Planet 9, the hypothetical planet predicted Batygin and Brown, is expected to have an apoasis near the galactic center. Is there a spacecraft that is heading in that direction? Specifically, they state:

perihelion position is straight overhead in late May. ... aphelion (the furthest point from the sun) at about 4 hours, or straight overhead in late November

Note that I realize that we don't know where this object is, and thus would have great difficulty pinpointing this exactly, but are any of the known objects leaving the solar system heading in that direction?

Also, of some note is that the inclination is expected to be 30 degrees, plus or minus 20 degrees.

  • 3
    $\begingroup$ Apoapsis near galactic centre?!? Surely you must be referring to the RA/declination coordinates?!? $\endgroup$ Jan 25, 2016 at 0:50

1 Answer 1


Galactic centre:
-29.01° declination and 17.76 hours right ascension,

Voyager 1
12.44° declination and 17.163 hours right ascension, missing by ~40°

Voyager 2
−55.29° declination and 19.888 hours right ascension, missing by ~50°

Pioneer 11
-8.80° declination and 18.83 hours right ascension, missing by ~30°

Pioneer 10
25.99° declination and 5.2 hours right ascension, missing by nearly ~180°

New Horizons:
-20.73° declination and 19.07 hours right ascension, missing by ~20°

But we do not know where in its orbit the potential ninth planet is, so we may hit it by pure luck ;) However, even an error of even one degree is going to be a miss of over 2 AU. (and the Pioneer probes are not operational).

stuff escaping

  • $\begingroup$ Its interesting that so many spacecraft have the same right ascension that are leaving the Solar System... It seems fairly likely then that one of them might be roughly in the vicinity, although not particularly close. Thanks! $\endgroup$
    – PearsonArtPhoto
    Jan 25, 2016 at 14:37
  • $\begingroup$ How about New Horizons? $\endgroup$
    – PearsonArtPhoto
    Jan 25, 2016 at 14:59
  • $\begingroup$ @PearsonArtPhoto Done! $\endgroup$ Jan 25, 2016 at 15:47
  • $\begingroup$ So then, New Horizons is heading in the right direction... Interesting... $\endgroup$
    – PearsonArtPhoto
    Jan 25, 2016 at 15:52
  • $\begingroup$ I don't know the numbers, but I doubt even New Horizons will have sufficient electrical power to do anything useful even if it passed close enough (by chance of course). Also, I think I read somewhere NH has less than a degree of steering available by the way (it's propellant limited). $\endgroup$
    – Andy
    Jan 25, 2016 at 16:07

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