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16 | NewScientist | 11 May 2013 COME on down to the ultimate demolition derby, a stellar smash-up of epic proportions that may be responsible for a new type of supernova. These bright bursts of radiation are normally the result of the dense core of a dead star blowing up or a gigantic star collapsing in on itself. Shmulik Balberg of the Hebrew University of Jerusalem, Israel, and colleagues say there should be another kind caused by sun-like stars caught in head-on collisions. When a pair of binary stars gets too close to a supermassive black hole, one can be ejected from the galaxy at high speed while the other remains in orbit at around 10,000 kilometres per second – 100 times as fast as our sun circles the Milky Way. Balberg calculates that, eventually, enough speedy First land dwellers kept fish faces THE first four-legged animals colonised land 400 million years ago, but it took them 80 million years to lose their fishy heads. Marcello Ruta of the University of Lincoln, UK, and colleagues examined the lower jaws of 89 tetrapod fossils, dating from 410 to 295 million years ago. During this period, fish fins evolved into limbs, allowing their owners to crawl out of the water onto land. The team found that all the animals had jaws of roughly the same shape. Major changes only started around 320 million years ago, mostly occurring in reptiles (Integrative and Comparative Biology, doi.org/mfd). The animals’ early fish-like jaws were suited to tearing flesh rather than chewing plants. Ruta’s finding supports the theory that reptiles evolved their jaws only after they had mastered breathing using their ribs, allowing them to devote their mouths to chewing. If all painted turtles turn female, it’s curtains MALES don’t stand a chance in a warmer world, if they happen to be painted turtles. A temperature rise of around 1 °C would be enough to turn the entire species female, earmarking them for extinction. Painted turtles (Chrysemys picta), found in lakes and streams across North America, are one of many reptile species whose sex is determined by temperature. Eggs in warm nests are likely to hatch as females, while cooler nests produce males, although no one is sure why. To find out if global warming might skew the sex ratio of hatchlings, Rory Telemeco and his colleagues at Iowa JOEL SARTORE/NGS IN BRIEF When suns collide it’s supernova time stars can build up to ensure an explosive collision (arxiv.org/ abs/1304.7969). The energy released would be equivalent to a small supernova but last just a few days, compared to weeks or months for other supernovae. Astronomers have yet to find one of these, but it should be possible to see up to 10 per year thanks to a new generation of telescopes capable of spotting small changes in bright galactic cores. State University in Ames developed a mathematical model to predict the sex ratio of eggs laid at different temperatures. The model draws on historical records of soil and air temperatures, along with the finding that females can shift their nesting dates by about 10 days. Conservative climate models predict that average temperatures in the US Midwest will rise by 4 °C over the next century. The group’s model suggests that this temperature hike would result in all-female hatchlings, even if the turtles nest earlier, when temperatures are cooler. In fact, average temperatures need only rise by 1.1 °C to have this effect (American Naturalist, doi.org/ mfr). “It’s ultimately extinction,” says Telemeco. Richard Shine at the University of Sydney in Australia hopes the animals will adapt to warmer temperatures. BAD news for bling-lovers: diamond worlds are much rarer than imagined. Material left over from a star’s birth can coalesce into planets. Stars with more oxygen than carbon give rise to rocky planets that are mostly oxygen-bearing silicates, like Earth. Stars with more carbon should make carbon planets, where internal pressure creates a thick layer of diamond. Previous work estimated that a third of all rocky planets might be carbon worlds. But a more detailed look at stellar spectra, by Poul Nissen of Aarhus University in Denmark, says diamond planets are much rarer (arxiv.org/ abs/1303.1726). Instead, there is possibly only one carbon planet for every 1000 silicate worlds. Diamond planets get more precious
