Habitable zone of a star

Hi,
habitable zone of a star. Sounds like a comfy place, right? Well it can be. It is at least on (tiny portion of) Earth which is an example of object in habitable zone. Such a „zone“ is important for astronomers, or maybe it’s just important for headlines in newspapers.


Habitable zone in a Solar System based on luminosity.

Habitable zone is an area around star where we, with quite limited knowledge on this subject, think that life could be. The simplest „definition“ is that it’s the area where satellite (such as planet) would be able to sustain liquid water. We cannot be sure of course if life needs it but it is the case for the one that evolved on Earth.

The true habitable zone is something a bit more complicated. The simplest case of a planet would be one that behaves as a black body, that means that it absorbs all radiation (light for example) regardless of its wavelength. This is immediately just an assumption because such a planet does not exist. Earth just as Uranus or Mercury reflect light, the planet’s albedo describes this. Albedo is an attribute telling us how much object reflects light. 0 means that it is a black body and 1 means that it is white body aka perfect mirror.

There are even more factors that one could consider. For example, when planet has thick atmosphere it can sustain liquid water (and life) even further out from habitable zone on the other hand if that happens to planet like Venus which is already pretty close, you have got hell. If satellite orbits with high eccentricity the conditions are again different.

It’s hard to combine all of this together which results in lot of different outcomes depending what model one picks. Estimates for Solar System are between 0.9 or even 0.6 to 1.3, 2 or 3 astronomical units. In most of them Earth is just on the inner edge. These numbers were pulled from Wikipedia.

When we hear in news that a new exoplanet was found in a habitable zone it might not mean much. This news usually come alongside the information that the planet has similar size that of Earth, it’s not like we could travel there or anything, now we are mostly collecting data and learning.

Dragallur

HZ picture: By Habitable_zone-en.svg: Chewiederivative work: Ignacio javier igjav (talk) – Habitable_zone-en.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8462897

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How did life arise?

Hi,
I bumped into this question when I was arguing over evolution and creationism. It is very favorite claim that life had to be made by God because humans were not able to create it from dead matter, rocks for example.

This is famous problem. It is true chemists were not able to create life when simulating the early time on Earth 3.6 billion years ago (this is for simplicity, it is kind of difficult to say when exactly life arose).


Now of course there are theories and one of them is the theory of primordial soup. This is theory that in the ancient ocean there were dissolved some basic molecules which we can find even on other planets (so we have proof for them that may have been here (and almost surely were)).

So as they are floating in the dead ocean there is some great radiation coming down and hitting these molecules. Also there is what is called “primordial lighting” which is the lighting that should be able to create more complicated molecules only by hitting ammonia, hydrogen and other stuff. It was proved that there should be monomers too. Those are simple organic compounds, such as lipids or proteins.

Chemists were able to create with some radiation and electricity even amino-acids. The last step was that we were able to create purines and pyrimidines, those are building blocks of DNA and RNA which is kind of important.

RNA and DNA, key components for modern living.

Nothing more, we were not able to create life, yet. What would the next step be? Something that is called replicator.

Replicator is any molecule or lot of molecules that are able to replicate itself. This is key. If we are able to create some kind of replicator from the primordial soup, we will take a giant leap forward, because then onwards evolution takes a place.

When replicator replicates it should make exact copy of itself like in asexual reproduction. But as good secretary makes roughly one mistake per page, even the replicator will eventually make a mistake. This is called mutation and it is either helping the organism or not. This process drives evolution even that only small part of all mutations may be helpful. Those who have good mutation will have more replicas of itself and eventually there will be only those which are better, this process will repeat in what is called evolution when after hudreds of millions of years you are standing here, originating from one simple replicator, as well as me, your class mates all other animals, bacteria and viruses. This was never observed but it should work like this.

In bottom you can see the LUCA, first original organism from which we originate!


 

So will we be able to create replicator? The problem with that is that only several laboratories over world are working on this. They are working on it only for about 100 years which is not much considering geological time.

While I did not see their laboratories I bet that they are working on small areas, maybe area of swiming pool and I found, I cite:

Liquid water covered much of the Earth’s surface by 3.6 (or 3.8?) Ga, but when before that it condensed from a dense atmosphere is undefined.

We can of course speculate on what “much” means though I would guess that we can start on reasonable 50% of Earth’s surface which is 255,036,000 square kilometers. When speaking about swimming pool I will take olympic swimming pool though I guess that the chemists work with much much smaller, they would not be able to control such a big area.

Imagine controling experiments on this thing!

It means that the Earth was able to use roughly 204,028,800,000 times bigger area than chemists not talking about the fact the oceans are deeper.[1] At the same time, there were couple of millions of years for this to happen compared to 100 in laboratory.

My point is that we maybe should not expect the life to rise in our laboratories, because if it does, life is much more probable that we thought[2].

Dragallur

PS: Do not ever argument by saying that Pasteur proved that life can not rise spontaneously, because he did not.

Read more: 1) 2) 3)

[1]Of course you could argue that in laboratory you can use lighting all the time and be purposeful with your selection of molecules.

[2]Maybe we should since our techniques improve and we are getting better in simulating and controling the environment of primordial soup.

Civilizations: Fermi paradox

Hi,
Fermi paradox is paradox made mainly by Enrico Fermi and what it asks is basicly: “Why are there no signs of other civilizations?”
That´s a question!
It is based on few things:
Our home star The Sun is quiet normal star which is not rare in our galaxy so lot of them should be here.
Next thing is that you must assume that the Earth is normal planet and lot of those stars will have similar rocks around itself in the right distance.
And civilization would develop on this planet and it would send some signals or travel through Galaxy.

There are really tons of stars like Sun and probably even similar planets but still we are not apparently hearing anything from space… lets see some solutions to this problem.

1) Civilizations are not common because either there is life on other planets but it is not developed or it is much rarer to survive through what is so called: Great Filter it is some event which would erase us, like meteorite or gamma burst.
2) There have to be much more specific things on planet. Without great source of energy it would probably not be able to send signals or even colonize other planets. Moon is very important for Earth since it stabilize its axis (which is important for normal seasons).
3) It is normal that life destroys itself when it has got enough good technology, nuclear war, lot of trash. OR it is normal that life destroys other lifes which means there would be some first great civilization which would keep Universe clean.
4) Another thing is that we are not sending signals really long time or listening really long time plus we are listening only to part of sky and only to some kind of signals. Maybe post-modern civilizations dont need to use our kind of communication but for example neutrino rays or something very different. AND what kind of radio signals we are using right now is not really long lasting for civilizations that would be thousands light years away.
5) Another thing is that maybe all civilizations are listening but none are sending which would cause in SETI-paradox. Or other civilizations do not want to interact because it is too dangerous.

So those are some ideas that I found, feel free to share yours!
Dragallur