Saturn

by Dominic Ford, Editor
Last updated: 24 Mar 2020

The planets of the solar system:
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune


Saturn is currently an early evening object. From San Diego, it is visible in the evening sky, becoming accessible around 19:14 (PDT), 30° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 21:16, 37° above your southern horizon. It will continue to be observable until around 01:28, when it sinks below 10° above your south-western horizon.

01 Aug 2021  –  Saturn at opposition
14 Aug 2022  –  Saturn at opposition
27 Aug 2023  –  Saturn at opposition
07 Sep 2024  –  Saturn at opposition
Saturn

Saturn, as seen by the Cassini spacecraft from orbit around it. Image courtesy of NASA.

Saturn is the sixth planet from the Sun, orbiting at a distance of 9.58 AU once every 29.5 years.

It is the solar system's second largest and most massive planet after Jupiter, with a mass of over 95 times that of the Earth, but less than a third that of Jupiter.

Its radius is 9.4 times that of the Earth, but like the other gas giants it rotates at phenomenal speed, completing one revolution every 10.57 hours.

Apparitions of Saturn

The table below lists apparitions of Saturn around the year 2021, computed from NASA's DE430 planetary ephemeris. To show events around other years, use the control below.

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Apparitions of Saturn around 2021

Date Event Declination Angular size Ring plane
inclination
Date Event Declination Angular size Ring plane
inclination
15 Apr 2012 11:18 PDTSaturn at opposition7°27'S19.1"13.7°N
28 Apr 2013 01:18 PDTSaturn at opposition11°38'S18.9"18.1°N
10 May 2014 11:20 PDTSaturn at opposition15°17'S18.7"21.7°N
22 May 2015 18:27 PDTSaturn at opposition18°18'S18.5"24.4°N
02 Jun 2016 23:29 PDTSaturn at opposition20°33'S18.4"26.1°N
15 Jun 2017 03:09 PDTSaturn at opposition21°57'S18.4"26.6°N
27 Jun 2018 06:20 PDTSaturn at opposition22°28'S18.4"26.0°N
09 Jul 2019 09:59 PDTSaturn at opposition22°02'S18.4"24.4°N
20 Jul 2020 15:19 PDTSaturn at opposition20°42'S18.5"21.7°N
01 Aug 2021 23:06 PDTSaturn at opposition18°31'S18.6"18.2°N
14 Aug 2022 10:02 PDTSaturn at opposition15°32'S18.8"13.9°N
27 Aug 2023 01:20 PDTSaturn at opposition11°52'S19.0"9.0°N
07 Sep 2024 21:27 PDTSaturn at opposition7°39'S19.2"3.7°N
20 Sep 2025 22:37 PDTSaturn at opposition3°02'S19.4"1.8°S
04 Oct 2026 05:21 PDTSaturn at opposition1°49'N19.7"7.5°S
17 Oct 2027 17:27 PDTSaturn at opposition6°43'N20.0"12.9°S
30 Oct 2028 10:25 PDTSaturn at opposition11°25'N20.2"17.9°S
13 Nov 2029 06:52 PSTSaturn at opposition15°38'N20.4"22.0°S
27 Nov 2030 07:47 PSTSaturn at opposition19°04'N20.6"25.0°S

The rings of Saturn

Saturn is undoubtedly best known for the system of rings which encircle the planet. These give Saturn perhaps the most iconic appearance of any of the planets.

The most obvious feature within the rings is the dark Cassini Division, which lies between the B- and A-rings and is striking even under poor seeing conditions. Under closer inspection, the rings show marked color and brightness contrasts which are much more apparent than any shown by the disk of the planet itself.

The inclination of Saturn's rings changes over time in a 30-year cycle, at times being inclined at nearly 30° to our line of sight and becoming prominently visible, meanwhile at other times being edge-on to our line of sight, making them barely visible at all.

As of 2018, the planet is tilted with its northern hemisphere towards us, and the northern polar region on display. The rings are open wide, showing their northern side, and will continue to be well placed for the next 3–4 years.

Saturn's atmosphere

Like the other gas giants, Saturn does not have a solid surface and is comprised almost entirely of gas, though it may have a small solid core at its center.

Within this gaseous atmosphere there are thick clouds of tiny solid crystals, predominantly of ammonia. It is these clouds which make Saturn opaque and determine its visual appearance.

Unlike Jupiter, however, these clouds are not strongly colored. While Saturn does have dark belts and bright zone, their color contrast is quite subtle in comparison to the corresponding features on Jupiter.

From time to time, cyclonic storms in Saturn's atmosphere manifest themselves as bright spots on the planet's disk.

Finding Saturn

Saturn comes to opposition once every 376 days – its synodic period – almost exactly once a year. The date it comes to opposition moves 10–11 days later each year.

Where it lies in the sky affects how easily it can be observed from the northern or southern hemispheres, and because, by definition, it lies almost directly opposite the Sun at opposition, there is a close relationship between the time of year when Saturn comes to opposition, and how well placed it is for observation.

When Saturn comes to opposition in the northern summer months, the Sun is high in the northern sky, which places the opposite side of the eclipic plane in the southern sky. This means that Saturn is poorly placed for observation from the northern hemisphere when at opposition in the summer.

Conversely, if Saturn is at opposition in December, it is sure to be high in the northern sky.

Because Saturn comes to opposition at almost the same time of year in successive years, this means that it remains in the northern or southern sky for a decade at a time. For example, it has currently been in the southern sky since 2011, and will remain poorly placed for northern observers until at least 2020.

The chart below shows the time of year of all of Saturn's oppositions between the years 2000 and 2115, together with the declination that Saturn will have at the time, measured on the vertical axis.

A table of the time of day when Saturn rises and sets on any given day of the year can be found here . A chart of Saturn's path relative to the background stars can be found here.

NORAD ID COSPAR ID Name Launch date Flight ended Owner
NORAD ID COSPAR ID Name Launch date Flight ended Owner
6421 1973-019A PIONEER 11 05 Apr 1973 United States
10271 1977-076A VOYAGER 2 19 Aug 1977 United States
10321 1977-084A VOYAGER 1 04 Sep 1977 United States
25008 1997-061A CASSINI 14 Oct 1997 14 Sep 2017 United States

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