Looking at the myriad stars on a clear night, one has to take a deep breath at the realization that each point of light is a sun with planets likely revolving around it. The stars come in various sizes and bizarre densities, some only 10% the mass of the sun and some hundreds of times bigger. They are given designations of O, B, A, F, G, K, M, with O being the hottest and brightest and M being the smallest and faintest. While M type stars are the most common, not one of the stars you see at night is an M star. None can be seen with the naked eye. But through powerful telescopes, they make themselves known. (Astronomy students remember the star classification using the sentence: Oh, Be A Fine Girl Kiss Me.) The sun is a G type star.
The temperature at the center of the sun is estimated to be about 27 million degrees Fahrenheit. This is hot enough to fuse hydrogen atoms into helium, a thermonuclear reaction that powers the sun. The temperature at the surface averages about 10,000 degrees. While these temperatures may seem extreme, the surface temperatures of the hottest stars reach an astonishing 72,000 degrees.
Recent exo-planet (planets bound to other stars) hunting technology has discovered over 4,000 planets orbiting over 3,000 other stars. Of those planets, about 20% may have the potential for life as they are at a distance from their sun to have liquid water on their surfaces. (From our limited perspective (the Earth), we assume that liquid water is a necessary ingredient for life.) If the number of potential earth-like planets is consistent throughout the galaxy, then there could be as many as 40 billion earth-like planets in the Milky Way Galaxy alone. And there are billions of galaxies. Which always brings up the question: With all those potential earth-like planets, where the heck is everybody? The “everybody” being other intelligent beings on other worlds.
There are many stars much older than the sun. Some of the small M type stars present today may be nearly as old as the Universe itself, upwards of 14 billion years, while the sun is young in comparison at “only” 4.6 billion years. If those ancient stars had planets conducive to life, then one might conclude they may have produced intelligent life long ago. So where are all those intelligent aliens?
For most of recorded history the stars were a great unknown and explained by various fanciful creations of man’s imagination. However, in the late 1500s Giordano Bruno, a Dominican friar, suggested that the heavens might be filled with other worlds like the earth and some might even have intelligent life. For this outrageous theory and other heresies, the Church executed Bruno in 1600. In the U.S. in 1924, there was an active search for radio signals from Mars from what many people believed might be a civilization of beings living there. None were found.
In the 1970s, NASA funded a program to look for artificial radio signals from sources up to a thousand light years away. These early attempts gradually grew into the current SETI program, the Search for Extraterrestrial Intelligence. It has survived politics and sometimes ridicule and has expanded today into a sophisticated search for other worldly intelligences. There seems to be, at least among a dedicated group, an almost obsession with finding the answers to the questions: Are we alone? If so, why? (If we are alone, as Carl Sagan said, “it seems like a lot of wasted space.”) If not, where is everybody? Yet after thousands and thousands of hours of searching, the Universe keeps its mystery.
So the search continues with more sophisticated and powerful methods. The deployment in space of the James Webb Space Telescope scheduled for March of 2021 may finally answer at least some questions. The James Webb will be able to determine the composition of the atmospheres of some of the earth-like exo-planets. Researchers will be looking for water vapor, oxygen, carbon dioxide, methane, and other atmospheric signatures that are indicative of life as we understand it. However, evidence of life doesn’t necessarily mean intelligent life. But even the discovery of a living microbe somewhere other than Earth would finally answer at least one question: Is there life beyond Earth?
Email Terry Mejdrich at firstname.lastname@example.org.