Supermoon Rising at the Big Nickel
The Moon’s orbit is slightly elliptical and it’s distance from Earth changes over time. At perigee (it’s closest point to us on Earth) it is 50 000 km closer than at apogee (it’s furthest point from Earth). When the Moon happens to be full at perigee it appears 14% bigger and 30% brighter than is would at apogee.
Even though half of the Moon is always illuminated, the direction that light is reflected changes as the Moon orbits the Earth. When the Moon is between the Earth and the Sun, we see none of the sunlight it reflects, so we call it a new moon. When it is on the far side of the Earth from the Sun we see all of the sunlight it is reflecting. Sometimes the Earth’s shadow falls on the Moon at this time causing a Lunar eclipse, but only if the Moon happens to be crossing the ecliptic plane in it’s orbit. The Moon’s orbit is at a 5° inclination to the ecliptic plane, which is the plane the Earth travels in around the Sun.
When visualizing the Earth, Moon, Sun system, remember the right-hand rule. If you point your thumb up and imagine it is pointing at the North star above the Earth’s axis of rotation, the direction your fingers curl would be the same direction the Earth spins, the same direction it orbits the Sun, the same direction the Moon spins (it spins once per month, so we always see the same side of the Moon from Earth) and the direction the Moon orbits the Earth.
The Sudbury Astronomy Club and Science North will be viewing tonight (November 14)’s supermoon (or as we scientists call it, perigee-syzygy) from Dynamic Earth. This full moon, very near perigee, will be the largest, from our perspective on Earth, since 1948 and we wont see another one this large until 2034. If you join us for the supermoonrise at 5:30 pm you will also witness the Moon illusion, which causes the Moon to look much larger on the horizon, and we can show you how to reveal the illusion. A telescope will be available until 7:30 pm to view details of the Moon and capture photos.