Uranus

by Dominic Ford, Editor
Last updated: 24 Mar 2020

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


Uranus is currently visible as a morning object. From Seattle, it is visible in the morning sky, becoming accessible around 23:16, when it reaches an altitude of 21° above your eastern horizon. It will then reach its highest point in the sky at 04:17, 58° above your southern horizon. It will be lost to dawn twilight around 05:33, 54° above your south-western horizon.

31 Oct 2020  –  Uranus at opposition
04 Nov 2021  –  Uranus at opposition
09 Nov 2022  –  Uranus at opposition
13 Nov 2023  –  Uranus at opposition
Uranus

Uranus, as seen by Voyager 2 in 1986. Image courtesy of NASA.

Uranus is the Solar System's second outermost planet, orbiting the Sun at a distance of 19.2 AU once every 84.3 years.

It is a giant planet with a mass 14.5 times that of the Earth and a radius 4 times that of the Earth. Like the other gas giants it rotates at phenomenal speed, completing one revolution every 17.2 hours.

Apparitions of Uranus

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

Change year

Timezone

Filter

Apparitions of Uranus around 2021

Date Event Declination Angular size
Date Event Declination Angular size
25 Sep 2011 17:06 PDTUranus at opposition0°15'N3.7"
29 Sep 2012 00:06 PDTUranus at opposition1°50'N3.7"
03 Oct 2013 07:03 PDTUranus at opposition3°25'N3.7"
07 Oct 2014 13:49 PDTUranus at opposition4°59'N3.7"
11 Oct 2015 20:41 PDTUranus at opposition6°32'N3.7"
15 Oct 2016 03:35 PDTUranus at opposition8°04'N3.7"
19 Oct 2017 10:26 PDTUranus at opposition9°34'N3.7"
23 Oct 2018 17:38 PDTUranus at opposition11°03'N3.7"
28 Oct 2019 01:07 PDTUranus at opposition12°28'N3.7"
31 Oct 2020 08:45 PDTUranus at opposition13°51'N3.8"
04 Nov 2021 16:49 PDTUranus at opposition15°10'N3.8"
09 Nov 2022 00:18 PSTUranus at opposition16°26'N3.8"
13 Nov 2023 09:12 PSTUranus at opposition17°37'N3.8"
16 Nov 2024 18:36 PSTUranus at opposition18°43'N3.8"
21 Nov 2025 04:17 PSTUranus at opposition19°44'N3.8"
25 Nov 2026 14:33 PSTUranus at opposition20°40'N3.8"
30 Nov 2027 01:13 PSTUranus at opposition21°28'N3.8"
03 Dec 2028 12:20 PSTUranus at opposition22°10'N3.8"
08 Dec 2029 00:03 PSTUranus at opposition22°44'N3.9"
12 Dec 2030 12:27 PSTUranus at opposition23°11'N3.9"

Discovery

Uranus was unknown to ancient astronomy, and was the first planet to be discovered in the telescopic era, by William Herschel in 1781.

Herschel was not the first to have seen it, however. Several earlier observations have been identified where Uranus was mistakenly thought to be a star, and its position recorded on star charts. Among the observers who made such pre-discovery observations is John Flamsteed, who gave Uranus the designation 34 Tauri.

At magnitude 5.6, Uranus is just within reach of the naked eye from exceptionally dark locations far away from any artificial lighting, but only under very clear skies. Through a modern telescope it is easily resolvable into a disk measuring 3.8" across.

Uranus's atmosphere

Like the other gas giants, Uranus does not have a solid surface and is comprised almost entirely of gas. It may well have a liquid core at its centre, however.

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

The predominant components of Uranus's atmosphere are hydrogen and helium, similar to the atmospheres of Jupiter and Saturn. However, Uranus also has substantial quantities of water, ammonia, methane, and other hydrocarbons. It is these that give rise to Uranus's liquid core, and also give it its blue hue.

Finding Uranus

Uranus comes to opposition once every 370 days – its synodic period – almost exactly once a year. The date it comes to opposition moves 4–5 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 Uranus comes to opposition, and how well placed it is for observation.

When Uranus 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 Uranus is poorly placed for observation from the northern hemisphere when at opposition in the summer.

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

Because Uranus 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 decades at a time.

The chart below shows the time of year of all of Uranus's oppositions between the years 2000 and 2160, together with the declination that Uranus will have at the time, measured on the vertical axis.

A chart of the time of day when Uranus rises and sets on any given day of the year can be found here . A chart of Uranus'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
10271 1977-076A VOYAGER 2 19 Aug 1977 United States

More »

Other Resources

Share

Follow

Seattle

Latitude:
Longitude:
Timezone:

47.61°N
122.33°W
PDT

Color scheme