Over the next several years, when will Jupiter be 90 degrees away from the Sun? Not in latitude or longitude, but along a great circle. Bonus points for when it’s 88 or 92 degrees from the Sun, although I’d expect it would just change about 1 degree per day.
As many of you know, the sky is polarized near 90 degrees from the Sun. Wearing polarized sun glasses, there’s a dark streak where the sky is most polarized. My goal is to see if Jupiter is visible when it is in the dark streak while I’m wearing my sunglasses, or using some other polarized glass.
Yesterday, I’d estimate the darkest part of the streak was about 2 - 4 degrees wide, presumably due to multiply scattered light, hence the range of days. (Today, there were many puffy clouds in the sky, and the streak wasn’t very well defined, presumably from light scattered from the cloud tops.)
This will be pretty close to the quadrature time for Jupiter (not exactly, since you’re looking for the angle from the sun and not just 90° in longitude). The next quadrature for Jupiter is 2010/06/23.
To get a better estimate you can find the angle given an ephemeris. For June 23, here’s the Sun’s position and Jupiter’s. Convert the polar-coordinate angles (right ascension and declination) to Cartesian and take the dot product to find the angle between Jupiter and the Sun; I get about 90.3°. Adjust the date in those URLs to get closer or find other dates if you want.
In broad daylight? Really? I’ve never seen any non-Earthbound objects in broad daylight except the Sun and the Moon. I’m guessing therefore that it’s really faint and requires you to stare at its exact location to have any chance of seeing it.
Venus is not too difficult to see in daylight. You have to know where to look though… it seems your eyes don’t pick it up easily unless they focus right at it.
Venus is about 5 times as bright as Jupiter, but Venus is an inner planet so it is always near to the sun from our point of view. It’s maximum elongation is 47 degrees. Jupiter being an outer planet can be on the far side of the sky from the sun. Having said all that, I doubt if it is that easy to see in daylight.
Everybody but me seems to understand this. What does “90 degrees from the sun” mean? Does this mean that a line from Jupiter to the sun is 90 degrees from the Earth’s line to the sun?
Wikipedia has a useful table of apparent magnitudes, according to which near-opposition Jupiter should be barely naked-eye visible when the Sun is low in the sky; near-quadrature Jupiter would probably not be visible. The Jupiter ephemeris linked above gives a magnitude of -2.3, compared to the Wikipedia value of -4.0 for the daytime sky. So the question is whether polarization will reduce that -4.0 by a couple of stops or better; I’d have to try metering the sky with a polarizing filter to see.
Thanks Omphaloskeptic. That gets me this year, and I’m able to jump ahead a year and a month to get to the next one. Will Jupiter be trailing the Sun, or leading it for this series?
I think this is right. What the OP is asking for is the moment when, if you drew a line from your eyes to the Sun, and another from your eyes to Jupiter, the angle between them would be 90 degrees. (Alternatively – both Jupiter and the Sun appear to circle around the Earth in the same path. A circle contains 360 degrees. Thus, the distance from one horizon to the other is 180 degrees. The OP wants to know when the Sun and Jupiter are 90 degrees apart.)
These times are in Greenwich Mean Time, so add or subtract however many hours depending on where on Earth you’re located. They also use the “apparent” position of each (accounting for speed of light), which is what you’re interested in.
Here’s a breakdown of when the 88-92 degree range will occur around those times, using a 3-hour time step.
