Exoplanets: Worlds beyond the Solar System

[VelesHomais]

This thread is for discussions concerning the extrasolar planets. That is, planets located outside the Solar System.



Image courtesy of: www.markelowitz.com

I recall being of pre-school age and my dad showing me an Astronomy book with pictures of the planets in the Solar System. There were 9 of them. I was astonished how we could know anything about worlds outside our own... Then Pluto was demoted and we were left with 8 planets.

Today we know of 854 planets. Tomorrow, this number is going to be greater. About 18,000 more are in the process of confirmation, since we need the planet to complete its transit at least several times for verification of its existence. The latter applies to the transit method, which is used by the NASA Kepler Space Telescope. In my opinion, this is one of the most exciting (top-10) developments in our lifetimes.

While we are curious about all planets, we are particularly interested in finding a specific Earth-like class planet. Earth-like planet has to satisfy the following requirements:
1.) Terrestrial.
2.) In the Habitable zone.
3.) Radius and mass similar to Earth's.

These conditions, if met, potentially lead to conditions similar to those that we find on Earth.

First Earth-like planet was discovered on September 29, 2010, it was named Zarmina, or Gliese 581-g. It's very existence is being questioned by some astronomers.


Artwork credit: (c) Lynette Cook

Zarmina's stability of climate suggests that if sentient/intelligent life had evolved there, it would be far ahead of us in its advancement due to age advantage. In which case, we wonder, when our own little world was discovered by them. The team's lead astronomer, Steven Vogt, a professor of astronomy and astrophysics at the University of California, has made a controversial statement that he is 100% positive that life exists on Zarmina.

Location of the system is 20 light years away, about 200 trillion kilometres. There are only approximately 100 stars in such proximity to Earth. This distance, in cosmic perspective, can be classified as "right around the corner." Even though that with modern technology, it is virtually unatainable, in one hundred years or so, it is conceivable that a probe will be sent in its direction.

In October 2008 a message from Earth was beamed, in international collaboration, from National Space Agency of Ukraine, in direction of Gliese 581 c, which is a neighbouring planet of Gliese 581 g (Zarmina), which was regarded as most Earth-like (just outside the habitable zone) planet, until the discovery of the planet in subject. The message will take 20 years to arrive there, any potential response will take another 20 years to get to Earth.

Discovery of an Earth-like planet finally allows scientists to make an educated guess on the frequency of habitable planets in the Milky Way Galaxy, they estimate the number to be in between 20 and 40 billions of planets. This estimate is beyond previous optimistic guesses.

There is little doubt that mankind will explore this planet in the distant future, colonization in the distant future is not out of the question either. Professor Steven Vogt calculates that it would take 200 years to get there using Nuclear Pulse Drive, which is close to our current technological capabilities. He proposes that works on such starship begin as soon as possible. It could either be fully automated with robotic artificial intelligence or contain a crew on a multigenerational mission.

[kicaj]

pity that the solar system is so far to the nearest star.
But in october european astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth.

http://www.eso.org/public/news/eso1241/

[tuanhung]

when u said habital zone, do you mean goldilocks zone?

they should redefine habital zone, cause i think its possible for life to exists outside that goldilocks zone, as long a planet is orbiting a star from a safe distance with good enough tempreture with water/land mass, then it doesnt matter whether its outside the goldilock zone

to solve the mass/gravity problem....cant they just start buildling underground the surface?

[VelesHomais]

Goldilocks zone is just a stupid way of saying Habitable zone, it's the same thing.

as long a planet is orbiting a star from a safe distance with good enough tempreture with water/land mass, then it doesnt matter whether its outside the goldilock zone - that's what a habitable zone is.

[Spartan_X]

I feel that we are in the most exciting age of space exploration thus far ... It is the first time in history that we are learning true information on planets outside of our solar system, something that, not many years ago - was science fiction.

Only sad thing is that it will be the job of some other generation of humans to go see these planets in person, and by then we will be long gone.

[Tepes]

Originally Posted by Spartan_X

Only sad thing is that it will be the job of some other generation of humans to go see these planets in person, and by then we will be long gone.

It's much more efficient to sent automated probes.

But even if humans are sent, they will most certainly require some kind of stasis pods to go themselves, as nothing can travel faster than light according to Einstein's theory. If we're lucky enough for those stasis pods to be invented within our lifetimes, we may also stand some chance of being sent off to explore other worlds.

[VelesHomais]

Originally Posted by Spartan_X

I feel that we are in the most exciting age of space exploration thus far ... It is the first time in history that we are learning true information on planets outside of our solar system, something that, not many years ago - was science fiction.

Only sad thing is that it will be the job of some other generation of humans to go see these planets in person, and by then we will be long gone.

In the next decade we will probe the atmospheric composition of thousands of exoplanets, something that was beyond comprehension when I was entering school. The whole field of Astronomy has been completely revolutionized in the last decade, it is very exciting.

I believe that by 2100 we will have sent first probes to the nearest stars, maybe even a few decades earlier than that. They will reach their destinations in the second half of the 22nd century.

[Jan]

Finding (some kind of) life on an exoplanet is just going to be a matter of time. It's rather frustrating though that even if there is something out there that communicates on our level, it takes decades just to do the formal introductions.

[EdgarsSTAR]

Why do they think that exoplanet should be same size, mass as earth? Why not bigger or smaller?

[The_Dude]

Originally Posted by EdgarsSTAR

Why do they think that exoplanet should be same size, mass as earth? Why not bigger or smaller?

