Context: The European Space Agency (ESA) has unveiled the first images captured by the Euclid space telescope.
Euclid Space Telescope
Euclid Space Telescope was launched on July 1, 2023 from Cape Canaveral in Florida on a SpaceX Falcon 9 rocket by the European Space Agency (ESA).
The telescope is stationed 1.5 million km away from the Earth at the Lagrangian Point 2.
It will observe the shapes, distances, and motions of billions of galaxies spanning over 10 billion light-years over the next six years.
Objective:
To create the largest cosmic 3D map of the universe to better understand the distribution of dark matterand reveal the influence of dark energy in the early universe.
Dark matter and dark energy together make up 95% of the universe.
To understand the evolution of the Universe by looking at the light emitted from galaxies 10 billion years ago.
Euclid is a 1.2 metre-wide telescope with a 600-megapixel camera to record visible light and a near-infrared spectrometer/camera and photometer to determine the redshift of detected galaxies.
Dark Energy
Around 68% of the Universe is made of dark energy while dark matter makes up 27%. Only the remainder is composed of fermionic matter, i.e., things on the Earth, planets, stars, etc.
Scientists theorised the existence of dark energy 25 years ago when a team of researchers found that instead of slowing down due to gravity (inwards pulling force), the expansion of the Universe was speeding up. Scientists hypothesised that this was happening due to a mysterious form of energy called dark energy.
The expansion of the universe is accelerating. Previously, it was thought that the pull of gravity will either slow down or even retract the expansion.
Dark energy has been hypothesised as a repulsive force — a sort of anti-gravity. As our universe is expanding, it indicates that Dark energy has a greater abundance than Dark matter.
Dark energy is a property of space so it does not get diluted as space expands. As more space comes into existence, more of this energy-of-space appears. As a result, dark energy causes the universe to expand faster and faster.
While Dark matter exerts a “pull” on the universe, Dark Energy has a contrasting expansionary effect.
Dark Matter
Dark matter has not yet been observed directly. It does not interact with matter and is completely invisible to light and other forms of electromagnetic radiation making it impossible to detect.
Scientists are confident it exists because of the gravitational effects it has on galaxies and galaxy clusters.
Context: Researchers discovered a remote blast of cosmic radio waves that lasted less than a millisecond in June 2022. This “fast radio burst” is the most distant ever detected and its source is in a galaxy that took eight billion years to reach Earth. It is also one of the most energetic ones ever observed. In a fraction of a second, it released the equivalent of 30 years of emissions from our Sun.
Fast Radio Bursts
Fast radio bursts are sudden releases of powerful radio waves that last just milliseconds.
In that time, they discharge as much energy as 500 million Suns. Most of them flare just once, making them unpredictable and difficult to study.
Origin: The origin of FRBs is still mysterious. However, one leading theory is that they are caused by magnetars.
Neutron Stars
Neutron stars are the incredibly dense remnants of supermassive stars (with masses around 1025 times the mass of the Sun)that have exploded as supernovae.
Neutron stars are about 12 miles (20 km) in diameter and have breathtakingly high rotation speeds – they have rotational periods that can be just 0.3 to 12.0 seconds.
Types of Neutron Stars
Pulsars: Pulsars are a type of neutron star that emits an electromagnetic beam from their poles The difference between pulsars and neutron stars is that other neutron stars do not shoot a pulse (beam) as strong as pulsars.
Pulsars rotate so fast (many times per second) that they generate an electric field that accelerates protons and electrons through their axis. These shoot out like a beam of electromagnetic radiation out of their poles.
Pulsars rotate so fast because even after the supernova, the momentum of the star remains, but since the resulting neutron star is many times smaller than the original massive star, it spins at a much faster rate. (In accordance with the principle of conservation of angular momentum)
Magnetars are types of neutron stars that have much more powerful magnetic fields than normal neutron stars. They are the most powerful known magnetic objects in the Universe.
Magnetars have magnetic fields in the range of 1015 gauss and they emit energy in the range given by luminosities of 1037 – 1040 joules per second.
