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18 | NewScientist | 19 February 2011 Star-less planets may be habitable LIQUID water may survive on free-floating planets that have no star to warm them. If they also support life, they could act as stepping stones to spread life around the galaxy. Gravitational tussles with other planets or passing stars can eject planets from their solar systems. But even in the cold of space, these wayward worlds could stay warm, thanks to the decay of radioactive elements in their rocky cores. Dorian Abbot and Eric Switzer of the University of Chicago calculate that rocky planets with a similar mass to Earth could remain warm enough to keep water liquid under thick, insulating ice sheets for over a billion years. A planet with the same fraction of water as Earth could keep a subsurface ocean liquid if it was 3.5 times Earth’s mass. But a planet with 10 times Earth’s water concentration could do this if it weighed just one-third as much as Earth, they say (arxiv.org/abs/1102.1108). “It’s a really interesting idea,” says Lisa Kaltenegger of the Harvard-Smithsonian Center for Astrophysics. “But we would have to land on [a planet] and burrow down to see if life is possible.” Black holes put light in a spin LIGHT curls up into corkscrew patterns when it passes near black holes, offering a powerful new way to probe the distorted space around them. In an ordinary light beam observed far from its source, successive peaks of light waves form essentially flat wave fronts. Not so for light with so-called orbital angular momentum, which has long been produced in the lab. Its peaks spiral around to form a corkscrew pattern. According to general relativity, spinning black holes drag the fabric of the surrounding space around with them. Fabrizio Tamburini of the University of Padua in Italy, and colleagues, calculated how light rays emitted by matter spiralling into a black hole are distorted by this effect, called frame dragging. They calculated that it transforms ordinary light into the corkscrew type that possesses orbital angular momentum (Nature Physics, DOI: 10.1038/nphys1907). In future, telescopes could be equipped with detectors to measure this light, says Martin A TINY hole at the end of an optical fibre lets more light through when it is covered. The startling discovery could lead to light-based components for ultrafast optical computers. Conventional optics forbids light from passing through holes much smaller than its wavelength. But plasmons – clouds of oscillating electrons found on the surface of metals – can help light pass through tiny holes in metal foil. For some wavelengths, plasmons grab photons and guide them to the other side. Now a team led by Hiromi Okamoto at the Institute for Molecular Science in Okazaki, Japan, have found another way to pull photons through tiny holes. They shone light down an optical fibre that tapered to a hole too small for the light to squeeze through. But eclipsing the hole with a gold disc caused light to stream through the hole and around the disc (Nano Letters, DOI: 10.1021/ nl103408h). Plasmons from the disc probably leaped up through the hole and dragged out photons, which then gushed around the edge of the disc. A similar set-up could control light signals in optical computers. Blocked hole lets more light through Bojowald of Pennsylvania State University in University Park. Physicists have measured frame dragging around black holes before by observing the rotation of discs of matter around them. But hydrodynamical processes also affect this rotation, making twisted light a more precise way to test relativity’s predictions about frame dragging, says Bojowald. Such light could also be used to measure a black hole’s spin more accurately than inferring it from the behaviour of a surrounding disc, he adds. Hate spiders? Try the ‘invisible’ cure IF YOU break out in a cold sweat at the thought of eight hairy legs, “invisible” images could help. Joel Weinberger at Adelphi University in Garden City, New York, found that exposing people to subliminal spider images helped them to overcome their fear. The usual treatment for phobias is maximum exposure to what you fear. To make things easier, Weinberger’s team asked 23 volunteers who were afraid of spiders to stare at an “x” on a screen as 20 images of spiders or outdoor scenes flashed onto the screen. The images appeared too briefly to be perceived. Following treatment, volunteers shown spider images were able to lift the lid off of a spider tank, while those who saw landscapes could only touch the tank (Consciousness and Cognition, DOI: 10.1016/j. concog.2011.01.003). The team suggest that repeated exposure to frightening stimuli without conscious perception creates non-threatening associations with spiders that override ingrained fear responses within the amygdala, a brain area involved in emotional memory. “It is impressive that such an effect can occur rapidly without the participants’ awareness,” says David Rakison at Carnegie Mellon University in Pittsburgh, Pennsylvania. ARCHIVE PHOTOS/GETTY IMAGES IN BRIEF For new stories every day, visit www.NewScientist.com/news
