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Daily Current Affairs 20.02.2022 (Night pollinators: how moths help the Himalayas, Pune telescope helps in major breakthrough, Can dark matter be composed, even partly, of black holes?, New observations help explain the universe’s most energetic objects)

Daily Current Affairs 20.02.2022 (Night pollinators: how moths help the Himalayas, Pune telescope helps in major breakthrough, Can dark matter be composed, even partly, of black holes?, New observations help explain the universe’s most energetic objects)

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1. Night pollinators: how moths help the Himalayas

These insects have so far received less scientific attention than bees and butterflies

Moths are vital to pollination in the Himalayan ecosystem of northeast India, reveals a recent study. The study establishes 91 species of moths as potential pollinators of 21 plant families in Sikkim and Arunachal Pradesh in the northeastern Himalayas.

The results assume significance as a majority of the pollination-related studies are based on diurnal pollinators (bees and butterflies) and the role of nocturnal pollinators have so far received less scientific attention.

The details of the study were recently published in Scientific Reports, a publication from the Nature group of journals.

“In the present study about 65% moths (91 species) carried sufficient quantities of pollen grains to be considered as potential pollinators. Teliphasa sp. (Crambidae) and Cuculia sp. (Noctuidae) are found to carry the highest quantity of pollen,” the paper reads.

Navneet Singh, lead author of the study, said that Geometridae (geometer moths) and Erebidae (erebid moths, tiger moths, lichen moths, among others) turned out to be the most important moth families for pollen transportation in the Himalayan region.

“We also found frequent interaction of moths with Betulaceae, Fabaceae, Rosaceae and Ericaceae . Though the Betulaceae is predominantly a wind-pollinated plant family, some recent studies indicate that wind-pollinated plant families also benefit from enhanced dispersal by insects,” Dr. Singh, who is associated with the Zoological Survey of India (ZSI), added.

Mutual benefit

Another interesting outcome of the study is that the moth species Achaea janata (a well-known pest of various economically important plants) was identified as a potential pollinator of three plant families, indicating that moths can provide net benefits as pollinators even when acting as larval herbivores of the same species.

According to Dr. Singh and his fellow authors, the research, which is part of a project funded by the Ministry of Environment, Forest and Climate Change, was among very few large scale studies at a global level where the research team studied the effect of various seasons and different altitudes on the pollination ecology of moths.

The research is based on the field work conducted in the Himalayan terrains, from the foot hills to elevations up to 3,000 m. Along with Navneet Singh, the other contributors to the publication are Rajesh Lenka, Pallab Chatterjee and Dipayan Mitra.

Dhriti Banerjee, Director of ZSI, said that generally moths are considered mysterious denizens of nights, and for a long time they were better known as pest species. “This study revealed the importance of moths in nature. When we are sleeping in our bedrooms, they are tirelessly working for the ecosystems to work, on which our survival is invariably dependent, and are helping in a great way towards food security,” Dr. Banerjee said.

Pollination

Pollination is the transfer of pollen grains from the anther of one flower to the stigma of the same or another flower. It is said to be the first process of sexual fertilization in flowering plants. Pollen grains contain the male gamete and are present in the anthers of the flower.

Types of Pollination

Pollination can be of two types:

  • Self- Pollination
  • Cross-Pollination

 

Self- Pollination

When the pollen is transferred from the anthers of a flower to the stigma of the same flower, it is called as self- pollination. This form of pollination is common in hermaphrodite or dioecious plants which contain both male and female sexual parts on the same flower.

In self-pollinating plants, there is less dependence on the external factors to cause pollination. These plants depend on wind or other smaller insects that visit the flower regularly. In self- pollinating flowers, the anthers, and stigma are of similar lengths to facilitate the transfer of pollen. Self – pollination can be further divided into two types:

  • Autogamy– In this type of self-pollination, the pollen is transferred from the anthers of one flower to the stigma of the same flower.
  • Geitonogamy– In this type of self- pollination, the anthers are transferred from the anthers of one flower to the stigma of another flower but on the same plant.

Advantages of self – pollination

  • In self- pollination, there is no diversity in the genes and therefore the purity of the race is maintained.
  • The plants do not depend on external factors for pollination and even smaller quantities of pollen grains produce have a good success rate in getting pollinated.
  • Self- pollination ensures that recessive characters are eliminated.

