In May, look up at the night sky and wave “hello” to Mars. The “Red Planet” will be at opposition on 22 May, bringing it to within 75.3 million km of Earth, the closest it has been since 2005.
When a planet is at opposition, the Earth is directly between it and the Sun with the planet and the Sun on opposite sides of the Earth. Earth orbits the Sun about 25% faster than Mars so every 26 months, Earth will overtake Mars. In May, Earth with catch up with, and overtake, Mars putting them on the same side of the Sun. This brings them closer together, so we see Mars not only much brighter but also larger when viewed through a telescope. The Earth passes Mars quite quickly, so the time for best telescope viewing is just a few weeks before and after the opposition.
Not all oppositions of Mars are equal because while the orbit of Earth is close to a circle, that of Mars is more elliptical. Mars reaches opposition roughly every 26 months, so while it’s not a rare occurrence, this is the closest Mars has been to Earth since 2005 when it was 69.6 million km from Earth. The red planet doesn’t get as close this time, but it will still be the best view of Mars we have had for ten years. To put this distance in some perspective, our Moon is on average 384,400 km away, and on average Mars is about 225 million km from the Sun.
The best views we get today are from the numerous spacecraft currently orbiting the planet. Still, there is something special about seeing Mars through a telescope and marvel how much astronomers of the past were able to learn – even if they got some of it wrong. There were no canals, the dark markings were not vegetation, and there are no advanced beings living there.
With a good telescope, you’ll expect to see the red colour of the planet mottled with dark and the white south polar cap. During the 2016 opposition of Mars, it will be late winter in the planet’s southern hemisphere.
But you don’t have to have a telescope because your naked eye will notice that Mars is much brighter than normal (rivalling Jupiter) and it will move noticeably against the background stars from night to night.
Make the most of this opposition opportunity and find Mars in the night sky. Mars will be rising as the Sun sets (because they are opposite in the sky) and Mars will be high in the sky around midnight for the best telescopic viewing. Wait a few hours after dark and look east. You will see Mars rising in the constellation Scorpius looking like a bright red/orange star.
The date of opposition is May 22nd, but the actual closest approach occurs on May 31st.