Time (UTCG) Sun/Jupiter Angle (deg)
------------------------ -----------------------------------
21 Jun 2010 05:25:42.713 88.000
21 Jun 2010 08:00:00.000 88.092
21 Jun 2010 11:00:00.000 88.199
21 Jun 2010 14:00:00.000 88.306
21 Jun 2010 17:00:00.000 88.413
21 Jun 2010 20:00:00.000 88.520
21 Jun 2010 23:00:00.000 88.627
22 Jun 2010 02:00:00.000 88.734
22 Jun 2010 05:00:00.000 88.841
22 Jun 2010 08:00:00.000 88.949
22 Jun 2010 11:00:00.000 89.056
22 Jun 2010 14:00:00.000 89.163
22 Jun 2010 17:00:00.000 89.271
22 Jun 2010 20:00:00.000 89.378
22 Jun 2010 23:00:00.000 89.486
23 Jun 2010 02:00:00.000 89.593
23 Jun 2010 05:00:00.000 89.701
23 Jun 2010 08:00:00.000 89.808
23 Jun 2010 11:00:00.000 89.916
23 Jun 2010 14:00:00.000 90.024
23 Jun 2010 17:00:00.000 90.131
23 Jun 2010 20:00:00.000 90.239
23 Jun 2010 23:00:00.000 90.347
24 Jun 2010 02:00:00.000 90.455
24 Jun 2010 05:00:00.000 90.563
24 Jun 2010 08:00:00.000 90.670
24 Jun 2010 11:00:00.000 90.778
24 Jun 2010 14:00:00.000 90.886
24 Jun 2010 17:00:00.000 90.994
24 Jun 2010 20:00:00.000 91.102
24 Jun 2010 23:00:00.000 91.211
25 Jun 2010 02:00:00.000 91.319
25 Jun 2010 05:00:00.000 91.427
25 Jun 2010 08:00:00.000 91.535
25 Jun 2010 11:00:00.000 91.643
25 Jun 2010 14:00:00.000 91.752
25 Jun 2010 17:00:00.000 91.860
25 Jun 2010 20:00:00.000 91.969
25 Jun 2010 20:52:09.493 92.000
Time (UTCG) Sun/Jupiter Angle (deg)
------------------------ -----------------------------------
14 Dec 2010 18:01:47.460 92.000
14 Dec 2010 21:00:00.000 91.885
15 Dec 2010 00:00:00.000 91.769
15 Dec 2010 03:00:00.000 91.652
15 Dec 2010 06:00:00.000 91.536
15 Dec 2010 09:00:00.000 91.420
15 Dec 2010 12:00:00.000 91.304
15 Dec 2010 15:00:00.000 91.188
15 Dec 2010 18:00:00.000 91.072
15 Dec 2010 21:00:00.000 90.956
16 Dec 2010 00:00:00.000 90.840
16 Dec 2010 03:00:00.000 90.724
16 Dec 2010 06:00:00.000 90.608
16 Dec 2010 09:00:00.000 90.493
16 Dec 2010 12:00:00.000 90.377
16 Dec 2010 15:00:00.000 90.261
16 Dec 2010 18:00:00.000 90.146
16 Dec 2010 21:00:00.000 90.030
17 Dec 2010 00:00:00.000 89.915
17 Dec 2010 03:00:00.000 89.799
17 Dec 2010 06:00:00.000 89.684
17 Dec 2010 09:00:00.000 89.568
17 Dec 2010 12:00:00.000 89.453
17 Dec 2010 15:00:00.000 89.338
17 Dec 2010 18:00:00.000 89.222
17 Dec 2010 21:00:00.000 89.107
18 Dec 2010 00:00:00.000 88.992
18 Dec 2010 03:00:00.000 88.877
18 Dec 2010 06:00:00.000 88.762
18 Dec 2010 09:00:00.000 88.647
18 Dec 2010 12:00:00.000 88.532
18 Dec 2010 15:00:00.000 88.417
18 Dec 2010 18:00:00.000 88.302
18 Dec 2010 21:00:00.000 88.187
19 Dec 2010 00:00:00.000 88.072
19 Dec 2010 01:52:42.586 88.000
Is that good enough?
(Working for a satellite analysis software company can sometimes come in really handy)
Light, like all electromagnetic radiation, has its electric field perpendicular to the direction it’s traveling. 90 degrees away from the Sun in the sky, the light is traveling perpendicular to the direction you’re looking, and so doesn’t have any electric field in that direction. The electric field of the light makes the charges in air or water molecules move in the direction of the electric field, and those moving charges then radiate. This scattered light is the cause of the blue sky. Since the electric charges only move in one direction perpendicular to the direction you’re looking, the light they radiate is also polarized in that direction (the charges moving towards and away from you also radiate, but can’t radiate in the direction they move).
ETA: This page has a nice animated image in the section Why scatter can polarize light? that may make it clearer.
Are you sure you’re not mistaking Venus for Jupiter? I’ve read many astronomy books, and Venus is the only one consistently mentioned as being visible in the daytime. And even then, seems to me the sun has to be going down…or eclipsed!
It is not as easy a Venus, but I’ve done it. I can’t recall if I have done it with the sun WAY high in the sky. I do know I’ve done it with the sun at least a fair bit above the horizon.
The biggest trick to it is have a good reference point, like the top of a distant tree. You observe Jupiter in the morning sky before the sun rises. You find a spot to stand where Jupiter is near the top of that tree in the sky. Then, as daylight gets brighter and brighter, you keep readjusting where you stand so Jupiter stays near that reference point. It really helps for your eyes to have something in the sky to focus on while you are trying to see Jupiter.
Venus is easy enough for me to often do it in strong daylight without the reference trick, though I havent tried it in the past few years.
Clear skies help too, but all my observing has been done in the deep south near sea level, so its not like we get really clear skies like out west, up north in the winter, or mountain top clarity either.
