You may have missed… glowing antimicrobial sutures, Neanderthals hunted elephants, ultra-rare binary star system, and ant-infecting fungus

Astronomers uncover one-in-ten-billion binary star system

Astronomers have identified the first example of an incredibly rare type of binary star system that has all the right conditions to eventually trigger a kilonova – an ultra-powerful explosion created by two colliding neutron stars.

“We know that the Milky Way contains at least 100 billion stars and likely hundreds of billions more. This remarkable binary system is essentially a one-in-ten-billion system,” explains Dr André-Nicolas Chené, astronomer at the National Science Foundation (NSF) NOIRLab in the US, and co-author of the study published in Nature.

“Prior to our study, the estimate was that only one or two such systems should exist in a spiral galaxy like the Milky Way.” 

Using the SMARTS 1.5-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, the researchers studied the unusual system known as CPD-29 2176. Located about 11,400 light-years from Earth, it includes a neutron star created by an ultra-stripped supernova and a closely orbiting massive star that is in the process of becoming an ultra-stripped supernova itself.

A computer illustration of the binary star system
This is an artist’s impression of the first confirmed detection of a star system that will one day form a kilonova — the ultra-powerful, gold-producing explosion created by merging neutron stars. These systems are so phenomenally rare that only about 10 such systems are thought to exist in the entire Milky Way. Credit: CTIO/NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani

Ultra-stripping supernovas are the end-of-life explosion of a massive star that has had much of its outer atmosphere stripped away by a companion star it’s orbiting with. This type of supernova doesn’t have as much explosive force as a traditional supernova, which would kick a nearby companion star right out of the binary system.

“The current neutron star would have to form without ejecting its companion from the system. An ultra-stripped supernova is the best explanation for why these companion stars are in such a tight orbit,” says Noel D. Richardson, assistant professor at Embry-Riddle Aeronautical University in the US, and lead author of the paper.

“To create a kilonova, the other star would also need to explode as an ultra-stripped supernova so the two neutron stars could eventually collide and merge.”

Noirlab2303b 850
This infographic illustrates the evolution of the star system CPD-29 2176, the first confirmed kilonova progenitor. Stage 1, two massive blue stars form in a binary star system. Stage 2, the larger of the two stars nears the end of its life. Stage 3, the smaller of the two stars siphons off material from its larger, more mature companion, stripping it of much of its outer atmosphere. Stage 4, the larger star forms an ultra-stripped supernova, the end-of-life explosion of a star with less of a “kick” than a more normal supernova. Stage 5, as currently observed by astronomers, the resulting neutron star from the earlier supernova begins to siphon off material from its companion, turning the tables on the binary pair. Stage 6, with the loss of much of its outer atmosphere, the companion star also undergoes an ultra-stripped supernova. This stage will happen in about one million years. Stage 7, a pair of neutron stars in close mutual orbit now remain where once there were two massive stars. Stage 8, the two neutron stars spiral into toward each other, giving up their orbital energy as faint gravitational radiation. Stage 9, the final stage of this system as both neutron stars collide, producing a powerful kilonova, the cosmic factory of heavy elements in our Universe. Credit: CTIO/NOIRLab/NSF/AURA/P. Marenfeld

New antimicrobial surgical stitches glow in medical imaging

Surgical infections occur in 2-4% of all patients. To help address this problem, a multidisciplinary team including experts in nano-engineering, biomedicine, textiles, and surgery, has designed a new antimicrobial suture material.

The material, which also glows in medical imaging, could be a promising alternative for mesh implants and internal stitches, according to the new study published in OpenNano.

“Our smart surgical sutures can play an important role in preventing infection and monitoring patient recovery, and the proof-of-concept material we’ve developed has several important properties that make it an exciting candidate for this,” says Dr Shadi Houshyar, lead author and senior research fellow at RMIT University’s School of Engineering, Australia.

A ct scan of a piece of chicken with filaments clearly visible throughout the sample
The filament visible in chicken samples, as seen under CT scan. Credit: RMIT

The team designed the material using iodine attached to nanoparticles, called carbon dots, that were incorporated into a biodegradable polyester.

