[edward2007]

For an SF story I'm working on, I have to "design" a new universe.
And even if most of it is imagination, it still has to be "possible". (I can fib a bit here)
It is not too far out from what is here right now, but there are several things that stump me, despite my web-search skills.

What I'd like to know is data on orange subgiant stars, eg diameter, mass, habitable zone.
The same for a neutron star.

Can anyone help me out?

[syhprum]

It would not be a good idea to orbit a Neutron star, they have a high surface temperature (100,000 °K) hence their radiation is predominantly in the ultravialot/soft Xray region

[Batroost]

I've never seen a surface temperature quoted for a neutron star before. Where did this come from? Is the estimate based on the x-ray 'beams' we've detected - in which case (if I understand things correctly) you are only talking about one class of neutron star. I'm guessing that a cold neutron star would be non-radiating so difficult to detect except by gravitational effects such as lensing?

[syhprum]

"In such a picture, a 1,000 year old neutron star (like the Crab pulsar) would have a surface temperature of a few million degrees Kelvin".
I cannot recall from whence I got the figure 100,000°K but the above is an extract from http://www.astro.umd.edu/~miller/nstar.html

[edward2007]

I agree, a neutron star would be too rich in lethal radiation. Same for a black hole.
That leaves me two choices, either play "Overlord" and invent some very heavy but small object, or forget it and stick with the orange sub-giant.

Any data on the orange? I looked at some H-R diagrams, but the parameters given there don't say anything about diameter and/or weight. Maybe that can be calculated from the given data, but I'm a writer, not a scientist ;-)

Edward.

[another_someone]

If one is talking about non-humans, then is radiation really an issue (i.e. can you not have a species with a far more efficient DNA repair mechanism that might tolerate heavy radiation).

Temperature could be a problem insofar as anything we recognise as life requires liquid water.

[Batroost]

"In such a picture, a 1,000 year old neutron star (like the Crab pulsar) would have a surface temperature of a few million degrees Kelvin".
I cannot recall from whence I got the figure 100,000°K but the above is an extract from http://www.astro.umd.edu/~miller/nstar.html

Wow. Thanks. Interesting stuff, I'd never seen this explained before..

[Raliel]

The problem is that life that can tolerate high levels of temperature and radiation would have evolved in a way that means that it would be incredibly alien to us.... and thus not much use for a sci-fi story, unless it is one that deals with utterly alien first encounters..... However, there is always the possibility of life as we know it, existing on a world with an atmosphere or orbit that shields it from these lethal climates, or even an artificially shielded world.... I feel it would be worth knowing exactly what sort of Sci-fi universe you were trying to create....perhaps a small earthlike planet closely follows the orbit of a gas giant which shields the harmful radiations for a long cycle, but that cycle may be about to end.......

[edward2007]

In one of the " naked" podcasts of a q&a broadcast, they mentioned the find of a fungus that grew inside a nuclear reactor. Evidently it fed on hard radiation. So nature always finds a way, to quote the Boffin in Jurassic Park ;-)

<If one is talking about non-humans, then is radiation really an issue (i.e. can you not have a species with a far more efficient DNA repair mechanism that might tolerate heavy radiation).>

I'm as yet undecided about using alien life forms.
Although it is science FICTION, I want to have the SCIENCE part as assurate as possible. That is hard enough to do as most of what I'll be using is an extrapolation of today's cutting edge stuff.
And even so, I sometimes find myself behind the facts.

An example:

One of my characters has an RFID implanted in her body. It is her passport aka wallet aka front door key. It needed to be a plastic based system as that would not set off metal detectors. Two weeks after I wrote that part, Phillips announced the prototyope on an RFID that was "printed" (with conducting ink) on plastic. They expect to replace the metallic parts (in the chip that contains the data) with conducting plastic within a year (or so).

Next I thought it would be a nice twist to have her ID changed or erased so she would be unable to identify herself. And she would be locked out of her own quarters, of course.
The very evening I finished that part, BBC's 'digital planet'  mentioned that someone had written a virus capable of changing the data stored in an RFID.

Somtimes it feels like I'm running just to stay in the same place ;-)

 Edward

[another_someone]

Not sure that the 'metal detector' aspect is really relevant.

All a metal detector does is detect a conductor by inducing a current into it.  A conducting plastic is for all practical purposes a metal as far as electrical induction is concerned.

In fact, the very nature of RFID is that they rely on obtaining energy from radio signals by induction, and using that energy to broadcast their information.  The only thing that might have an impact on metal detectors is that there small size may limit their response to metal detectors that use low frequency (long wavelength) signals.

If an RFID is incapable of having a current induced into it, then it will not work as an RFID (at least as we know it - they could on the other hand use other technologies - such as a system that had an on board fuel cell that used glucose from the body to generate power to transmit the required data).

[edward2007]

<All a metal detector does is detect a conductor by inducing a current into it.> There by detuning an oscillator, I know. I'm a radio amateur.

<A conducting plastic is for all practical purposes a metal as far as electrical induction is concerned.> True, but the plastic is just the matrix, only the contucting printed conduits are capable of detuning said oscillator. And the total mass of those miniature conduits is too small to trigger the detector, unless that happens to work on the exact same frequency that is used to read the RFID's data.

 The distance between antenna and RFID is also dependant on the used frequency. So I can still use the RFID idea.