The upcoming opposition of Mars promises to be an exciting event for planetary observers – here is the Who, What, When, Where, and Why on the 2020 opposition.
Who: The planet Mars and you – to observe it! Mars is the 4th planet from the Sun and is named after the Roman god of war. It is also called the red planet because of its rusty red surface. It is the second smallest planet with a diameter that is about ½ that of Earth’s and whose gravity is only 37.5% of Earth’s. A big attraction of Mars as an observing target is that it is the only planet to reveal its surface features to us with backyard telescopes with oppositions being the best times for a chance to view those features.
What: Oppositions occur when the Earth passes directly between an outer planet and the Sun placing the planet opposite the Sun in our sky – the planet rises when the Sun sets and it can be viewed throughout the entire night. An added bonus is that a planet at opposition is close to Earth and therefore appears bigger and brighter.
Mars displays the greatest changes in size because it is the first outer planet away from the Sun from us. It can go from being a fairly small and faint dot to the 2nd brightest planet in the sky (after Venus). Surface features like the polar ice caps, volcanoes, and darker regions of exposed volcanic rock become visible at opposition. A Martian sol lasts slightly longer than an Earth day so new surface features appear night after night and you get a chance to see much of Mars’ surface in the weeks surrounding opposition. Mars appears small, even at its maximum size, so a telescope is required to see surface features. Bumping up the magnification and some patience can help in picking out the details.
When: Opposition occurs at 23:20 UT on October 13, 2020. That is 04:20 pm Pacific Daylight Time but you don’t need to aim for the exact date or time – views of Mars will be good for several weeks around opposition. In fact, Mars makes its closest approach to Earth on Oct 6, 2020, a little bit earlier than the opposition date due to the elliptical (non-circular) shape of its orbit.
Oppositions of Mars occur on average every 780 days or approximately every 26 months. The distance from Earth to Mars varies between oppositions as does its size. Mars will be about 0.41 AU from Earth at this year’s 2020 opposition with a size of 22.6 arc-seconds. The 2020 opposition ranks high with respect to distance and size as Mars will not be as close nor as big during the next three oppositions in 2022, 2025, and 2027.
Where: Mars will be in a good position for observers in the Northern Hemisphere during its 2020 opposition. Mars will rise in the east at sundown (06:30 pm PDT) and will climb higher into south-eastern and southern skies closer to midnight. It reaches a maximum altitude at opposition of 46 degrees above the horizon at 1:00 am PDT on Oct 14th – there is likely to be better seeing and less atmospheric distortion with Mars that high in the sky.
Why: Oppositions of Mars occur because the orbits of Mars and the Earth make them align in a straight line with the Sun where the Sun and Mars are on opposite sides of the Earth.
The Earth moves more quickly in its orbit than Mars so it passes and then catches back up to Mars every 780 days on average.
That’s it. Go out and see Mars for yourself. Try to observe it over a few nights around the opposition to take in more of its surface. Keep an eye on this website for additional upcoming articles on Mars. With some luck with the weather and clear skies, Mars will reveal its surface details to us Earthbound observers.