As the month comes to an end, it’s time to look at some of the most remarkable scientific achievements in March 2021. I would call March 2021 the ‘Month of Particle Physics.’ From discovering four new particles to signs of a hidden force in nature, March was full of exciting updates from the quantum world. So here are the top discoveries in physics and astronomy. I have also provided links to research papers for your reference.
Scientific achievements in March 2021
Four new particles
Particle physicists at CERN found four new particles, expanding our knowledge of the quantum universe. All four particles are tetraquarks. In physics, quarks are the smallest particles known to exist. Molecules are made up of atoms; atoms are made up of electrons and the nucleus; the nucleus is further composed of protons and neutrons; and finally, protons and neutrons are made up of quarks. There are six quarks according to the Standard Model: up, down, top, bottom, strange, and charm.
All the four new tetraquarks contain a pair of charm quarks and two other quarks. The discovery of these new particles is crucial for the ultimate goal of the LHC. Currently, the theory that explains the constituents of matter is the Standard Model. The model was completed when the last missing piece of the puzzle, the Higgs boson, was discovered in 2012. However, the theory is not the final word on the understanding of the particles.
About 95% of the universe is composed of dark matter, and dark energy, and the standard model of physics has no description of this unknown universe. The discovery, like any good one in science, has raised a few important questions. Why does the universe allow a combination of specific quarks only? Why all the tetraquarks, except one, contain a pair of charm quarks? And why are there no corresponding particles with strange-quark pairs? These questions have no explanation at the moment.
The secondary atmosphere on an exoplanet
Astronomers found a strange phenomenon happening on Gliese 1132b, a rocky exoplanet about 39 light years (234 trillion miles) away in Vela. The planet lies so close to its parent star that it takes a mere 1.6 days to go around it. Scientists believe that the planet started as a Neptune-sized gas giant with a thick atmosphere. The star’s intense radiation stripped away the planet’s primordial hydrogen and helium atmosphere. The planet did not have enough gravity to hold its atmosphere in such harsh conditions and because of that, Gliese 1132 b was reduced to a bare core about the Earth’s size.
But when the Hubble Space Telescope was pointed at it, scientists found something strange. The new observations show that the planet has developed a secondary atmosphere rich in hydrogen, hydrogen cyanide, methane, and ammonia. If the planet lost its atmosphere in the first place, from where did the new one come?
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Astronomers have theorized that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. Hence, this second atmosphere is directly coming from the interior of the planet. But it is believed that its crust is fragile, going just a few hundred meters below. Such a soft crust probably cannot hold up to the weight of mountainous volcanoes, and hence the surface of the Gliese 1132 b is reasonably like a cracked eggshell.
The upcoming James Webb Space Telescope can detect hot areas of volcanic activity on the planet. This discovery will help us improve our theories about the formation and evolution of planets. A paper on the findings will be published in the Astronomical Journal.
Exciting new results from the LHCb (Large Hadron Collider beauty) experiment at CERN showed signs of a possible hidden force in nature. While studying the decay of the B mesons (a hadron containing a beauty quark), scientists found an anomaly. According to the Standard Model of Physics, this composite particle’s decay must produce electrons and muons (another elementary particle similar to the electron but 200 times heavier) with equal probabilities. This is known as the law of lepton universality.
However, observations show that nature favors the decay channel that creates electrons more than the one that creates muons. A hidden force, unknown to us, might be hindering the decay of the B mesons into muons. Although it’s one of the most exciting scientific achievements in March 2021, there’s a 1 in 1000 probability that this observation is a statistical fluctuation. In particle physics, we can only be sure about it if the probability goes down to 1 in 3.4 million. Read this article for a simple and detailed explanation of this anomaly.
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Smallest gravitational field
When Newton formulated his theory of gravity, he thought this force is reserved for astronomical objects. Years later, Henry Cavendish demonstrated that even objects on Earth can produce gravitational effects. In the past couple of centuries, the Cavendish experiment has been greatly refined.
Now, scientists from Austria have measured gravity at the smallest scale to date. In their miniature version of the experiment, the team’s gravitational source is a nearly spherical gold mass with a radius of 1.07 mm and a mass of 92.1 mg. A similarly sized gold sphere acts as a test mass of 90.7 mg. The team moved the gold spheres back and forth, creating a varying gravitational field, causing the torsion pendulum to oscillate at that particular excitation frequency.
The experiment was conducted in a high vacuum to prevent interference by gas molecules. Pedestrians around the lab and tram traffic were a source of seismic disturbances, and hence the team got the best results at night and around the Christmas holidays when there was little traffic. The team published their results in the journal Nature.
New photo of the black hole
In 2019, the first black hole image rocked the scientific world. It was one of the most significant scientific achievements of the previous decade. Following the mind-boggling release of the first image ever captured of a black hole, astronomers have done it again, revealing a new view of the massive celestial object and shedding light on how magnetic fields behave close to black holes. The Event Horizon Telescope (EHT) collaboration has revealed a new look at the black hole, showing what it looks like in polarized light.
In 1960, Sheldon Glashow, a postdoc back then, proposed that an anti-neutrino could interact with an electron and produce a previously unknown particle through a Glashow resonance process. This new particle called the W boson was discovered in 1983. W boson is the carrier of the weak force (responsible for the beta decay of atoms.) However, this particle was way too heavier than the one predicted by Glashow. To produce a W boson using Glashow’s formula required a highly energetic anti-neutrino, way beyond current accelerators’ capacity.
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On 6 December 2016, a highly energetic anti-neutrino crashed into the Antarctic ice and was detected by the IceCube Neutrino Observatory at the South Pole. The particle had an energy of 6.2 PeV and traveled across billions of light years before reaching the Earth. After five years of careful analysis, particle physicists have confirmed the Glashow resonance, an interaction predicted 50 years ago! The results have been published in the journal Nature.
To end this article here’s something absolutely mind-blowing: Since Glashow theorized it half a century ago and the particle came from a distant galaxy billions of light years away, this means while Sheldon was thinking of it 50 years ago, a particle was already on its way to prove it!