The luminosity of the sun is in the order of 1026 joules per second.
Recent findings
In 2020, for the first time, a fast radio burst was detected from inside the Milky Way – which enabled scientists to trace the very star that emitted it (that star was a magnetar).
A possible explanation for these colossal eruptions could be that:
The magnetic field of magnetars is so powerful that it distorts the magnetar's shape, exerting an outward pull.
Meanwhile, the density of the collapsed stellar core results in a powerful inward gravitational pull.
The tension between these two opposite forces causes the magnetar to rupture and quake, releasing powerful flares and large amounts of electromagnetic energy in the form of radio waves – fast radio bursts.
Plots that compare the energy and time distributions of fast radio bursts and quakes produce similar graphs. The results show notable similarities between FRBs and earthquakes and meanwhile, there was no notable similarity with solar flares.
Significance
Starquakes in neutron stars have opened up the possibility of gaining new insights into very high-density matter and the fundamental laws of nuclear physics.
Context: A global team of scientists led by the University of Oxford have announced the source of the largest-ever seismic event recorded on Mars.
Major Highlights about Marsquake
The quake of magnitude of 4.7 on Mars was recorded by NASA’s InSight lander in May 2022.
Since its seismic signal was similar to previous quakes known to be caused by meteoroid impacts, the team believed that the event was caused by a meteorite impact.
However, the recent study suggests that the quake was the result of enormous tectonic forces (release of stress) within Mars’ crust.
These stresses are the result of billions of years of evolution; including the cooling and shrinking of different parts of the planet Mars at different rates.
This indicates that the planet is much more seismically active than previously thought.
Mars vs Earth:
Earth's crust is divided into immense plates that continually shift which triggers quakes. However, the Martian crust is a single solid plate.
Though it is believed that Mars does not have any active plate tectonics, there are faults still active on Mars. These faults can trigger quakes.
Context: China plans to expand its space station to six modules from three in coming years, offering astronauts from other nations an alternative platform for near-Earth missions as the NASA-led International Space Station nears the end of its lifespan.
Tiangong Space Station (TSS)
TSS is a permanently crewed space station constructed by China and operated by China Manned Space Agency.
Placed in: Low Earth orbit between 340 and 450 km above the Earth's surface.
Operational lifetime: More than 15 years.
It has been fully operational since late 2022, hosting a maximum of three astronauts.
TSS will weigh 180 metric tons after its expansion to six modules.
International Space Station (ISS)
ISS is a modular space station (habitable artificial satellite) and the single largest man-made structure in the low Earth orbit.
Launched in 1998,it is a multinational collaborative project involving five participating space agencies:
NASA (United States)
Roscosmos (Russia)
JAXA (Japan)
ESA (Europe)
CSA (Canada)
The ownership and use of the space station are established by intergovernmental treaties and agreements.
It circles the Earth in roughly 92 minutes and completes 15.5 orbits per day, hosting a maximum of seven astronauts.
It serves as a microgravity and space environment research laboratory in which scientific research is conducted in astrobiology, astronomy, meteorology, physics, and other fields.
NASA intends to keep operating the ISS until the end of 2030, after which the ISS would be crashed into Point Nemo over the South Pacific Oceanic Uninhabited Area (SPOUA).
Context: The OSIRIS-REX mission has ended with the return of regolith (space sample) from the primordial asteroid Bennu.
OSIRIS-RExMission:
Origins, Spectral Interpretation, Resources Identification and Security-Regolith Explorer (OSIRIS REx) is an asteroid study and sample return mission by NASA.
The spacecraft set out in 2016 to study asteroid Bennu (a carbon-rich near-Earth asteroid) and return to Earth with a sample for detailed analysis in 2023.
Asteroid Bennu:
Bennu is a small asteroid, a little less than 500 metres in depth and is more than 4.5 billion years old.
It is classified as a “near-Earth object” because it passes relatively close to our planet every six years.
