Final answer:
A planet with a highly eccentric orbit has an elongated path around its star, distinct from a circular orbit. This indicates gravitational interactions and a chaotic planetary formation process, influencing climate and habitability.
Step-by-step explanation:
When we say that a planet has a highly eccentric orbit, we mean that the path of the planet around its star is not a perfect circle but is elongated, resembling an oval or ellipse. An orbit's eccentricity is a measure of its deviation from circularity; the higher the eccentricity, the more elongated the orbit. For example, in our solar system, Mercury has the most eccentric orbit with an eccentricity of 0.21, and all other major planets have eccentricities less than 0.1, indicating less elongated, more circular paths.
The discovery of exoplanets with large orbital eccentricity was unexpected, based on early models of planets forming in disks which would naturally lead to more circular orbits. This has led to the understanding that gravitational interactions between planets, where they can change each other's motions, can cause orbits to become more eccentric. This indicates a more chaotic process of planetary formation, akin to a roller derby rather than a polite dance. The eccentricity of a planet's orbit can affect its climate and the potential for it to be habitable due to the varying distances from its star, leading to significant temperature swings.