Biggest Mystery

The biggest mystery of science is how and why does life develops and could it develop on alien planets?

We now know that there are billions of Earth like planets in our galaxy. If life is not a miracle than it's all over the place.
But, and this is a big 'But', life has not yet been found outside of the Earth. However, there are many Earth-like planets outside of our solar system. Kepler 186f is one such planet. It's an Earth-like planet that orbits its star every 130 days but only receives 1/3 the amount of light that we do. It's at the outer edge of the habitable zone of its star. This planet was discovered by the Kepler Space telescope and is 492 light years away. It's only 10% larger than Earth.

The number of stars in our galaxy that could have Earth-like planets is a billion. Surely, life could have formed on these planets in some of them. Kepler 62e and Kepler 62f, which are 1.2 to 1.4 times the size of Earth respectively, are believed to be ocean worlds. Kepler 62f is probably cold, but still could contain life. These planets are 1200 light years away.
Another interesting Earth-like planet is Kepler 452b, which is a rocky planet that orbits a G-class star like our sun, which is 10% brighter. Its solar year is 385 days. It's a super sized planet with a gravity of 2G. It's also expected to have volcanoes and oceans. It has orbited its star for 6 billion years, which makes it much older than Earth. It certainly had time to develop life. The existence of a twin Earth planet gives astronomers the hope that they'll find many more Earth twins in our galaxy.

Three planets were found orbiting around Trappist-1, a very dim red dwarf star. These planets are similar Earth, and they are candidates for the discovery of life because very powerful telescopes could find the evidence of life on these planets.

Because of these discoveries the chance of finding life outside our Earth is very high.

Kepler 16b is a planet orbiting two binary stars. This was at one time not thought to be possible. This opens up a lot of interesting possibility to find a Earth-like planet.

What's required for a planet to be habitable is that it be in the circumstellar habitable zone. This is also called the Goldilocks Zone. It's neither too hot nor too cold.

I've already discussed what it would take to develop life. The requirements are complicated. One definite requirement is liquid water. This implies that a planet has a good atmosphere and is at the correct temperature to allow water to exist in oceans. The estimate of this possibility is that there are 40 billion in our galaxy, with 11 billion orbiting around a star like ours.

However, wred dwarf stars are very common in our galaxy. Trappist-1 is a good example of a red dwarf star that has planets in the habitable zone. There are untold billions of these systems in our galaxy alone. What this suggests that life could have developed all over our galaxy.

The main problem with trying to determine if planets are habitable is the extreme distances that are involved. The two methods of determining this involve Doppler wobble, which involves measuring the spectrum shift of a star, and the transit effect, which involves measuring a slight drop in star's light. What is needed is a method of detecting the atmosphere of these planets. This ability will come soon. If a method could be found to determine if alien planets have oxygen in their atmospheres. The James Webb telescope may have this ability.

None of this determines if the chemicals to produce life exist on these planets. However, many of the chemicals have been found in nebulae both in our galaxy and in galaxies beyond ours. There is the possibility that the panspermian method of life formation is common throughout the universe. This theory says that life comes from outer space. In other words, life could form on a planet and then be distributed all over the universe.

Another possibility for Earth-like worlds is as moons around gas giants orbiting their star in the habitable zones. Remember the movie Avatar? This type of planetary system could be very common throughout the universe.
The hope is that life on some of these older could have evolved into intelligent life. The estimate is that there are a million planets with intelligent life in our galaxy.

Thanks for reading.