Over time, the asteroid has drifted closer to Earth, closely approaching it every six years, owing to which it has a small chance of impacting the Earth in future (2182 CE).
Why was Bennu chosen?
Bennu fits in three criteria: accessibility, size and composition.
For a mission like OSIRIS-REx, the most accessible asteroids are somewhere between 0.08 – 1.6 AU. Scientists needed an asteroid that could be easily travelled to, retrieve a sample from and return to Earth all within a few years. Further, Bennu had an orbit similar to Earth.
One theory is that small worlds like Bennu seeded Earth with the prebiotic ingredients for life
Significance:
Researchers believe that this pristine space dirt will reveal clues about the birth of our solar system (4.5 billion years ago) and the genesis of life on Earth.
Key Fact:
One AU (Astronomical Unit) is approximately equal to 93 million miles - the distance between the Sun and the Earth. The closest asteroids which travel within 1.3 AU of the sun are called near-Earth objects.
Context: An earthquake is caused when tectonic plates shift. But quakes themselves aren’t restricted to the earth. For example, small tremors have also been detected on the moon.
About moonquakes
It seismic tremors or vibrations that occur on the Moon's surface.
It is less intense than earthquakes on Earth. The strongest moonquakes can reach magnitudes of up to 5.5 on the Richter scale, but most are much weaker.
It is measured using seismometers placed on the Moon's surface by Apollo missions. These instruments recorded data from 1969 to 1977.
Between 1972 and 1977, 28 shallow moonquakes were observed.
It has helped scientists learn about the Moon's internal structure, composition, and history.
Causes and types of moonquakes:
Tidal forces: Gravitational interactions between the Moon and Earth can cause stress and strain on the Moon's surface, leading to moonquakes, known as deep moonquakes (~700 km below the surface).
Meteorite impacts: Craters on the moon can also form when meteors hit its surface, and since the moon doesn't have an atmosphere, even small impacts can make big craters. There are thousands of these craters on the moon's surface.
Thermal stress: The moon gets very hot and very cold, with temperatures ranging from 121 degrees Celsius to -133 degrees Celsius, a difference of 250 degrees Celsius,the expansion and contraction of the lunar surface can induce moonquakes.
Volcanic activity: Movement of magma or the collapse of lunar lava tubes.
The first three kinds of moonquakes mentioned above tend to be mild; however, shallow moonquakes caused by volcanic activity can register up to mB=5.5 on the body-wave magnitude scale.
Context: The Small Nuclear Reactors and Small Satelite Vehicles have increased the presence of private sector in these sectors, which may lead to cost efficient, environmentally sustainable and competitive future technologies.
Nuclear Fusion and Energy
Nuclear fission is a reaction where the nucleus of an atom splits into two or more smaller nuclei, while releasing energy.
For instance, when hit by a neutron, the nucleus of an atom of uranium-235 splits into two smaller nuclei, for example a barium nucleus and a krypton nucleus and two or three neutrons.
These extra neutrons will hit other surrounding uranium-235 atoms, which will also split and generate additional neutrons in a multiplying effect, thus generating a chain reaction in a fraction of a second.
Each time the reaction occurs, there is a release of energy in the form of heat and radiation.
The heat can be converted into electricity in a nuclear power plant, similarly to how heat from fossil fuels such as coal, gas and oil is used to generate electricity.
Nuclear Power Plant Working
In a nuclear reactor heat is produced through the chain reaction happening through the fission.
The heat warms the reactor’s cooling agent, typically water, to produce steam.
The steam is then channelled to spin turbines, activating an electric generator to create low-carbon electricity.
Small modular reactors (SMRs)
SMRs are advanced nuclear reactors that have a power capacity of up to 300 MW(e) per unit, which is about one-third of the generating capacity of traditional nuclear power reactors. SMRs, which can produce a large amount of low-carbon electricity, are:
Small – physically a fraction of the size of a conventional nuclear power reactor.
Modular – making it possible for systems and components to be factory-assembled and transported as a unit to a location for installation.
Reactors – harnessing nuclear fission to generate heat to produce energy.
