Potentially Habitable Exoplanets

[PB666]

9 hours ago, KerikBalm said:

I assume nothing... I was just listing the assumptions they were making for "predicting" the existence of an exo-moon. I'm thoroughly unconvinced that such a moon exists. There is 0 observational evidence that such a moon exists.

They saw a gas giant at a distance from the star that was appealing, and then they used a mass ratio based on a sample size of 4 (our gas giants... which have data skewed by moons like triton and titan), then assumed nearly all the mass was concentrated in one moon (definitely not the case for Jupiter, which would be the planet with the greatest similarity to it in our solar system), then proceeded to "predict" the presence of a "potentially habitable exomoon"

There are sooooo many problems with this prediction... it doesn't belong in a list with places for which there is direct observational evidence.

It is speculation... hypothetically, that planet could have a habitable exomoon... hypothetically... but we can pick pretty much any star in the sky, and without any data, say that hypothetically that star could have a habitable planet around it... that doesn't mean we should start making a list of speculative planets around pretty much every star we can see.

So much of the things presented here are. I count habitable like a primative campsites. If you can't walk out of a lander without a pressurized suit or a firemans suit , might as well be the moon or venus.

[PB666]

35 minutes ago, Spaceception said:

Well then theoretically, with the sample size we have, and ignoring ESI, which planet is the most likely to have at least temperatures comfortable for a human?

They have to have an atmopheric pressure and surface water levels comparable to earth, also you have to consider the length of the day. If the day is too long, then by the time a planet makes a full rotation basically everything on the dark side has been frozen solid.

Instanteous
A planet close to the center of the habitable zone.
It needs to have a dense, turbulable heat sink (like oceans)
It needs to have an atmosphere
The planet needs to rotate say at least one revolution per 48 hours. (and would need more atmospheric CO2 and more turbulant oceans, so a moon might be desirous)
To have an atmosphere it needs to have a magnetic field or be much larger than earth
It it is much larger than earth it needs to be silightly further from its star,
If the planet is larger the atmospheric pressure cannot make oxygen in space-suite poisonous, Therefore the atmospheric pressure should be about the same.
Also the atmosphere cannot be corrosive (for example it cannot have SO2 or SO3 in high concentrations), this would destroy even stainless steel.
It should not have an atmosphere that contains high levels of ethylene, ethane, propane as these would dissolve a parachute and spacesuits.
Its atmosphere should not contain high levels of cyanide or other toxins that are immediately deadly in small quantities

Longer term
Its primary star should not be a flare star, or a high UV or X-ray emitter.
If its a binary the two stars should not be so close that material from one star is being ejected into the other.
If it secondary star is a red-flare star it should be far enough away that flares are survivable.
It should not be in a period of great bombardment, it should have cleared its orbit.
It should have, at least the appropriate starting conditions for the growth of condition tolerant cyanobacterium. Even if that growth requires some human assistent.
It should not already have notable life (otherwise its an inhabited planet)
The ground should not have widely distributed high levels of mercury or arsenic.
The ground should not be more radioactive than the soil of the chernobyl's red forest.
There should be widely available sources of carbon, hydrogen and oxygen.
There should be water bearing rainfall.

And finally the planet should have an indigenous population of women in need of spacemen. . . . :^).

 

 

 

[Spaceception]

ALMA spies Earth like planet in the habitable zone in the middle of formation around a very young Sun like star

http://www.techtimes.com/articles/146084/20160331/alma-earth-like-planet-forming-habitable-zone-nearby-star.htm

Also, 1000 posts

Edited April 1, 2016 by Spaceception

[fredinno]

9 hours ago, PB666 said:

If the day is too long, then by the time a planet makes a full rotation basically everything on the dark side has been frozen solid.

