Titanic slice

Bad Astronomy
The entire universe in blog form
June 28 2011 11:00 AM

Titanic slice

A quirk of physics can lead to some real drama. Two quirks of physics can lead to very dramatic pictures.

"Why Phil, what could you possibly mean?", I hear you thinking*.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


This is what I mean: Saturn's moon Titan, sliced in twain by the planet's rings:

[Click to enchronosenate.]

Due to a quirk of physics (aha!) all the moons and rings of Saturn orbit the big planet in the same plane. There are two reasons for this: one is that they almost all formed out of the same disk of material orbiting the Sun. As the pieces clumped together, they naturally all stuck to the same plane. A second reason is that any object that tries to stray out of that plane (or that gets captured by Saturn like some of its bizarre outer moons) feels a torque on it, forcing it back down. That torque is provided by Saturn itself, which has tides that tend to circularize and flatten all the orbits of the moons, confining them to the planet's equatorial plane. The physics of this is a little hairy, but I do have a simplified explanation using the Earth and Moon as an example.

The Cassini spacecraft orbits Saturn, but it has rockets on board that can push it around into any orbit the engineers and scientists back home want. That usually means a tilted path, plunging it through the equatorial plane twice each orbit. When it is precisely in that plane it sees the rings edge-on, and if the geometry is right it can spot one or more moons.

In this case, the gigantic moon Titan was in its sights, and the angle was such that the rings slice right across it.

Titan is so big it has a substantial atmosphere, murky and thick, which hides its surface. So why do we see details on the moon in this picture?

Due to a second quirk of physics (aha aha) infrared light can penetrate Titan's soupy air. Different surface features (like lakes of liquid methane and ethane!) emit and reflect different amounts of IR light, and that goes up through the clouds and into Cassini's detectors, which were cleverly designed to detect that specific wavelength of light.

And that, you see, is how some nifty physics can provide you with a very dramatic picture. Well, that and a few hundred million dollars, a team of very smart people, and a decade or two to design, build, and get your spacecraft to its target.

... which, again, involves an awful lot of physics. So really, if you want to see just how spectacular and awesome the universe is, science is the way to go. We deliver.

Image credit: Credit: NASA/JPL/Space Science Institute

* All professional bloggers can read minds. It's how we know exactly what to say to tick off the largest fraction of our readers.

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