Advantages of SMR
Given their smaller footprint, SMRs can be sited on locations not suitable for larger nuclear power plants.
refabricated units of SMRs can be manufactured and then shipped and installed on site, making them more affordable to build than large power reactors, which are often custom designed for a particular location, sometimes leading to construction delays.
SMRs offer savings in cost and construction time, and they can be deployed incrementally to match increasing energy demand.
In areas lacking sufficient lines of transmission and grid capacity such as rural areas, SMRs can be installed into an existing grid or remotely off-grid, as a function of its smaller electrical output, providing low-carbon power for industry and the population.
SMRs have reduced fuel requirements. Power plants based on SMRs may require less frequent refuelling, every 3 to 7 years, in comparison to between 1 and 2 years for conventional plants
In comparison to existing reactors, proposed SMR designs are generally simpler, and the safety concept for SMRs often relies more on passive systems and inherent safety characteristics of the reactor, such as low power and operating pressure.
Moore’s Law
Moore’s Law is a reductive title for the idea, first postulated by American engineer Gordon Moore in the 1960s, that approximately every two years, technology doubles the total number of transistors that manufacturers can squeeze into an integrated circuit. In general terms, it implies that computing power increases exponentially over time. A simplified definition of Moore’s Law indicates that the speed of individual microchips as well as the overall amount of computing power available doubles around every two years.
Small Satellite Launch Vehicle
Small Satellite Launch Vehicle (SSLV) is the new launch vehicle of ISRO capable of launching Mini, Micro or Nano satellites (10 to 500 kg mass) to 500 km planar orbit.
SSLV is a three-stage vehicle with all solid propulsion stages.
The satellite insertion into the intended orbit is achieved through a liquid propulsion-based Velocity Trimming Module (VTM).
Image Source: ISROImage source: India Today
Advantages:
Its has low production cost.
It has a low turnaround time.
It has high flexibility in accommodating multiple satellites.
It has launch-on-demand feasibility.
It needs minimal launch infrastructure requirements.
The advantage of SSLVs is that each rocket can be integrated within as short a span of time as 72 hours, against more than a month taken for other launch vehicles.
Context: Researchers studying the findings of the Solar Orbiter Aircraft, a joint mission by the European Space Agency and the U.S. space agency NASA, recently announced that they have detected picoflare jets from the sun’s outer atmosphere.
About Picoflare jets:
It is a tiny jet (plasma ejections) of charged particles emanating from the Sun's outer atmosphere.
According to the researchers, these charged small particle jets, which are ejected intermittently are a source of the solar wind. This flow is not actually uniform, the ubiquity of the jets suggests that the solar wind from coronal holes might originate as a highly intermittent outflow.
These widespread yet faint jets, only a few hundred kilometers across, were seen to last between 20 to 100 seconds, achieving speeds of approximately 100 kilometers per second. Their energy appears to be derived from magnetic reconnection.
Significance of Picoflare jets:
Due to their relatively low kinetic energies, researchers named these structures picoflare jets. Based on their calculations, they suggest that plasma outflows from these numerous, frequent picoflare jets, channeled along the open magnetic field lines of coronal holes, might supply a considerable amount of mass and energy to the solar wind throughout the solar cycle.
It has significant effects on the large-scale solar system as well as on Earth's magnetic field and poses risks to satellite electronics.
Solar Orbiter Aircraft
It is a next-generation solar-observing satellite developed by a collaboration between the European Space Agency (ESA) and NASA.
It was launched in 2020.
It will provide unprecedented details about the solar system and the images of the sun’s poles while investigating the heliosphere.
It is equipped with a suite of scientific instruments to observe the Sun up close and provide new insights into its behaviour, including its magnetic fields, solar wind, and how it influences the solar system.
Solar winds
The outermost layer of the Sun's atmosphere, known as the corona, is composed of extremely hot plasma. Some of this plasma escapes the Sun's gravitational pull and flows outward into space, creating the solar wind.
