Massive black hole devours star

16 June 2011 Last updated at 20:58 GMT By Jennifer Carpenter Science reporter, BBC News Infalling star shown in an artist's conception; 10% of its mass is turned into energy and radiated as X-rays Astronomers have spied a star's swan song as it is shredded by a black hole.

Researchers suspect that the star wandered too close to the black hole and got sucked in by the huge gravitational forces.

The star's final moments sent a flash of radiation hurtling towards Earth.

The energy burst is still visible by telescope more than two-and-a-half months later, the researchers report in the journal Science.

The Swift spacecraft constantly scans the skies for bursts of radiation, notifying astronomers when it locates a potential flare.

These bursts usually indicate the implosion of an ageing star, which produces a single, quick blast of energy.

But this event, first spotted on 28 March 2011 and designated Sw 1644+57, does not have the marks of an imploding sun.

What intrigued the researchers about this gamma ray burst is that it flared up four times over a period of four hours.

Astrophysicist Dr Andrew Levan from the University of Warwick, and his colleagues suspected that they were looking at a very different sort of galactic event; one where a passing star got sucked into a black hole.

The energy bursts matched nicely with what you might expect when you "throw a star into a black hole", Dr Levan told BBC News.

Gasless centres

Black holes are thought to reside at the centres of most major galaxies. Some black holes are surrounded by matter in the form of gas; light is emitted when the gas is dragged into the hole. However, the centres of most galaxies are devoid of gas and so are invisible from Earth.

These black holes only become visible when an object such as a star is pulled in. If this happens, the star becomes elongated, first spreading out to form a "banana shape" before its inner edge - orbiting faster than the outer edge - pulls the star into a disc-shape that wraps itself around the hole.

As material drops into the black hole it becomes compressed and releases radiation that is usually visible from Earth for a month or so.

Events like these, termed mini-quasars, are incredibly rare - researchers expect one every hundred million years in any one galaxy.

The researchers used some of most powerful ground-based and space-based observatories - the Hubble Space Telescope, the Chandra X-ray Observatory and the Gemini and Keck Telescopes.

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Giant insect devours baby turtle

26 May 2011 Last updated at 09:17 By Ella Davies Reporter, BBC Nature Role reversal: insects prey upon reptiles A giant water bug has been photographed eating a juvenile turtle in an unusual predatory role reversal.

Large bugs in the Lethocerinae family have been known to prey upon small vertebrates including fish and frogs.

But unlike insects that often fall prey to reptiles, scientists have observed one particular species of bug eating snakes and a turtle.

Dr Shin-ya Ohba recorded the unusual behaviour during night sampling in western Hyogo, central Japan.

Writing in the journal Entomological Science, Dr Ohba describes observing a Kirkaldyia deyrolli eating a Reeve's pond turtle in a ditch next to a rice field.

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These bugs are also known as "giant fish killers" for their carnivorous tastes

Their attraction to artificial lights at night has also earned them the title "electric-light bugs"

Americans also refer to them as "toe-biters" because they have been known to bite unsuspecting swimmers

Using its front legs the giant water bug gripped the turtle, inserting its syringe-like rostrum into the prey's neck in order to feed.

The giant water bugs are known to only attack moving prey, so it is likely that the 58mm insect captured and killed the young turtle before feeding on it.

Dr Ohba has also photographed giant water bugs eating snakes in the past.

"Everyone thinks that Lethocerinae bugs live on fishes and frogs. Although eating a turtle and snake are rare in the natural condition, [this evidence] surprises naturalists [by showing] voracious feeding habits," said Dr Ohba.

He suggests that these observations of bugs predating reptiles call into question previously held opinions about predator-prey dynamics in freshwater habitats.

K. deyrolli are native to Japan where they have been found living in rice fields, feeding primarily on small fish and frogs.

The species is listed as endangered by the Japanese Environment Agency following serious declines over the last forty years, reportedly due to habitat loss and water pollution.

A giant water bug successfully takes on a snake

Giant water bugs are the largest of the true bugs (Hemiptera) and members of the sub-family Lethocerinae are found in freshwater ponds, lakes and slow-moving streams and rivers across North America, South America and East Asia.

Lethocerus species can grow up to 15cm long, are nocturnal and can fly, relying on the light of the full moon to migrate.

They possess a venomous bite which they use to subdue prey and are occasionally known to bite humans, resulting in a burning pain that can last several hours.

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