Re: conskies available!
|From:||michael poxon <m.poxon@...>|
|Date:||Thursday, December 5, 2002, 9:47|
Quick astro-lesson follows...
As on a terrestrial map, you can locate an object by means of a coordinate
system. The astro version is very similar to the terrestrial one.
'Declination' corresponds to Latitude, and is measured in degrees N or S of
the celestial equator, which, like the celestial poles, is simply a
projection out to infinity of the Earth's equator and poles. As with
latitude, a degree is subdivided into 60 minutes, and each minute further
subdivided into 60 seconds.
'Right Ascension', abbreviated to RA, corresponds to Longitude. It can also
measured in degrees, but is nearly always found calibrated instead into
hours, minutes and seconds, and is measured Eastwards from a point in the
sky called the 'First Point of Aries'. It's easier than Longitude, since
there is no sky version of the International Date Line, so you just keep
measuring round the sky until you come back to where you started! As an
example, a right ascension of 5h 20m is one third of the way from 5h to 6h.
All star charts will use this RA/Dec coordinate system.
The other set of output figures relates to a star's brightness, or
magnitude. What you need to know here is that the system works 'backwards',
so the brighter the star, the smaller its magnitude. Some examples: Sun is
magnitude -26; Full moon
-12.5; Sirius (brightest star in the sky) -1.5; faintest star visible to
human naked eye +6. Faintest star yet seen; about +30. Usually, the plus
sign is omitted.
As regards life on a planet orbiting a double star, the jury's still out on
that one. It depends on lots of things such as the separation of the stars,
their type, distance of the planet, its inclination to the plane of the
My own view about contact as regards distance is that once we are able to
travel interstellar distances, the difference between 20 and 200 lightyears
won't be very important any more. 20 lightyears to an astronomer is 'in the
> I don't know how to interpret the output figures, but then it wouldn'ttake
> to long to explain to somehow how to plot latitutde and longitude.
> Hopefully I can pick up how to do the plotting. Care to give an
> abbreviated lesson to the astro-newbies in the group? :)
> To be honest, my conlang-speaking peoples haven't informed me yet where
> their planet is. Which, in practical terms, means I can pick whicheversun
> is most convenient. :)
> Double stars sound fun... Would there be any complications for life? I
> absolutely have to be able to support an Earth-like environment, and even
> more specifically, I need to support us homo sapiens. Distance away from
> Earth really doesn't concern me _that_ much. Over 20 light years away is
> okay by me. They're not supposed to have any contact with other planets
> besides the initial group of humans, anyway.