The solar wind is a stream of charged particles, primarily electrons and protons, that constantly blows away from the Sun and interacts with objects in the solar system, including the Earth.
Corona
It is the outermost layer of the Sun's atmosphere, extending millions of kilometers into space.
It is composed of extremely hot and tenuous plasma (ionized gas).
It is visible during a total solar eclipse as a pearly-white halo of light surrounding the dark disk of the Moon.
It is much hotter than the Sun's surface, with temperatures reaching millions of degrees Celsius.
Context: India must contribute towards drawing up an international space resource management framework that balances competing objectives in pursuit of the use of outer space for peaceful purposes.
What is outer space?
From the perspective of an individual on Earth, outer space is a zone that occurs about 100 kilometres (60 miles) above the planet.
Outer space is the expanse that exists beyond Earth and between celestial bodies.
Outer space is not empty but contains a low density of particles (predominantly a plasma of hydrogen and helium) as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays.
The Karman line at an altitude of 100 km above sea level, is conventionally used as the start of outer space in space treaties and for aerospace records keeping.
What are the related agreements and conventions?
The Outer Space Treaty (1967): Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies.
The Rescue Agreement (1968): Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space.
The Liability Convention (1972): Convention on International Liability for Damage Caused by Space Objects.
The Registration Convention (1976): Convention on Registration of Objects Launched into Outer Space.
The Moon Agreement (1984): Agreement Governing the Activities of States on the Moon and Other Celestial Bodies.
Outer Space Treaty (1967): The Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies forms the basis of international space law.It prevents any claims of national sovereignty and permits all states to freely explore outer space.It entered into force on 10 October 1967. As of August 2023, 114 countries are parties to the treaty including the US, Russia, China, and India.Key Prohibition:Prohibits placing of nuclear weapons in space.Limits the use of the Moon and all other celestial bodies to peaceful purposes only.
Establishes that space shall be free for exploration and use by all nations, but that no nation may claim sovereignty of outer space or any celestial body.Exclusion:It does not ban military activities within space, military space forces, or the weaponization of space, except the placement of weapons of mass destruction in space.It is mostly a non-armament treaty and offers insufficient regulations to newer space activities such as lunar and asteroid mining.
What are Global commons?
Traditionally, “global common” is used to define those parts of the planet that fall outside the sovereignty of any state. The term is used typically to describe supra-national and global resource domains in which common-pool resources are found. The UN identifies four “global commons”, namely the high seas, the atmosphere, Antarctica and the outer space.
In the absence of an authoritative definition, “global commons” could be viewed from two lenses. First rooted in geopolitical or military relevance - it is not surprising that security establishments across the world recognise domains beyond the national jurisdictions, including the high seas, the air space outside territorial bodies of a state, and outer space, as vital connecting channels for the international order.
Others recognise outer space as a vital operational domain for keeping their nation safe while upholding international law.
Second, “global common” is viewed based on the economic and commercial implications of shared resources, which could be overused by some at the expense of others, regardless of national jurisdiction. “Commons” is seen as constraining because it is associated with notions of shared ownership, public governance or limitations on use.
What are the associated issues and why there is a need for better governance of outer space?
Outdated space laws: Space laws do not have a dispute settlement mechanism, are silent on collisions and debris and offer insufficient guidance on interference with others’ space assets.
State-centric legislation: The legal framework is state-centric, placing responsibility on states alone. However, non-state entities are now in the race for commercial space exploration and utilisation. Some states are providing frameworks for resource recovery through private enterprises as it is not expressly forbidden for non-state actors. E.g., According to NASA, the asteroid named 16 Psyche is so rich in heavy metals that it is worth $10,000 quadrillion. So, there is a risk of starting a race for mineral exploration among both state and non-state actors.
Misuse of strategic position: Reliance of militaries on satellite systems means that space assets become potential targets. E.g., Satellite constellations are commercial but governments can use their data to monitor military movements.
