A previous paper published in 2015 theorized that giant elliptical galaxies would be 10,000 times more likely than spiral disk galaxies (like our lovely Milky Way) to be home to planets that could sustain intelligent life. Now research published today in the journal Monthly Notices of the Royal Astronomical Society contradicts that theory, arguing that it goes against the Copernican Principle.
The Copernican Principle, also known as the principle of mediocrity in statistics, states that in the absence of evidence to the contrary, an object or some property of an object should be considered typical of its class rather than atypical (Eureka Alert).
The 2015 study theorized that the increased likelihood of intelligent life in large elliptical galaxies would be due to the fact that giant elliptical galaxies have many more stars and low rates of potentially lethal supernovae. The author of the study published today is a University of Arkansas astrophysicist Daniel Whitmire, who is currently an instructor in the U of A mathematics department, had a problem with that logic.
"The 2015 paper had a serious problem with the principle of mediocrity," said Whitmire. "In other words, why don't we find ourselves living in a large elliptical galaxy? To me, this raised a red flag. Any time you find yourself as an outlier, i.e. atypical, then that is a problem for the principle of mediocrity."
Following the Copernican Principle, Earth and its intelligent life would be considered typical, not atypical, as would its location in a spiral-shaped disk galaxy. In order to debunk the 2015 paper, Whitmire reasons that the lethal radiation that surrounded large elliptical galaxies when they were younger accounts for why they, in fact, may not hold intelligent life.
"The evolution of elliptical galaxies is totally different from the Milky Way," said Whitmire. "These galaxies went through an early phase in which there is so much radiation that it would just completely have nuked any habitable planets in the galaxy and subsequently the star formation rate, and thus any new planets, went to essentially zero. There are no new stars forming and all the old stars have been irradiated and sterilized."
Whitmire thus concludes that according to the principle of mediocrity, galaxies such as the Milky Way may in fact be the primary sites of these technologically advanced civilizations.