Stargazers are in for a treat come July! Mars’ orbit will be closer to Earth than it has in more than ten years, in what is called a perihelic opposition.

Mars in 2018

NASA explains that Mars oppositions happen about every 26 months. Every 15 or 17 years, opposition occurs within a few weeks of Mars’ perihelion (the point in its orbit when it is closest to the sun).

Starting in mid-June, Mars will officially enter the evening sky and noticeably brighten and grow in size, leading up to opposition on July 27, 2018 and will appear brightest between July 21 and Aug. 3, 2018.

When Mars is closest to Earth, it will be 35.8 million miles (57.6 million kilometres) away from our planet, the average distance being 140 million miles (225 million kilometres).

Those living in the northern hemisphere, look to the sky before dawn; those in the southern hemisphere will have the best view about two hours after sunset!

Mars in Night Sky July 2018

An opposition can occur anywhere along Mars’ orbit. When it happens while the red planet is closest to the sun (called ‘perihelic opposition’), Mars is particularly close to Earth. If Earth and Mars both had perfectly stable orbits, then each perihelic opposition would bring the two planets as close as they could be. That’s almost the way it is.

But once again, nature throws in a few complications. Gravitational tugging by the other planets constantly changes the shape of our orbits a little bit. Giant Jupiter especially influences the orbit of Mars. Speaking of which, Mars will outshine Jupiter as being 1.8 times brighter in the night sky.

Also, the orbits of Earth and Mars don’t lie in quite the same plane. The paths the planets take around the sun are slightly tilted with respect to each other.

So, with all these added factors, some perihelic oppositions bring us closer together than others. The 2003 opposition was the closest approach in almost 60,000 years!

Mars’ orbit is more elliptical than Earth’s, so the difference between perihelion and aphelion is greater. Over the past centuries, Mars’ orbit has been getting more and more elongated, carrying the planet even nearer to the sun at perihelion and even farther away at aphelion. So future perihelic oppositions will bring Earth and Mars even closer. But we’ll still have bragging rights for awhile. Our 2003 record will stand until August 28, 2287…

BhagawatiBhagawati is a regular contributor

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