Increased space debris: The issues of overcrowded and congested space are becoming real. The Kessler syndrome, where a collision between two space objects could set off a cascading chain reaction, cannot be dismissed. Given the speed at which space objects travel—around 17,000 miles an hour—any collision between two objects in space could set in motion a disastrous turn of events with more and more collisions, creating an unmanageable amount of space debris.
Technological advances: Although on Earth, natural resources are being exhausted, many of them are present on celestial bodies, including asteroids, in enormous quantities. Technological advances have made it possible to mine even space.
Role of space in meeting sustainable development goals: Space applications and technology directly and indirectly prevent and reduce poverty, for example, through disaster monitoring and response – and through supporting other Sustainable Development Goals. Earth observation data is used to improve coffee quality and productivity in Timor-Leste, increasing the revenue of coffee growers. Satellite data are essential for mapping and monitoring natural and protected areas, fishing vessel tracking and navigation, monitoring illegal fishing, assessing marine and coastal health and identifying algal blooms. Land surface monitoring, biodiversity monitoring, the monitoring of poaching and smuggling routes, deforestation, forest fire risk, vegetation health and the protection of endangered species all benefit from space-derived data.
What is the concept of space sustainability?
Space sustainability is the concept to use outer space for peaceful purposes and socio-economic benefits to meet present needs without compromising needs of future generations.
Initiatives on Space Sustainability:
Indian: Project NETRA by ISRO to monitor space debris to aid planning on protecting space assets. IS4OM platform to aid Space Situational Awareness by providing accurate information on on-orbit collision, fragmentation, hazardous asteroids, space weather forecast etc. 2+2 dialogue between India and U.S. for monitoring space objects.
Global: UN Committee on Peaceful Uses of Outer Space, 2019 adopted 21 voluntary, non-binding guidelines to ensure long-term sustainability of outer space activities.Summit for Space Sustainability- global summit focused on developing solutions for space sustainability. Space Sustainability Rating by World Economic Forumto score sustainability of spaceflight operators to encourage responsible behaviour in space.
Context: ISRO's Aditya L1 mission was successfully launched from Satish Dhawan Space Centre on 2 September 2023.
About Aditya L1:
Aditya L1 is the first space-based observatory class to study the Sun.
It was launched to the low earth orbit using ISRO's reliable Polar Satellite Launch Vehicle (PSLV).
Aditya-L1 will undergo multiple apogee-raising orbital manoeuvres and is expected to exit the Earth’s orbit on the fifth day after launch.
After leaving Earth’s gravity, it will get into a heliocentric path. Later, getting into the orbit around L1 is the most crucial aspect. L1 is not an object, just a location in space, which also co-moves with Earth around the Sun.
Once launched, it will take 125 days to travel to its destination at L1.
Objectives:
Study of Solar upper atmospheric (chromosphere and corona) dynamics.
Study of chromospheric and coronal heating, physics of the partially ionized plasma, initiation of the coronal mass ejections, and flares
Observe the in-situ particle and plasma environment providing data for the study of particle dynamics from the Sun.
Physics of solar corona and its heating mechanism.
Diagnostics of the coronal and coronal loops plasma: Temperature, velocity and density.
Development, dynamics and origin of CMEs.
Identify the sequence of processes that occur at multiple layers (chromosphere, base and extended corona) which eventually leads to solar eruptive events.
Magnetic field topology and magnetic field measurements in the solar corona.
Drivers for space weather (origin, composition and dynamics of solar wind.
Payloads:
Weighing 1,475 kg, it will carry seven payloads. The payloads include-
Solar Ultraviolet Imaging Telescope (SUIT) is designed to image the Sun in the 200-400 nanometre (nm) of the ultraviolet band. SUIT’s imager will continuously record the entire disk of the Sun through 11 filters. The images of these layers could help improve our understanding of the Sun’s immediate atmosphere.
Visible Line Emission Coronagraph (VELC) is the Corona/Imaging and Spectroscopy payload that Aditya-L1 will use to focus on the Sun's Corona.
Solar Low Energy X-ray Spectrometer (SoLEXS) and High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) payloads will study the X-ray flares emitted by the Sun over a wide range of X-ray energy range.
