Be sure to look up at the moon this Friday night! Not only will the Harvest moon be full, but it may look smaller than an average moon.
According to NASA Solar System Ambassador Tony Rice, “The moon turns full on Friday, September 13 at 11:32 pm CDT — only about 1% of full moons fall on a Friday the 13th. This one is even rarer occurring near apogee, the furthest point in the Moon’s orbit. This last happened in 1832 and won’t happen again for more than 500 years.”
This month’s full moon occurs nearest to the autumnal equinox, which will take place on September 23. The full moon closest to the autumnal equinox is known as the “Harvest moon”.
We often hear that a particular full moon is a “supermoon”, but what does that mean? And what is a “micromoon”?
“Super” Full Moon
A supermoon is a full moon occurring at perigee, the moon’s closest point to Earth in its orbit. A supermoon can appear up to 14% bigger and 30% brighter than a “micromoon”, or 7% bigger than an average full moon.
As previously mentioned, the difference in size and brightness is due to the moon’s proximity to Earth. We often think of the moon orbiting around the Earth in a perfect circle, but the reality is that the orbit is more elliptical in nature. As a result, the moon can be as “close” as 225,310 miles from Earth during perigee — this is known as a “supermoon”.
“Micro” Full Moon
On the other side of the orbit, the moon is 251,904 miles away from Earth — this is apogee, and the moon looks smaller (hence the nickname “micromoon”).
We don’t tend to hear of micromoons very often (compared to supermoons), but the next micromoon will occur on September 13, 2019.