…gazing at the stars is to feel closer to other forms of Life.
It is fair to believe that not having the proof that there are other forms of life elsewhere than our planet, is not a reason to neglect its existence. In fact, within the vastness of the Universe, it is its infinity and wonderfulness what makes, at least to me, obvious the fact that we are definitely not alone in it. In its infinity, it is fair to think that life is abundant.
As it is well known, life can adopt several forms, from microorganisms to intelligent beings, and the capacity of a planet to hold it depends on a fundamental basis: liquid water. Hand by hand with water is the planet’s atmosphere, which must gather specific conditions in order to conserve the planet’s ecosystems and protect it against the radiation coming from, mainly, the star it orbits.
Earth is about 4 billion years old, and the Sun its in the halfway of its lifetime, which is about 10 billion years.
Our star enters into the category of G-type stars, which are short-lived, bigger and more luminous than the most abundant type of stars in our galaxy, the so called red dwarfs. These latter are M-type stars that can be distinguished because of their cooler temperature, long lifetime, lower luminosity and small size, therefore not visible to the naked eye from Earth.
However it is important to notice that not all M-type stars are red dwarfs. For example, super giants Antares and Betelguese do also belong to this category and are actually visible to the naked eye: Antares visible at certain times of the year, and Betelguese seen in Orion’s constellation.
Planets and Habitable Zones
So far we have talked about stars. Something that is always referred to when we talk about planets, especially when it comes to the possibility of holding life, is the so-called habitable zone, also known as goldilock region. This is a zone around the star which is warm enough to hold life if the planet’s atmosphere gathers the proper conditions.
This zone must be at certain distance to the main star such that its radiation ejection does not dry the planet’s atmosphere. In the case of M-class red dwarf stars, their habitable zone is so narrow and close to it that any planet within would experience X-ray and UV radiation about x1000 times what Earth receives from the Sun. Red dwarf habitable-zone planets would end up with their atmospheres stripped away and therefore not developing into hospitable worlds.
Contrary to these long-lived M-sized stars, G-type stars like our Sun live for much less years. Furthermore, a star limits how long a planet’s atmosphere can remain stable. Earth is clearly within the Sun’s habitable zone. Let us open a parenthesis and recall Newton’s law of universal gravity which states that two bodies will be attracted with a force proportional to the product of both masses, and inversely proportional to the squared distance between them. Consequently, and closing the parenthesis, in some billion years the Earth will orbit its inner habitable zone region, approaching the Sun.
In parallel, the Sun will grow with time, getting warmer and brighter, and therefore the habitable zone will move outwards. Eventually, the Sun will become a red giant, one of the latest phases of stellar evolution, ranging from dwarfs (brown, red, etc.), to giants (super and hyper).
Goldilock Stars: K-type stars
These stars are mid-size and have a lifetime between M-type red dwarfs and G-type giant stars. Also, these stars are warm enough such that the habitable zone around them provides the best qualities for developing hospitable planets and therefore makes them the right place to look for life. Furthermore, a longer lifetime from these stars means a slower migration of the habitable zone, which is the zone outward shifting due to the star increase in size.
There are approximately three times more K-type stars than G-type stars in our galaxy, the Milky Way. Also, these stars have less intense magnetic fields that power strong X-ray and UV emissions and energetic outbursts. In fact the X-ray emissions gotten by their surrounding planets would be about 1/100th times of those received in the habitable-zone of M-type stars.
An example of a promising system is Kepler-422, which is a goldilock star that hosts a goldilock planet: Kepler-442b. This is a rocky planet whose mass is about twice that of the Earth. The system’s name Kepler is due to the Kepler satellite whose mission is to examine similar Earth-sized exoplanets.
Life is everywhere, although at first sight it does not seem so. We see an empty space, but when we observe closer we discover energy and matter all around. The fact that we have not yet, in the vast infinity of this Universe, found other forms of life, does not mean that it doesn’t exist. Or maybe we were just seeing and not observing.
Regarding life as we know it in our planet, not having found it elsewhere to date doesn’t give us a justification to neglect it. Essentially, it would be like looking at the Ocean and try to convince ourselves that there is no life underwater just because we are looking at the surface. And extrapolating this to an infinite Universe, we are just seeing the surface compared to its vast depth.
No matter if they are G-, M-, or K-type stars, every time we look at them on top of our heads it is very possible that we are looking at the Home star of another Being who, at the same instant within its own space-time frame, is looking to its sky, directing the eyes to our Sun, and unintentionally returning the look to ourselves, making that at a middle point within the “empty” space that separates us, our gazes cross.
In essence, in an infinite, full of life Universe, gazing at the stars is to feel closer to other forms of Life.