No, if you have an atmosphere, the far side should not freeze too much:

Quote

 

In the past, it was believed that efficient heat transfer between the sides of the planet necessitate an atmosphere so thick as to disallow photosynthesis. Due to differential heating, it was argued, a tidally locked planet would experience fierce winds blowing continually towards the night side^{[citation needed]} with permanent torrential rain at the point directly facing the local star,^[21] the subsolar point. In the opinion of one author this makes complex life improbable.^[22] Plant life would have to adapt to the constant gale, for example by anchoring securely into the soil and sprouting long flexible leaves that do not snap. Animals would rely on infrared vision, as signaling by calls or scents would be difficult over the din of the planet-wide gale. Underwater life would, however, be protected from fierce winds and flares, and vast blooms of black photosynthetic plankton and algae could support the sea life.^[23]

In contrast to the previously bleak picture for life, 1997 studies by Robert Haberle and Manoj Joshi of NASA's Ames Research Center in California have shown that a planet's atmosphere (assuming it included greenhouse gases CO₂ and H₂O) need only be 100 millibar, or 10% of Earth's atmosphere, for the star's heat to be effectively carried to the night side, a figure well within the bounds of photosynthesis.^[24] Research two years later by Martin Heath of Greenwich Community College has shown that seawater, too, could effectively circulate without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Additionally, a 2010 study concluded that Earth-like water worlds tidally locked to their stars would still have temperatures above 240 K (−33 °C) on the night side.^[25] Climate models constructed in 2013 indicate that cloud formation on tidally locked planets would minimize the temperature difference between the day and the night side, greatly improving habitability prospects for red dwarf planets.^[4] Further research, including a consideration of the amount of photosynthetically active radiation, has suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.^[26]

However, if the rotation is not tidally locked, like Venus', the life will need to all be mobile, or at least be able to hibernate very well to adapt to the heavier temperature changes- something that can make life much more difficult.

9 hours ago, PB666 said:

It should not already have notable life (otherwise its an inhabited planet)

What do you mean by "notable?" Would it have intelligent life, or...?

[KerikBalm]

First, lets be clear that when they say habitable, they don't mean for complex life... just bacteria.

Also, they are talking about the surface of the planet... as we all know that some places well outside the habitable zone show signs of promise for being habitable... but only in subsurface environments.

15 hours ago, PB666 said:

A planet close to the center of the habitable zone.

No, earth is not at the center of the habitable zone, its near the inside of it. The habitable zone moves outward with time. Early earth was closer to the other edge of the habitable zone... but here we are 4 billion years later, with at most 1 billion years of habitability left... much less than that for complex macroscopic multicellular life.

The center is surely a good place to be, but you just need to be in the habitable zone. One could take earth and move its orbit to mars, and we'd still be in the habitable zone... that mars is in the habitable zone should also tell us that being in the habitable zone in no way indicates a habitable planet. Ditto for venus, you could move Venus to Earth's orbit, and it would still be hellishly hot (although it may not have become that way if it was farther out)

15 hours ago, PB666 said:

It needs to have a dense, turbulable heat sink (like oceans)

It needs to have an atmosphere

I don't think it needs a particularly dense heat sink, but that is nice for smoothing out temperature variations and buffering climate and atmospheric concentrations, but its not absolutely required. Take the middle of the sahara desert, the temperature variations between day and night are higher, and the effect of the oceanic heat sink doesn't do much to smooth out the day-night variation.

An atmosphere and the itself is able to provide enough of a "heat sink" to keep day/night temperature variation from being too extreme.

oceans would be nice... but a planet with oceans covering only a small fraction of its surface... like the lakes of titan rather than the oceans of earth (just talking about relative size/proportion... I'm not saying methane seas) would be enough to have it be habitable. The small lakes of titan are enough for a methane cycle where evaporation and precipitation balance out... it should work similarly with water.

16 hours ago, PB666 said:

The planet needs to rotate say at least one revolution per 48 hours. (and would need more atmospheric CO2 and more turbulant oceans, so a moon might be desirous)

I think a week or even a month or two would be fine, but the longer the rotation perion, the more substantial atmosphere/oceans it would need. Temperature variation from 2 month day-night cycles could be quite high, but 1 month in the sun should be plenty enough for organisms to grow and multiply and then go dormant for the next month.

