Final answer:
A supermoon is when a full moon is at its perigee, appearing larger and brighter due to its closer proximity to Earth. The elliptical orbit of the Moon leads to varying distances from Earth, which causes this phenomenon.
The correct statement is option 1. A moon that appears larger and brighter than usual.
Step-by-step explanation:
A supermoon is a term used when a full moon appears larger and brighter in the sky. This happens because it's at the nearest point in its orbit around the Earth, known as perigee. Not only does it gleam brighter due to its proximity, but it also coincides with the full moon phase, making it seem larger than an average full moon. When the supermoon occurs, the moon can appear up to 14% larger and 30% brighter to us on Earth than at its farthest point, which is called apogee.
The Moon's orbit is elliptical, meaning at certain times it's closer to the Earth and at others it's farther away. When a full moon phase aligns with its closest approach to Earth (perigee), the result is what we call a supermoon. This phenomenon causes more direct sunlight to hit the moon and reflect back to Earth, which is why it appears brighter. The earthlight, or sunlight reflected from Earth, also plays a role in illuminating the moon’s surface, especially visible during a crescent phase.
The supermoon is not only fascinating for observers but also has an effect on the Earth, such as higher tides due to the Moon’s gravitational pull being stronger at perigee.