16 | NewScientist | 31 August 2013

FORGET supernovae. Something more exotic and elusive may have been spotted – quark-novae.

When a very massive star runs out of fuel, it can explode in a supernova. The blast sometimes leaves a dense stellar remnant made mostly of neutrons.

But neutrons are made of even smaller particles called quarks. In theory, the core of a neutron star can get dense enough to undergo

an additional explosive transition to create a star made mostly of quarks. Such an object would offer clues to how matter behaves at extremely high densities.

Rachid Ouyed of the University of Calgary in Alberta, Canada, and colleagues say the best evidence yet for quark stars lies with blasts called SN 2009ip and SN 2010mc. Both had two brightness peaks, unusual for supernovae.

Cannonball planet has 4-hour year

AN IRON planet orbiting a sun-like star has the shortest known year: 4 hours, 15 minutes.

Found by NASA’s Kepler space telescope, KOI 1843.03 is so close to its star that one side is probably locked facing the star and feels more of its gravitational pull. This would create tidal forces that squash and stretch the planet.

To withstand the star’s wrath, the planet must be at least 70 per cent iron, says Roberto Sanchis-Ojeda, a graduate student at the Massachusetts Institute of Technology (Astrophysical Journal Letters, doi.org/njr).

It’s a puzzle how such closely orbiting planets form, says Dimitar Sasselov of Harvard University, who was not involved in the work. They could have been born as more distant rocky worlds that migrated inwards. Or they could be the cores of massive planets whose outer layers have been blasted away by stellar radiation.

Acid ocean plants will accelerate global warming

WHAT goes around comes around. Our greenhouse gas emissions don’t just warm the planet, they also acidify the oceans. Now it turns out that the change in ocean chemistry they cause will feed back into the climate, further driving up temperatures.

This wasn’t always thought to be true. Climatologists consider the carbon dioxide that is absorbed by the ocean to be stored – and unable to affect the climate. But a study now suggests that the acidification it causes will rebound on the entire planet, by acting on tiny marine plants called phytoplankton . These produce a chemical

ESA

IN BRIEF

Double bangs may be quark star births Intriguingly, SN 2009ip was labelled a supernova imposter because it flared up periodically, before finally exploding in a double-peaked burst.

Ouyed and colleagues instead think the first peak in both events was a normal supernova (arxiv.org/abs/1308.3927v1). The blasts left massive, rapidly spinning neutron stars, which, as their spin slowed, got so dense that their neutrons became quarks, triggering quark-novae.

called dimethyl sulphide (DMS) that drifts up into the air and reflects sunlight back into space, cooling the planet.

Katharina Six of the Max Planck Institute for Meteorology in Hamburg, Germany, and her team gathered experimental data showing that phytoplankton produce less DMS as seawater becomes less alkaline. After feeding these figures into climate models, they estimate that 18 per cent less DMS will be released from the oceans in 2100, compared to pre-industrial times (Nature Climate Change, DOI: 10.1038/NCLIMATE1981).

If the concentration of CO2 in the atmosphere doubles – which is likely to happen later this century – temperatures are expected to rise between 2 and 4.5 °C. Ocean acidification will add between 0.23 and 0.48 °C to that figure, Six estimates.

EYE and hair colour are traits we inherit from our parents. Snail embryos can add the timing of developmental leaps to their list.

Oliver Tills of Plymouth University, UK, and colleagues tracked the time hermaphroditic pond snails (Radix balthica) took to reach 12 developmental milestones, and compared the timings with those of their parent. For two events – attaching the foot to the wall of the egg, and then crawling along this surface – the timings matched closely enough to be inherited (Proceedings of the Royal Society B, doi.org/njs).

Variations in developmental speed within a species are thought to be a key aspect to some individuals splitting off to form new species.

Embryonic snails offer evolution clue

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