When the moon reaches perigee (that's the scientific term) twice in the same month, it's a called a "blue moon". A supermoon only occurs when a full moon coincidentally falls during the period when the moon is the closest distance from Earth during its orbit. It's more like an oval, so at times it's closer to the Earth than it is at other times. The idea merely reflects the fact that the moon's apparent size varies depending on how close it gets in its elliptical orbit around Earth.
On Sunday, the moon will shine brighter and appear larger than it has all year.
The Moon will lose its brightness and take on an eerie, fainter-than-normal glow from the scant sunlight that makes its way through Earth's atmosphere. "Sometimes during the year we get an opportunity to see the full moon when it is at its closest point and that's what we'll be seeing on December 3". Based on the moon's rotation this month's full moon - which is also being called the Cold Moon - will be at its closest point to Earth, creating the Supermoon.
It's hard for our eyes to distinguish these small changes in size when the Moon is high amidst the vastness of the night sky. "Don't be so focused on your sensor that you miss such an otherworldly sight", they said.
When the supermoon is viewed low on the horizon, it appears huge.More news: Now Qualcomm files new patent infringement complaints against Apple
A supermoon is also believed to have an impact on the Earth's waters.
"The supermoons are a great opportunity for people to start looking at the moon", said Noah Petro, a research scientist from NASA's Goddard Space Flight Center.
Will you be sky-watching on Monday night?
The moon will be roughly 10,000 miles closer to Earth on Sunday evening, creating our first and only Supermoon of the year.
The moon is nearly full Saturday night and will be full Sunday.