In the posting yesterday I described the shape, or eccentricity, or the Earth’s orbit as not being a factor in how we have seasons. As we all should have learned it is the tilt of the Earth’s rotational axis relative to the plane of the ecliptic. This tilt is approximately 23.5o and this combined with revolution around the Sun is as they say ‘the reasons for seasons.’
But this is not the point of this posting, but rather it is the plane of the ecliptic and where planets, dwarf planets, and our Moon orbit relative to the plane of the ecliptic. This relationship is known as inclination and it is the angle, in degrees, above the plane of the ecliptic. What this means is that the Earth’s orbit the bright green line, which is in reality the ecliptic, is the reference plane from which the other Sun orbiting objects respective orbit is tilted from. If you follow this explanation, and perhaps have read or noticed that each month I have posted when the Moon reaches its ascending or descending node. This ascending and descending node also applies to the other planets and dwarf planets as well because the planets and dwarf planets, like our Moon, have orbital paths tilted away from the plane of the ecliptic as this graphic shows. The table below shows the inclination for the planets and one dwarf planet.
What got me started on this was in part from what I wrote yesterday but also yesterday evening as I was attempting to get some pictures of the rising full Moon through some trees. This was despite the air temperature being near 0° F! Nonetheless as I was looking around enjoying the first really clear sky evening in a several weeks I couldn’t help but notice how Mercury, Venus and Mars were lined up from west to east along where I visualized in my mind the location of the ecliptic. Then using my ‘go to’ Astronomy simulator I set up a slideshow with the ecliptic, planets, a few dwarf planets, and our Moon displayed and set to 1-hour intervals starting with sunrise 7:30 am CST, my local time. You can see how the planets are very close to the ecliptic compared with the dwarf planets. The Moon is sometimes below, sometimes above, and sometimes right on the ecliptic – which if timed right gives us an eclipse.
Inclinations of 8 Planets and 1 Dwarf Planet
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.