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Saturn's apparent magnitude from Uranus is +3.228. Jupiter orbits closer to the sun than Saturn. Can we therefore expect Jupiter’s apparent magnitude from Uranus to be dimmer than Saturn's, or is it in fact brighter?

Constantthin
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    In the light of the similar previous questions and their answers: please use the general adivice and strategy given there and /or consult a programme like Stellarium to give you these simple look-up answers. – planetmaker Nov 27 '21 at 14:58
  • @planetmaker. I have had a look at that app and I don't understand it. In other words, I don't know how to operate it towards desired goal. – Constantthin Nov 27 '21 at 15:03
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    "Saturn's apparent magnitude as watched from Uranus is +3.228. Is it? I'd think it would vary a lot and not be a fixed number. Where did you get +3.228? – James K Nov 27 '21 at 17:40
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    @James K. https://astronomy.stackexchange.com/questions/47458/what-is-saturn-s-apparent-magnitude-at-its-brightest-when-viewed-from-uranus – Constantthin Nov 27 '21 at 21:48
  • 22/9/23 result of Jupiter seen from Uranus = 2037, 2051 and 2120 = -0.93 – Constantthin Sep 22 '23 at 12:50

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I started Stellarium on my computer and pressed F6 to bring up the "Location" window.

Then I changed the planet to "Uranus", and marvelled at the view of the many rings and many moons from the planet's "surface"

For convenience I clicked the buttons to remove the ground and the atmosphere. then I found and clicked on Saturn. It had a magnitude of 3.74. I then pressed F5 to get a time window and stepped one month at a time while watching the change in Saturn's brightness. The maximum I could get was +3.55 (in 2042) though it is believable that it could get brighter at a more favourable elongation in it's elliptical orbit. I also noted that as Saturn passes in front of the sun, its magnitude gets much less, well below naked eye.

I then repeated with Jupiter. It has a maximum brightness of +1.55 (in about 2031) but again, it is believable that it would be brighter at a more favourable elongation.

At its brightest, Jupiter is a lot brighter than Saturn when viewed from Uranus.

James K
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  • I just downloaded the Stellarium Plus app. Had to pay $14.99 for it. I don’t know how to use it. Could you please guide me through it. – Constantthin Nov 27 '21 at 22:47
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    You were robbed. Stellarium is free software for Windows, Mac and Linux. https://stellarium.org/ I hope the step by step in the above answer would enable you to check the answer. The use of "F6" and "Window" should have made it clear that this isn't a mobile app. But I've added "on my computer" just in case it wasn't clear. I can't help with some similarly named mobile app. I don't really use a phone. – James K Nov 27 '21 at 22:50
  • Ok thx I’ll try that – Constantthin Nov 27 '21 at 22:58
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    Got it working! "Magnitude" seems to mean "Apparent Magnitude" since Absolute Magnitude is listed separately. The figures I got was: Uranus - Saturn = +2.77 (2027). Uranus - Jupiter = -0.02 (2021). What was striking was that both Venus (+1.32/49) and the earth (+2.44/59) were brighter than Saturn when viewed from Uranus. Mercury's apparent magnitude was +3.41 (2067). And the dimmest planet - Mars was +5.61 (2033) – Constantthin Nov 28 '21 at 06:04
  • I don’t understand why my latest Stellarium search came up with a different figure than half a year ago? I did exactly the same thing, I think. Stellarium may not be functioning properly. It is also strange that my two figures, the old and new, differed from yours. I am just wondering if you would get the same figure if you carried out the exercise today? Check out the update in my answer. – Constantthin Jan 31 '23 at 11:22
  • Well, since last year, both Jupiter and Uranus will have moved in their orbits, so the distance between them will have changed. Moreover the phase of Jupiter will have changed, so the apparent magnitude of Jupiter will have changed. Planets don't stay at constant magnitude. – James K Feb 01 '23 at 00:04
  • Yes. But doesn’t a properly working Stellarium take the movements of the planets into consideration when calculating the brightest Apparent Magnitude between the planets? Otherwise what is the time meter that pops up when you press f5 there for? – Constantthin Feb 01 '23 at 07:56
  • Yes that is what I said. Stellarium takes the movements of the planets into consideration when calculating the Apparent Magnitude. Hence the apparent magnitude of Jupiter from Uranus in 2023 is different from the apparent magnitude of Jupiter from Uranus in 2021. – James K Feb 01 '23 at 21:19
  • Ok. But the value of a certain year should be the same whenever you check that value, shouldn’t it? Like if you scroll forwards in time with the f5 button’s time meter the values for 2050 should be the same if you check it today or if you check it ten years from now? – Constantthin Feb 01 '23 at 21:49
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According to James K suggestion I downloaded the astronomical program “Stellarium” unto my desktop. Fiddled around with the different settings and got it working!

"Magnitude" seems to mean "Apparent Magnitude" since Absolute Magnitude is listed separately. The figures I got was: Uranus - Saturn = +2.77 (2027). Uranus - Jupiter = -0.02 (2021). What was striking was that both Venus (+1.32/49) and the Earth (+2.44/59) were brighter than Saturn when viewed from Uranus. Mercury's apparent magnitude was +3.41 (2067). And the dimmest planet - Mars was +5.61 (2033).

Thus, according to the excellent astronomical program “Stellarium” Jupiter’s apparent magnitude when watched from Uranus at its most favourable elongation in recent times (2021) was -0.02. And was then just a tad dimmer than the third brightest star in our night sky, Arcturus (-0.04).

Update 1: Strange is that today 30 January 2023 when I opened up Stellarium and went over the stats I got a slightly different figure than when I did the exercise in June 2022. Today the brightest apparent magnitude of Jupiter when watched from Uranus was not in 2021 but in January 2052. Namely at an apparent magnitude of -0.96. This is a big difference to the earlier figure of -0.02 in Dec 2021. By the way when I checked the brightest apparent magnitude of 2021 I found it to be -0.28, not -0.02. I wonder what is going on here?

Update 2: Today 22 September 2023 the figure for the brightest future apparent magnitude of Jupiter as going to be seen from Uranus is according to Stellarium -0.93, which it predicts will happen in 2037, 2051 and in 2120. Strange, different data again.

Constantthin
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