrestrial’s). We have also been sending our own messages out into space. In hopes that we may spur contact with an alien species. Scientists have been studying the probability of ET existence since the 1900’s. In a universe of over 100 billion galaxies each with 100 billion stars there simply must exist other life forms. If not than the probability of us existing would literally be zero. Earth would actually be one out of 1000 quintillion. From a non-humancentric point of view, that statistic is impossible to swallow. Many studies have been done to attempt to find or communicate with these aliens. The Drake Equation gave a qualitative and quantitative analysis of the probability of there being other aliens. The Kardashev paper classifies different types of aliens. The Dyson paper reports on possible astroengineering projects advanced aliens might conduct. Then there is the Fermi Paradox, which questions why in a universe that is suppose to be thriving of life and intelligence, have we not yet found ET’s. This question epitomizes the endless search many have done, to only turn up nothing. A study published this year by (Zackrisson et al) attempted to advance the search for alien life forms even more. This time the team of scientists wanted to know, instead of trying to directly communicate with aliens, could we probe for galactic class aliens by searching for the effects of their existence in the night sky, in their galaxies.

Earlier searches for aliens sent out messages and attempted to find other messages from other civilizations. However, this would mean that an alien species would have to know of our existence. Because a message that can be read must be aimed directly at Earth. If they wanted to send a signal out in all directions an immense amount of energy would be needed. This is how Kardashev, a Soviet scientist began to classify three types of civilizations. The questions started by attempting to solve how much energy would be needed to send a signal in all directions. Then turned into classifying energy levels of advanced civilizations. Kardashev determined that there are 3 civilization types. They are planetary, solar, and galactic, a species becomes solar, for example when it has used all the energy from its sun, and galactic when all the energy from its galaxy. This classification leaves little to dispute with. This is because Kardashev offers no means of getting these energies, only that this energy would be necessary to support these civilizations, and their massive projects. And it indeed would be necessary. Also it follows the growth of humans energy needs up till now, and quantifies that in terms of suns, as the sun outputs an very high amount of energy. It is a possibility that these aliens would get the energy needed from the sun. This is when Dyson proposed the Dyson sphere. Keep in mind a true Dyson sphere is not a hollow ball that surrounds a star like in sci-fi movies, rather a cloud of solar panel satellites that orbit their star. This lead to a change in direction in how scientists were searching for aliens. However, scientists later determined that it is better to search for aliens in a more indirect way, such as finding traces of their existence. In creating a Dyson sphere or cloud, the solar panels would absorb much of the energy from the sun. However, via the 1st law of thermodynamics thermal radiation would be re radiated by these panels. This would give a star this weird light curve, and scientists know the common light curves of a star, and if the light curve does not look like the normal, there may be a Dyson sphere there. This was the premise for a 1999 study by Annis that attempted to find these changes on a galactic scale. However, though the study turned up a conclusion that such dimmed galaxies did not exist, they only used 50 galaxies. That is where this more current study picks up.

Published in the September version of The Astrophysical Journal is a paper that attempts to advance the search for ET’s. This time the researchers will be using a massive database of galaxies from which they will study 1400 galaxies. There is also a known relationship in astrophysics known as the Tully Fisher relationship. Essentially, for certain galaxy types (such as spiral) there is a clear relationship between the brightness and the rotation speed and the mass of a galaxy. This dataset is much larger than the previous study done in 1999. But the researchers also made sure to minimize the uncertainty wherever they could. They used only galaxy clusters that could very easily have the cluster’s distance measured. This is important because the farther out a galaxy is the greater its redshift will be. Scientists use this redshift to measure the true brightness of galaxies (making them all comparable despite different distances and dimming). Thus having an accurate reading of the clusters brightness means a more accurate reading on any galaxy within that cluster that may have galactic aliens taking over, and thus be dimmer. These candidates would appear to be outliers relative to the rest of their galaxy cluster. The researchers had to carefully select their galaxies. For instance a set of galaxies within a cluster were weirdly dimmed. It was a possible “Eureka” moment. But the scientists determined that they were instead another cluster much farther away and that they needed to ignore those galaxies in their results. In the end the researchers determined that around .3% or slightly less of the galaxies surveyed could be Kardashev type 3 (galactic aliens) candidates. For many of these candidates natural phenomena both known or unknown was attributed to the findings. The paper determined that current methods might not be enough. One of the possible additions to the study could be to look for semi-galactic civilizations, where instead of an entire galaxy being dimmed and trying to search for that, only a portion of the disk of a galaxy would be oddly darkened. This would still be difficult to study because of all of the dark clouds that exist in our galaxy and others that might create false data.

