A sun-like star seems to have devoured some of its own planetary offspring, prompting researchers to nickname it after the titan Kronos from Greek mythology.

The star HD 240430 is part of a binary system with HD 240429, and the two have now been nicknamed Kronos and Krios. The pair travel through the galaxy side by side some 320 light years from Earth.

They both seem to be about 4 billion years old, suggesting they were born from the same interstellar cloud, and initially shared the same chemical make-up.

But an analysis by at Princeton University and her team suggests the twins have led very different lives. Krios has noticeably smaller concentrations of elements like lithium, magnesium and iron floating in its atmosphere than its companion Kronos does.

In fact, the stars are more chemically different than any pair yet discovered. “I initially thought these two stars must not be in a binary,” says Oh.

Separated after birth

Perhaps they weren’t born together and hooked up later in life. Maybe the cloud they came from endowed them with different concentrations of elements.

But Oh and her team argue that Kronos has devoured several orbiting rocky planets throughout its life. Hence why they are calling the star Kronos, after the titan of Greek mythology who devoured his own children, fearing they would overthrow him.

By contrast, the team refer to HD 240429 as Krios, a rather more anonymous titan who was Kronos’s brother.

Oh’s team calculate that it would take the chemical elements from 15 Earth masses crushed up and scattered throughout Kronos’s roiling atmosphere to explain the star’s blend of excess elements.

“I was really excited when I saw this,” says at the Carnegie Observatories in Pasadena, California, who has looked at similar pairs to see if stars known to host planets have different chemical compositions to those without the hangers-on. “A lot of those signatures were very small,” she said. “This is a huge signature.”

Chowing down

How the star would eat its planets isn’t clear, though. Perhaps another star flew past, disrupting the orbits of outer planets around Kronos, which then distorted the paths of inner worlds and sent them careening into their star.

The Krios system, two light years away, might have escaped unscathed, however.

If this did happen to Kronos, any remaining outer giant planets around it might have stretched-out orbits, suggesting they participated in the same cataclysm that led to the demise of their siblings. To test this, the team has begun looking for giant planets around both Kronos and Krios.

The group hasn’t found any such worlds yet – but the ongoing European Space Agency’s Gaia mission should have good chance of turning them up as it releases more data.

Reference:

Read more: ĚýFlamingo stars turn pink when they gobble iron-rich planets

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Flirting with the limitĚý

Headed towards detonation

Species: scattered primates, including chacma baboons (Papio ursinus) and ring-tailed lemurs (Lemur catta)

Habitat: limestone caverns and cliffs

They’re not afraid of the dark. A group of chacma baboons in South Africa’s De Hoop Nature Reserve and a group of ring-tailed lemurs in Madagascar have been spotted taking shelter and even sleeping in caves – much as early humans used to do.

For the baboons, it started when the group lost their leader. The charismatic alpha male from a neighbouring territory took over – and brought with him a revolutionary idea.

The troop moved to the new alpha’s home range, near the reserve’s Dronkvlei cave. Then they began to disappear at night.

“They started using that area and we could never find them,” says of the University of Lethbridge in Alberta, Canada.

Researchers eventually spotted the one evening, bravely following their new leader to an underground sleeping spot.

Spelunking primates

Some early humans also made use of caves, but although colobus monkeys, langurs, chimps and gorillas have been seen entering caves on occasion, this behaviour seems to be rare in modern primates. We used to think this was because early humans had some unique advantages – their mastery of fire making it easy to light the way, for example.

But the baboons don’t need to light their way to the sleeping spot, some 5 metres down a narrow shaft then across a 40 metre passage in pitch-blackness. Instead, they keep in touch with each other through calls and grunts.

It’s no walk in the park – one newcomer to the group refused to enter the cave for two weeks – and the South African caves are not free of danger. During Henzi’s study a leopard haunted a nearby cavern, and a Cape cobra lived in the cave system.

But ultimately, the benefits may outweigh the risk. The cave offers protection from other predators and the temperatures within stay stable through cold winter nights as well as summer heat waves.

Hide and seek

Another group of primate have also figured out the benefit.

In Madagascar’s Tsimanampetsotsa National Park, from the University of Colorado Boulder was surprised to find the ring-tailed lemurs she studied appear as if by magic in the mornings.

