Wikipedia:Reference desk/Archives/Science/2020 July 19

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July 19

Astronomy question

Can there be you see both Venus and Mars together in the same sky? How often does that happen? Preferably in the same direction. 166.137.83.31 (talk) 10:05, 19 July 2020 (UTC).

See Conjunction (astronomy). The external links include a site that will allow you to look up future conjunctions. If you know your astronomy, you might even be able to work out where those will be visible from, based on the provided celestial coordinates. Someguy1221 (talk) 12:27, 19 July 2020 (UTC)

Both are currently visible, with Mars rising around midnight in the Northern Hemisphere and Venus about 3 hours or so later: they're about 25° apart (say, 5 widths of your fist at arm's length).

For interest, Jupiter and Saturn are also visible, quite close together, for the whole night, Mercury rises around dawn, and both Uranus and Neptune are also visible if you know where to point a telescope. See here for a run down of this week's positions.

As to how often, Venus is visible for about 10 months of the year one side or the other of the Sun, and Mars easily visible for most of every other year (when it's not close to the Sun and thus up during daylight), so allowing for which side of the Sun they're on (as seen from Earth), I'd say they can be seen together (at night) for a total of about 5 months every other year (though that total is not one continuous period). Doubtless others can provide more precise figures, but working out exactly when these periods occur is complicated, because of course Venus orbits closer to the Sun faster than Earth while Mars orbits further away and slower than Earth. {The poster formerly known as 87.81.230.195} 90.200.41.197 (talk) 15:05, 19 July 2020 (UTC)

The geographic position of the observer also makes a difference. There will be conjunctions of Venus and Mars on Tuesday, 13 Jul 2021 at 02:06 CDT (07:06 UTC) and on Saturday, 12 Feb 2022 at at 19:54 CST (01:54 UTC). They may be difficult to observe from your position; a high vantage point in an area with little light pollution may help, and to see the second one you'll have to get up early.  --Lambiam 17:11, 19 July 2020 (UTC)

Cue for one of my favourite words, see Syzygy. Richard Avery (talk) 19:18, 19 July 2020 (UTC)

I like to view syzygys from Zzyzx. It is quite xeric there. --Guy Macon (talk) 15:10, 20 July 2020 (UTC)

You should invite Mr. Szymczyk along the next time you go... --Jayron32 14:09, 21 July 2020 (UTC)

Every 2 decades is a great conjunction aka Jupiter and Saturn. Named for rarest pair amongst the planets known to cavemen/pre-1780s people, not brightness though they're still pretty bright. Mark your calendar, the best great conjunction in 4 decades is December 21 or so and the 2040 pass is probably even better cause got damn how many times can they occur near the Sun? They are approximately 4 zodiac constellations further back each time so the c. 2060 pass would be really good for the Northern Hemisphere if it's winter. It's almost 2020.97 AD now on a 2 decade timescale, and theirorbits are far enough for earth's POV to mimic the Sun's POV with some similarity so the 2 planets are relatively near now, as mentioned earlier.Sagittarian Milky Way (talk) 02:08, 21 July 2020 (UTC)

"Classical planets" is a more concise term for them. --47.146.63.87 (talk) 01:37, 22 July 2020 (UTC)

Now I remember, 2020 is very close as well, a 2060s conjunction (Venus and Jupiter?) is even closer, maybe even superimposing in a telescope from the right parts of Earth (or is that the one 1 or 2 centuries from now?, anyway make sure to look at it through a telescope in the 2060s. Sagittarian Milky Way (talk) 02:29, 21 July 2020 (UTC)

If you get a book like this [1] and scroll forward to page E44 you will see the time each planet crosses the meridian for every day of the year. If the times are similar they are close together, but have regard to when they cross - obviously if they cross about noon you're not going to see them. I see Venus and Mars were together on 19 February 1992. In a book like this [2] you will see that Mars and Venus are socially distanced throughout 2020. 2A00:23C1:E101:D700:34A6:251C:F895:A8E8 (talk) 11:18, 25 July 2020 (UTC)