I initially thought that tidaly locking = no chance... but it turns out that the margin for which an atmosphere won't just freeze out on the dark side of the planet is wider than I thought. However.... stopping atmosphere collapse isn't all of it... You maye still have all the water freeze on the far side of the planet in massive glaciers... with virtually no water available for any area where there is sunlight... no photosynthesis... the habitability wouldn't be much better than subsurface geothermal places. There are conditions for which enough water could be "liberated" from the darkside to have life in the sunny side (geothermal melting of the water, subsurface aquifers, a contiguous ocean with mixing currents)... but the situation of tidal locking will surely reduce the proportion of worlds which are habitable. There's also the possibility that the sunny side gets too warm, and its just a band of habitability around the terminator.

Rotation is good... but not 100% needed, and 48 hours is a bit too conservative. I'm still not very enthusiastic about red dwarfs because so many of the planets would be tidally locked... and other things about dwarfs...

16 hours ago, PB666 said:

To have an atmosphere it needs to have a magnetic field or be much larger than earth
...

If the planet is larger the atmospheric pressure cannot make oxygen in space-suite poisonous, Therefore the atmospheric pressure should be about the same.
Also the atmosphere cannot be corrosive (for example it cannot have SO2 or SO3 in high concentrations), this would destroy even stainless steel.
It should not have an atmosphere that contains high levels of ethylene, ethane, propane as these would dissolve a parachute and spacesuits.
Its atmosphere should not contain high levels of cyanide or other toxins that are immediately deadly in small quantities

Disagree with pretty much all of these due to the anthocentric viewpoint... None of these are required for a surface that can support life.

Keep in mind that 3 billion years ago... we'd die on the surface of Earth pretty darn fast, but earth was teeming with life.

Venus has an atmosphere, but no magnetic field. Its atmosphere is deficient in hydrogen... the water was split but UV and the hydrogen escaped... now the thick atmospehre protects most of the remaining hydrogren and what little water vapor is left. Similar things happened to mars... loss of much of the water/hydrogen, excess oxygen... a surface filled with superoxidizers... a magnetic field is needed to protect the water, basically. The atmospheric pressure can be much higher, your space suit can just use a lower % oxygen... just keep the same partial pressure of oxygen as on Earth. Some spacecraft used 100% oxygen atmosphere, but at 0.2 bar... its not a problem... the problem was when they used 100% oxygen at 1 bar for testing on earth... big fires...

Corrosive might be a problem for anylife... but how corrosive?

Ethan, ethylene, propane... not a problem for life per se... and parachute durability is not a criteria for *habitability*

Cyanide and other "toxins" may be just fine for alien biochemistry... not a problem per se for "habitability"... but is a problem for human habitation.

 

Longer term, for more advanced indiginous life: Should be G type or smaller so that its output is relatively stable over the period of billions of years so that life has adequate time to evolve.

Large stars have their habitable zones more outward faster, and go nova/supernova much sooner.

Red dwarfs will last hundreds of billions/trillions of years, while really large stars won't even make it to 1 billion.

Red dwarfs aren't good because they radiate mostly in the IR which is blocked by most significant atmospheres, planets are liekly to get tidally locked, etc.

Stars should be G, K, and maybe F type... but F type starts to have lifespans that wouldn't have allowed us to evolve, assuming a similar rate of evolution

[fredinno]

5 hours ago, KerikBalm said:

Take the middle of the sahara desert, the temperature variations between day and night are higher, and the effect of the oceanic heat sink doesn't do much to smooth out the day-night variation.

 

5 hours ago, KerikBalm said:

 

Rotation is good... but not 100% needed, and 48 hours is a bit too conservative. I'm still not very enthusiastic about red dwarfs because so many of the planets would be tidally locked... and other things about dwarfs...

