Is intelligent alien life possible?

There are many theories about this, and in some cases they are weird. The main problem is that the only intelligent species we know of is we humans, and we don't fully understand exactly how and why we are intelligent. We also don't understand how the planet Earth's development helped in this evolutionary process. The bottom line is that we don't really know what intelligent aliens would be like or how they could evolve on alien worlds. This is new ground for astrobiology.

We now know that there are billions of Earth-like planets in our galaxy, but one thing is for certain: Our planet is in a very unusual solar system. Many of the solar systems that have been discovered are different than ours. I believe that the reason for this is that our star is essentially a single star, not a binary like most other stars.

What has caused astronomers and cosmologists to change their thinking about planetary formation is the discovery of these totally alien solar systems. Our planet Earth is in a very stable planetary system compared to others systems. The gas giants in our system are out there away from our star, and the rocky planets are in close to our star, which is the Sun. We got lucky. Many alien systems formed gas giants beyond the so-called snow line, where water is frozen, but they moved very close near the star, wiping out any rocky planets, or capturing them as moons. In other words, many inhabitable planets in these alien systems are orbiting gas giants that are in the Goldie Locks region where liquid surface water is possible. Many habitable alien worlds are not planet but are moons.

Then, there are the planetary systems around K-class and M-class dwarf stars, which are much less luminous than our G-class dwarf star but are more populated in our galaxy that our Sun's type of star.

Take, for example, M-class stars. It turns out that seventy percent of the stars in our galaxy are M-class, but no one can see them because they're too dim. M-class stars have a temperature of 2400-3700K. Our sun, a G-class star, has a temperature of 5778K. An M-class star is only 0.08 to 0.45 times the mass of our sun. But, what's really significant is that they're only 0.08 times the luminosity of our sun. They radiate energy mostly in the infrared part of the spectrum and appear to be reddish in color. The fact is that many Earth-like planets have been found around these M-class stars, but they are orbiting very close to the star, close enough to be tidally locked, which means that one side always faces the star. The good news is that if the planet is in the habitable zone, liquid surface water is a strong possibility. However there is a problem with M-class stars because they have powerful magnetic fields that often tangle and send out coronal mass ejections that even more deadly than those that our Sun emits. Couple this with the fact that habitable planets would have to orbit close to the star and one could come to the conclusion that planets around M-class stars are not good candidates for life, at least life as we know it, unless that planet has a more powerful magnetic field.

What would it be like to live on one of these M-class planets? Well, for one thing, life that evolves there would see well in the infrared part of the spectrum. On an Earth-size planet in the habitable zone, the star would appear in the sky to be five to ten times the size of our sun, but it would be blood red. The vegetation would be black. Think of what it would be to see black grass and black leaves on trees. The reason our grass and leaves appear green is that they absorb the red and blue light from the sun. On a M-class star's planet, the leaves and grass would have to be black to absorb the red light and infrared.

Aliens that evolved there would have big eyes sensitive to infrared light. Their skin might also be dark, to help keep them warm. One thing is for certain: they would be truly alien. The problem is that we have no idea how they could evolve on such a planet to become intelligent. We have nothing to go on.

Tidally locked planet close to M-class stars might not have the same problem that Mercury does. Some astronomers believe that a planet like that with an atmosphere would equalize the temperatures on both the side facing the star and the side not facing it. Winds would distribute the temperature. The good news is that M-class stars stay on the main sequence for trillions of years, so evolution can take its good old time on planets that orbit them.

K-class stars are another possible star system choice for life. A K-class star is considered an orange dwarf star with a temperature of between 3900-5200 K. They are usually lower in mass, but not by much when compared to our Sun, which is a G-type yellow dwarf star. The good news is that there are three to four times as many K-class stars as there are G-class. Alpha Centauri B is a K-class star with known planets. The other good thing about K-class stars is that they stay on the main sequence for 30 billion years as compared to the 10 billion years that our sun does.

I should point out here that the 10 billion years that our Sun is on the main sequence doesn't mean that all 10 billion years are good for life. The main problem is that a star like ours becomes hotter by 10% every billion years. That means that in another billion years the planet Earth will have its oceans vaporized out into the atmosphere where this will cause our planet to heat up even hotter than Venus, which has a surface temperature of 900 degrees. So even though the Earth will be safe from complete destruction for another 4 to 5 billion years, the planet will not be habitable for that long.

Aliens that live on planets that orbit K-class stars wouldn't have to deal with their planet being tidally locked like those that orbit M-class stars. They also wouldn't necessarily have plants with black leaves. Their plant leaves could be purple, violet or even red in color to capture the orange light from their star. Even though their star would be not quite as bright as our Sun, it would be bright enough to see well in visible light. That means that intelligent life that evolves on a planet in the habitable zone of a K-class star could resemble us.

One problem we have with alien Earth-like planets is that some of them might not have land. They would be considered water worlds. It is possible for intelligent life to evolve on a water world? The answer is no because they can't discover fire and work with metals. However, flying creatures on such a planet might have a chance to do these things. Again, they would be alien to us.

Finding intelligent alien life is not going to be easy, but at least we are now on the path to finding possible habitable planets nearby to us. Since we don't have any possible scenarios for evolution on alien planets, we are just guessing as to how intelligent life could evolve. Astronomy and especially astrobiology will be interesting fields of study in the future.

The truth is that life is probably everywhere, but intelligent life is rare and we just have to get used to that. It's not going to be easy to find other intelligent species, but they're out there. I'm certain of it.

Thanks for reading.