World Habitability in a binary system

[fusor]

Fusor, your timescale is off by a few orders of magnitude. To be a K... that's at the cold end. Either it was rather small (≤0.5 solar masses) or very old. It may even be a capture situation. Dwarves are often billions of years old

The white dwarf classifications as described in CT are wrong. There's no such thing as "DK" or "DM". see : http://en.wikipedia.org/wiki/Stellar_classification#White_dwarf_classifications .

White Dwarfs are just as likely to be billions of years old as they are to be very recent. The fact that it's orbiting an A6 V star implies that the system is young (A6 V stars are only a few hundred million years old), and the progenitor star was probably similar in mass to the A6 V. For a dwarf to have cooled down to around 4000K (which is what spectral type K would be) would require billions of years, and if you're suggesting that a billions of years old white dwarf just happens to have been captured by a young star in its habitable zone, and also somehow has planets around it then you really need to read up some more about astronomy.

My point remains though. It was a red giant before, so it would have roasted any planets nearby and certainly wouldn't have its own planets that close to it.

 

[fusor]

Well, I don't suppose it would apply much here, given that this is a K-type and likely too hot for it, but for theory's sake, what about a Brown Dwarf?

I could be wrong, but I think I remember reading once that at least some brown dwarfs were theorized to be stars that didn't have sufficient mass to perpetuate stellar fusion, like super-massive Jovian planets. Or am I mistaken and they're currently theorized to be more like white dwarfs - stellar remnants following novae, et al?

On that note, is it theoretically tenable that the companion could actually be a super-massive gas giant that never achieved stellar fusion and instead is a form of brown dwarf? These orbiting 'planets,' then were more like satellites of the GG-brown dwarf.

Food for thought.
-asp

Replacing the WD with a brown dwarf would be better (and yes, they're substellar objects. They're essentially really massive gas giants). They're not commonly found that close to A V stars, but that scenario is a lot less crazy than having a white dwarf there.

Either way the brown dwarf's "moons" wouldn't be that habitable. Since the system is so young, the brown dwarf could possibly still be warm enough to warm its closer moons, but since it's only a few hundred million years old at most then you won't have any habitable earthlike environments on any of them.

 

[altasilvapuer]

Replacing the WD with a brown dwarf would be better (and yes, they're substellar objects. They're essentially really massive gas giants). They're not commonly found that close to A V stars, but that scenario is a lot less crazy than having a white dwarf there.

Either way the brown dwarf's "moons" wouldn't be that habitable. Since the system is so young, the brown dwarf could possibly still be warm enough to warm its closer moons, but since it's only a few hundred million years old at most then you won't have any habitable earthlike environments on any of them.

Would it matter that the Dwarf doesn't have the heat, though? The original thought was that the planets in small-numbered Companion orbits might be close enough to what would otherwise be the "Habitable Zone" of the primary.

Also of note concerning Traveller is that a HZ need not necessarily mean life is present, but that habitation by colonies is easier. Planet's not old enough to have created life of its own? That's fine; just means fewer predators for the colonists to dodge while they're planting genetically modified crops and raising domesticated livestock and otherwise setting up shop.

-asp

 

[fusor]

Would it matter that the Dwarf doesn't have the heat, though? The original thought was that the planets in small-numbered Companion orbits might be close enough to what would otherwise be the "Habitable Zone" of the primary.

Yeah that would be OK in that scenario. Though since they're moons of the brown dwarf, the planets would be tidelocked to the brown dwarf, which means that their days (relative to the A6 V star) would be as long as their orbital period around the dwarf.

Also of note concerning Traveller is that a HZ need not necessarily mean life is present, but that habitation by colonies is easier. Planet's not old enough to have created life of its own? That's fine; just means fewer predators for the colonists to dodge while they're planting genetically modified crops and raising domesticated livestock and otherwise setting up shop.

(a) you're assuming the worlds would have a remotely usable atmosphere. Planets in the habitable zone are not guaranteed to have breathable or even close to breathable atmospheres. All being the habitable zone really means is that the surface temperatures of planets is likely to be within a habitable range (depending on the atmosphere). At this stage the planets would probably have an exotic atmosphere like early earth, and you would need to terraform them for them to be at the stage of growing any kind of GM crop or raising animals; they aren't "shirtsleeve" environments at all.

(b) the planets are young. That means:
- lots of volcanic/tectonic activity (if they are large enough)
- frequent asteroid impacts (there will still be a lot of debris flying around the system)
- no oxygen in the atmosphere (the planet's atmosphere would probably consist of nitrogen, carbon dioxide, methane, and/or water vapor).

 

[aramis]

The white dwarf classifications as described in CT are wrong. There's no such thing as "DK" or "DM". see : http://en.wikipedia.org/wiki/Stellar_classification#White_dwarf_classifications .

