re: No Joke
If it's 3 times the distance from it's primary as Neptune is to the sun, then it
has an orbital radius of roughly 80 A.U.
Assuming the planet's primary is about the same mass as our sun, then
the planet should have an orbital velocity of about?
I'll use Jupiter's orbital velocity [roughly 12,000 meters/second] as a reference point.
V = 12,000 / [80AU / 5AU]^1/2 = 3,000 meters/second
So that exoplanet's faint spectrum should be Doppler-shifted accordingly,
while the primary should not