  A new class of Kuiper belt objects that lie beyond Neptune with semimajor
axes greater than 250 astronomical units show orbital anomalies that have been
interpreted as evidence for an undiscovered ninth planet. We show that a
modified gravity theory known as MOND (Modified Newtonian Dynamics) provides an
alternative explanation for the anomalies using the well-established secular
approximation. We predict that the major axes of the orbits will be aligned
with the direction towards the galactic center and that the orbits cluster in
phase space, in agreement with observations of Kuiper belt objects from the new
class. Thus MOND, which can explain galactic rotation without invoking dark
matter, might also be observable in the outer solar system.