White Dwarfs are just as likely to be billions of years old as they are to be very recent. The fact that it's orbiting an A6 V star implies that the system is young (A6 V stars are only a few hundred million years old), and the progenitor star was probably similar in mass to the A6 V. For a dwarf to have cooled down to around 4000K (which is what spectral type K would be) would require billions of years, and if you're suggesting that a billions of years old white dwarf just happens to have been captured by a young star in its habitable zone, and also somehow has planets around it then you really need to read up some more about astronomy.

My point remains though. It was a red giant before, so it would have roasted any planets nearby and certainly wouldn't have its own planets that close to it.

Just look up spectral type K on the dwarf line of the Hersprung-Russel chart. It's the cool end. Which, as I said means either very small initial star, or very old, since the temperature drop rate is pretty well a physics granted....

 

[aramis]

The white dwarf classifications as described in CT are wrong. There's no such thing as "DK" or "DM". see : http://en.wikipedia.org/wiki/Stellar_classification#White_dwarf_classifications .

White Dwarfs are just as likely to be billions of years old as they are to be very recent. The fact that it's orbiting an A6 V star implies that the system is young (A6 V stars are only a few hundred million years old), and the progenitor star was probably similar in mass to the A6 V. For a dwarf to have cooled down to around 4000K (which is what spectral type K would be) would require billions of years, and if you're suggesting that a billions of years old white dwarf just happens to have been captured by a young star in its habitable zone, and also somehow has planets around it then you really need to read up some more about astronomy.

My point remains though. It was a red giant before, so it would have roasted any planets nearby and certainly wouldn't have its own planets that close to it.

Just look up spectral type K on the dwarf line of the Hersprung-Russel chart. It's the cool end. Which, as I said means either very small initial star, or very old, since the temperature drop rate is pretty well a physics granted....

 

[fusor]

Just look up spectral type K on the dwarf line of the Hersprung-Russel chart. It's the cool end. Which, as I said means either very small initial star, or very old, since the temperature drop rate is pretty well a physics granted....

Again, we're talking about white dwarfs. And as I showed you (if you had bothered to check the link I posted), there's no such thing as a "DK" white dwarf. I realize that you think that a DK dwarf is a white dwarf that has cooled to type K temperatures, and that this is how CT defines it, but CT is not correct about this.

And as I have said, the point is moot since the red giant would destroy or roast any planets in the system. Nitpicking about the white dwarf scenario serves no further purpose.

 

[Icosahedron]

I hadn't realised from the code that the companion in question was a white dwarf, but there would be nothing to stop you from colonising a 'roasted' planet comfortably warmed by the primary - there's plenty of vacuum rockball mainworlds in the 3I. A situation like this would at least give you a rationale for the UWP.
'Seasons' would be a bit radical though...

 

[aramis]

Again, we're talking about white dwarfs. And as I showed you (if you had bothered to check the link I posted), there's no such thing as a "DK" white dwarf. I realize that you think that a DK dwarf is a white dwarf that has cooled to type K temperatures, and that this is how CT defines it, but CT is not correct about this.

And as I have said, the point is moot since the red giant would destroy or roast any planets in the system. Nitpicking about the white dwarf scenario serves no further purpose.

Since CT defines it as a dwarf cooled to a K type, and the reference in question is a Traveller one, not a Gliese 3 entry, and Traveller uses an outdated notation for internal consistency, you're the one perseverating and being particularly unhelpful. We get that it's not realistic. It is what Traveller says is there, and saying it can't happen doesn't make it any less the result of the rules.

It's entirely possible that the star it's companion to was formed separately.

For what it's worth, Traveller astrography is not, and never has been, a good match to current astronomy state of the art, ever -- not even in 1980 or so when Book 6 was written. (Book 6 used out of date tables even then.)

So, since Traveller defines D_ as a dwarf of color _, that means that it's an old, cooled down dwarf. Don't like it that way, convince MWM to do it better.

 

[fusor]

The OP wanted to know if the system he designed worked. It doesn't. The WD would roast any planets nearby in its red giant stage (whether Traveller says so or not is completely irrelevant), so everything else is moot. Both he and I have moved on from this now and you're still "perseverating" over an incorrect definition.

I'm actually being quite helpful here (at least, the OP seems to think so, and his opinion is what matters here), whereas you're the one who insists on derailing the thread by nitpicking over irrelevancies, and you did exactly the same thing in a previous discussion about lagrange points. You also made several statements here that were factually incorrect, and that I corrected - please have the good grace to accept that and don't harangue me (or anyone else) for correcting you. And please stop making personal attacks against me (I would report your post, but the report button doesn't seem to be working).