Normal solar pressure doesn't tend to speed up an object in its orbit since it comes in perpendicular to the direction of motion. However if the object is rota

Normal solar pressure doesn't tend to speed up an object in its orbit since it comes in perpendicular to the direction of motion. However if the object is rotating it can absorb light on its inner side the re-emit it on its trailing side as that side cools down. This can alter orbits substantially over millions of years.