A planet with an eccentricity of 0.5 has a. nearly equal semimajor and semiminor axes. b. a longer semiminor axis than semimajor axis. c. a longer semimajor axis than semiminor axis. d. the Sun at the center of its orbit.

Orbits can take various shapes, and one common form is the ellipse. Unlike a circle, an ellipse has two focal points. For planets orbiting the Sun, the Sun is at one of these focal points, not at the center.
When we say an orbit is elliptical, we mean it’s shaped like a squashed circle.
The major reason planets have elliptical orbits is because of the gravitational pull from the Sun. This pull is not uniform, which leads to stretches in different directions, thus creating an elliptical path.
It's important to note is that elliptical orbits vary in shape. Some can be almost circular, while others can be very stretched out, depending on a value called eccentricity. More on eccentricity next!

To understand elliptical orbits, we need to know about the semimajor axis. It’s the longest line that you can draw across an ellipse, going from one side to the other, passing through the center. The semimajor axis is essentially half of the major axis.
Think of it as the 'average' distance from the planet to the Sun. This measurement is crucial in determining the shape and size of the orbit. It’s used in many important calculations, such as a planet’s orbital period.
For our planet with an eccentricity of 0.5, the semimajor axis represents the longest distance within its elliptical path. This tells us that the path the planet follows is noticeably stretched out.

Just like the semimajor axis is the longest line through the ellipse, the semiminor axis is the shortest. It stretches across the ellipse perpendicular to the semimajor axis, crossing the center.
The length of the semiminor axis is influenced by the orbit’s eccentricity. When the eccentricity is larger, the ellipse becomes more oval-shaped, meaning the semiminor axis gets shorter compared to the semimajor axis.
So for our example with an eccentricity of 0.5, we understand that the semimajor axis is longer than the semiminor axis. This relationship helps us confirm that the orbit is not a perfect circle but a balanced stretch, leaning towards an oval shape.