“I’m looking forward to the period towards the end of August when all five naked-eye planets will be visible in the sky at the same time, just after sunset,” said a recent comment.
Yes, this evening, for instance, all five are above the horizon.
Jupiter and Saturn are well up in the east and will get higher as the night goes on; over in the west, Venus is fairly high and Mars and Mercury are about to set. (Those two are close together; Mercury will pass less than a degree south of Mars a few hours later.) ).
This provoked me to think about times when all those five are in the sky. I devised several kinds of illustration, which don’t yet entirely work, but at least the spans of time can be found. I think, so far, that each year has only one such span or none. A span begins when one of the five first becomes above the horizon at this time of day, the others already being so, and ends when one ceases to be so.
For 2021, the span is from August 11 to 29.
But what we mean by “visible in the sky” depends on our location on Earth, and the number of minutes after sunset when we think we could begin to see a bright planet only just above the horizon.
For this picture, and this calculation, I’ve chosen latitude 40° north, but longitude 0 (as for Greenwich). For an American longitude of 90° west, the all-five span is slightly shorter: August 11 to 26. Latitude can make a great difference. I think Roberto, who made the comment, is in Australia, and for there the all-five span is from around August 1 to September 20. Mercury and Mars are lying north of the ecliptic, so they are above the horizon longer.
Let’s see what the all-five span of days is for some other years, assuming the American location of latitude 40° north, longitude 90° west, and the observing time of 30 minutes after sunset.
For 2022, it will be exactly the whole of December! But that’s because on Dec. 31 Venus will be still 5° above the horizon, so that span stretches to 2023 Jan. 4.
For earlier years there was no all-five span at all, back to 2016 when there was a long span from July 12 to August 27.
And what underlies this difference between years? Good question! Perhaps there’s some answer in the relations among planetary orbits, which I may or may not have found by the time I put a bit on the all-five problem into the upcoming Astronomical Calendar 2022.
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Actually there are 6 naked eye planets visible. Look below the horizon to see the sixth one.
I recall that you included an extensive description of the grand planetary alignment of 1982 in that year’s Astronomical Calendar (40 years ago!) and that you used one of your paintings from a trip you made to Mexico in 1974 (I believe) for the cover. You described the gathering of planets visible over a bay in Baja California, depicted in your painting, as a “prelude gathering to the grand congress which was to occur 8 years later” or something to that effect. Pretty good insight right there as to the patterns at work!
I’m not sure if I’ve written to you about this in the past – but;
A photo I was particularly excited about taking was a grouping (that fit in a 35mm frame) of all seven Classical planets.
I took this on 2002-5-14 from the island of Lesbos with my Zenit film camera braced against a pole. I know not the exposure details since I triggered the shutter duration by hand!
From West to East (with the Sun just below the horizon enough to spot the others) Sun, Mercury, Saturn, Moon, Mars, Venus, Jupiter – in one shot.
Apart from the day before and after, I haven’t found another date where this photo was possible – where the Sun is at one extreme of the grouping. Sounds like a problem for Jean Meeus.
You can see a small version on my LibraryThing page (PBDavis) – I’ll send a larger one if you ask for it.
Eric, such a photo is surely a unique achievement: all seven classical “planets” or wanderers including the sun, counting as visible because its glow is present. But I don’t see your photo in or by means of this comment. Do you think that if you send it to me it should then be shown in a blog post?
I wonder how you came to be in 2002 on Lesbos, now the site of camps full of miserable refugees from Asia (and seen by me in 1987 only in the distance, as in my cover painting for the Troy Town Tale).
Paul here (not Eric)
My wife is German and Greek – we were visiting her Lesbian father (resident of Lesbos, and descendant from Lesbian Greeks from before the Turkish centuries) with our one-year-old first son along. We were living in her grandfather’s mansion in Molybos (Platanos Kyriakou, 39 22’11.06 ‘N 26.10’25.59″E) . Since it was not tourist season, I had the undivided and enthusiastic attention of a photo-kiosk man who ran off several prints with varying exposure developments. From there we joined my wife’s brother making summer (Alpen) cheese, high over the world near Valendas, Switzerland (46 46’16″N 9 19’04″E) – where #1 son turned two. Unfortunately, at some point in our travels the prints became damp and stuck together. We returned to the U.S. where our belongings were in storage – and dropped into NH where we moved a few times before settling into a therapeutic community for adults – where we’ve raised our three sons. I’m not sure where the negatives are (for years now) – and keep hoping to run into them at some point! The only e-copy I have is a scan done when I’d found the stuck prints and scanned the best one – which I posted on my LibraryThing page. Perhaps I’m motivated now to look afresh and get you a copy – you’re the first person to show any interest in a photo I was elated to have taken. (shot at 39 22’15.11″N 26 10’26.04″E)
Interesting story, Paul!
Indeed. There were glorious views last night (18 August) here in Sydney of all five planets in the clear late-winter evening sky.
Don’t you mean “over in the west” when referring to Venus, Mars, and Mercury
Tes – corrected.
Poor Uranus always gets missed from the naked eye planets which it technically is but it’s not easy to see without an optical aid but then nor is Mercury.A dark place,a lack of moonlight,a good altitude and spy out Uranus noting nearby stars using something like an 8×25 monocular and then have a go naked eye.