Monday, 27 June, 2022
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When fish do the ‘wave’ to keep predators at bay & bird-like dinosaurs from 100 mn years ago

ScientiFix, our weekly feature, offers you a summary of the top global science stories of the week, with links to their sources.

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New Delhi: Much like spectators in stadiums sometimes simulate a wave, as successive groups stand up in unison to yell with arms in the air, researchers from the Leibniz-Institute of Freshwater Ecology and Inland Fisheries in Germany have shown that a species of small freshwater fish, known as sulphur mollies, do a similar thing — to protect themselves from predatory birds.

The collective wave action produced by hundreds of thousands of fish working together came as a surprise to the researchers.

There are up to 4,000 fish per square metre and sometimes hundreds of thousands of fish participate in a single fish wave. Fish can repeat these waves for up to two minutes, with one wave approximately every three to four seconds.

When someone is in the vicinity of these unusual fish, found in sulphuric springs that are toxic to most fish, this behavior is hard to miss.

That is because the mollies do the same thing in response to a human presence nearby.

The researchers found that experimentally induced fish waves also doubled the time birds waited until their next attack to substantially reduce their attack frequency.

For one of their bird predators, capture probability decreased with wave number. Birds also switched perches in response to wave displays more often, suggesting that they’d decided to direct their attacks elsewhere. Read more.

Matterhorn sways every two seconds

In a new study this week, researchers from ETH Zurich  found that the Matterhorn — a massive mountain that has towered over the landscape between Switzerland and Italy — is constantly in motion, swaying gently back and forth about once every two seconds.

This subtle vibration with normally imperceptible amplitudes is stimulated by seismic energy in the Earth originating from the world’s oceans, earthquakes, as well as human activity.

Every object vibrates at certain frequencies when an external energy is applied to it, like a tuning fork or the strings of a guitar. These so-called natural frequencies depend primarily on the geometry of the object and its material properties.

The phenomenon is also observed in bridges, high-rise buildings, and now even mountains. The team wanted to know whether such resonant vibrations can also be detected on a large mountain like the Matterhorn.

For the study, scientists installed several seismometers on the Matterhorn, including one directly on the summit, at 4,470 meters above sea level, and another in the Solvay bivouac, an emergency shelter on the northeast ridge.

Another measuring station at the foot of the mountain served as a reference.

The seismometers recorded all movements of the mountain at high resolution, from which the team could derive the frequency and direction of resonance.

The measurements show that the Matterhorn oscillates roughly in a north-south direction at a frequency of 0.42 Hertz, and in an east-west direction at a second with similar frequency.

In turn, by speeding up these ambient vibration measurements 80 times, the team was able to make the vibration landscape of the Matterhorn audible to the human ear, translating the resonant frequencies into audible tones. Read more.

Also read: New mineral from deep inside Earth found trapped in a diamond

Scientists capture a blackhole eruption

In a first, scientists from International Centre for Radio Astronomy Research in Australia have captured the image of radio emissions to the Earth from the nearest actively-feeding supermassive black hole. The emission is powered by a central black hole in the galaxy Centaurus A, about 12 million light years away.

As the black hole feeds on in-falling gas, it ejects material at near light-speed, causing “radio bubbles” to grow over hundreds of millions of years.

When viewed from Earth, the eruption from Centaurus A now extends eight degrees across the sky — the length of 16 full Moons laid side by side.

It was captured using the Murchison Widefield Array (MWA) telescope in outback Western Australia. Read more.

Magnetic field of exoplanet detected for the first time

Researchers from the University of Arizona have for the first time identified evidence of a magnetic field surrounding a planet outside of our solar system. Since the Earth’s magnetic field acts as a shield against energetic particles from the sun known as the solar wind, magnetic fields could play similar roles on other planets.

Astronomers used data from the Hubble Space Telescope to discover the signature of a magnetic field in a planet outside our solar system. The finding marks the first time such a feature has been seen on an exoplanet (a planet outside the solar system).

A magnetic field best explains the observations of an extended region of charged carbon particles that surround the planet and stream away from it in a long tail.

Magnetic fields play a crucial role in protecting planetary atmospheres, so the ability to detect the magnetic fields of exoplanets is a significant step toward better understanding what these alien worlds may look like.

The team used Hubble to observe the exoplanet HAT-P-11b, a Neptune-sized planet that is 123 light-years away from Earth and pass directly across the face of its host star six times, in what is known as a “transit.”

The observations were made in the ultraviolet light spectrum, which is just beyond what the human eye can see.

Hubble detected carbon ions, which are charged particles that interact with magnetic fields, surrounding the planet in what is known as a magnetosphere.

A magnetosphere is a region around a celestial object — such as Earth — that is formed by the object’s interaction with the solar wind emitted by its host star.

The discovery of HAT-P-11b’s magnetosphere is a significant step toward an improved understanding of the habitability of an exoplanet. Not all planets and moons in our solar system have their own magnetic fields, and the connection between magnetic fields and a planet’s habitability still needs more study, according to the researchers. Read more.

Also read: All corals reefs of western Indian Ocean could collapse in next 50 years, study warns

New bird-like dinosaur species dates back over 100 mn years

Scientists from the University of Bath have discovered a new species of bird-like dinosaur that used brute strength to overcome its prey, dating back to over 100 million years ago.

The new animal has been named Vectiraptor greeni after local collector Mick Green, who discovered its bones after they became washed from the rocks on the south coast of the Isle of Wight.

It was an older, more heavily built, relative of the predator Velociraptor. The fearsome animal was about the size of a wolf, around 3 meters long from nose to tail, and would have used huge slashing talons on its feet to dispatch its prey.

Its finely serrated teeth were then used to bite off pieces of the kill.

The dinosaur would have prowled through the forests that covered the land in the Early Cretaceous, 125 million years ago. It died and lay buried until 2004, when storms and waves eroded away the rocks that had kept its bones hidden.

Yet another 20 years passed before scientists from the Universities of Bath and Portsmouth studied the fossils and made the surprising find that the bones represented a new species.

Vectiraptor belonged to a group of dinosaurs called dromaeosaurs, or raptors. These bird-like dinosaurs were specialist hunters and, like their modern-day avian relatives, were covered in long feathers. Their jaws were full of blade-like, serrated teeth and they had huge scythe-shaped claws on their feet, which they used to slash at their prey, causing it to rapidly bleed to death. Read more.

(Edited by Poulomi Banerjee)

Also read: Found in Australia — a ‘true’ millipede with more than 1,000 legs


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