IGCSE›Oxford AQA IGCSE Physics›Mind mapsSolar System & Orbital MotionOxford AQA IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat is in it?Sun, a medium-sized starEight planets, including EarthMoons orbit planetsAsteroids are rocky, mostly in the beltDwarf planets orbit the Sun, e.g. PlutoComets are icy with elliptical orbitsScaleThousands of millions of galaxiesEach has thousands of millions of starsSun is one star in the Milky WaySolar Systemand orbitsSun8OrbitsGravity provides the centripetal forceForce acts towards the centreChanges direction, not speedForce always at right angles to motionSpeed and radiusGreater separation → weaker gravityWeaker force → lower orbital speedOne speed per orbital radiusSmaller radius → faster speedExam tipsGravity doesn't speed up or slow a circular orbitGive both numbers for universe scale