On Jan. 31, observers will experience a supermoon, blue moon, and total lunar eclipse at the same time.
This full moon is the third one in a row to be a supermoon, following the ones on Dec. 3 and Jan. 1. A supermoon occurs when the moon is at perigee, which is the closest point in its orbit to Earth, and in the full moon phase. The distance from Earth to the moon varies since its orbit is elliptically shaped and influenced by the gravity of other objects in our solar system. During a supermoon, the moon will appear larger in size, although this difference isn’t noticeable to the naked eye.
It will also be considered a blue moon, which just means that it’s the second full moon of the month. Since the moon’s orbital period is about 28 days, it is rare for a month to see two full moons. On average, a blue moon occurs every 2.7 years. The term blue moon does not refer to its color, however, on this date the moon will appear red to some observers.
The red color of the moon will be the result of a total lunar eclipse that will occur on Jan. 31. Unfortunately, Charleston, S.C. will not get to experience totality, unlike for August’s total solar eclipse. A lunar eclipse takes place when the tilt of the moon’s orbit lines up with the shadow of the Earth from the sun. The shadow of the Earth will block light from the sun from reaching the moon, and the moon will appear red because the light that reaches the moon is refracted by the Earth’s atmosphere.
Lunar eclipses, unlike solar eclipses, occur simultaneously in all parts of the world in which they are visible. A lunar eclipse take places when the moon is directly opposite the sun, in the full moon phase, while a solar eclipse takes places when the moon is between the Earth and the sun, during a new moon phase. Eclipses never happen alone though. Two weeks later, there will be a partial solar eclipse visible in some other parts of the world.
The lunar eclipse will begin close to the time the moon sets in Charleston on the morning of Jan. 31. The penumbral phase of the eclipse will begin at 5:51 a.m. EST. This is when part of the Earth’s shadow, the penumbra in which only some of the light from the sun is blocked, passes over the moon and begins to darken its appearance. Then at 6:48 a.m., the umbra, the part of the shadow where all the light from the sun is blocked, will start to cover the moon and the moon will begin to appear red. The shadow will continue to cover more of the moon until the moon sets at 7:13 a.m., while the eclipse is still in the partial phase. Totality, where the moon is completely covered by the Earth’s umbra will last for about an hour, but will not be visible from Charleston. The moon will be close to the western horizon during the beginning phases of the eclipse that are visible, so to observe it, find somewhere with a clear view to the west-northwest.