Aquila said:
Tomorrow the 17th there is a grand trine between these 3 planets.
Astrologically it is called a water grand trine because the 3 planets transit the 3 water element zodiac constellations.
Jupiter 4° Cancer | Saturn 4° Scorpio | Neptune 4° Pisces
The planets being at 120° of each other to the ecliptic? I think it is..and will form a perfect triangle.
It’s apparently quite rare.
There are two main geocentric coordinate systems used in astronomy. The principle system, equatorial coordinates, is basically a projection of terrestrial longitude & latitude onto the celestial sphere. The projection of the Earth’s equator is the celestial equator, the projections of the north & south pole of the Earth are the north & south celestial poles. Thus if you stand at the south pole & look up, the south celestial pole is directly overhead. The celestial equivalent of latitude is called declination, and like terrestrial latitude it’s usually measured in degrees. The celestial equivalent of longitude is called right ascension and it is traditionally measured in hours (24 hours = 1 full circle = 360°).
The other main geocentric system is ecliptic coordinates , which is based on the ecliptic plane, rather than the equatorial plane. The ecliptic plane is the plane of the Earth’s orbit (and hence the plane of the sun’s apparent orbit in Earth’s sky). The coordinates of this system are known as ecliptic longitude and latitude, and they are both measured in degrees. The 0° point of ecliptic longitude is the point on the ecliptic where where the Sun crosses the celestial equator going from the southern celestial hemisphere to the northern celestial hemisphere, which happens on the March equinox.
The major bodies of the solar system (and many of the minor bodies) orbit the Sun in roughly the same plane, so they’re always fairly close to the ecliptic. So it’s convenient to give planetary locations in terms of their ecliptic longitude (and latitude).
Western astrology gives planetary positions in terms of ecliptic longitude, dividing the ecliptic into 12 30° signs; but planetary astronomers use this traditional system as well.
So the figures given above for the positions of Jupiter, Saturn & Neptune are their ecliptic longitudes. So they probably won’t be exactly 120° apart from each other, unless they also all happen to be crossing the ecliptic as well.
Yes, this is a fairly rare event because Neptune has such a long period (around 165 years), and there isn’t a simple relationship between the periods of all 3 bodies. (FWIW, the period of Jupiter is roughly 12 years, and that of Saturn is 29 years). However, the “grand trine” configuration may be approximately repeated a few times over the coming months and years, due to retrograde motion. Remember, the position of a planet on the celestial sphere is not purely determined by the planet’s orbit, it also depends on earth’s orbit, so planets can appear to travel backwards in the sky.
Aquila said:
I’m not sure if I can even see all three planets this time of year tomorrow night (weather permitting)
Well, you can’t see all 3 bodies that are in a grand trine at the same time, unless you have very good x-ray vision, since the Earth will be in the way. :)