Disadvantages of self- pollination

  • Since there is no mixing up of genes, there are no new characters or features that are introduced into the lineage of the offsprings.
  • Self- pollination is said to reduce the vigor and vitality of the race as there are no new features introduced.
  • Without new characters introduced, the resultant offsprings’ immunity to diseases reduces.

Cross-Pollination

In this type of pollination, the pollen is transferred from the anthers of one flower to the stigma of another flower. In this case, the two flowers are genetically different from each other. Cross-pollination is always dependant on another agent to cause the transfer of pollen. The agents of pollination include birds, animals, water, wind, and insects. Based on the agent of pollination, cross-pollination can be of different types:

  • Hydrophilous Flowers-These flowers are pollinated by water means. The flowers are often very small and inconspicuous to other agents. They do not have any fragrance or too much color on their petals. The pollen is adapted to be able to float in water.
  • Zoophilous flowers– In this type of pollination, the pollinating agents are animals like human beings, bats, birds etc. The zoophilous flowers have pollen that is designed to stick on to the body of the animal so that they can be easily carried from one flower to another.
  • Anemophilous flowers– These flowers are pollinated by the agency of wind. These flowers, like zoophilous flowers, are small and inconspicuous. Another important feature of flowers that are wind pollinated is that they are very light so that they are easily carried by the wind. The pollen grains are very light, non-sticky and sometimes winged.
  • Entomophilic flowers– These flowers are pollinated by insects. These flowers are often attractive to look at with bright petals and are fragrant to attract the insect visitors to them. They often have broad stigmas or anthers to allow the insect to perch on it. Many of the insect-pollinated flowers also secrete nectar which attracts bees, butterflies or other similar insects to the flowers. The pollen grains in these flowers are often spiny or have extensions that help them to stick on to the body of the insects.
  • Ornithophilous flowers– These flowers are pollinated by birds. Very few flowers and birds show this form of pollination.

Advantages of cross-pollination

  • Cross-pollination is beneficial to the race of the plant as it introduces new genes into the lineage as a result of the fertilization between genetically different gametes
  • Cross-pollination improves the resistance of the offsprings to diseases and changes in the environment.
  • The seeds produced as a result of cross-pollination are good in vigor and vitality.
  • If there are any recessive characters in the lineage, they are eliminated as a result of genetic recombination.
  • It is the only way unisexual plants can reproduce.

Disadvantages of cross-pollination

  • There is a high wastage of pollen grains that need to be produced to ensure fertilization occurs.
  • There are high chances that the good qualities may get eliminated and unwanted characteristics may get added due to recombination of the genes.

2. Pune telescope helps in major breakthrough

Astronomers of National Centre of Radio Astrophysics (NCRA-TIFR) in Pune and the University of California in the U.S. have used the Giant Metrewave Radio Telescope (GMRT) to map the distribution of atomic hydrogen gas from the host galaxy of a fast radio burst (FRB) for the first time.

Fast radio bursts

Fast radio bursts are extremely bright radio pulses from distant galaxies that last for only a few milliseconds, and though they were first detected fifteen years ago and over a thousand have been found so far, researchers still don’t know what kind of astronomical objects can produce so much energy in so little time.

The exercise has revealed exciting clues about the origin of the burst.

“The GMRT results indicate the FRB host galaxy has undergone a recent merger and that the FRB progenitor is most likely a massive star formed due to this merger event. This is the first case of direct evidence for a recent merger in an FRB host, a major step towards understanding the progenitors of FRBs,” Balpreet Kaur, a PhD student at NCRA-TIFR and the lead author of the study, said.

“Observations of the gas and stars in the vicinity of FRBs and within their host galaxies are critical to understanding how the bursts were formed,” Kaur said, adding that their target FRB (FRB20180916B) produces repeated, very short bursts, and these have been found to arise in the outskirts of a spiral galaxy half a billion light-years away.

She said FRB20180916B is thus one of the closest known FRBs, an ideal candidate to study the local burst environment.