Aditya Solar wind Particle Experiment (ASPEX), during the cruise phase, will turn on and start performing in situ measurements of solar particles and ions.
Plasma Analyser Package for Aditya (PAPA) will study the solar wind and energetic ions.
Magnetometer (MAG) payload is meant to measure the low-intensity interplanetary magnetic field in space.
Significance of the mission:
Aditya-L1 would help in understanding the effect of the Sun on the Earth and its surroundings. The mission hopes to generate user-friendly informationto issue space weather alerts that can help safeguard a range of satellite-dependent operations such as telecommunications, mobile-based Internet services, navigation, power grids, etc.
Disturbances in the form of solar flares, Coronal Mass Ejection, or solar winds directed towards Earth, can adversely impact space weather; studying the Sun is, therefore, of paramount importance.
It would study solar upper atmospheric (chromosphere and corona) dynamics and understand the physics of the solar corona and its heating mechanism.
The difference between the Sun's upper atmosphere's temperature of 1-3 million degrees Celsius and its lower temperature of 5500 degree Celsius is one of the most significant unresolved problems in the study of solar physics.
To understand this issue, it will capture near-simultaneous photos of the many layers of the Sun's atmosphere, revealing how energy is routed and transported from one layer to the next.
Aditya-L1 can potentially pave the way for future Indian astronomy missions. After the launch, India entered into an elite group of nations that have sent probes to study the Sun.
Aditya-L1 is ISRO’s second astronomy observatory-class mission after AstroSat.
AstroSat, weighing 1,515 kg, lifted off with five in situ instruments, is India’s first dedicated astronomy mission aimed at studying celestial sources in X-ray, optical, and UV spectral bands simultaneously, and remains operational almost eight years after its launch in 2015.
Lagrange points:
Lagrange points, named after mathematician Josephy-Louis Lagrange who discovered them, are positions in a moving two-body system where forces acting on a third body of smaller mass cancel each other out.
At these special locations in space, the combined gravitational forces of two large bodies (such as the Sun and Earth or Earth and the Moon) equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium (net of all forces is zero) where a spacecraft may be "parked" to make observations.
There are five Lagrangian points, denoted L1 to L5, which are located along the line connecting the two larger celestial bodies. Of these, three are unstable and two are stable.
Unstable Lagrange points are labelled L1, L2 and L3. Unstable means that if an object/satellite located at these points is nudged, it will break out from the orbit and drift off into interplanetary space.
Stable Lagrange points are labelled as L4 and L5. This means that if a small object at L4 or L5 is nudged, there would be an effective restoring force to bring a satellite back to the stable point.
L1 point: L1 is located roughly 1.5 million kilometres from Earth, where the Sun and Earth's combined gravitational pull permits a spacecraft to remain nearly stationary to the Sun. The L1 point provides an uninterrupted view of the Sun as the satellite can continuously view solar activities without eclipses.
L2 point: L2 point is used as a location for space-based observatories, as it provides an unobstructed view of the Universe and is stable enough to allow long-duration observations. James Webb Space Telescope is placed at the L2 Lagrange point.
L3 point: L3 point lies behind the Sun, opposite to Earth. Objects in L3 cannot be seen from Earth and offers the potential to observe the far side of the Sun. There is no known natural object at the L3 point, but it is sometimes discussed as a possible location for a future space-based observatory.
L4 and L5 point: L4 and L5 are good and stable locations, but are much farther from Earth compared to L1, which is directly between the Sun and the Earth.
Context: The Indian Space Research Organisation (ISRO) announced that Pragyan, the rover of the Chandrayaan-3 mission, has confirmed the presence of Sulphur on the moon’s surface, near its South pole.
Major Highlights:
Laser-Induced Breakdown Spectroscopy (LIBS) instrument aboard the rover has made the first-ever in-situ measurements on the elemental composition of the lunar surface near the south pole.
These in-situ measurements confirm the presence of Sulphur (S) in the region unambiguously, something that was not feasible by the instruments aboard the orbiters.
