Friday and Saturday mornings, December 21st and 22nd, the outer planet Jupiter and the inner planet Mercury will be within a couple of degrees from each other. Both rise about an hour before sunrise local time and will easily fit within the field of view of binoculars.
On Saturday December 15th Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 21.3o. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows. Even though it sounds confusing at western elongation for either Mercury or Venus the inner planet will be to the right of the Sun as we view them, meaning that at western elongation an inner planet rises in the east before the Sun rises. And at eastern elongation with the inner planet on the left side of the Sun the inner planet follows the Sun across the sky setting after the Sun sets.
From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – out to the left (east) from the Sun to eastern elongation, then reverse and move westward (inferior conjunction) between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun (superior conjunction) and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
Mercury is visible in the morning skies just before sunrise local time, as this graphic shows. Venus, to the west from Mercury rises about 2 hours before Mercury, and Jupiter rises shortly after Mercury.
Wednesday morning December 5th the very thin 28-day old waning crescent Moon will be within 4-5o from the innermost planet Mercury. Venus shines very brightly above or west from the Moon. About an hour after the Moon and Mercury have risen the outer planet Jupiter will rise above the eastern horizon.
Tuesday November 27th the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.
At this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this inferior conjunction Mercury will be about 5o north from the ecliptic, approaching its maximum angle of 7o.
Our Moon reaches apogee, (greatest distance from Earth), on Wednesday November 14th. At that time the Moon will more or less be at a distance of 31.70 Earth diameters 404,341 km (251,246 miles) from the Earth.
Does our Moon actually go around the Earth? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
On the day of the apogee the 7.5-day old waxing crescent Moon, at sunset local time (5:05 pm CST), will be over the southern horizon and joined by several planets. Just over the western horizon are the naked-eye visible planets from west to east: Jupiter, the inner planet Mercury, Saturn, and finally Mars. Neptune is shown however at 8th requires optical assistance or a camera to become visible.
Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”
Tuesday November 13th the 6-day old waxing crescent Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.