Mars' paths: celestial and local

Event Date: September 27th
Time: 7:15 AM


Brief

   Yesterday's journal ended with a tease about what I will talk about this evening with Mars.  As mentioned then, the change of separation with the Sun and improving western, evening geometry of the sky will mean that Mars will not seem to change much in altitude.  Unlike the other outer planets, Jupiter through Neptune, Mars is much closer to us and therefore, it takes longer for us to separate from it between the time of opposition and conjunction; a little over a year. With the other outer planets, it takes a little over 6 months between opposition and conjunction, depending on how far they are from us; Jupiter takes closer to 7 months, depending on how it and Earth are positioned relative to each other on the celestial dome.
   Below, is Mars shown just after Sunset, along with its celestial and local paths.  The increment dots are 10 days, covering a period of three months.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Try not to let the direction of the paths deceive you.  Instead, let's look at the spacing between the increment dots.  Although not obvious, the spacing between them for the celestial path (orange) become a little further with each one; looking closely, this may be noticeable.  This indicates what I said yesterday: as we move further from Mars, from our perspective it moves against the stars a little faster each day; specifically, every minute, although there is no way that I could visibly plot that many times!
   As for the local path (green), it shows where Mars was at the time above each day for the last three months.  It was about that time in June, that the Sun set at its latest and almost as far north as it does on the celestial dome.  As the Sun has set earlier each day, it meant that for awhile, Mars was too.  However, as the geometry of the western, evening sky improves between now and late-February, given Mars' separation from the Sun during each of those months, we will witness the aforementioned.  When I recreate this plot over a 6-month period at the end of the calendar year, you may see what I mean.  In the meantime, enjoy Mars, albeit far and dim.  As conjunction with the Sun gets close near the vernal equinox and we then lose Mars behind our star, it will not be easily visible again until late summer.