Extrasolar planets

[Trapper]

I was reading about this topic yesterday on Wikipedia:

en.wikipedia.org/wiki/Extrasolar_planets

and I noticed a chart/picture in the article outlining the habitable zones:

en.wikipedia.org/wiki/Image:Habitable_zone-en.svg

Is it possible that there are Earth-like planets that we could possibly inhabit around blue-white stars and red dwarfs?

Previously I had somehow formed the opinion that star-types other than those like Sol put out radiation that was incompatible with life as we know it even if the planet was at the same temperature as ours.

[Phantasm]

Previously I had somehow formed the opinion that star-types other than those like Sol put out radiation that was incompatible with life as we know it even if the planet was at the same temperature as ours.

There is the crux of the matter. "life as we know it".

We have no way of knowing, at the moment, what kind of life is out there - and make no mistake, there MUST be other life in a place as big as this.

[Fist and Faith]

I believe Trapper is asking if it's likely that we could live on other planets. A lot more is involved than merely the distance from the star, as is suggested by the "habitable zone" image. Size, composition, and age, for example. Since we've found such a small number so far, we can't even calculate it, but the percentage of planets that we could live on must be way less than 1%.

[Avatar]

But 1% of only 1000,000,000 is still ten million... It's only relevance depends on the number of planets in the first place I think.

--A

[aTOMiC]

There is also the distances involved. I could buy a theory that allows for advances in technology that would enable earth based ships to travel Rigel Kentaurus (provided the three stars involved were fortunate enough to have suitable planets circling them) in or less than say 10 years time. Thats only 4.2 and 4.3 light years away. Something truly remarkable will have to happen for humans to travel much farther in the span of a sigle lifetime or even multi generational voyages.
There are plenty of hurdles to leap over before we can even contemplate trying to settle on worlds beyond our own relative neighborhood. Which sucks because it would be very cool indeed.

[Trapper]

I agree with all the above posts.

My question, in more specific terms, was whether or not different types of stars put out different types of radiation.

I was indeed talking about human habitation.

A big obstacle to that IMHO is the possibility (as HG Wells described in "War of the Worlds") of alien viruses. Such a rudimentary form of life (please excuse my arrogance any viral Watchers ), but one that could destroy any attempt we made at inhabiting another planet. We would IMHO need to make greater advancements in our medical science (and in our life-support mechanisms for a journey of any appreciable length) than we would in propulsion technology to make such a trip.

There's also the ethical question of whether we should colonise another planet that has even microbial life. My view is... meh... stuff it... why not?

I love hearing any kind of conjecture on these topics.

[Xar]

Then again, who says that alien viruses (or their alien counterparts) could infect us? They might not use DNA at all; they might use a completely different genetic code, perhaps with different bases; in fact, I would be surprised if such viruses existed and could infect us. Microbial life would already be more likely to be a potential danger, but even then, much depends on its composition.

[Trapper]

Then again, who says that alien viruses (or their alien counterparts) could infect us? They might not use DNA at all; they might use a completely different genetic code, perhaps with different bases; in fact, I would be surprised if such viruses existed and could infect us. Microbial life would already be more likely to be a potential danger, but even then, much depends on its composition.

Here in Australia the Northern Territory advertises itself to tourists like this:

You'll never-never know if you never-never go.

(The "never-never" is connected to the Dreamtime mythology of Aboriginal Australians).

I hope you're right about viruses. But I still think advances in medical science are the key to anything other than forced colonisation (along the lines of the Romans saying "every fourth man shall emigrate to XYXY or be put to death").

Potential colonists would be more prepared to take the risk if they had faith in the ability of medical science to address foreseeable problems. (ie conquering the majority of ailments on Earth).

[Avatar]

Well, I think Xar made the point I was going to...still, I suppose that in theory it's possible, if, say, all life was carbon-based O2 breathing.

(Where's SandgorgonRider? Doesn't he do this type of thing as a job?)

--A

[aTOMiC]

As I mentioned in my first post, I believe we have a rather large hurtle (that has no viable solution at present or in the immediate future) to overcome before we need concern ourselves with whether an extra solar planet may have a lethal virus inhabiting it. I have to presume that after, what will likely be decades perhaps centuries of technological advancement, we will have anticipated nearly any fathomable scenario that might present itself with an attempt to colonize a world outside our solar system. Which will likely include a defense against alien virus, shielding from lethal radiations, the creation of liquid water from a variety of sources, protection from any inhospitable combination of atmospheric gases and a non interference directive toward the natural development of alien civilizations. etc, etc, etc. Its pretty much like an infant worrying about how he will swim the English Channel. Got a lot on his plate what with learning to walk an all. IMHO of course.

