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This post is a part of our current affairs series for the UPSC IAS Prelims 2022. In this post, we have covered the Science and tech current affairs of the Space technology section. This post covers the current affairs of September, October 2021 and April 2022 months.
Science and Tech Current Affairs 2021-22
Space technology
Contents
- 1 Mission Lucy
- 2 Nebra Sky Disc
- 3 White Dwarf
- 4 Blue Stragglers
- 5 Inspiration4 mission
- 6 Coronal Mass Ejections(CME)
- 7 Chang’e-5 lunar mission
- 8 XENON1T experiment
- 9 Landsat 9
- 10 Wright Mons in Pluto
- 11 UVIT J2022
- 12 Space Equity Action Plan
- 13 Europa
- 14 Earendel
- 15 Episodic Accreting young stars
- 16 Blue stragglers stars
- 17 Bernardinelli-Bernstein
- 18 Axiom-1 Mission
- 19 Jupiter-like protoplanet formed
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Mission Lucy
News
NASA has launched a probe toward clusters of asteroids along Jupiter’s orbital path. They are known as the Trojan swarms. It represents the final unexplored regions of asteroids in the solar system.
About Mission Lucy
The spacecraft, a deep-space robotic archaeologist named Lucy will study the geology, composition, density and structure of the Trojans. Mission Lucy is NASA’s first mission to explore the Jupiter Trojan asteroids.
After a six-year cruise, Lucy will fly close to seven Trojan asteroids by 2033.
Named After: The mission is named after ‘Lucy’, a 3.2 million-year-old ancestor who belonged to a species of hominins (which include humans and their ancestors).
Aim of the project
As per some planet formation and evolution models, the Trojan asteroids are believed to be formed from the same material that led to the formation of planets nearly 4 billion years ago when the solar system was formed.
Therefore, the mission is designed to understand the composition of the diverse asteroids that are a part of the Trojan asteroid swarms, to determine the mass and densities of the materials and to look for and study the satellites and rings that may orbit the Trojan asteroids.
Duration of mission
It is a solar-powered mission. It is estimated to be over 12 years long, during the course of which the spacecraft will visit eight asteroids covering a distance of about 6.3 billion km to deepen the understanding of the “young solar system”.
About asterioids
Asteroids are divided into three categories:
The first group are those that are found in the main asteroid belt, between Mars and Jupiter. This region is estimated to contain somewhere between 1.1-1.9 million asteroids.
The second group is that of trojans (the name comes from Greek mythology), which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.
The Jupiter asteroids can be found in what are referred to as “swarms” that lead and follow the planet Jupiter along its orbit around the Sun. ‘Lucy’ will reach the first swarm of these asteroids that precede Jupiter by August 2027.
The third classification of asteroids is under Near-Earth Asteroids (NEA), which has orbits that pass close to the Earth. Those that cross the Earth’s orbit are called Earth-crossers. More than 10,000 such asteroids are known, of which over 1,400 are classified as potentially hazardous asteroids (PHAs).
Other asteroid missions
Dawn mission (NASA) orbited Ceres and Vesta the two largest worlds in the belt between Mars and Jupiter.
Hayabusa mission (JAXA-Japan) probed asteroid “Ryugu”
OSIRIS-REX(NASA) spacecraft probed asteroid “Bennu” and collected samples from there.
Nebra Sky Disc
News
The British Museum in London will display an ancient object called the Nebra Sky Disc, which is thought to be the world’s oldest concrete depiction of stars.
About Nebra Sky Disc
Nebra Sky Disc is an ancient object that is considered as the world’s oldest concrete depiction of stars.
The object is widely believed to be 3,600 years old, dating from the Bronze Age. However, the date of origin of the disc has been called into question by some archaeologists.
The disc measures about 30 cm in diameter and has a blue-green patina emblazoned with gold symbols representing the Sun, Moon, stars, solstices and other cosmic phenomena.
Discovery of Nebra Sky Disc
The disc was unearthed in Germany in 1999 and is considered one of the most important archaeological finds of the 20th Century.
It was ritually buried along with two precious swords, two axes, two spiral arm-rings and one bronze chisel circa near Nebra in Germany. The burial of these objects is thought to be made as a dedication to gods.