These indirect astrophysical studies of aliens create a few theoretical qualms. For instance the Kardashev Type civilizations are based off of energy necessity, which is difficult to dispute. However, the proposed solution to attaining such energy, a Dyson sphere is not theoretically sound. Of course there a myriad of other unforeseeable technologies that could be invented on Earth in the next hundred years that could make solar power technology obsolete. Stating that solar technology is a must is a very difficult statement to make. However, considering probability, it could indeed be possible that at least one advanced civilization is using solar power. Then there is the other problem about assuming that civilizations need to reach a galactic scale or ever will. Current theoretical restrictions on the speed of light and a lack of a way around that restriction make galactic travel seem impossible. But again unforeseeable technology could arise and make that previous statement false. Then there is also this. In 1999 Annis (a different paper) published an article that suggested that a phase shift was currently occurring in our galaxy. That GRB, or massive concentrated bursts of energy from various astronomical phenomena could easily cause extinctions around the galaxy and on Earth. The paper also found that the mean time between GRB occurrence and the mean time for intelligent life evolution have for a long period of time been at odds with one another. An intelligent species would be on the verge of evolving and then “flash” and all of a sudden they are extinct. Only recently (meaning the past hundreds of thousands of years) has the period of GRB flashes and intelligent evolution become the same. Meaning that soon a phase shift will be occurring, where intelligent life thrives all around the galaxy as GRB’s become less frequent. This is good news for our galaxy but poses a question for researchers attempting to search for ET’s in other galaxies. If we consider that for spiral galaxy (same galaxy type as us) that this phase transition time is the same per galaxy, and that we are looking at galaxies in their past due to restrictions forced by the speed of light then it’s entirely possible that these galaxies too are undergoing a phase transition currently, but that we are looking at them at a much younger age, before this transition occurs. It would mean that we would not be able to see these aliens, even if these galaxies have the right properties to allow for their existence. This would limit our capacity to ever look for such aliens until these galaxies, from our perspective of us in the past become old enough for us to see intelligent life thrive there as well. This phase transition too poses another question, why are we one of the few planets to be spared by a GRB during our evolution. Some theories state that the late Ordovician Extinction occurred via a GRB event, but the paper states that every day civilizations in our galaxy are being killed by GRB’s, yet we have not been. This points to a statement that Earth is statistically lucky in not having its species killed off. Or perhaps there are other reasons and even more phase transitions like this related to life thriving in the habitat of the universe.

Though this paper provided a conclusion that did not find aliens, and though there are some fundamental theoretical questions that remained unsolved, this paper pioneers a way to search for aliens. This method of searching for aliens in galaxies far away by their effects on a galaxy is definitely going in the right direction. These studies need more work, but these researchers are determined to end the Fermi Paradox. And to finally answer that great question, are we alone?

Main Citation

Zackrisson, E; Calissendorff, P; Asadi, S; Nyholm, A. 2015 Extragalactic Seti: The Tully-Fisher Relation as a probe for Dysonian Astro Engineering in disk galaxies, The Astrophysical Journal, 39, 511-548

Other Citations

Annis, J. 1999, An Astrophysical Explanation for the Great Silence, Experimental Astrophysics Group

Annis, J. 1999, Placing A Limit on Star-Fed Kardashev Type III Civilisations, JBIS, 52, 33

Dyson, F. 1960, Search for artificial stellar sources, Science, 131, 1667

Kardashev, N. S. 1964,Transmission of information by extraterrestrial civilizations, Soviet Astronomy, 8, 217