“We heard movement along the limestone face,” she says. “Once the sun came up we realised there were these numerous small caves.”

For these ring-tailed lemurs, small overhangs in the that their predators, cat-like fossa, can’t reach.

The danger in this case it that switching from the trees to the cliff brings lemurs briefly low to the ground, making them vulnerable to fossa. “Getting up and going to bed were clearly the most dangerous periods for them,” Sauther says. “They needed to literally scale this vertical rock face, much like little furry rock climbers.”

Just like us?

To both Henzi and Sauther, continued loyalty to caves shows a behavioural flexibility that may run deeper in our primate lineage than we realised. For animals that need to balance the demands of group living with reliable shelter, caves seem to be worth the risk – even without fire and light.

Henzi thinks such a basic, elemental use for caves might even help explain the recent discovery of hominids in the Dinaledi cavern in South Africa.

H. naledi have been hailed as the newest species of humans: bones belonging to 15 individuals were found deep inside a dark chamber, some 80 metres from the entrance. What was such a big group doing so deep inside a cave?

The authors controversially speculated that the chamber represents a burial site. More recently, some have even .

But judging by the chacma baboons and the ring-tailed lemurs, the explanation might be much simpler. “It seems more parsimonious to argue that they were using the caves because it was a comfortable place to stay,” Henzi says. The jury is still out.

Meanwhile, Sauther’s former student Marni LaFleur continues to study the lemurs – we may not have heard the last word on cave-dwelling primates just yet.

Journal reference: Journal of Human Evolution, DOI: ; Madagascar Conservation and Development, DOI:

Read more: “Prehistoric cinema: A silver screen on the cave wall”

Image credit: Marni LaFleur/bloglafleur.blogspot.co.uk/

Ghostly arcs that haunt the sky may come from an expanding shock-wave shell that is pressing in on our solar system.

Although they are invisible at optical wavelengths, looking at the sky in radio waves, X-rays or gamma rays turns up giant streaks across the heavens. Dubbed “radio loops”, they have .

Previous explanations included the idea that these glowing filaments are the from nearby supernova explosions, or streams of gas that sprout from the Milky Way’s centre and sprawl out on galactic scales.

Now, Matias Vidal and his team at the Jodrell Bank Centre for Astrophysics at the University of Manchester, UK, say new data support a different answer. “The idea is that there’s an expanding shell of gas that was powered by a number of supernova explosions,” he says, and it is now nearing our sun.

The shell, they argue, is the outside edge of a well-known bubble of hydrogen gas whose centre lies about 400 light years from us. The bubble has young, massive stars at its centre.

As this shell expands – powered by supernova blasts and winds from stars inside the bubble &nash; it compresses the magnetic field lines of the galaxy as it ripples through. That squeeze along the bubble’s outer edges boosts the local magnetic field strength, forcing electrons and other charged particles along spiralling paths. These spiralling particles in turn give off electromagnetic radiation with unique, polarised signatures – the glowing radio loops.

The filaments are most pronounced where the growing bubble presses into the galaxy’s ambient dust and gas particles.

Deeper puzzle

Vidal’s team looked at polarised light using NASA’s – which observed the oldest light in the universe between 2001 and 2010. They found five previously undiscovered loops and six that were already known about. These glowing arcs are best explained if they hug the shell of a growing bubble that has our sun at its edge, says Vidal.

“I think they make a good case that this is part of this big local structure,” says theoretical astrophysicist at Princeton University, an expert on WMAP.

The glowing filaments mask a deeper cosmological issue, says Spergel. Earlier this year, the BICEP2 telescope team claimed to see signals from primordial gravitational waves, which would be evidence that the universe went through an exponential growth spurt called inflation in the first moments after the big bang.

But the signal was stymied by foreground emissions from dust inside the Milky Way, which must be carefully accounted for to see the gravitational waves. The radio loops might pose a similar problem for future observations.

That means mapping these filaments and seeing how they vary across radio frequencies is more than just a cool puzzle, Spergel says. “This is one of these cases where one scientist’s annoying foreground is another one’s fascinating, 50-year-old mystery.”

Journal reference: Submitted to Monthly Notices of the Royal Astronomical Society ()