We are halfway through 2021, and many exciting discoveries have happened so far in the regime of scientific research and development. And when it comes to breakthroughs in astronomy and particle physics, June has been a pretty active month. Here are some of the most spectacular scientific events that June has treated us with. For your reference, the links to research papers have been provided below.

Neutron Star – Black Hole merger

For the first time, scientists have caught a glimpse of a colossal merger of a black hole and a neutron star taking place about 900 million light-years away from Earth. As the gravitational waves resulting from the collision of two massive bodies propagate through space-time fabric, they stretch it in one direction and compress it in the other. It is like pulling a rubber band. When we pull it, it gets elongated on one side and squeezes on the other side. The measurement of this distortion with the aid of interferometers helps in the detection of gravitational waves.

In 2015, LIGO reported the first-ever detection of gravitational waves, and since then, researchers have observed dozens of mergers of pairs of black holes and a couple of mergers of pairs of neutron stars. Although a crash between a black hole and neutron star was predicted, it was never observed. Finally, in January 2020, researchers got a glimpse of it by observing the unique ripples in space-time caused by such a collision, and that too not only once but twice.

June 2021 scientific achievements
An illustration depicts the warping of time and space as a black hole is about to swallow a neutron star. (Image: Soheb Mandhai/LIGO India/AP)

Both the observations were made in January 2020,  just 10 days apart, and dubbed as GW200105 and GW200115 for the observed dates.

Although the first observation wasn’t definite, looking at the signature, it was suspected to be an outcome of a merger between a black hole about nine times the mass of the Sun and a neutron star about twice the Sun’s mass. The event took place between 550 million and 1.3 billion light-years away from Earth. 

Another spectacular observation was made by three facilities just ten days later. This time, the merger involved a black hole nearly six times the mass of the Sun, devouring a neutron star about one a half times the Sun’s mass. Moreover, the merger appeared to have taken place between 650 million and 1.5 billion light-years away. 

Although it is the first ever confident observation of gravitational waves emanating from black holes merging with neutron stars, it is still unclear where and how these binary systems formed. So to analyze such mergers in greater detail, twin LIGO detectors, Virgo and KAGRA, are all undergoing preparations for another set of observations scheduled to begin next summer.

The largest spinning structures in the universe

In a major turn of events, observations have revealed that the cosmic filaments, or gigantic tubes made of galaxies, apparently spin and that too at speeds of about 223,700 mph. Although from planets to stars and galaxies, all celestial bodies spin rapidly, when it comes to larger structures, like the giant clusters of galaxies, they often spin very slowly. This made researchers believe that this is where spinning ends on cosmic scales and stability peeps in. But the new research has turned the tables completely.

As a part of the Sloan Digital Sky Survey, scientists examined more than 17,000 filaments. They analyzed the velocity at which the galaxies making up these giant tubes were moving within each tendril. Surprisingly, the movement of these galaxies suggested that they were actually rotating around the central axis of each filament. Although the observations don’t hint at the fact that every single filament in the universe spins, there definitely exist some filaments that are actually spinning.

While looking for probable answers for the cause of spinning for such gigantic structures, one theory proposes that as the powerful gravitational fields of these filaments pulled gas, dust, and other material within, the structures started collapsing inwards. The gravitational collapse further resulted in shearing forces that probably imparted a spin to these magnificent structures.

Still, the exact cause behind the spinning of these giant tendrils of galaxies is not very clear. Scientists are now seeking to understand the origin of spin in filaments through computer simulations.

Betelgeuse’s mysterious dimming explained

In 2019, Betelgeuse mysteriously started dimming. Although it’s a semi-variable star that brightens and darkens over 400 days, it showed unusual behavior in 2019. The red supergiant plummeted to 35% of its brightness, which led many to speculate that the end of the star is near.

However, new research finally found an answer to Betelgeuse’s mysterious dimming, and the culprit is a cloud of gas and dust. While the observations were going on, two ideas were dominant regarding the unexpected dimming. Either there was a large cool spot on the surface of the Betelguese, or maybe, there was a cloud of dust forming right in front of the star as viewed from Earth. Now, the team of researchers working on this mystery has released images explaining the sequence in which the star’s brightness changed, and it seems like we have finally got the answer for the giant’s dimming mystery.

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An artist’s illustration explaining the new research (Image: NASA/ ESA/ E. Wheatley (STScI)/ CfA.)

Surprisingly, the explanation has turned out to be a bit of both the proposed ideas. In the new research, researchers revealed that the star actually got partially concealed by a cloud of dust which eventually led to its dimming. This means that the great dimming did not indicate any sign of an impending supernova. Rather it was a dust cloud playing its part.

Although this revelation has shattered our hopes of witnessing an onrushing stellar explosion, it has laid a basic groundwork for unraveling the properties of a similar population of stars!

A new type of supernova

For the first time, astronomers have observed an example of the third type of supernova known as the electron-capture supernova. Only two types of supernovae were well known to date: the core-collapse supernova and the thermonuclear supernova. The former occurs when an extremely massive star, more than ten times the mass of our Sun, runs out of fuel. As the core reactions shut down, the core starts collapsing into a black hole or neutron star, and the surrounding material rebounds back, leading to a supernova. Coming to the latter one, it occurs when a white dwarf star undergoes an explosion. 

In 1980, the third type of supernova, the electron-capture supernova, was predicted by Ken’ichi Nomoto of the University of Tokyo. It was theorized that as the core runs out of fuel, gravity forces the electrons in the core to move to their atomic nuclei, thereby causing the star to collapse and leading to a completely different type of supernova. It was also predicted that such a supernova should show an unusual stellar chemical spectrum. 