A couple reasons, I think. First is that we only know of one planet with life on it currently so we treat that as the standard by which to judge the likelihood of other planets to bear life. Second probably has to do with the fact that unlikely as it may be we still want to one day visit these worlds so looking for something even slightly Earthlike has to be a factor.

[VelesHomais]

Originally Posted by EdgarsSTAR

Why do they think that exoplanet should be same size, mass as earth? Why not bigger or smaller?

Nobody thinks that, most known exoplanets are Jupiter-like gas giants. We are just more interested in Earth-like planets, because we live on one such planet. Basically, astrobiologists are most curious about Earth-like planets, while astronomers are interested in all of them.

[RTM84]

Jupiter size planets could have moons even bigger than earth. Which for themselves could be very interesting (even home to life itself). However they are almost impossible to detect nowadays.

The current estimate for exoplanets is around 200 billion for our galaxy alone.
and this a estimate for close orbit planets only. So on avarage every star has 2 planets in close orbit.
The "neptunes" and even "saturns" around other stars are still very difficult to detect and therefore impossible to predict how much tere are.

[-:UberMann:-]

I have a noob question about our solar system. Do the planets' orbits form a disk? or that's only for visualization purposes?

[Spartan_X]

Yes their orbits do form a disk around the sun. Basically the gravitational force of the sun plus the centrifugal force generated from the spin of the planets around it, forces them to spin in a disk around the equator of the sun. Smaller objects than planets generally have more chaotic orbits ( for examble, Pluto, comets, etc ) and they do not orbit in the same disk.

[RTM84]

Originally Posted by EdgarsSTAR

Why do they think that exoplanet should be same size, mass as earth? Why not bigger or smaller?

Small worlds like mars are not likely places to bear advanced life because the core of these planets cool overtime, stopping vulcanic activity and the magnetic field. Both are believed to be essential for complex life to evolve.
Bigger wolds have much more gravity which could make life like we know it impossible.

[Spartan_X]

But life as we don't know it yet, might be possible. I believe that if one planet has a potential for life to exist on it, the kind of life that will be produced will adapt to the particular planet characteristics.

[VelesHomais]

Originally Posted by RTM84

Jupiter size planets could have moons even bigger than earth. Which for themselves could be very interesting (even home to life itself). However they are almost impossible to detect nowadays.

The current estimate for exoplanets is around 200 billion for our galaxy alone.
and this a estimate for close orbit planets only. So on avarage every star has 2 planets in close orbit.
The "neptunes" and even "saturns" around other stars are still very difficult to detect and therefore impossible to predict how much tere are.

My opinion is that there are approximately 2000 billion planets in the galaxy and billions of Earth-like planets among them with billions more exomoons with habitable conditions. While these estimates are optimistic, they are pessimistic regarding the search for intelligent life, because with such an astronomic pool there should be at least one civilization that has extended its reach to the entire galaxy by now - where are they?

The galaxy is approximately one hundred thousands of light years across. The civilization that has evolved, let's say, a million years beyond where we are (considering the age of the galaxy - it's not that much) they should have had the time to send out unimaginable numbers of probes to every corner in the galaxy and reach every corner, even at half-light velocities.

[Spartan_X]

Well... Maybe they don't want to reveal their existence ? I can think of many reasons for this:

1. Humans are some kind of a expirement of a extra-terrestrial intelligence and they want to see what we will do without any intervention

2. We are not ready to meet them, in galactic terms. They might fear that humanity, as it is now, armed with space-technology might evolve into a galaxy-conquering civilization

3. There are no civilizations in our galaxy with space-travel capabilities. This is unlikely i believe, but yet can't rule it out.

4. They are here, in some kind of disguised form, and they are in control. That's the most unlikely scenario i can think, it is very unlikely in fact, but i don't rule it out completely.

[RTM84]

My opinion is that there are approximately 2000 billion planets in the galaxy and billions of Earth-like planets among them with billions more exomoons with habitable conditions. While these estimates are optimistic, they are pessimistic regarding the search for intelligent life, because with such an astronomic pool there should be at least one civilization that has extended its reach to the entire galaxy by now - where are they?

I can completely agree to your estimate of billions of habitable worlds.
If the estimate is true. than you might have already answered the question to why a civilization has not extended it's reach over the entire galaxy. There might not be a need to do that with so many habitable worlds within let's say 100 lightyear reach around the homeworld. Life would already be so complex for them that the need to extend further is not a priority. It coud be just much more of thesame.

On the other hand, alien civilization might not feel a urge to explore the enitre galaxy at all. It might just be to much.

1. Humans are some kind of a expirement of a extra-terrestrial intelligence and they want to see what we will do without any intervention

We can't rule that out. I even considdered that life on earth could have started intentionally or by accident due to the visit of a probe or alien spacecraft in the early days of planet earth. It's not likely, but it is still a option.

2. We are not ready to meet them, in galactic terms. They might fear that humanity, as it is now, armed with space-technology might evolve into a galaxy-conquering civilization

Interesting option, so we as humanity might be under a restriction of the ingalactic society.

Options 3 and 4 are highly unlikely

[Simon91]

Some sources of variable credibility (including ex-astronauts) state that humanity in fact already is in contact with at least one ET civilization but this is kept classified. According to the accounts I came across, the alleged ETs are benign and if they were hostile we'd be long gone. Some even suggested that the sudden explosion in electronic science was directly assisted by visitors and that Apollo 13's crew was saved by them as the LM itself had not enough fuel to get them through all the necessary correction burns on the way back.

Obviously this is to us, the mere mortals, still a purely speculative subject but I personally find it far more possible than vast majority of other conspiracy theories. Even if none of those were real, I'd be surprised if breaking the speed of light and making the first contact did not happen in my lifetime.