 

5 hours ago, KerikBalm said:

Stars should be G, K, and maybe F type... but F type starts to have lifespans that wouldn't have allowed us to evolve, assuming a similar rate of evolution

The higher end of M-type is probably fine (M4 or 3 to M0), as those stars go from 20-60% of Solar Mass, and emit much more radiation. However, these stars do not last for more than 1 Trillion years. 

https://en.wikipedia.org/wiki/Red_dwarf

http://www.astrobio.net/news-exclusive/could-alien-life-cope-with-a-hotter-brighter-star/

Quote

However, the new paper cautions completely writing off the rare, ephemeral, UV-blasting F-type stars as incubators of life. Instead, F-types likely represent the brightest and hottest main-sequence stars that could plausibly allow life to form 

F-type is also perfectly fine, as they have a lifetime of 2-4 billion years in the main sequence. A-type is when things start getting too bad for life to stand a chance.

[KerikBalm]

Earth is 4.54 billion years old about 540 million years ago was the cambrian explosion. Even a long lived F type would have died before there was much of anything multicellular.

Thats assuming the planet stays habitable throughout the stars life... which it wont, just as Earth won't...

Heck, Earth didn't have an oxygen rich atmosphere until 2.3 billion years ago... or when it was about 2.3 billion years old... so, again, an F type star on the short end of the spectrum would not have lasted long enough for even Eukaryotes to evolve. One on the longer end with a 4 billion year lifespan would have its habitable zone move outward so much, that a planet would probably only stay in it for half that time... still not even Eukaroytic life would have time to evolve (assuming it takes a similar amount of time as on Earth).... so yea... F types are definitely not ideal, M types aren't so great... G and K types are where its at.

[fredinno]

47 minutes ago, KerikBalm said:

Earth is 4.54 billion years old about 540 million years ago was the cambrian explosion. Even a long lived F type would have died before there was much of anything multicellular.

Thats assuming the planet stays habitable throughout the stars life... which it wont, just as Earth won't...

Heck, Earth didn't have an oxygen rich atmosphere until 2.3 billion years ago... or when it was about 2.3 billion years old... so, again, an F type star on the short end of the spectrum would not have lasted long enough for even Eukaryotes to evolve. One on the longer end with a 4 billion year lifespan would have its habitable zone move outward so much, that a planet would probably only stay in it for half that time... still not even Eukaroytic life would have time to evolve (assuming it takes a similar amount of time as on Earth).... so yea... F types are definitely not ideal, M types aren't so great... G and K types are where its at.

No, F-types are in the main-sequence from 2-4 Billion Years, and complex life took 2 Billion years to form.

https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System

Besides, the habitable zones are wider on larger stars.

[KerikBalm]

if its only in the mainsequenc, for 2 billion years, that would mean it would have left the main sequence(ok, maybe not nova, but swelling to a red giant is no good either) before Eukaryotes formed on Earth.

The habitable zone may be wider, but it will move by similar proportions, and it will go between those proportions faster... We don't know how fast evolution would produce complex life on other worlds (nor is there an agreement as to what complex life is... multicellular, or just something like eukaryotic?) I wouldn't say its impossible... but the timing is pretty darn tight. Our sun is 4.6 billion years old... 600 million years ago... when our sun reached the age of 4 billion... there wasn't much on Earth to look at besides bacterial mats.

Our Sun will be in the main sequence for about 10 billion years total... but only half of that is suitable for us... although maybe if we were always where mars was, we'd be in a better position. It would seem that mars would be outside of the habitable zone early on... even Earth had massive freezing periods.. yet there is the:

https://en.wikipedia.org/wiki/Faint_young_Sun_paradox

and its even worse for mars... but clearly, at some point 4 billion or more years ago... mars had liquid water... although its not clear how long this lasted... maybe it was only during a period like Earths Hadean (when, it was initially believed, Earths surface was still mostly motlen, but that seems not to be the case and the surface was mostly solidified then... but anyway, mars would have been quite hot shortly after its formation)... lasting  20 million years before freezing is enough to make the macroscopic geological features that indicate water in the past... but not so much in the way of life.

F types may host habitable worlds, but I think the odds of an intelligent, communicative civilization forming on them are pretty low.

[fredinno]

10 hours ago, KerikBalm said:

if its only in the mainsequenc, for 2 billion years, that would mean it would have left the main sequence(ok, maybe not nova, but swelling to a red giant is no good either) before Eukaryotes formed on Earth.