Although the electron capture supernova was there in theory for four decades, it was never observed. However, in 2018, an unusual supernova called 2018zd was observed. It was detected about three hours after the explosion. The images obtained from the Hubble Space Telescope and Spitzer Space Telescope revealed a faint object that was probably the star that underwent an explosion. 

Surprisingly, a spectral analysis of the supernova performed after two years of the explosion has revealed that one of the spectral lines demonstrates that 2018zd was actually an electron capture supernova. This has made supernova 2018zd to be the first one ever observed to belong to the electron-capture category. It is expected that this observation will play a key role in shedding light on some of the mysteries associated with the crab nebula.

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A particle changed into its antiparticle and back again

A charm meson has been observed to change into its antiparticle and back again. This means that this strange subatomic particle can be itself and its antiparticle all at once.

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The charm meson, also known as the D0 meson, precisely consists of a charm quark and an up antiquark, while its antiparticle consists of a charm antiquark and an up quark. Continuous observations and data have revealed that charm meson lives in a state of superposition of being itself and its antiparticle. This superposition results in two particles, one being a heavier one and the other being a lighter version of charm mesons, allowing the particle to oscillate into its antiparticle and back again.

For more than a decade, it was known that charm mesons could travel as a mixture of their particle and antiparticle state. However, for the first time, they have been found to oscillate between the two states.

Measurements have shown that both these particles differ by 1×10-38g in mass. Researchers compared the charm meson particles that decayed after traveling a short distance with those that traveled a little further to measure the mass difference between the two classes of the particles to calculate such a precise value.

Theories suggest that only four types of particles in the Standard Model can turn into their antiparticle.  Until now, the only other one of the four particles that has been seen to oscillate in this way is the strange-beauty meson, the measurement of which was made back in 2006. However, what makes the discovery of oscillation in the charm meson particle so impressive is that, unlike the beauty mesons, the oscillation is very slow in this case. This makes the transition extremely difficult to be measured within the short time of 4×10-13 seconds that the meson takes to decay. Due to this, the majority of the particles decay even before enjoying an oscillation.

This discovery has surely opened up a new door for particle exploration. It can potentially prove to be a major step in solving the mystery of matter-antimatter asymmetry and shed some light on why our Universe is entirely made up of matter, even though matter and antimatter were created in equal amounts after the Big Bang.

Stephen Hawking’s theory proved correct after 40 years

In 1971, Stephen Hawking had given his theorem according to which a black hole couldn’t decrease in size over time. Known as the black hole area theorem, it was based on Einstein’s theory of relativity that defined gravitational waves and black holes and worked on a similar thermodynamic principle according to which entropy cannot decrease over time.

After 40 years, scientists have finally proved Stephen Hawking’s black hole area law by analyzing the gravitational waves produced by two black holes 1.3 billion years ago. These were the first gravitational waves detected in 2015 by LIGO and VIRGO.

Researchers split the gravitational wave data registered by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) into two categories: before and after the merger. Later, they used both the measurements to calculate the black holes’ surface areas in each category. It was found that the total surface area of the combined black hole was greater than the sum of the two smaller black holes, thereby solidifying Hawking’s area law. This confirmation oddly contradicts another crucial theory of Hawking radiations as proposed by the physicist.

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Toshiba set a new record in quantum communication

Engineers at the world-renowned Cambridge Research Laboratory of Toshiba have achieved quantum communications over optical fibers exceeding 600 km in length, thereby setting up a new world record.

While dealing with quantum communication, even tiny fluctuations in temperature or vibrations can make it difficult to transmit quantum information over long distances. The team used a setup that allowed the transmission of two reference signals to deal with these complications. The first signal was used to cancel out fluctuations, while the second one was used to fine adjust the phase. The setup made it possible for the researchers to maintain the optical phase within a fraction of the wavelength even through hundreds of kilometers of optical fiber.

The demonstration of quantum key distribution (QKD) of optical fibers over such long distances is a breakthrough in long-distance quantum communications. It can prove out to be instrumental in quantum–secured information being sent between metropolitan areas. Moreover, the researchers claim that the work represents a significant advancement towards building a future quantum internet.

New missions to Venus

The vigorous conditions of Venus have made it extremely tough for scientists to operate Venusian spacecraft. This is the reason that no NASA mission has been planned for Venus since 1989. But after a dormant period of more than 30 years, NASA is going back to Venus with its two new missions that will be launched in this decade. One of the missions will be an atmospheric probe known as DAVINCI+, while the second one will be an orbiter called VERITAS. Both the missions have been capped at around $500 million.

Davinci+, which is the first of the two selected NASA missions, is actually a descent mission, which means that it includes a descent probe that will be dropped through the atmosphere of Venus. It will take measurements on its way. The descent has been planned to have three stages. The first stage will involve the investigation of the entire atmosphere. The probe will look at the atmosphere’s composition in detail and provide information about each layer as it falls. The second stage will observe lower altitudes, while the last one aims at taking surface images in high resolution.

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Venus (Image: Credits: NASA/JPL-Caltech)

Coming to the second mission, VERITAS is more like a standard planetary orbiter with two instruments on board to map the planet’s surface. The first instrument will investigate the atmospheric and ground composition of Venus. The second instrument onboard VERITAS is a radar that utilizes techniques extensively used in Earth observation satellites. Besides creating a 3D map of Venus’ topography, VERITAS will also look for the rock types and the tectonic or volcanic activity happening there to determine the planet’s geological history.

Since their announcement, both the missions have become the talk of the town. It is expected that these missions will probably help in adding evidence to the theory that the surface of Venus completely melted and reformed 500 million years ago. Moreover, the missions would also shed light on how an Earth-like planet evolved to become such a hostile world. Undoubtedly, many unexpected mysteries are bound to unfold in the coming years.

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