Professor Nissim Kanekar, who is co-author in the research, said GMRT was apt for conducting such studies as one can use different combinations of the 30 GMRT antennas to map the atomic hydrogen within the FRB host galaxy in detail.

This is the first case of direct evidence for a recent merger in an FRB host, they said.

3. Can dark matter be composed, even partly, of black holes?

Most ‘visible’ galaxies are like discs embedded in a dark matter halo that is much larger in size

Astronomical observations suggest that a significant part of the universe is made up of dark matter which interacts with the rest of the universe only through the gravitational pull. Many large lab experiments have tried to detect elementary particles that could be candidates for dark matter. However, such dark matter particles have not been detected until now. So, the question arises – could dark matter be composed, at least partly, of compact objects such as black holes? New research by an international team of scientists, presents a new way of addressing this question. The paper has been accepted for publication in The Astrophysical Journal Letters.

Several astronomical observations suggest that all galaxies are embedded in a “halo” of dark matter. The “visible” galaxy is like a disc embedded in a dark matter halo that is much larger in size. “One hypothesis is that dark matter comprises a large number of compact objects such as primordial black holes,” says P. Ajith from International Centre for Theoretical Sciences, Bengaluru, in an email to The Hindu.

He is the senior author of the paper and an expert on gravitational waves.

Primordial black holes

When the universe was very young, hot and dense – soon after the Big Bang, it must have had quantum fluctuations of its density. This, in turn, would have caused some regions to become extremely dense, and therefore, to collapse under their own gravity to form the primordial black holes.

“While we have no conclusive evidence of spotting these objects, some of the binary black hole mergers detected by the LIGO gravitational wave detectors might be primordial black holes. The question is open,” says Prof. Ajith. From a theoretical standpoint, there is good reason to believe that primordial black holes did form in the young universe.

Gravitational lensing

The paper explores what happens when such objects get in the way of gravitational waves travelling towards the Earth from the distance. They invoke a phenomenon called gravitational lensing that is used regularly in astronomy. When light travels through space and passes near a massive or compact body – a star, a galaxy or a black hole, for example, the intense gravity of that body may attract the light towards it, bending it from its rectilinear (straight line) path.

This phenomenon is known as gravitational lensing and was first observed by Arthur Eddington in 1919. Massive objects like galaxies can bend light significantly, producing multiple images, this is called strong lensing. Lighter objects like stars or black holes bend light less, and this is called microlensing. A similar lensing can happen to gravitational waves travelling towards the Earth, and this would leave signatures in the detected gravitational waves. This can be used to detect the presence, or the existence, of primordial black holes.

Assessing dark matter

Until now, individual black holes have not marked out these signatures on gravitational waves detected by the LIGO-VIRGO detectors. However, if all of the dark matter is made of primordial black holes, they should have produced detectable signatures on the gravitational wave signals. The researchers use the non-observation of the lensing signatures to assess what fraction of the dark matter could be made of black holes.

New avenue

“This provides a new way of constraining the nature of dark matter,” says Prof Ajith. He adds, “Our study concludes that black holes in the mass range from a hundred to a million solar masses can contribute only up to 50-80% of the dark matter in the universe.” This is an upper limit and the actual fraction can be much smaller. “These upper limits will get better and better with more and more observations.”

The work is significant in being the first to use this method, which presents a new avenue for probing dark matter.

What is Dark Matter?

  • Dark matter is a mysterious substance that composes about 27% of the makeup of the universe.
  • It isn’t ordinary atoms – the building blocks of our own bodies and all we see around us.
    • Atoms make up only somewhere around 5% of the universe, according to a cosmological model called the Lambda Cold Dark Matter Model
  • Again, Dark matter isn’t the same thing as dark energy, which makes up some 68% of the universe.
  • Dark matter is invisible; it doesn’t emit, reflect or absorb light or any type of electromagnetic radiation such as X-rays or radio waves.
  • Thus, dark matter is undetectable directly. This is because all our observations of the universe, involve capturing electromagnetic radiation in our telescopes. The exception is detection of gravitational waves.

Properties of Dark Matter

Optically Dark (Dissipationless)

  • Dark matter does not shine. Thus, dark matter particles must have very weak electromagnetic interactions.
  • An important consequence of this is that the dark matter cannot cool by radiating photons, and thus will not collapse to the center of galaxies as the baryons do, by radiating their energy away electromagnetically.
  • In other words, the dark matter is very nearly dissipationless.