The habitable zone may be wider, but it will move by similar proportions, and it will go between those proportions faster... We don't know how fast evolution would produce complex life on other worlds (nor is there an agreement as to what complex life is... multicellular, or just something like eukaryotic?) I wouldn't say its impossible... but the timing is pretty darn tight. Our sun is 4.6 billion years old... 600 million years ago... when our sun reached the age of 4 billion... there wasn't much on Earth to look at besides bacterial mats.

Our Sun will be in the main sequence for about 10 billion years total... but only half of that is suitable for us... although maybe if we were always where mars was, we'd be in a better position. It would seem that mars would be outside of the habitable zone early on... even Earth had massive freezing periods.. yet there is the:

https://en.wikipedia.org/wiki/Faint_young_Sun_paradox

and its even worse for mars... but clearly, at some point 4 billion or more years ago... mars had liquid water... although its not clear how long this lasted... maybe it was only during a period like Earths Hadean (when, it was initially believed, Earths surface was still mostly motlen, but that seems not to be the case and the surface was mostly solidified then... but anyway, mars would have been quite hot shortly after its formation)... lasting  20 million years before freezing is enough to make the macroscopic geological features that indicate water in the past... but not so much in the way of life.

F types may host habitable worlds, but I think the odds of an intelligent, communicative civilization forming on them are pretty low.

Mars likely had liquid water back then due to the fact that it had so much GHGs due to a much higher rate of volcanism. But yeah, it's probably impossible for much more than plants to develop before it becomes uninhabitable.

[Spaceception]

Here's some interesting news;

The first exoplanet was found 70 years before the first confirmed exoplanet

http://gizmodo.com/astronomers-found-evidence-for-exoplanets-70-years-ago-1770485757

[insert_name]

the gilese 581 system isn't in here, it has possibly 3 worlds in the habitable zone

[Spaceception]

3 hours ago, insert_name said:

the gilese 581 system isn't in here, it has possibly 3 worlds in the habitable zone

They're not on the list from PHL, so I'm not adding them, as far as I'm concerned, they don't exist.

[ProtoJeb21]

I have pretty high hopes for Kapteyn b and KOI-2626.01. Kapteyn b is over 11 billion years old, so odds are there is intelligent life there. It's also possible that all UFOs ever seen that have no natural cause could have come from that planet! KOI-2626.01, despite being much farther away than the Kapteyn system, could be our first "Mini-Earth," with a possible radius of 0.97 Earth radii. I'm also a big fan of Kepler-442b, which I think is the closest thing we have to an Earth analogue: similar size, temperature, and host star. Might be pleasant to live there.

[Spaceception]

There could be a previously unseen Eathlike planet round star, Gliese 832, 16 ly away, and me hoping that Astronomers take another look at other stars with confirmed potentially habitable worlds, to see if there's more where that came from

http://news.discovery.com/space/alien-life-exoplanets/stars-wobble-could-reveal-nearby-earth-like-exoplanet-160419.htm

Edited April 19, 2016 by Spaceception

[ProtoJeb21]

I find it somewhat hard to believe that the Earthiest KOI-planet (And the Earthiest overall) orbits an F-Class star: KOI-4878.01. Then again, the possibility of red plantlife is pretty cool.

[Spaceception]

2 hours ago, ProtoJeb21 said:

I find it somewhat hard to believe that the Earthiest KOI-planet (And the Earthiest overall) orbits an F-Class star: KOI-4878.01. Then again, the possibility of red plantlife is pretty cool.

I think it's on the dimmer side of the F type sequence due to it's orbital period.

[Spaceception]

NASA's Kepler Mission Announces Largest Collection of Planets Ever Discovered. Some of these planets might be added to the Habitable Exoplanets Catalog soon.

http://phl.upr.edu/projects/habitable-exoplanets-catalog

So there you have it, I'll update the poll, and list once these planets are up

Personally, i find Kepler 1229b and Kepler 1410b to be the most promising. Also, why hasn't anyone talked about Kepler 1410b!? Everyone is talking about Kepler 1593b despite being more like a gas dwarf, but no one is talking about 1410b! It's slightly smaller than Kepler 452b, receives closer to the amount of sunlight Earth gets, and because it orbits a red dwarf, it'll last a long time too!

