This is a great question! It's true that Neptune sometimes appears to be farther from the Sun than Pluto. This is because Pluto's orbit is highly elliptical, meaning it's very elongated, while Neptune's orbit is much more circular.

Here's the breakdown:

* Neptune's orbit is nearly circular, so it maintains a relatively consistent distance from the Sun, averaging about 2.8 billion miles.

* Pluto's orbit is highly elliptical, with its distance from the Sun varying drastically. At its closest point (perihelion), it's about 2.7 billion miles from the Sun, putting it closer than Neptune. At its farthest point (aphelion), it's about 4.6 billion miles from the Sun, much farther than Neptune.

Therefore, for a period of time, Pluto's elliptical orbit causes it to be closer to the Sun than Neptune. This happens approximately every 248 years.

So, it's not that Neptune suddenly moves further away, but rather Pluto's highly eccentric orbit brings it closer to the Sun than Neptune for a portion of its orbital period.