Monday, January 06, 2020

considered Mars 2020 show

Got to thinking about the conversation with Rhonda. Did a big of digging into the next apparition of Mars.

A few quick key facts. Opposition will occur on or around 13 October. It will cross the meridian (or over the south cardinal point) at midnight on that date. Approximately, it will rise at 5:50 PM and set at 6:35 AM. Visible all night long. The red planet will be bright at magnitude -2.6. It will be 0.4 astronomical units (AU) away i.e. 60 000 000 kilometres. Or to put it another way, less than half the Earth-Sun distance. While still below the ecliptic (the path of the planets and the Sun) line, it will be pretty high in the sky. At midnight it will be above 51 degrees in altitude or elevation. That's very good news. In the summer of 2018 it was only about 20° up.

That's all data I culled from using Stellarium on the web (link).

(Actually, this whole time is gonna be awesome for planet viewing as Jupiter and Saturn will be putting on an incredible show as well.)

I also visited the ALPO site for information. In fact, I had a look at the heliocentric chart for Earth and Mars. This was the main discussion point. I was trying to explain to rho that Earth drew close to Mars about every 2 years but there was a longer cycle of interest where, due to Mars unique orbit, that there were periods where it was better for us. I couldn't remember that period but I thought it something like 20 years. ALPO says it's 15.8 years.

From Association of Lunar and Planetary Observers web site, I took in the Mars page. It had been updated by Jeffrey Beish in March 2016. I noted Figure 2-3, the chart showing the maximum apparent diameter of Mars. Yep, peaking in the fall of 2020. Not quite as high at 2003 but still pretty good! Between 23 and 25 seconds-of-arc.

Examined table 2-3 listing future apparitions of Mars. Found the 2020 data:
  • opposition date: 13 October
  • diameter in arc-seconds: 22.3
  • closest approach: 6 October
  • diameter in ": 22.6
  • distance in AU: 0.41
A general search thanks to Google helped me find a heliocentric chart with annotations for 2020. I was surprised that the one on the ALPO site wasn't marked. That said, the chart shows Ls, is the planetocentric longitude of the Sun along the ecliptic of Mars's sky. And the various tables refer to Ls. 

Oh. Hold the phone. I found a different page, one specifically for the 2020-2021 apparition of Mars. And it has an updated and annotated chart (see Figure 2). Noted the radial line marking 2020, from Earth's October orbit through Mars's January season.

Still, while I'm happy to find the updated chart, I thought I'd make my own, a bit cleaner, and astronomer-friendly...

chart of Mars and Earth orbits

This is a top-down view of the inner solar system. The planets orbit counter-clockwise.

The inner blue ring shows Earth's orbit, nearly circular, and nearly perfectly centred on the Sun. Earth's months are inscribed. The outer orange ring shows Mars's orbit. The Martian seasons, in the northern hemisphere, are noted. You'll note the orbit is elliptical so at times Mars can be half the distance from Earth. The Line of Apsides shows the points of closest approach (250°) or when Mars would be distal (70°).

Opposition times are marked with the red radial lines. The past 2018 event is noted—you can see it occurred in July, where the ecliptic is low for those in the northern hemisphere. Also noted is the "great" 2003 opposition where the event occurred right on the proximal Line of Apsides! Mars was 0.37 AU or 55.8 million klicks away and rose over 25" in size. That's why it was such a big deal.

Ah. That crazy night at York University...

Found the old 2003 perihelic apparition of Mars page on SEDS.

In all this searching, I also found the Opposition Cycle of Mars article. It talks about even longer cycles still as to how close/large Mars can be. 2003 was a really big deal.

The sad bit of news is that we're heading into the long 15-16 year cycle where Mars is moving away. Well, to be fair, for half that time. So that puts some emphasis on this year's apparition of Mars. Don't miss it. If you skip it, 2022 will be problematic: Mars will be further from Earth; and it will be December on our home world. And that will like scupper things for us in the northern hemisphere... So, again, view Mars this year!

Before I forget, planetary oppositions are not one-night-only events. So start enjoying the fourth planet in the summer, any clear nights you can. Go on high-alert in October. That will be the best time for visual observing and astrophotography. And if it's cloudy for much of October, it will still be OK to view and image in November.

I tried, without success, in 2018 to get the moons of Mars.

Stellarium says the tiny moons will be in the magnitude 10 and 11 range...

I'm pumped to tag Phobos and Deimos this year!

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