January 21, 2023: Closest New Moon Since the Middle Ages
This Saturday’s New Moon will be the closest New Moon to Earth in a period of 1337 years.
A Remarkably Close New Moon
According to our calculations, on January 21, 2023, the New Moon will be at its closest distance to Earth for the last 992 years.
The next time the New Moon is this close to Earth will be 345 years from now, making this the closest New Moon in 1337 years.
Earth-Moon Distance Always Changing
The Moon’s orbit around Earth is not a perfect circle. Instead, it has an elliptical shape, like a slightly stretched circle. This means the distance between the Moon and Earth changes over the course of a month.
The point on the Moon’s orbit that is closest to Earth is called perigee; the farthest point is called apogee.
Extreme Near and Far Distances
If perigee or apogee coincides with a New Moon or Full Moon—when the Earth, Moon, and Sun are in alignment—the Moon’s closest and farthest distances become more extreme.
The most extreme Earth-Moon distances of all occur when Earth is near its closest point to the Sun, which is called perihelion. Currently, perihelion falls around the beginning of January.
Closest New Moons of the Current Era
We looked into the closest Earth-Moon distances at New Moon over a 2000-year period, and found three New Moons where the distance was less than 356,570 km (221,562 miles).
Our calculations used the best available figures for the Moon’s position over long periods of time. This is a set of data called DE431, which was produced by the Jet Propulsion Laboratory at the California Institute of Technology.
The Three Closest New Moons, 1000 CE to 3000 CE
|1030||December 3||356,562 km (221,557 miles)|
|2023||January 21||356,568 km (221,561 miles)|
|2368||January 20||356,559 km (221,555 miles)|
Sources: JPL Ephemeris DE431, timeanddate.com
It should be noted that, according to this data, there is only a few kilometers’ difference between these distances. It can also be seen that the three dates fall close to perihelion (around December and January).
As a comparison, the farthest Earth-Moon distance is typically around 405,000 km (252,000 miles).
What Does This Mean for Us?
So this will be the closest New Moon—and also, therefore, the largest—since the 11th century.
In practical terms, we won’t be able to see anything, because the New Moon is known as the invisible phase: it’s where the Moon disappears from view for a few days.
The Next Day: Two Planets Almost Touch in the Sky
In fact, this will be a weekend of astronomical close encounters.