Significance of Nebra Sky Disc
The Nebra Sky Disc is considered to be one of the most important archaeological finds of the 20th century and has been associated with the Unetice culture that inhabited parts of Europe around 1600 BC.
The Unetice culture comprised early Bronze Age communities in Central Europe, including in Bohemia, Bavaria, southeastern Germany and western Poland.
White Dwarf
News
An international team has reported a unique phenomenon where they saw the white dwarf losing its brightness in 30 minutes. These gaps in brightness have been previously reported, but the process usually takes place over a period of several days to months.
About the White Dwarf
White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel.
A typical white dwarf is half the size of our Sun and has a surface gravity 100,000 times that of Earth
Formation of White Dwarf
Main sequence stars including the sun are formed from clouds of dust and gas drawn together by gravity. However, once a star runs out of its fuel, it dies and becomes compact. The lifetime of a star depends on its mass.
The most massive stars with eight times the mass of the sun or more will never become white dwarfs. Instead, at the end of their lives, they will explode in a violent supernova, leaving behind a neutron star or black hole.
Smaller stars, such as the sun, will eventually swell up into red giants. After that, the stars shed their outer layers into a ring known as a planetary nebula. The core that is left behind will be a white dwarf, a husk of a star in which no hydrogen fusion occurs.
About the Switch on and off Phenomena
The white dwarf discussed here is part of a binary system called TW Pictoris, where a star and a white dwarf orbit each other. The two objects are so close to each other that the star transfers material to the white dwarf.
As this material approaches the white dwarf it forms an accretion disk or a disk of gas, plasma, and other particles around it.
As the accretion disk material slowly sinks closer towards the white dwarf, it generally becomes brighter. There are cases when the donor stars stop feeding the white dwarf disk. However, the reasons for this are still not clear.
When this happens, the disk is still bright as it “drains” material that was previously still there. It then takes the disk about 1-2 months to drain most of the material.
However, TW Pictoris drop in brightness in 30 mins was totally unexpected, and it may be due to the process called magnetic gating.
Note: Magnetic gating happens when the magnetic field is spinning so rapidly around the white Dwarf it creates a barrier, disrupting the amount of matter the white dwarf can receive.
Significance of these findings
This discovery will help us understand the physics behind accretion – how black holes and neutron stars feed material from their nearby stars.
Blue Stragglers
News
Indian researchers have done a comprehensive analysis to understand the formation of blue stragglers.
About Blue Stragglers
Blue stragglers are a class of stars on open or globular clusters. They stand out as they are bigger and bluer than the rest of the stars.
Note: A globular cluster is a spherical collection of stars. Globular clusters are very tightly bound by gravity giving them their spherical shapes and high concentrations of stars toward their centers.
First Discovered by: Blue stragglers were first discovered by Allan Sandage in 1953.
About the study by Indian Researchers
Indian Researchers have studied 228 clusters with a total of 868 blue stragglers. They compared the mass of the blue stragglers to the mass of the turnoff stars (which are the most massive ‘normal’ stars in the cluster) and predicted the formation mechanisms. They have found that:
- Half of the blue stragglers are formed through mass transfer from a close binary companion star,
- One third are likely formed through collisions of 2 stars and
- The remaining are formed through interactions of more than 2 stars.
Significance of this study
The study will help improve understanding of stellar systems. It will help uncover exciting results in studies of large stellar populations including galaxies.
Inspiration4 mission
News
SpaceX has announced that it is planning to launch the Inspiration4 mission by September 15.
About Inspiration4 mission
Inspiration4 is a spaceflight planned for four people aboard the SpaceX Resilience capsule.
The three-day flight will be the first human spaceflight to orbit Earth with exclusively private citizens on board.
The flight will be privately operated by SpaceX using a previously-flown Crew Dragon capsule launched to low Earth orbit.
The objective of the Inspiration4 mission
The mission involves circling the Earth for three days and then splashing down into the Atlantic Ocean.
It will orbit the Earth at 575 km, higher than the International Space Station (408 km) and the Hubble Space Telescope (547 km).This will be the farthest distance travelled by a crewed mission since 2009, when astronauts last went to repair the Hubble.
