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An “approximately” true color image of Ceres taken by the Dawn spacecraft as it approached the dwarf planet in May, 2015. (credit: NASA)

A team of researchers has used data from the Dawn spacecraft to piece together clues about the interior of the dwarf planet Ceres. The new data indicates that while Ceres, which is the largest body in the asteroid belt, was once warm enough for water to have shifted internally, those temperatures were never high enough for an iron core to separate from the rest of the dwarf planet's interior.

Measuring gravity

The new information comes in part from an estimate of Ceres' moment of inertia, a measure of a body’s resistance to being spun on its axis. A body's moment of inertia depends on two factors. First is the variation of its gravity field over its surface: even though Ceres is roughly spherical, its gravitational strength isn’t uniform. These variations can’t be measured from Earth, though.

The second factor is whether Ceres’ gravity is strong enough to collapse it into a roughly spherical shape, bringing the internal forces into balance with each other. This state is called hydrostatic equilibrium, and it can only be estimated if researchers can determine Ceres’ precise precession rate, which is too small to observe from Earth.

Those controllers don't track themselves. And now, you too can create your own with a free license from Valve Software. (credit: Valve Software)

For now, if you want to play any of the virtual reality games or apps in the SteamVR ecosystem, the only hardware you can use comes from HTC. That may soon change, however. SteamVR creator Valve has opened the floodgates to a new wave of VR peripherals with a surprise Thursday announcement: all licenses for the system's VR tracking interface will be free.

What does this mean? To be clear, this isn't an announcement for new headsets, though SteamVR has always been advertised as a platform that will eventually be open to other VR headset manufacturers. Rather, this is all about virtual reality add-ons.

If a hardware maker wants to create physical objects that will interface with SteamVR—like a pair of gloves, a two-handed shotgun, a piece of fake medical equipment, or whatever else you can imagine—the object in question needs to be tracked by the system's "room-scale" pair of infrared boxes. The HTC Vive's headset and wands play nicely in VR mostly because they're each covered by dozens of IR receiver dots. The headset and wands are spread out in such a way that, no matter how you hold or use them, one of the Vive's two tracking boxes can see enough of the IR dots to translate those physical objects' positions and rotations in 3D space. That's why you see them appear smoothly in a virtual play space. (You can read more on how this all works at Valve's licensing announcement page, which includes peripheral suggestions, such as table-tennis paddles and golf clubs.)

(credit: Iain Watson)

The United States Copyright Office has sided with cable companies in their fight against a Federal Communications Commission plan to boost competition in the TV set-top box market.

The FCC proposal would force pay-TV providers to make channels and on-demand content available to third parties, who could then build their own devices and apps that could replace rented set-top boxes. Comcast and other cable companies complain that this will open the door to copyright violations, and US Register of Copyrights Maria Pallante agrees with them. The Copyright Office provided advice to the FCC at the FCC's request, and Pallante yesterday detailed the concerns her office raised in a letter to members of Congress who asked her to weigh in.

"In its most basic form, the rule contemplated by the FCC would seem to take a valuable good—bundled video programming created through private effort and agreement under the protections of the Copyright Act—and deliver it to third parties who are not in privity with the copyright owners, but who may nevertheless exploit the content for profit," Pallante wrote. "Under the Proposed Rule, this would be accomplished without compensation to the creators or licensees of the copyrighted programming, and without requiring the third party to adhere to agreed-upon license terms."

At Ars Technica Live #4, Hannu Rajaniemi talks to Annalee Newitz and Tiffany Kelly about his double life as a scientist and a science fiction writer. (video link)

Last week at Oakland's legendary Longitude tiki bar, we filmed our fourth episode of Ars Technica Live, with special guest Hannu Rajaniemi. Born in a small town in Finland, Rajaniemi has had a fascinating career at the nexus of science, tech, and science fiction. He earned a degree in physics in Scotland and then founded a research consulting firm that worked with groups like the European Space Agency to solve what Rajaniemi called "math-related problems." And then he got inspired by sci-fi author (and neighbor) Charles Stross to start writing fiction. In 2010, he published the first book in his critically acclaimed Quantum Thief trilogy.

Ars contributor Tiffany Kelly and I asked him about his double career in science and sci-fi. He said it all started with a Jules Verne obsession. He wanted to build a vessel like Captain Nemo's Nautilus, so he decided to become a physicist. At the same time, he became fascinated by role-playing games and LARPing (live-action role-playing), which is treated like an art form in Finland and other Nordic countries. He told us some terrifying tales about gaming and then discussed his transition into a fiction writer and entrepreneur in Scotland. Along the way, he regaled us with stories about how his work in science and fiction have fed into each other in some surprising ways (he once got a gig because the hiring manager had read one of Rajaniemi's novels and wanted to develop some of the sci-fi tech in the book). We asked whether there's any science fiction that he's excited about, and Rajaniemi said he loved the Best American Science Fiction and Fantasy 2015 anthology, edited by John Joseph Adams and Joe Hill (he also liked Hill's new novel, The Fireman). As for TV, he recommended that everyone watch Person of Interest, the recently concluded CBS series about the emergence of AI.

An artists' rendering of an eclipsed Io, lit by its own volcanic activity. (credit: Image Courtesy of Southwest Research Institute)

Jupiter's innermost large moon, Io, is one of the most dramatic bodies in the Solar System. It's the most volcanically active thing we've ever seen, and its surface is spotted with pools of liquid sulfur and punctuated by some of the largest mountains in the Solar System. The Jovian environment bombards it with intense radiation, and the giant planet's magnetic field sweeps away material from Io and sends it on to other moons.

Now, researchers have found evidence that the moon's thin atmosphere has its own dramatic behavior, condensing and collapsing to the surface whenever deprived of sunlight. In making this discovery, we've probably also learned where the atmosphere originated.

The atmosphere of Io doesn't make it the sort of place you'd want to draw a deep breath. For one, it's incredibly thin, so nothing like a deep breath would even be possible. But the kicker is that its major component is sulfur dioxide, which would react with the water in your lungs to form a strong acid.