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Astronomy 2021: Closer to Home – The Solar System

“Uncle Bob”

Uranus: Blandest Planet?

This month’s planet takes 84 yers to round the Sun, but has a mere 17 hours in its day. Uranus has had but one visit from a spacecraft from Earth, that in 1986. After that scientists assumed that telescopes like the Hubble ST would do the monitoring. Uranus gets its color by reflecting blue/green light. Its atmosphere is 3-4% methane which absorbs red light, as happens on Neptune as well.

Worlds in Comparison

The Blandest Planet? Unlike other planets, Uranus emits no more heat than it receives from the Sun – Jupiter, Saturn, and Neptune have shed much of their heat of formation. Uranus may be trapping its original heat, and one result is a less turbulent upper atmosphere. White ice clouds occasionally rise above the uniformly blue-green surface, but any storms seem to stay below.


Not a Bland Past. Scientists think that an Earth-sized object either struck Uranus or came close enough to spin it like a top and tip it on its side. Its axis tilts 98 degrees.

Bland planet in a Busy and Entertaining Neighborhood. Uranus has 13 dark rings. Five of them were detected blocking sunlight in 1977. The tilt of the planet means that twice in the 84-year orbit, a pole points at the Sun and the rings are face-on.

The number of Uranian moons is 27 and counting. They are named after characters from the plays of William Shakespeare: Miranda, Queen Mab, Puck, Juliet, Desdemona, Cordelia, Ophelia, and Portia, to name a few. Some moons patrol the rings keeping them shipshape with gravitational force as happens with Saturn’s rings. The Uranus moons are densely packed and run the risk of destruction by collision, but not at the hands of jealous husbands, mad princes, poisoned sword tips, or snakes, as happens in plays of the Bard.

Questions for you to look into.

What might become of Uranus’s trapped heat?

What does it mean that an axis is tilted more than 90 degrees?

What might happen if Uranian moons began colliding?

Primary source: Sky & Telescope. December, 2019

We’ll end with the best known tribute to these near twin ice giants: the Uranus and Neptune movements of Gustav Holst’s The Planets. Uranus the Magician has both mysterious and jocular moments. Neptune’s watery world, cliched often in other works, ends with a wordless chorus pointing us outward to, as was believed, the void of endless space. The YouTube presents an amazing restoration of a defining performance led by Holst himself. The tempos are brisk and the fidelity is more than any listener would hope for.


Uranus begins at 31:24; Neptune at 37:25

Next month: Mercury

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