Preliminary analyses have unveiled the presence of Aluminum (Al), Sulphur (S), Calcium (Ca), Iron (Fe), Chromium (Cr), and Titanium (Ti) on the lunar surface. Further measurements have revealed the presence of manganese (Mn), silicon (Si), and oxygen (O). A thorough investigation regarding the presence of Hydrogen is underway.
LIBS is a scientific technique that analyses the composition of materials by exposing them to intense laser pulses. A high-energy laser pulse is focused onto the surface of a material, such as a rock or soil, and generates localised plasma.
The collected plasma light is spectrally resolved and detected by charge-coupled devices. Since each element emits a characteristic set of wavelengths of light when in a plasma state, the elemental composition of the material can be determined.
Key Fact:
In the commemoration of the Chandrayaan-3 mission, August 23 will be celebrated as National Space Day.
Context: The Vikram lander of Chandrayaan-3 made it one of the closest approaches of a lunar mission to the moon’s South Pole. However, like most of the lunar-landing missions before, Vikram too landed on the near side of the moon.
What are the moon’s ‘near’ and ‘far sides’ and is there a ‘dark’ side?
Near side: The near side refers to the portion of the moon — about 60% — that is visible from Earth. This side of the Moon always faces the Earth and it is the side that humans have visited during various lunar missions.
Far side: The far side of the Moon is the side that is not visible from Earth. The reason it is less visible from Earth is due to a phenomenon called "tidal locking”. The phrase "dark side of the Moon" does not refer to "dark" as in the absence of light, but rather "dark" as in the unknown. In reality, both the near and far sides receive (on average) almost equal amounts of light directly from the Sun.
The ‘dark side’ was mysterious and its various topographical features were hidden until the Soviet spacecraft Luna 3 in 1959 photographed it and the Soviet Academy of Sciences released an Atlas of these images.
Astronauts aboard the Apollo 8 mission of 1968 were the first humans to see the far side of the moon.
All crewed and uncrewed soft landings had taken place on the near side of the Moon, until 3 January 2019 when China’s Chang'e 4 spacecraft made the first landing on the far side. This vehicle landed on the Von Karman crater situated within a larger 2,500 km wide crater called the South Pole Aitken basin.
Hence, both the near and far sides experience sunlight and darkness as they orbit the Sun, but the far side has historically been less explored and observed from Earth due to the Moon's tidally locked rotation.
Is the dark side very different from the near side?
The major difference between the two sides is that the near side is relatively smoother and has many more ‘maria’ or large volcanic plains compared to the far side.
On the far side, there are huge craters, thousands of kilometres wide, which have likely resulted from collisions with asteroids.
While both sides of the moon in its formative phase were similarly bombarded, the crust on the near side is thinner because of which, over millions of years, the volcanic lava in the lunar crust has flowed more extensively into the thinner side and filled up its craters. The resulting plains that have thus formed are far more conducive to space missions because they provide a relatively flat terrain for landers and rovers.
What is special about the Chandrayaan-3’s landing?
The Chandrayaan-3 mission, while still on the near side, has managed to land Vikram the closest ever to the lunar South Pole . The coordinates of Chandrayaan-3 at 69.36 S and 32.34 E make it about 600 km away from the South Pole.
The choice of being as close as possible to the South Pole was to get closer to a “permanently shadowed region” or where no sunlight ever reaches. This would mean increasing the chances of encountering frozen water-ice along with several “interesting deposits” that can reveal more about the moon and its harvestable resources.
Tidal locking:
Tidal locking, also known as gravitational locking or synchronous rotation, is a phenomenon that occurs when a celestial body's rotation period matches its orbital period around another body. This phenomenon is most commonly observed in natural satellites like moons, but it can also occur between planets and their stars.
In the case of the Moon, its rotation period is nearly the same as its orbital period around the Earth, which is about 27.3 days as well. This tidal locking has resulted in the Moon always showing the same face, the near side, to the Earth.
