Miss The Evening Planets? Cheer Up With A Visit To Uranus

The Great Square stands high in the southern sky around 6-7 p.m. local time in early to mid-December. Once you find the Square, reach your fist to the sky and mark off about two fists to the left of Pegasus to arrive at Aries. Then use the “finger” of Aries to point to Omicron Piscium. Once you’ve got Omicron in binoculars, use the detailed map below to pinpoint Uranus. Stellarium

Planets are scarce these nights. Look around the late fall sky and you won’t find a single one. At least not without optical aid. Only Uranus and Neptune swim among the evening stars. Venus, Saturn and Mercury are currently too close to the sun and swamped in its glare, and Jupiter and Mars shine low in the eastern sky at dawn.

Because most of us like watching bright planets with naked eye and telescope, we sometimes forget to look at the dimmer ones, Neptune and Uranus. Neptune is the fainter, about magnitude 8, and requires fairly dark skies and a pair of 50mm binoculars to spot. Currently located just south of the naked eye star Lambda (λ) Aquarii and well-placed at nightfall in Aquarius, you can use the maps in this earlier Sky & Telescope article to find it. Thanks to Lambda, it’s super-easy to locate.

You’ll see a view something like this in binoculars. Once you’ve got Omicron, you’re good to go for Uranus. The planet will nearly stay put for the remainder of December, moving only a very small amount to the right by month’s end. Stellarium

Uranus stands higher in the southern sky not far from one of fall’s most prominent asterisms, the Great Square, a part of the sprawling constellation Pegasus the Winged Horse. Uranus is out in the “weeds” as far as having any bright stars around to help. But we can use the Great Square to take us the the “bent finger” of Aries, a small constellation just a little more than two fists to the left (east) of the Square. Exactly one fist (10°) below the fingertip, you’ll find the star Omicron (ο) Piscium in neighboring Pisces the Fish.

OK, we’re getting close. The planet Uranus lies just 3° to the right (west) of Omicron. All you have to do is point your binoculars at Omicron and then use the binocular-view map for an easy star-hop to the planet. Omicron and neighboring Nu (ν) and Mu (μ) Piscium will be the three brightest stars in view. Several other stars are near Uranus, but they’re fainter than the planet, which helps to secure its identity. Uranus shines at magnitude +5.7 (just above the naked eye limit and visible with the naked eye from a dark sky), while the stars are all around magnitude 6.5.

Uranus, Earth and moon compared. Uranus has an atmosphere of hydrogen and helium with clouds of ammonia and methane. Methane absorbs red light and reflects blue, giving the planet its characteristic color. The white dot over Uranus is the moon Ariel casting a shadow on the cloud deck below. NASA/ESA/L.Sromovsky

Uranus in binoculars looks exactly like a star, but a small telescope magnifying around 60x or higher will clearly show a tiny, bluish-green disk. The remote planet is currently 1.8 billion miles (2.9 billion km) from the Earth. Traveling at the speed of a transcontinental jet, it would take more about 370 years to get there. But when you combine looking at the planet with a bit of knowledge and imagination, you can arrive in seconds.

Uranus and its moons – moving counterclockwise as seen from the planet’s north pole – photographed by the Hubble Space Telescope. Also pictured are its faint rings. NASA/ESA

First off, Uranus is bitter cold and perpetually cloudy, not unlike Duluth, Minn. lately. Winds of up to 560 mph (900 kph) screech across its hydrogen and helium atmosphere. Four times the size of Earth, beneath its cloudy exterior Uranus percolates with a mix of water, methane and ammonia ices under tremendous pressure. There’s no place anywhere to land a spaceship; the best we might do is settle down on one of its 27 known moons or put a satellite in orbit about the blue planet. All the Uranian moons are about a 50/50 mix of rock and ice and range in size from teeny Trinculo at just 6.2 miles (10 km) across to Titania at 980 miles (1,578 km), about three-quarters the size of our own moon. Observers with 10-inch or larger telescopes can track its two brightest moons, Titania and Oberon, by clicking here.

The five largest moons of Uranus with their relative sizes shown. NASA/JPL-Sen

The oddest thing about the planet is that it rotates sideways instead of more up and down like the Earth and other planets. Astronomers speculate that the Uranus received a powerful sideways blow from a giant impactor long ago that literally knocked it over on its side. At least 13 rings encircle the planet, adding to its unique qualities. They likely formed from the remains of long-ago, colliding moons.

Only after 84 years would a hypothetical Uranian citizen be able to celebrate their 1st birthday. Uranus rotates on its side with each of its four seasons lasting 21 years. It will be fall in the planet’s northern hemisphere until the 2028 winter solstice. Nature of the Universe with additions by the author

Uranus spins once about every 17 hours and circles the sun with a period of 84 years, about equal to the average human lifetime. I’m hoping to live to celebrate my first Uranian birthday. You gotta have goals, right?

2 Responses

  1. Edward M. Boll

    I occasionaly consider Uranyus, but have not done it lately, since Jupiter is now visible in a dark sky.

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