Carbon dots are inherently fluorescent and can be tuned to levels of luminosity that stand out from surrounding tissue in medical imaging. The material, threaded through chicken meat samples, was easily visible in CT scans even three weeks later.

The suture’s antimicrobial properties also killed 99% of highly drug-resistant bacteria after six hours at body temperature.

Next, the team plan to produce larger suture samples to use in pre-clinical trials.

Neanderthals hunted elephants 125,000 years ago

The first indisputable proof that early humans hunted elephants has been published in the journal Science Advances.

Archaeologists studying the world’s largest collection of the remains of European straight-tusked elephants (Palaeoloxodon antiquus) at the Neumark-Nord site near Halle in Germany, have found that Neanderthals deliberately hunted these animals 125,000 years ago.

A woman stands next to a massive reconstruction of a adult male european straight-tusked elephant
Professor Sabine Gaudzinski-Windheuser standing next to a life-size reconstruction of an adult male European straight-tusked elephant (Palaeoloxodon antiquus) in the State Museum of Prehistory in Halle, Germany. Credit: Lutz Kindler, LEIZA

The elephants, which had unusually long and essentially straight tusks, roamed Europe and Western Asia from 800,000 to 100,000 years ago. They were significantly larger than today’s African and Asian elephants and were even bigger than the woolly mammoth – reaching up to 4 metres high and weighing as much 13 tonnes.

Until now, it was unclear whether prehistoric hominins actively hunted these enormous animals, or whether they only scavenged from the carcases of individuals that had died a natural death.

Analysis of lesion distribution across the skeletal remains of the elephants suggests that Neanderthals continuously hunted them in the area over a period of 2,000 years. The findings suggest Neanderthals came together – at least temporarily – in much larger social groups than had been previously assumed.

Neanderthal inflicted incisions on a bone
Deep incisions in the surface of the calcaneus (heel bone) of a male elephant that was around 50 years old at time of death. The incision in the center has a length of some 4 centimeters and is clearly recognizable. Removal of the foot bones provided access to the rich deposits of fat in the foot pads of the elephant. Credit: Wil Roebroeks, Leiden University

Fungus can invade and infect ants by hiding from them

Disease-causing organisms like fungus develop mechanisms to outsmart and evade their hosts’ immune systems. Some social groups, like ants, fight back against these infections with “social immunity” – collective hygiene and health care measures to avoid spreading disease throughout the community.

Now, scientists have shown that fungal pathogens are adapting to overcome these social immunity measures through reducing their natural chemical signals, according to a new study in Nature Ecology & Evolution.

“Fungi infect the ants from the body surface and grow inside, but nestmates groom off many of the spores before they can cause internal infection,” explains Dr Barbara Milutinović, an evolutionary biologist at the Ruđer Bošković Institute in Croatia and co-lead author of the paper.

Argentine ants (Linepithema humile) were infected with pathogenic Metarhizium fungi, either in the absence or presence of caregiving colony members. The team found that, over ten infection cycles, fungi which experienced grooming nestmate ants, boosted their spore production compared to fungi surrounded by only individual ants.

A fungus infected ant carcass next to a live, uninfected ant
The insects get sick when enough fungal spores infect them internally. Metarhizium is dependent on killing its host, so it can then grow out new spores that spread from the carcass. Credit: Matthias Konrad/ISTA

But the researchers were surprised to see that the ants also showed less grooming against the spores, suggesting that they had become more difficult to detect.

“The fungi that adapted to social hosts were perceived less strongly due to a strong reduction of a fungi-specific compound called ergosterol,” explains co-author Professor Thomas Schmitt, a chemical ecologist from the University of Würzburg, Germany.

By exposing the ants to pure fungal ergosterol or a slightly different non-fungal vertebrate equivalent, the researchers showed that only the fungal compound induced intense grooming.

“This demonstrates that fungal pathogens react to the presence of caregiving ants by reducing their characteristic fungal signals. They are no longer recognised as a disease threat and can escape the social immunity of the colony,” says Milutinović.

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