New study examines which galaxies are best for intelligent life

The article, published May 1 in the magazine. Monthly notices from the Royal Astronomical Society, contradicts a 2015 study that theorized giant elliptical galaxies would be 10,000 times more likely than spiral disk galaxies, such as the Milky Way, to host planets that could nurture advanced technological civilizations.

The higher probability, the authors of the 2015 study argued, would be because giant elliptical galaxies have many more stars and have low rates of potentially lethal supernovae.

But Daniel Whitmire, a retired professor of astrophysics who is an instructor in the U of A Department of Mathematical Sciences, believes that the 2015 study contradicts a statistical rule called the mediocrity principle, also known as the Copernican Principle, which states that in the 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.

Historically, the principle has been used several times to predict new physical phenomena, such as when Sir Isaac Newton calculated the approximate distance to the star Sirius by assuming that the sun is a typical star and then comparing the relative brightness of the two.

“The 2015 document 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? For me this raised a red flag. Every time you come across as an outlier, that is, outlier, that’s a problem for the mediocrity principle. “

He also had to demonstrate that most stars, and therefore planets, reside in large elliptical galaxies to make his argument that the earlier document violated the principle of mediocrity concrete.

According to the principle of mediocrity, Earth and its resident technological society should be typical, not atypical, of planets with technological civilizations in other parts of the universe. That means its location in a spiral disk galaxy should also be typical. But the 2015 article suggests otherwise, that most habitable planets would not be located in galaxies similar to ours, but rather in large elliptical spherical galaxies.

In her article, Whitmire suggests one reason why large elliptical galaxies may not be cradles of life: They were awash in lethal radiation when they were younger and smaller, and went through a series of quasar supernova events and starbursts. at that moment.

“The evolution of elliptical galaxies is totally different from the Milky Way,” said Whitmire. “These galaxies went through an early phase where there is so much radiation that it would have simply completely bombarded any habitable planet in the galaxy, and subsequently the rate of star formation, and therefore any new planet, was essentially zero. No new stars are forming and all the old ones have been irradiated and sterilized. “

If habitable planets that host intelligent life are unlikely in large elliptical galaxies, where most of the stars and planets reside, then by default galaxies like the Milky Way will be the main sites of these civilizations, as expected by the mediocrity principle, Whitmire said.