Also, Kepler has found, not 1, not 2, not 3, not 4, but 5 exoplanets smaller than 1.5 Earth radii that are potentially Earthlike!

Edited May 11, 2016 by Spaceception

[Spaceception]

They updated!!!!!

http://phl.upr.edu/projects/habitable-exoplanets-catalog

And I have to mention, there's a metric tonne of planets around sunlike stars.

Edited May 11, 2016 by Spaceception

[Scotius]

Oh, to have a functioning warp drive now Well, if we ever get one we will have plenty of targets for exploration.

[PB666]

8 hours ago, Spaceception said:

They updated!!!!!

http://phl.upr.edu/projects/habitable-exoplanets-catalog

And I have to mention, there's a metric tonne of planets around sunlike stars.

Oh the thread that just keeps on misrepresenting the science goes on and on. Its all the more credible because of all the exclamation points used. 

Habitable planet given its mass and atmosphere is a relativley thin zone, of course there are alot of planets around sunlike stars, there simply are no earths around sun-like in a comparable position in its habitable zone, except of course Earth. There may but you are simply trying to lead the argument. 

I wonder why you feel the need to be the engineer of the hype train?

[ProtoJeb21]

Wow, I'm shocked nobody's talking about this:

http://www.wired.co.uk/article/super-earth-kepler-62f-could-support-life-and-is-just-1200-light-years-from-earth

My guess is that Kepler-62f has several large islands with over 75% plant life. All that CO2 in the atmosphere would make this planet a plant paradise. I also think that this modeled atmosphere was the case earlier in the history of Kepler-62f. The high amounts of CO2 got plant life off the ground quicker, started photosynthesis without a snowball Earth, and quickened the evolution of multicellular organisms. Kepler-62f's modern atmosphere may be 35% Methane (released by life), 32% CO2, 19% Oxygen, and 1% trace gases. The atmosphere could've shrunk to 1-3 times the pressure of Earth's atmosphere.

[PB666]

36 minutes ago, ProtoJeb21 said:

Wow, I'm shocked nobody's talking about this:

http://www.wired.co.uk/article/super-earth-kepler-62f-could-support-life-and-is-just-1200-light-years-from-earth

My guess is that Kepler-62f has several large islands with over 75% plant life. All that CO2 in the atmosphere would make this planet a plant paradise. I also think that this modeled atmosphere was the case earlier in the history of Kepler-62f. The high amounts of CO2 got plant life off the ground quicker, started photosynthesis without a snowball Earth, and quickened the evolution of multicellular organisms. Kepler-62f's modern atmosphere may be 35% Methane (released by life), 32% CO2, 19% Oxygen, and 1% trace gases. The atmosphere could've shrunk to 1-3 times the pressure of Earth's atmosphere.

I read the article, i found it weak and trivial and decided not to repost it here.. They created alot of special things like an atmosphere with 2500 itmes the CO2 as ours to make it not be a snow ball planet. 

[ProtoJeb21]

33 minutes ago, PB666 said:

I read the article, i found it weak and trivial and decided not to repost it here.. They created alot of special things like an atmosphere with 2500 itmes the CO2 as ours to make it not be a snow ball planet. 

I also found it weird that they didn't ever think about methane, which is 30 times more powerful than CO2. But I can understand how all that carbon dioxide could get into the atmosphere: super-volcanoes caused by the larger core and size of Kepler-62f.

[PB666]

24 minutes ago, ProtoJeb21 said:

I also found it weird that they didn't ever think about methane, which is 30 times more powerful than CO2. But I can understand how all that carbon dioxide could get into the atmosphere: super-volcanoes caused by the larger core and size of Kepler-62f.

Thats a hell of alot of CO2 when you haven't done any atmospheric studies,mthis is on top of nitrogen and other gases.