Significance of the Inspiration4 mission
The mission is a part of an effort to raise millions for the Tennessee-based St. Jude Children’s Research Hospital, a paediatric treatment and research facility that focuses on children’s catastrophic diseases, particularly leukaemia and other cancers.
Moreover, the mission will also present an opportunity for collecting large amounts of health data that will aid in planning future crewed space missions.
Coronal Mass Ejections(CME)
Coronal Mass Ejection(CME) is an ejection of highly magnetised particles from the sun. During a CME, enormous bubbles of superheated gas – called plasma – are ejected from the sun.
Cause: The underlying cause of CMEs is not well understood. However, astronomers agree, that the sun’s magnetic field plays a major role.
Occurrence of CMEs: Though CMEs can occur anywhere on the Sun, it is primarily those which originate from regions near the centre of the visible solar surface (called the photosphere) that are important for study, since they may propagate directly towards the Earth.
Impact of CMEs: When a really strong CME blows past the Earth, it can damage the electronics in satellites and disrupt radio communication networks on Earth.
Chang’e-5 lunar mission
News
China’s Chang’e-5 lunar mission has delivered to Earth nearly 2 kg of rocky fragments and dust from the Moon.
About the Chang’e-5 lunar mission
Chang’e 5 lunar mission is the Chinese National Space Administration’s (CNSA) mission to send a robotic spacecraft to the moon to collect samples and return them to Earth for scientific study.
The spacecraft landed on an area of the Moon (the ‘far side’) not sampled by the American or Soviet missions nearly 50 years ago, and thus retrieved fragments of the youngest lunar rocks ever brought back for analysis in laboratories on Earth. The rocks are also different to those returned decades ago.
About the findings from the samples brought by Chang’e-5
Around 90% of the materials collected by Chang’e-5 likely derive from the landing site and its immediate surroundings, which are of a type termed ‘mare basalts’. These volcanic rocks are visible to us as the darker grey areas that spilled over much of the nearside of the Moon as ancient eruptions of lava.
Yet 10% percent of the fragments have distinctly different, ‘exotic’ chemical compositions.
Significance of these findings
The distinct 10% fragments may preserve records of other parts of the lunar surface, as well as hints of the types of space rocks that have impacted the Moon’s surface.
Moreover, scientists have also looked at the potential sources of beads of rapidly cooled glassy material. They have traced these glassy droplets to extinct volcanic vents known as ‘Rima Mairan’ and ‘Rima Sharp’. These fragments could give insights into past episodes of energetic, fountain-like volcanic activity on the Moon.
XENON1T experiment
News
Recently, an international team of researchers made the first putative direct detection of dark energy.
About the XENON1T experiment
The XENON1T experiment is the world’s most sensitive dark matter experiment and was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy. In this experiment scientists noticed certain unexpected results. As per them, dark energy may be responsible for it. Hence, this experiment can also be used to detect dark energy.
About the dark energy and dark matter
Everything we see makes up less than 5% of the universe. About 27% is dark matter and 68% is dark energy.
Dark energy is the mysterious form of energy that makes up about 68% of the universe. Dark energy has been noted as “the most profound mystery in all of science”.
While dark matter attracts and holds galaxies together, dark energy repels and causes the expansion of our universe. Both components are invisible.
More is known about dark matter, since its existence was suggested as early as the 1920s, while dark energy wasn’t discovered until 1998. Large-scale experiments like XENON1T have been designed to directly detect dark matter, by searching for signs of dark matter ‘hitting’ ordinary matter. Dark energy is even more difficult to find.
Direct detection of dark energy
The team is hopeful that upcoming upgrades to the XENON1T experiment and similar experiments such as LUX-Zeplin – a next generation dark matter experiment located at the Sanford Underground Research Facility, and PandaX-xT – another project at China Jinping Underground Laboratory could help directly detect dark energy within the next decade.
Landsat 9
News
Recently, a NASA satellite was successfully launched the earth monitoring satellite, Landsat 9. It is a joint mission of NASA and the US Geological Survey (USGS).
The first Landsat satellite was launched in 1972. Since then, Landsat satellites have collected images of our planet and helped understand how land usage has changed over the decades. Images have also been used to study the health of forests, and coral reefs, monitor water quality and melt glaciers.
