Mars opposition
Mars will be directly opposite to sun on July 27, 2018. NASA

As sky-watchers continue to gear up for the longest total lunar eclipse of the 21st century, another celestial event is set to dazzle the night sky — the brightest and closest approach of Mars in the last 15 years.

Over last few weeks, the red planet has been growing brighter in the night sky, and on July 27, it will sit directly opposite to sun, as seen from Earth, in a state called “opposition.”

Earth and Mars are in an elliptical or egg-shaped orbit around the sun, but as our world is closer compared to the red planet, it takes less time to complete a single orbit of the star. This means that sometime we can complete our round and pass by our planetary neighbor.

Earth can complete two orbits around the sun in just about the same time as Mars takes to complete a single trip, which means the opposition occurs every two years or so.

But, in every 15 or 17 years, this sun, Earth, Mars alignment gets even more special due to Mars being at perihelion or at the point closest to the sun in its orbit. Due to this, Mars makes its closest approach to Earth, giving sky-watchers a rare opportunity to watch the red planet.

This year, after attaining opposition on July 27, Mars will make its closest approach on July 31, somewhere around 4:00 a.m. EDT. The planet, as described by NASA, will be just 35.8 million miles away from our world.

The opposition occurs a few days before the closest approach due to the egg-shaped orbital paths of the planets. If Earth and Mars both were in circular orbits in the same plane, the opposition and closest approach would have occurred on the same day. Also, the minimum distance between the planets would have been the same.

However, in the real scenario of elliptical orbits, the distance keeps changing. In 2003, during the closest approach, Mars and Earth were just 34.6 million miles away, the least distance in some 60,000 years.

Though such close approach won’t happen until 2287, the upcoming encounter will also give some breath-taking views. Mars will be visible all night, but you will be able to see it depending on the visibility in your region. Also, it is worth noting that the planet will appear brighter during the opposition (from July 27 to July 30) due to the angle of sunlight hitting it than during the close approach.

According to Sky & Telescope, Mars will be seen in the constellation of southern Capricornus. Over the ensuing weeks, it will start moving away from Earth and fading in the darkness of the night sky. Viewers who cannot find a dark open spot to see the red planet directly on July 31 can watch the closest approach on NASA TV or on Griffith Observatory's live stream channel after midnight.