More about “parades”: times when the five bright planets are in our sky in their order outward from the Sun.
Their starting and ending dates are not quite simple. When the planets are all, as now, in the morning sky – all west of the Sun – that doesn’t necessarily mean they are all visible from your location. One, usually Mercury, may be on or below your horizon, because it is close to the Sun or is in a part of its orbit that is south of the ecliptic. Thus, the observable span of a parade may be shortened at one or both ends compared with the theoretical span. But let’s keep talking about the theoretical span because it’s simpler.
We are now enjoying the longest morning parade between 1864 and 2069.
elong.of Mercury Venus Mars Jupiter Saturn
2022 May 29 -11.0 -37.2 -64.6 -64.4 -102.4
2022 May 30 -12.3 -37.0 -64.9 -65.2 -103.3
2022 Jul 16 -1.7 -26.0 -76.0 -105.0 -149.5
2022 Jul 17 1.6 -25.7 -76.3 -105.9 -150.5
2022 May 30 to 2022 Jul 16 = 48 days
As shown by that little table (in which negative elongations mean westward), Mars began it by changing places with Jupiter on May 29, and Mercury will end it by passing the Sun on July 16.
There seemed no rule about the occurrence of parades, when I investigated them for this century. But, running the calculation for a longer span, three centuries, I’m surprised to find exactly 14 parades for both the evening and the morning skies.
1800-2100
parades of planets in the evening sky
1801 Feb 15 to 1801 Mar 29 = 43 days
1816 Aug 18 to 1816 Aug 25 = 8 days
1839 Jun 28 to 1839 Jul 18 = 21 days
1861 May 23 to 1861 May 24 = 2 days
1899 Oct 1 to 1899 Oct 9 = 9 days
1901 Jul 6 to 1901 Jul 13 = 8 days
1901 Aug 28 to 1901 Oct 10 = 44 days
1939 Nov 19 to 1939 Nov 28 = 10 days
1957 Jul 5 to 1957 Jul 11 = 7 days
1995 Oct 1 to 1995 Oct 4 = 4 days
1997 Oct 14 to 1997 Oct 26 = 13 days
2040 Jun 23 to 2040 Jun 25 = 3 days
2040 Aug 13 to 2040 Aug 18 = 6 days
2100 Apr 19 to 2100 May 3 = 15 days
14 parades
1800-2100
parades of planets in the morning sky
1823 Oct 20 to 1823 Nov 14 = 26 days
1825 Oct 14 to 1825 Nov 1 = 19 days
1862 Feb 27 to 1862 Mar 11 = 13 days
1864 Feb 7 to 1864 Apr 3 = 57 days
1881 Jul 23 to 1881 Aug 30 = 39 days
1921 Nov 28 to 1921 Dec 27 = 30 days
1926 Apr 24 to 1926 May 14 = 21 days
1964 Jun 23 to 1964 Jun 27 = 5 days
1966 Aug 13 to 1966 Sep 9 = 28 days
2002 Nov 4 to 2002 Nov 14 = 11 days
2004 Dec 11 to 2004 Dec 28 = 18 days
2022 May 30 to 2022 Jul 16 = 48 days
2041 Mar 28 to 2041 Apr 4 = 8 days
2060 Oct 17 to 2060 Dec 5 = 50 days
14 parades
Can you make a guess at what might underlie that, or see any pattern in the frequency and length of the parades? I don’t think I can.
The shortest parades, such as 1861 May 23-24, 1995 Oct. 1-4, 2040 June 23-25, may not really contain even a single date when all five planets are high enough to be seen. They have a status a bit like penumbral eclipses!
Then there’s the variation in which we include Uranus and Neptune – try to find parades of not just the five naked-eye planets but the seven major planets.
In those three centuries there is no such extended parade – not a single time when the planets from Mercury to Neptune happen to be in order as seen from our own third planet. Let’s try (gasp) more centuries. Yes: just one brief parade.
1500-2200
parades of planets in the evening sky
elong.of Neptune Uranus Saturn Jupiter Mars Venus Mercury
1622 Apr 19 165.5 94.6 76.3 54.1 24.2 25.0 9.1
1622 Apr 20 164.5 93.6 75.3 53.3 24.0 23.9 7.7
1622 Apr 24 160.5 89.8 71.7 50.1 22.8 18.9 1.7
1622 Apr 25 159.6 88.8 70.8 49.3 22.6 17.6 -0.9
1622 Apr 20 to 1622 Apr 24 = 5 days
It began when Venus overtook Mars, and ended when Mercury passed in front of the Sun.
Here is a sky scene from back then. The arrows through the seven planets and the Sun show their motion over five days.
See the end note about enlarging illustrations.
I’ve had to choose the earliest date, and a far northern viewpoint, to get Mercury even as high as the horizon. And, if this is a parade, Mars and Venus are undisciplined soldiers.
This is one of Edwin Tunis’s brilliant drawings in his book on Weapons. The hapless legionary being chewed out by a centurion is me being bawled at by a drill sergeant on a long-ago parade ground.
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as always, thanks for the information. i remember the drill sergeants… more fondly with each passing year.
I use SkySafari planetarium app to create finder charts with the planets and the stars, then I find them with 10×42 image stabilized binoculars. The app makes it a lot easier, but I still need to star hop to find the planets. Here in the city I can only see stars between third and fourth magnitude with the unaided eye, so some of the star hops are several binocular fields wide. That gives the thrill of the hunt. After I’ve seen a planet a few times I can follow it without resort to the app, which is more satisfying.
Even if you’re using a go-to telescope, you still need to figure out which eighth magnitude star in your field of view is the planet.
I don’t see any patterns but it is interesting that it happens every 21 years on average, which is about one generation apart. The limiting factor would be the superior planets. Mercury and Venus would have their little parade every few months.
I probably need to return to the subject, because of other variations, such as inward order, inclusion of Vesta… so may try other spans.
In 1622 nobody would have known to look for Uranus and Neptune.
I saw the current parade, all the major planets plus the Moon and the asteroid Vesta, yesterday morning, June 15, in a perfectly clear sky. I’ve been following Saturn, Jupiter, Mars, and Venus as they’ve danced along the ecliptic. I got my first view of Vesta on May 3, and my first confident view of Neptune May 21. I saw Uranus for the first time during his current apparition day before yesterday, and my first confident view of Mercury only yesterday! This is what I call a solar system bingo!
I would not have been able to find Vesta, Neptune, and Uranus from scratch all on the same morning. It takes a few tries to find a dim object. First I need to find the right place and familiarize myself with the brighter fixed stars in the same field of view. Then I need to make at least a couple of wrong guesses as to which dim “star” is really a planet. Then I notice that one of those dim stars has moved relative to the others! Uranus is about sixth magnitude, so not so hard once he reached a decent elongation, but Vesta and Neptune were eighth magnitude when I first observed them. There are a lot of eighth magnitude stars.
I suspect that the equal number of evening and morning parades over the course of 300 years is one of those coincidences that falsely suggest an underlying regularity that is not there. Checking a few other spans of 300 years would show if the pattern holds up.
Superb feats of observing, apparently without resort to apps and go-to systems.