4. New observations help explain the universe’s most energetic objects

The study focussed on the supermassive black hole at the centre of galaxy Messier 77

Observations showing a roughly dough-nut-shaped cloud of cosmic dust and gas shrouding a huge black hole at the heart of a galaxy similar in size to our Milky Way are providing scientists with new clarity about the universe’s most energetic objects.

Scientists said on Wednesday that their observations involving the supermassive black hole at the centre of galaxy Messier 77 and its surrounding cloud lend support to predictions made three decades ago about what are called “active galactic nuclei.”

Centres of activity

These are places at the centres of many large galaxies that have tremendous luminosity – sometimes outshining all of a galaxy’s billions of stars combined – and produce the universe’s most energetic outbursts seen since the Big Bang event 13.8 billion years ago. The energy arises from gas violently falling into a supermassive black hole that is surrounded by a cloud of tiny particles of rock and soot along with mostly hydrogen gas.

Black holes are extraordinarily dense objects possessing gravitational pulls so powerful even light cannot escape them. Supermassive black holes, which reside at the centre of many galaxies, including our own, are the largest of them.

Messier 77, also called NGC 1068 or the Squid Galaxy, is located 47 million light years – the distance light travels in a year, 9.5 trillion km – from the Earth in the constellation Cetus. Its supermassive black hole has a mass roughly 10 million times greater than our sun.

Unified model

The observations, using the European Southern Observatory’s Very Large Telescope in Chile’s Atacama Desert, provided strong support for what is called the “unified model” of active galactic nuclei. This model holds that all active galactic nuclei are basically the same but that some appear from the vantage point of Earth to have different properties.

Some look intensely bright because the position of their ring-like cloud does not obscure the gas plummeting into the black hole from our viewing angle. Others look dark because the cloud blocks our view of what is truly happening.

Messier 77’s active galactic nucleus is one of the dark ones, but the new observations indicate that it actually possesses the same qualities as the bright ones.

Strong attraction

“The dust and gas in these clouds are probably blown out of the atmospheres of stars at a larger distance – hundreds of light years – from the black hole, and are falling in towards the centre under the influence of the black hole gravity,” said Violeta Gamez Rosas, an astronomy doctoral student at Leiden University in the Netherlands and lead author of the research published in the journal Nature.

“Some clouds spiral in towards the black hole while others are pushed up into a ‘fountain’ that falls back onto the galaxy. Because of the dust, it is very difficult to see with telescopes what is going on in this region, but it is easier at infrared wavelengths than at normal visible wavelengths because the dust does not absorb infrared light as much,” said study co-author Walter Jaffe, a Leiden University astronomy professor.

The Milky Way’s supermassive black hole, which has a mass 4 million times greater than the Sun, is currently “fairly quiet,” Gamez Rosas said, but previously may have been more active like Messier 77’s.

Gamez Rosas expressed satisfaction at studying active galactic nuclei.

“A lot of it is pure fascination with explosions on such gigantic scales, and the challenge of trying to explain them with what we think we know about physics,” Gamez Rosas said.

“There is also the challenge of trying to build and operate telescopes to make these images of things so far away,” Gamez Rosas added. “And there is the peace of mind that results from the knowledge that there is a large, complex, varied universe that goes its own way whatever we do on Earth.”

Black Hole

  • It refers to a point in space where the matter is so compressed as to create a gravity field from which even light cannot escape.
  • The concept was theorized by Albert Einstein in 1915 and the term ‘black hole’ was coined in the mid-1960s by American physicist John Archibald Wheeler.
  • Usually, the black holes belong to two categories:

    • One category ranges between a few solar masses and tens of solar masses. These are thought to form when massive stars die.
    • The other category is of supermassive black holes. These range from hundreds of thousands to billions of times that of the sun from the Solar system to which Earth belongs.
  • In April 2019, the scientists at the Event Horizon Telescope Project released the first-ever image of a Black Hole (more precisely, of its shadow).
  • Gravitational waves are created when two black holes orbit each other and merge.
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