On 22/9/21 9:44 am, Rupert Boleyn - rupert.boleyn at gmail.com (via tml list) wrote: > > > On 22Sep2021 0432, Alex Goodwin - alex.goodwin at multitel.com.au (via > tml list) wrote: >> IIRC, GT:FI also mentions that stars should receive a _bonus_ to their >> signature (above and beyond their size - eg Sol having +56, Rigel having >> +67 and Rho Cassiopeiae having +73) from their intrinsic luminosity. >> Assuming hyperspectral telescopes, I'd expect brown dwarfs to get no >> bonus, and active stars would get a bonus depending not on their >> _spectral_ class but their _luminosity_ class (M-class hypergiants >> getting a bigger luminosity bonus than B-class main sequence stars). > In that case, the luminosity bonus would be including the size bonus. > So spotting a star would be a roll vs senor quality (or character > perception) + luminosity bonus - range penalty. Now it's 'just' a > matter of getting those bonuses and penalties scaling right... > Thankfully, Rupert, at least IMO, GURPS has got that reasonably right, and was part of the reason I was proposing brown dwarfs as a luminosity-bonus baseline. According to el wiki, a difference of 5 magnitudes between the _absolute_ magnitudes of two objects corresponds to a ratio of 100 in their luminosities. Ceteris fnordibus, the brighter object can be detected 10x further away than the dimmer one - which is +6 to its signature (combined size + luminosity mod) - thus a unit decrease in absolute magnitude is a +1.2 on the GURPS scale. Frinstance, (eyeballing from https://en.wikipedia.org/wiki/File:HR-diag-no-text-2.svg ), and taking brown dwarfs as the zero point at abs mag +15, hypergiants (at roughly abs mag -8) are 23 unit magnitudes brighter, thus meriting a +28 luminosity bonus (and detectable, ceteris fnordibus, 46,000x further away than a hypothetical same-size brown dwarf). Sanduleak -69 202, aka Fond Of A Good Banger, aka supernova 1987A's progenitor, approx 51.4 kpc away, was a blue supergiant until its catastrophic round of double-parking. Blast, I'd galloped on ahead - good point about convolving the bonus. FOAGB had a radius of 39.6 solar radii, thus meriting an additional +10 for size mod relative to Sol. Its wiki page notes a relative luminosity of ~100,000x that of Sol, spread over ~ 1600x more radiating area, for 62.5x luminosity per unit area. That works out to -4.5 abs magnitudes on a unit basis, for a luminosity-related signal modifier of +5 (again, relative to Sol - still trying to find (or cook up) a brown-dwarf equivalent). I wonder if that second approach is worth chasing down further? Alex