Difference between Landsat 9 and previous Landsats
Landsat 9 carries instruments similar to the other Landsat satellites, but it is the most technologically advanced satellite of its generation. It can see more colour shades with greater depths than the previous satellites. It can help scientists capture more details about our ever-changing planet.
Significance of LandSat
Landsat 9 will help make science-based decisions on key issues such as impacts of wildfire, coral reef degradation, the retreat of glaciers, and deforestation.
Monitoring climate change by Lansat
If a forest is affected by drought, it will be seen in Landsat images and can help the researchers decode the areas at risk.
Similarly during a wildfire, the Landsat images will capture the plumes of smoke and help study the extent of a burning.
The satellite images can also help recovery experts plan sites for replanting.
Landsat images can also help identify water bodies affected by potentially harmful algal blooms. According to NASA, scientists are now developing computer programs that would use Landsat and other satellite data to automatically warn lake recreation managers when blooms pop up.
Landsat images have helped glaciologists study the melting ice sheets of the Antarctic and Arctic regions. The images can help track cracks in the glaciers, the movement of glaciers, and decode how further global warming will impact them.
Wright Mons in Pluto
News
The National Aeronautics and Space Administration’s(NASA) New Horizons probe has reported new findings of Pluto.
The probe reported that icy lava flows have recently (no more than a billion years ago) covered substantial tracts of its surface. The findings drew particular attention to a mountainous feature named Wright Mons.
About Wright Mons
Wright Mons is a mountainous feature found on Pluto. It was informally named by the New Horizons team in honour of the Wright brothers.
It is about 150 km across its base and has a central depression (a hole) 40-50 km wide, with a floor at least as low as the surrounding terrain.
Scientists claim that Wright Mons is a volcano and cite the lack of impact craters as evidence that it is not likely to be older than 1-2 billion years.
The volume of Wright Mons exceeds 20 thousand cubic kilometres. Although considerably less than the volume of Mars’s biggest volcanoes, this is similar to the total volume of Hawaii’s Mauna Loa, and much greater than the volume of its above sea-level portion.
The slopes of Wright Mons and much of its surroundings are seen to be crowded with hummocks (humps or ridges in an ice field).
These hummocks were likely created by some sort of ice volcanism, known by the technical term “cryovolcanism” – erupting icy water rather than molten rock.
UVIT J2022
News
Indian astronomers have discovered a Faint Galaxy named UVIT J2022 that remained hidden until now.
About Faint Galaxies
Faint Galaxies are called low surface brightness galaxies or ultra-diffuse galaxies and have a surface brightness that is at least ten times fainter than the surrounding night sky.
Such faint galaxies may account for up to 15 % of the mass of the universe. However, they are difficult to detect because of their inherent low luminosities.
About UVIT J2022
It is a faint galaxy. It was discovered while studying a known galaxy, NGC6902A. This faint galaxy is in the Milky Way’s neighbourhood situated 136 million light-years away.
It remained undetected because it lay in front of a much brighter galaxy that is further away. Moreover, it is extremely faint – about ten times fainter than the surrounding night sky.
Significance of this study
Firstly, this study raises the possibility that there could be similar diffuse galaxies that have been wrongly interpreted as interacting galaxies due to their superposition with foreground or background galaxies.
Secondly, the material that the humans see around is known as baryonic matter. Studies suggest that baryonic matter makes up 5% of the Universe’s mass. The rest of the mass should be contributed by unknown forms such as dark matter and dark energy.
— However, humans still do not have a clear understanding about the 5% of the baryonic content present in the Universe. These faint galaxies can act as a link for understanding the origin of missing baryons in the universe, as they may contribute significantly to the baryonic mass in the universe.
Space Equity Action Plan
News
NASA has released its first-ever Space Equity Action Plan.
About the Space Equity Action Plan
Released by: NASA
Objective: To allow the agency to track progress toward improved diversity, equity, inclusion, and accessibility both internally and externally.
Focus Areas: The four focus areas the plan addresses are:
– Increasing integration and utilization of contractors and businesses from underserved communities and expanding equity in NASA’s procurement process;
– Enhancing grants and cooperative agreements to advance opportunities, access and representation for underserved communities;
– Leveraging Earth Science and socioeconomic data to help mitigate environmental challenges in underserved communities;
– Advancing external civil rights compliance and expanding access to limited English proficient populations within underserved communities.
