[Arter21]

Greetings everyone...

I'm new here and was wondering if any of you chaps/ladies had any idea of the following?

For a species similar to ourselves to exist on a planet, at what approximate distance would a planet need to be from the various types of star?

I appreciate that there are lots of variables both with regards the star and the planet that will make this question difficult to answer accurately, so really you could say I'm interested in the approximate upper and lower limits.

Primarily I'm interested in red\white\blue supergiants, white\blue main sequence stars and white dwarves.

Many thanks

[maddog]

Originally Posted by Arter21

For a species similar to ourselves to exist on a planet, at what approximate distance would a planet need to be from the various types of star?

I appreciate that there are lots of variables both with regards the star and the planet that will make this question difficult to answer accurately, so really you could say I'm interested in the approximate upper and lower limits.

Primarily I'm interested in red\white\blue supergiants, white\blue main sequence stars and white dwarves.

Many thanks

Given these parameters, I'd suppose the following. Suppose that our star went nova (G2 main sequence star). Once done its size would extend out to just past mars. So any planet
from Mercury to Mars wouldn't exist. It is thought that a moon of Jupiter or better Saturn
would then be in a "habitable life zone". Thus Titan 4 or 5 billion years hence will become
a habitable planet (maybe).

As you go up the main sequence of stars (hotter) towards F or A type stars. The distance
would have to be further out. For O and B stars the end is more likely a black hole at the
center (most of these stars exceed 10 solar masses), and so would not likely be habitable
at all.

Hope this helps.

Maddog

[Arter21]

That does help a bit, cheers maddog, but it's not really exactly what I was after...

Basically I'm writing a short story and I want the information in it to be based in reality. As it'll be set on several different planets in different star systems, I don't really need to know about the habitable distance over a period of time, rather just at the specific stage of the stars life.

Waht I don't want is to have a planet goign round a blue giant at say, 45 AU's and then later find out that at that distance the radiation/heat/electromagnetic field of the star would rip the planet to shreds and any life thereon.

Thanks for the reply though, I can at least get an agreeable distance for a red giant, thanks to you...

[maddog]

Originally Posted by Arter21

Basically I'm writing a short story and I want the information in it to be based in reality. As it'll be set on several different planets in different star systems, I don't really need to know about the habitable distance over a period of time, rather just at the specific stage of the stars life.

Waht I don't want is to have a planet goign round a blue giant at say, 45 AU's and then later find out that at that distance the radiation/heat/electromagnetic field of the star would rip the planet to shreds and any life thereon.

Thanks for the reply though, I can at least get an agreeable distance for a red giant, thanks to you...

You're welcome. I would caution against using much bluer beyond about B8 or so. They tend
to be bigger as they get hotter and have less of lifetime. I would think towards the end life
of any main sequence star A-K would generate a nice system nicely.

I would like to read it when the story is done. Let me know where you plan to publish, so I
can find it. Later.

Maddog

[pgrmdave]

Wouldn't a larger star also produce more harmful radiation than a smaller star, meaning that any life around it would either need to have developed ways to counter it, or the planet would need to have an atmosphere that could deflect it, like our ozone layer, but thicker?

[maddog]

Originally Posted by pgrmdave

Wouldn't a larger star also produce more harmful radiation than a smaller star, meaning that any life around it would either need to have developed ways to counter it, or the planet would need to have an atmosphere that could deflect it, like our ozone layer, but thicker?

Actually, I don't know exactly what would be best for his story as I only answere from what
was given.

The rule of thumb is going up the main sequence towards O type star the surface temperature
goes up. Mass of the star goes up as well (O type stars are more likely larger than A's). The
harmful radiation is indicitive of the temperature (being O or B). The bulk of radiation is in
the band where the center would nearly be UV. Yes, this would much more harmfull. So
either a thicker atmosphere, with more other things in it, a thicker Ozone layer, etc. This
still would all be temporary independant of type of star. Once all the fuel ran out and the
star goes nova (or supernova), even for a star of our size not much would habitable inside
of pluto or so. Not enough current data, it is speculative that a supernova would make all
object inside the equivalent of an Oort's cloud melt or molten (nothing left).

It all depends.

Maddog