[dANdeLION]

The truly sad thing is that even if we were to stumble on the solutions to these potential problems and post said solutions here, I doubt that there are any NASA scientists paying attention to this thread anyway.

[Avatar]

Except SandGorgon Rider. Or at lest, if he were here and paying attention.

--A

[Sandgorgon rider]

I'm here, I'm here! I've just been a little busy lately.

I don't think we have any thing to worry about alien viruses. Viruses work by essentially taking over the DNA or RNA replication apparatus of our cells and it is unlikely an alien virus would even have DNA, at least not the same kind of DNA that life on earth has. I think there could be a danger of alien microorganisms acting as parasites and causing diseases due to interference in our ability to absorb nutrients or retain water or even interfere with the chemical transmission of nerve impulses. Alien caused diarhea could be a major problem. Of course there would also be the danger from macroorganisms e.g. alien land sharks trying to eat you before it figures out it cannot digest your alien protein.

But all of this is largely irrelevent, as others here have said, unless there is a way to go faster than the speed of light. It seems unlikely, due to the amount of time and energy needed, that there will be a lot of travel to alien worlds. I haven't done the calculations, but I would imagine that it would be far easier to terraform various planets or moons in our solar system or even build a Dyson Sphere around our sun than to send ships to other stars.

In answer to the original question I think most stars would be okay for habital planets although I would imagine some would be putting out just too much radiation for molecules to be able to hang together. It is amazing how much radiation a little atomosphere can absorb before it hits the ground and affects the life forms on the surface. I would imagine if you had a thick enough atmosphere or an atmosphere made up of the right kind of gasses even a lot of radiation would not be a problem.

The idea of habital zones has expanded a lot over the years. It used to be considered that the habital zone of our soalr system was roughly from somewhere between Earth and Venus to just inside Mar's orbit. But with the greenhouse effect you can probably get warm enough temperatures much further away from the sun if you have the right atmosphere.

[Avatar]

Glad you found it. I remembered this sort of thing was in your sphere. (Haha, no pun intended.)

You seriously think a Dyson sphere would be easier? Wow...A solid one or a shell?

Good post though, and very interesting.

I take it that is is (theoretically) possible to alter the atmosphere to suit us? Terraforming huh? A onderful and terrible idea at the same time. But can we create atmosphere out of nothing? And I thought that Mars for example didn't have the gravitational mass to hold an atmosphere in place?

--A

[Chuchichastli]

Mars does have an atmosphere, but a very thin one averaging 10 millibars (or 1% of Earth's). Good point though - even if we got a bit of a greenhouse effect going to warm the place up with increased CO2 levels, I don't think we'd ever get a useful Earth-like atmosphere out of it.

[Avatar]

Haha, yeah, sorry, I know about the incredibly thin one it appears to have...I meant that it wouldn't be able to hold any more atmosphere.

--A

[Sandgorgon rider]

I think if you were to warm up Mars and get a decent biosphere going I think you could gradually build up a decent atmosphere. It would slowly flow out to space so you would have to keep adding to it, but it could be done. It would be difficult and expensive but probably easier than sending a ship to a distant star.

[Trapper]

Thanks for the answer Sandgorgon rider

A Dyson sphere? Gosh.

If we had a sphere (rather than a ring) I guess there would be the added benefit of having our radio transmissions contained within it. We'd have a "stealth" sun as well. As I recently saw on the Dyson Sphere infomercial: "No more pesky alien invasions."

But that would only be a temporary solution, surely. It's only a few billion years until Sol becomes a Red Giant. The clock is ticking, dude...

[A Gunslinger]

I think if you were to warm up Mars and get a decent biosphere going I think you could gradually build up a decent atmosphere. It would slowly flow out to space so you would have to keep adding to it, but it could be done. It would be difficult and expensive but probably easier than sending a ship to a distant star.

Given the relative proximity, the risks and costs would be vastly reduced as well.

Eventually, however, you know mankind will (if we last long enough) will identify earth-like planets and attempt to send people there. I hope I see the attempt made or at least planned for in my lifetime.

[Trapper]

I think if you were to warm up Mars and get a decent biosphere going I think you could gradually build up a decent atmosphere. It would slowly flow out to space so you would have to keep adding to it, but it could be done. It would be difficult and expensive but probably easier than sending a ship to a distant star.

Getting the raw materials from Venus and the gas giants, I take it?

On a survival-of-the-species level I would have thought it would be easier to perfect suspended animation (yes, I have watched too much Red Dwarf ) and send some colonisation ships to the other spiral arms, even if it would take billions of years to get there.