The summer haze is gradually lifting, and with the Sun setting that much earlier we don’t have to wait as long to enjoy a spot of stargazing. Plus, there’s the added bonus of not needing to bundle up for sub-zero temperatures.
Now is the best time of the year to view Saturn, and it will go into opposition this weekend, on 27 August 2023. But what exactly does it mean when we say a planet is in opposition? How can you spot Saturn in opposition? And, which constellation will Saturn appear in?
The best time to see Saturn
Saturn will reach opposition this weekend, on Sunday 27 August 2023, where the planet and its rings will appear brighter than usual, shining at magnitude +0.3. For context, magnitude is a measure of brightness; the lower the number, the brighter the object. Essentially, we’ll be able to see a ‘full’ Saturn.
“Saturn will be at opposition on 27 August and being more distant than Jupiter, its brightness and size changes are less dramatic,” says veteran astronomer and The Sky at Night presenter, Pete Lawrence.
But don’t be disheartened; Saturn has a trick up its sleeve:
“Its rings are mostly formed of water ice particles ranging in size from micrometres to metres. Away from opposition, particle shadows darken the particles behind them. However, for a few days around opposition, the shadows fall in line and become less obvious. As a result, if you view Saturn through a telescope, its rings appear to brighten,” explains Lawrence.
The ringed planet will rise at 8:06pm on 26 August 2023, as the Sun sets at the same time, and will sink below the horizon at 6:11am the next morning, on 27 August 2023.
What is opposition?
In astronomy, opposition is when two objects appear in opposite directions in the sky, when viewed from our vantage point here on Earth. In this instance, the two objects are Saturn and the Sun. During opposition, the sunlight that shines on Saturn is fully reflected back to us, and we can see the whole of its planetary disk. For us here on Earth, that means that Saturn will appear brighter in the sky.
“Opposition describes an object being opposite the Sun in the sky,” says Lawrence. “For some planets, this can be a big deal – the weeks around opposition giving us our best views of them. At opposition, a planet is also visible all night long.”
When a planet is in opposition, this straight-line configuration (this weekend being Sun-Earth-Saturn) often provides excellent opportunities to observe and photograph the subject.
But not every planet reaches opposition.
“The inferior planets (the inner planets with orbits smaller than the Earth) Mercury and Venus can’t reach opposition. For superior planets (the planets further away from the Sun with larger orbits than Earth) the effect of opposition decreases with distance,” Lawrence explains.
Why do the rings change appearance?
Like Earth, Saturn has seasons, where the planet experiences seasonal tilts (Saturn is tilted at around 27 degrees with respect to its orbit around the Sun) pointing towards, and away from the Sun. But unlike Earth, which takes one year for our planet to return to position, on Saturn it takes 29 Earth years.
During these 29 years, as Saturn is constantly moving in its orbital path, its orientation to Earth changes. This causes the rings to look as though they’re changing shape.
From our point of view, the rings appear to widen and shrink, with an edge-on alignment occurring twice in each orbit, roughly once every 15-ish years.
We are currently experiencing what many people would call the ‘classic’ view of Saturn, but as the planet is tilting away from us, it’s gradually becoming more edge-on, before becoming fully edge-on in 2025. After that, it’s a long wait until the rings are fully exposed; 2032.
So, if you want to see the classic view of the ringed planet, now is the time as it won’t be in this configuration again for another 29 years. We’ll have a similar view in around four years’ time, but we’ll be looking up at Saturn’s hemisphere, rather than having the northern hemisphere as the more prominent.
What else can you see when Saturn is in opposition?
The almost-full Moon will be lingering near the southwestern horizon in the constellation Sagittarius, but you needn’t worry too much about the light disrupting your view of Saturn; the Moon sets at around 00:17am BST (just after midnight).
Jupiter will be visible if you turn towards the eastern horizon, and at magnitude -2.42, will appear to shine brighter than Saturn (remember, the lower the number the brighter the object - so a negative number is really bright).
Just a little further to the east than Jupiter, Orion can be seen making its annual reappearance having been absent from our skies during the summer months. Almost like welcoming an old friend, it starts to peep over the horizon at around 1am, with the distinctive red supergiant Betelgeuse joining the party from around 2am.
How can I spot Saturn in the night sky?
For naked-eye observers, Saturn will appear as a very bright point of light that (unlike the stars) does not twinkle. But you’ll need at least 40x magnification with either binoculars or a telescope to see the rings and bring them into focus.
If you’re using binoculars, make sure you steady them with a tripod, or Saturn will be bouncing all over the shop. Keen eyes (through binoculars) might also be able to make out Titan, Saturn’s largest moon.
Telescopes 3” and larger will give you good views of Saturn and its rings, while 10” and larger will allow you to identify discernible gaps in the rings. If you are using a telescope, then you might also want to use a blue filter to enhance the rings, to make them stand out against the dark sky background.
To locate Saturn, look towards the south-eastern sky, close to the horizon after sunset. If you’re not sure which direction is southeast, look for where the Sun sets, and physically turn around 180 degrees and you’ll be facing Saturn (remember, opposition is when a planet is opposite the Sun).
Saturn is currently in the constellation Aquarius, the water bearer. The ringed planet is nestled between the double star Sigma Aquarii and the binary star system Iota Aquarii, which make up the water bearer’s waist, depending on which reconstruction of constellation art you look at.
How often do oppositions occur?
Each of the planets that reach opposition, do so roughly once every Earth year. This is because Earth, being the innermost planet, has a faster orbit and passes between these planets and the Sun.
But like with most things, there is usually an exception to the rule, and this time it’s Mars that likes to do things a bit differently.
Because Earth can achieve nearly two full orbits in the time it takes Mars to make one, the red planet only goes into opposition roughly once every 26 months.
When are the planets in opposition?
- Mercury: Never
- Venus: Never
- Mars: 15 January 2025
- Jupiter: 3 November 2023
- Saturn: 27 August 2023
- Uranus: 13 November 2023
- Neptune: 19 September 2023
- The Moon: 31 August 2023
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