The galaxy may swarm with billions of wandering planets

[aramis]

But when rules say sensors can detect them up to 2 parsecs away, they're talking (IMHO) about GG orbiting a star. THere you have sevral advantages to locate them: you know where to look for, gravitational disturbances in th star's EM emmisions, etc...

Looking for them on the void, without those advantages may be quite more difficult, ans so, sensor range may be quite less.

Given that it takes under a day to find them with commercial grade sensors...

You're not looking for gravitational disturbances (too short a window) nor for occulations (again, too short a window).

You're looking for IR and visual confirmation of them, probably using a fairly short span interferometer with some fairly small but very sensitive CCD scopes.

A GG on internal heat should be detectable for at least a parsec with a similar gear, tho' probably not in the same few hours as a stellar orbiting one.

Traveller's astrography is not that of our universe... In the OTU: there are not enough brown dwarves, the Titus-Bode relationship is much more dominant, there are too many bright stars, and people live in places that don't make a lot of sense.

 

[far-trader]

Actually, the odds are identical regardless of whether surveyed or not. This isn't a Schröders cat situation where observation changes the result...

Schrödinger's cat actually

 

[whartung]

What about the issue of a rogue planet being in line with your jump and pulling you out of it. That's kind of the premise with Jump Masking, no?

 

[far-trader]

What about the issue of a rogue planet being in line with your jump and pulling you out of it. That's kind of the premise with Jump Masking, no?

Yes, however...

...space is big. Really big. etc. etc.

In short the chances of your course accidentally intersecting the 100d line of a planetary body (even a stellar body) in a hex between your departure and destination is so vanishingly small as to be impossible for all practical definitions of the odds*. Save it for a deus ex machina event. Use it once and never again.

* the odds are marginally better for intersecting a body in the relatively crowded space close to a full solar system. Enough so that you might stretch the believability of the event to using it twice

 

[aramis]

let's do some math.

1 pc hex is 3.08568025e16 meters across center to center.
largest diameter of a star roughly 2100 solar diameters. Solar diameter is roughly 1.39e9m. so, its exclusion is 201 times that in diameter, or 5.86719e14 m across... roughly a 1/2500 chance if there's an undetected star that it would be along a given 1 pc long course, assuming it's the biggest possible. About 1/4410000th that for a typical main sequence... a planet is much less still.