Uranian moons in new light

More than 230 years ago astronomer William Herschel discovered the planet Uranus and two of its moons. Using the Herschel Space Observatory, a group of astronomers led by Örs H. Detre of the Max Planck Institute for Astronomy now has succeeded in determining physical properties of the five main moons of Uranus.

The measured infrared radiation, which is generated by the Sun heating their surfaces, suggests that these moons resemble dwarf planets like Pluto. The team developed a new analysis technique that extracted the faint signals from the moons next to Uranus, which is more than a thousand times brighter.

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Credit: T. Müller (HdA)/Ö. H. Detre et al./MPIA

The images show the position of the five largest Uranian moons and their orbits around Uranus on 12 July 2011 as seen by Herschel. Left: Calculated positions and orbits of the moons.

The left side of the orbital plane is pointing towards us. The size of the objects is not shown to scale.

Right: False-colour map of the infrared brightness at a wavelength of 70 µm after removal of the signal from the planet Uranus, measured with the PACS instrument of the Herschel Space Observatory.

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Credit: NASA/JPL/MPIA

Images of the five largest Uranian moons Miranda, Ariel, Umbriel, Titania and Oberon. The space probe Voyager 2 took these images during a fly-by on 24 January 1986.

The diameters of the moons are shown to scale.

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Credit: Ö. H. Detre et al./MPIA

These images explain how the Uranian moons were extracted from the data.

Left: The original image contains the infrared signals from Uranus and its five main moons, measured at a wavelength of 70 µm. Uranus is several thousand times brighter than a single moon. Its image is dominated by artifacts due to interference from the telescope and the camera. Titania and Oberon are barely visible.

Center: Using these data, a sophisticated procedure created a model for the brightness distribution of Uranus alone. This is subtracted from the original image.

Right: Finally, the signals of the moons remain after the subtraction. At the location of Uranus the not quite perfect extraction method slightly affects the result.

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1.8 billion miles away, you can find the mysteriously ugly moon, Miranda.

But what would it be like to stand on the surface of Miranda?

Uranus Moon Miranda

Miranda is about 500 km in diameter, and only one-seventh as large as Earth's moon.

Its weird shape makes it one of the most interesting moons in the Solar System.