Written by: Lucia Brimer
April 7 is a Full Moon. This one is rather special because it is a Supermoon. And it is the Full Moon just before Easter. What is a Supermoon? Let’s first review lunar phases.
Our Moon goes through phases as it orbits the Earth. It takes 29 ½ days for the Moon to orbit the Earth and to complete all its phases, or about one month. The diagram below from Space.com shows the Moon’s phases. When the Moon is basically between the Earth and the Sun (see position A), it is a New Moon. The New Moon is very close to where the Sun appears in the sky, so it is only up in the daytime. We cannot see a New Moon because the sunlit side is not visible.
When the Moon is Full (see position E), then the Earth is basically between the Sun and the Moon, so we can see the entire lit side. This is the only time that the Moon rises at sunset and sets at sunrise so that it is visible the entire night.
So, what is a “Supermoon”? Well, the orbit of the Moon is not completely circular, but rather, an ellipse. The Earth is not located at the center of this ellipse, but rather at a focus, so it is slightly off-center. The Moon’s orbit is also much farther from the Earth than it seems in illustrations. The average distance of the Moon from the Earth is about 239,000 mi (385,000 km). This is about 30 times the diameter of the Earth. (See Activities to make a scale model of the Earth and the Moon.) The diagram below shows the size, shape, and position of the Earth (E), the Moon (M) and the Moon’s orbit, to scale.
The Moon’s closest approach to Earth is perigee (P), and it is 225,622 mi (363,104 km). Its farthest distance from Earth is apogee (A), and it is 252,088 mi (405,696 km). When a Full Moon occurs near perigee, this is called a Supermoon. The Full Moon looks 14 % larger and 30 % brighter at perigee than at apogee. See diagram to the left from Space.com for what this looks like. And if you watch the Video below, you can see how the size of the Moon appears to get larger and smaller during a month, as it orbits the Earth. Supermoon is not an actual astronomical term, but it has been defined as a Full Moon that occurs when the Moon is within 90% of its closest approach. Every year has at least one Supermoon, and actually, Supermoons will occur 2 or 3 months in a row. The Full Moon on March 9 was also a Supermoon, but this one will be the largest and most Super of the year.
Also note that this month’s Full Moon is known as the Pink Moon. The April Full Moon has been called the Pink Moon by the Farmer’s Almanac, not because the Moon looks pink, but because of pink wildflowers that bloom at this time.
Now, what does this have to do with Easter? Some of you may wonder why the date of Easter changes every year. Well, Easter is usually connected with the Jewish holiday of Passover, because Jesus died after celebrating Passover with his disciples. Jewish holidays are celebrated according to the Jewish calendar, which is based on lunar months starting with the celebration of Rosh Hashana in late September or early October. Passover is celebrated on the 14th day of the seventh month, Nisan, at the time of the full moon. Christians wanted to keep it at about the same time as Passover, but use the solar-based Julian calendar. Therefore, it was decided to celebrate Easter on the first Sunday after the first Full Moon after the Vernal Equinox. So Easter this year is on April 12, which is the first Sunday after the Full Moon on April 7, after the Vernal Equinox on March 19, 2020.
The Moon rises on April 7 at 7:44 pm. The best time to notice the increased size is while it is still low in the sky. So, if the weather is clear, be sure to go outside after sunset and enjoy the second and last Supermoon of 2020!
If it is cloudy or you would prefer to stay inside and see a webcast of the Super Pink Moon, check it out here: https://www.space.com/super-pink-moon-2020-webcasts.html.