Graphic showing the opposition of Mars, where the Sun, Earth, and Mars form a line
When the superior planets Mars, Jupiter, Saturn, Uranus, and Neptune are travelling round in their orbits they’re at different positions in relation to Earth. Opposition of a planet occurs when the Earth and the planet in question would form a straight line if you were stood at the Sun’s position.
Inferior planets Mercury and Venus are not included as they are inside Earth’s orbit, and so closer to the Sun.
So what’s so great about opposition when it comes to observing the planets? Well think about the Moon, it goes through its different phases during the month. But when it’s at full Moon, meaning directly opposite the Sun from our vantage point, you’ll know just how bright it is. It’s the same analogy for the superior planets as they orbit around the Sun. When the Earth gets directly between the planet in question and the Sun, you have opposition. This is when the planet will be closest to Earth, brightest in the sky, and will also at a large angular diameter. A planet will gradually get larger and brighter in the sky as it comes up to opposition, peak, then slowly decrease in angular size and brightness as it moves away.
Here I list when the planets Mars, Jupiter, Saturn, Uranus, and Neptune come to opposition. You’ll also find their times, magnitudes, angular size, and highest point above the horizon …
Times are GMT, 1 hour is added for BST between March 25th and October 28th
Mars
The red planet will next be at opposition on the 8th of April 2014, when it will be at magnitude -1.25, with an angular diameter of 15 arc seconds. Mars will be in the constellation Virgo making a nice pairing with the bright star Spica, where it will be 6 degrees north/north-east of. You can see Mars on the night of the 8th rising from the east in early evening, and get to its highest point in the sky due south at 1.15 am, where it will reach 31 degrees above the horizon (UK).
Mars’ best year will be in 2018 when it will be at magnitude -2.78, with an angular diameter of 24 arc seconds.
Jupiter
Jupiter from Cassini
The biggest and most massive planet in the solar system, Jupiter will next be at opposition on the 5th of January 2014, when it wil have a magnitude of -2.23, with an angular diameter of 47 arc seconds. Jupiter will be in the constellation Gemini, making a triangle with the stars Castor and Pollux. Jupiter will rise from the north-east in early evening, and get very high in the south at 12.15 am where it will reach 59 degrees above the horizon (UK). It will be visible all night, eventually setting in the north-west just as day breaks.
Saturn
Everyone’s favourite the ringed giant Saturn will next be at opposition on 10th of May 2014, where it rises from the south eastern horizon in late evening inside the constellation Libra. It will have a magnitude of 0.27, and an angular diameter of 44 arc seconds from ring tip to ring tip, the disk of the planet will be 19 arc seconds wide. As you can see from the image, the rings will be tilted very nicely for viewing. Saturn will get highest point in the south at 1.05 am, and reach 21 degrees above the horizon (UK). It then moves to the south west where it sets after daybreak.
Here we arrive at the ice giants Uranus and Neptune. Because of their vast distance you’ll notice their brightness and angular size increase will be less pronounced at opposition, than planets such as Jupiter and Mars…
Uranus
Uranus from Voyager
The solar system’s coldest world Uranus will next be at opposition on the 3rd of October 2013, just inside constellation Pisces. It rises from the east in early evening before darkness falls, with a magnitude of 6.06, and an angular size of 4 arc seconds. The blue world will reach its highest point beyond midnight 40 degrees above the southern horizon (UK) at 12.57 am. Uranus will then set in the west shortly after day break.
Neptune
Neptune from Voyager
The furthest planet in the solar system Neptune reaches its next opposition on the 27th of August 2013, where it rises from the east during early evening in constellation Aquarius. It will have a magnitude of 7.64, and an angular size of 2 arc seconds. Neptune will reach its highest point beyond midnight in the south at 1.05 am, and get to 25.5 degrees above the horizon (UK). It then moves to the west where it sets after day break.
John Brady.