Monitoring of the Plan: An executive team, led by NASA’s deputy administrator will lead the organization’s efforts towards equity.
The space agency has also established a leadership council that will be led by the Office of Diversity and Equal Opportunity and will provide quarterly reports to the executive team.
Europa
News
A team of researchers from Stanford University have said that one of Jupiter’s moons Europa, a prime candidate for life in the solar system, might have an abundance of water pockets beneath formations called double ridges.
About Europa
Europa is the sixth-largest moon in the solar system and Jupiter’s fourth-largest satellite. It was discovered in 1610 by Galileo Galilei.
Europa is slightly smaller than Earth’s moon and its diameter is about one-quarter that of the Earth. Europa’s surface is mostly solid water ice. It is crisscrossed by fractures.
Even though Europa has a very thin oxygen atmosphere, it is considered one of the most promising places in the solar system to find present-day environments that are suitable for life beyond the Earth.
It is also believed that underneath Europa’s icy surface the amount of water is twice that on Earth.
Future Missions to Europa
NASA is expected to launch its Europa Clipper in 2024. The module will orbit Jupiter and conduct multiple close flybys to Europa to gather data on the moon’s atmosphere, surface and its interior.
Findings about Europa
The researchers have found that double ridges found on Europa’s surface are similar to those seen on Earth’s Greenland ice sheet.
Based on these findings, the researchers suggest that if a similar process is responsible for the formation of double ridges there, it could indicate that shallow liquid water is present over Europa’s ice shell at all times and in all places.
Note: Double ridges are symmetrical mountain-like structures running hundreds of kilometers in length. They are a common geographical feature found in Greenland.
Significance of these findings: The findings increase the potential habitability of Europa.
Earendel
News
NASA’s Hubble Space Telescope has discovered the farthest star ever seen to date. They have nicknamed that star as “Earendel”.
About Earendel
Earender is the most distant star discovered by the Hubble Space Telescope.
The star has been officially called WHL0137-LS, but it has been nicknamed “Earendel”, which means “morning star” in Old English.
The star is more than 12.9 billion light-years away and likely existed within the first billion years after the beginning of the universe.
This discovery of the most distant star was made possible by a phenomenon known as ‘gravitational lensing’.
About Gravitational Lensing
A gravitational lens can occur when a huge amount of matter, like a cluster of galaxies, creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight.
The effect is like looking through a giant magnifying glass.
Significance: This effect allows researchers to study the details of early galaxies too far away to be seen with current technology and telescopes.
First Predicted by: This effect was predicted to exist by Albert Einstein’s General Theory of Relativity in the early 20th century.
Episodic Accreting young stars
News
Indian astronomers from the Aryabhatta Research Institute of Observational Sciences (ARIES) as part of an international research have discovered Gaia 20eae.
About Gaia 20eae
Gaia 20eae is an extremely rare group of young stars that exhibit episodic accretion.
About the Episodic Accreting young stars
Episodically accreting young stars are young, low-mass stars that have not initiated hydrogen fusion in their core and are fuelled by gravitational contraction and deuterium fusion (pre-main-sequence phase of the star).
These pre-main-sequence stars are surrounded by a disc from which it steadily feeds on the matter from the disc-shaped region of gas and dust surrounding the star to gain mass. This process is known as mass accretion from the circumstellar disc of the star.
On occasions their feeding rate increases. This is known as the periods of enhanced mass accretion from their circumstellar disc. During such episodes, the brightness of the star increases by 4-6 magnitudes in the optical bands.
So far 25 such rare groups of stars have been discovered.
Significance of this discovery: This discovery could help probe into this group of Episodic Accreting young stars and their formation mechanism in greater detail.
Blue stragglers stars
News
Indian Institute of Astrophysics, Bengaluru has conducted a study on Blue Stragglers to understand their aberrant behaviour.
For this, the researchers used the UVIT instrument (Ultra Violet Imaging Telescope) of ASTROSAT, India’s first science observatory in space.
About the Blue Stragglers
Blue Straggler Stars are hot, blue, massive stars and seem to have a different trajectory of evolution from the norm.
