Planets orbit the Sun along an imaginary plane called the Ecliptic, which traces an orbit that intersects with our view of celestial sphere. Solar eclipses occur here, hence its name. Other planes define the orbits of other planets and comets. While all orbital planes are affected by gravity’s pull, not all objects move in an identical manner – some move at different speeds while some even collide with each other or alter their paths altogether. Tempel-Tuttle was one of the more notable comets to experience this effect; its orbit intersected with that of Earth and caused debris from it to fall back onto our planet and spark what has since been known as Leonid Meteor Shower.
Planetary speed depends on their distance from the Sun; at closest approach (perihelion), a planet moves quickly, while further out (aphelion), it slows and moves away slowly – hence why an ellipse is often used as a visual representation of a planets orbit rather than its perfect circle shape.
Astronomers are fascinated with the orbital paths of other planets because this provides valuable insights into their formation. Astronomers learn much from observing celestial bodies’ movement around our solar system – for instance when two planets from our system appear close together, scientists take great interest in studying what is happening there.
One of the greatest astronomers ever was Johannes Kepler, living during turbulent early 17th century Europe and widely recognized as the father of modern planetary science. Kepler developed three laws which accurately described the planets and moons. Kepler’s First Law stated that an orbit around the Sun should resemble an ellipse with major and minor axes respectively; where one intersects the celestial sphere this becomes known as an Aphelion or Autumn Equinox respectively.
The Ecliptic is the path followed by planets and their moons every year in our skies, providing us with visibility of Mercury and Venus during evening hours in spring and summer – sitting low in the evening sky before rising higher into morning skies.