Life: In part it’s a numbers game. The possibility of life on other planets (or moons, or other space objects) presumably increases with greater numbers. This is the quantitative argument. So, when Yale University (USA) scientists led by Pieter van Dokkum used updated information on the composition of star-types that make up other galaxies than the Milky Way (our home), he realized that the estimates of the number of stars in the universe – set at 100 sextillion – was too small by a factor of 3. In other words, in a paper published by Nature [A substantial population of low-mass stars in luminous elliptical galaxies] they put the likely number of stars in the universe at 300 sextillion.
This is a big number (heh): 300,000,000,000,000,000,000,000. If you started counting, say three numbers a second or 180 times a minute, it would require 317,000,000,000,000 years to count 300 sextillion. You could call that jaw-dropping.
The increase in the estimate springs from the growing realization that a particular class of star, the red dwarf, has been undercounted. For a long time astronomers assumed that the relative frequency of red dwarfs in our own galaxy (the only one available for observation), would hold for the entire universe. Now, with more powerful telescope systems such as the Keck Observatory in Hawaii (USA), observation of red dwarfs in other galaxies have revealed that the shape of the galaxy correlates with more red dwarf stars. Elliptical galaxies have about 20 times the number of red dwarfs than the Milky Way. Since elliptical galaxies make up 10%-15% of known galaxies, this accounts for the major increase in the estimated number of stars.
Red dwarf stars have already been linked to possibly life-bearing planets. By the numbers, the chance of a life supporting planet is…astronomical, and growing.
“There are possibly trillions of Earths orbiting these stars,” van Dokkum said, adding that the red dwarfs they discovered, which are typically more than 10 billion years old, have been around long enough for complex life to evolve. “It’s one reason why people are interested in this type of star.”