Reason for calling them Blue Stragglers
There are a few stars that, when they are expected to start expanding in size and cooling down, do just the opposite. They grow brighter and hotter as indicated by their blue color. Thus, standing out from the cooler red stars in their vicinity in the color-magnitude diagram.
– Since they lag their peers in evolution, they are called stragglers more specifically, blue stragglers, because of their hot, blue color.
First Discovered by: Blue stragglers were first discovered by Allan Sandage in 1953 while performing photometry of the stars.
Reason for more massive and energetic nature of blue stragglers
Blue Stragglers are more massive and energetic than expected may be due to the following reasons:
First Possibility: They do not belong to the family of stars in the cluster and hence are not expected to have the group properties. But if they actually belong, the evasive behaviour is due to these stars gaining mass from a binary companion.
Second Possibility: The straggler draws matter from the giant companion and grows more massive, hot and blue, and the red giant ends up as a normal or smaller white dwarf.
Third possibility: The straggler draws matter from a companion star, but that there is a third star that facilitates this process.
Bernardinelli-Bernstein
News
The National Aeronautics and Space Administration’s(NASA) Hubble Space Telescope has confirmed that the huge Bernardinelli-Bernstein comet is indeed the largest icy comet nucleus ever seen by astronomers.
Note: Comets are cosmic snowballs of frozen gases, rock and dust that orbit the Sun.
About Bernardinelli-Bernstein
It is the largest icy comet nucleus ever seen by astronomers. It is also called the C/2014 UN271.
Discovered by: It was discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey at an astronomical observatory in Chile. It was discovered in 2010 and has been intensively studied since then.
Origin: The comet has been travelling towards the sun for over a million years, and it is believed to have originated in the Oort Cloud.
Note: Oort Cloud is a distant region of the solar system that is predicted to be the source of most comets. However, the Oort Cloud is still only a theoretical concept.
Features of Bernardinelli-Bernstein Comet
Diameter: It has an estimated diameter of almost 129 kilometres.
Nucleus: The nucleus of the comet is around 50 times larger than that of most known comets, and its mass is estimated to be around 500 trillion tonnes.
Temperature: It has an estimated temperature of minus 348 degrees Fahrenheit. This is warm enough to sublimate carbon monoxide (CO) from the surface to produce the dusty coma.
Axiom-1 Mission
News
The first-ever private mission to the International Space Station (ISS) named Axiom-1 has reached the ISS.
About the Axiom-1 Mission
Axiom Mission 1(Ax-1) is the first all-private astronaut mission to the International Space Station.
Organized by: US Based company Axiom Space.
Launched from: The mission was launched from NASA’s Kennedy Space Center in Florida and is flying on the SpaceX Crew Dragon Endeavour.
Under the mission, the astronauts will spend more than a week conducting scientific research, outreach and commercial activities on the space station.
About Axiom Space
Axiom Space is a company that is focusing on making space travel more commercially available. Besides this, it also aims to improve the understanding of space and the human body by bringing researchers into space.
Jupiter-like protoplanet formed
News
The Hubble Space Telescope has photographed a Jupiter-like protoplanet forming through a process that researchers have described as intense and violent.
About the Jupiter-like protoplanet formed
The newly forming planet captured by the Hubble Space Telescope is called AB Aurigae b.
It is embedded in a protoplanetary disk with distinct spiral structures swirling around and surrounding a young star that is estimated to be about 2 million years old.
This protoplanet is about the same age our solar system was when planet formation was underway. It is also 531 light-years away from our sun.
Further, this protoplanet is probably around nine times the size of Jupiter and orbits its host star at a distance of 8.6 billion miles, over two times the distance between Sun and Pluto.
About the Protoplanets
Protoplanets are small celestial objects that are the size of a moon or a bit bigger. They are small planets, like an even smaller version of a dwarf planet.
Astronomers believe that these objects form during the creation of a solar system.
Significance of this discovery
According to NASA, this discovery supports a long-debated theory called “disk instability,” which tries to explain how planets similar to Jupiter are formed.
About the Disk Instability Theory
According to this theory, matter slowly moves inwards in this disc as dust particles grow into centimetre-sized pebbles.
This is seen as the first step towards the formation of kilometre-sized planetesimals that eventually come together to form planets.
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