Daily Prelims Notes 22 February 2024

February 22, 2024
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Daily Prelims Notes

22 February 2024

Table Of Contents

1. ISRO completes key test, CE20 cryogenic engine is now human-rated for Gaganyaan missions

Subject: Science and tech

Section: Space tech

Context:

Isro has accomplished the human rating of its cryogenic engine (CE20), which powers the cryogenic stage of the human-rated LVM3 launcher for India’s first human space flight mission Gaganyaan.

More on news:

ISRO’s CE20 cryogenic engine is now human-rated for Gaganyaan missions. Rigorous testing demonstrates the engine’s mettle.
The CE20 engine identified for the first uncrewed flight LVM3 G1 also went through acceptance tests.
Human-rating refers to rating a system that is capable of safely transporting humans.
The final test was carried out on February 13.
It was the seventh in a series of vacuum ignition tests carried out at the High Altitude Test Facility at ISRO Propulsion Complex, Mahendragiri, to simulate flight conditions.

About CE20 cryogenic engine:

The CE-20 is an indigenous cryogenic engine ISRO developed to use with the GSLV Mk III, now called the LVM-3, launch vehicle.
It represents an improvement on the CE-7.5 cryogenic engine and is instrumental to ISRO successfully realizing its human spaceflight, a.k.a. Gaganyaan, mission.
The CE-20 engine uses the gas-generator cycle, which discards the exhaust from the pre-burner instead of sending it to the combustion chamber.
This reduces fuel efficiency but, importantly for ISRO, makes the CE-20 engine easier to build and test.
The CE20 engine is a vital component, serving as the powerhouse of the Cryogenic Upper Stage (CUS) responsible for propelling the upper stage (C25) of the LVM3 vehicle.
While the CE-7.5 engine is lighter and sports higher fuel-use efficiency, the CE-20 engine achieves a higher maximum thrust (~200 kilonewton v. 73.5 kilonewton) with a shorter burn duration.
It has demonstrated its capability by successfully operating at a thrust level of 19 tonnes in six successive LVM3 missions, including the Chandrayaan-2, Chandrayaan-3, and two commercial OneWeb missions.
The ground qualification tests for the human rating of the CE20 engine involved life demonstration tests, endurance tests, and performance assessment under nominal operating conditions as well as off-nominal conditions w.r.t thrust, mixture ratio, and propellant tank pressure.

Updates on first unmanned Gaganyaan (G1) mission:

ISRO has also successfully completed the acceptance tests of the flight engine identified for the first unmanned Gaganyaan (G1) mission, tentatively scheduled for Q2 of 2024.
This engine will power the upper stage of the human-rated LVM3 vehicle and has a thrust capability of 19 to 22 tonnes with a specific impulse of 442.5 seconds.
This engine will power the upper stage of the human-rated LVM3 vehicle and has a thrust capability of 19 to 22 tonnes with a specific impulse of 442.5 seconds.

About Gaganyaan Mission:

Gaganyaan is a mission by the Indian Space Research Organization (ISRO).
Under the Gaganyaan schedule:
- Three flights will be sent into orbit.
- There will be two unmanned flights and one human spaceflight.
The Gaganyaan system module, called the Orbital Module will have three Indian astronauts, including a woman.
It will circle Earth at a low-earth-orbit at an altitude of 300-400 km from earth for 5-7 days.
Payloads:
- Crew module –spacecraft carrying human beings.
- Service module –powered by two liquid propellant engines.
- It will be equipped with emergency escape and emergency mission abort.
GSLV Mk III, also called the LVM-3 (Launch Vehicle Mark-3,)the three-stage heavy lift launch vehicle, will be used to launch Gaganyaan as it has the necessary payload capability.

2. Cabinet approves amendment in the Foreign Direct Investment (FDI) policy on Space Sector

Subject: Economy

Section: External sector

Context:

The Union Cabinet chaired by Prime Minister Shri Narendra Modi approved the amendment in Foreign Direct Investment (FDI) policy on the space sector.

More on news:

The satellite sub-sector has been divided into three different activities with defined limits for foreign investment in each such sector.
The Indian Space Policy 2023 was notified as an overarching, composite and dynamic framework to implement the vision for unlocking India’s potential in the Space sector through enhanced private participation.
The FDI policy reform will enhance Ease of Doing Business in the country.
It will further lead to greater FDI inflows and thereby contributing to growth of investment, income and employment.

FDI in Space sector:

As per the existing FDI policy, FDI is permitted in establishment and operation of Satellites through the Government approval route only.
Under the amended FDI policy, 100% FDI is allowed in the space sector.
The liberalized entry routes under the amended policy are aimed to attract potential investors to invest in Indian companies in space.

The entry route for the various activities under the amended policy are as follows:

Upto 74% under Automatic route:
- Satellites-Manufacturing & Operation, Satellite Data Products and Ground Segment & User Segment.
- Beyond 74% these activities are under government route.
Upto 49% under Automatic route:
- Launch Vehicles and associated systems or subsystems, Creation of Spaceports for launching and receiving Spacecraft.
- Beyond 49% these activities are under government route.
Upto 100% under Automatic route:
- Manufacturing of components and systems/ sub-systems for satellites, ground segment and user segment.

Benefits of Increased FDI:

This increased private sector participation would help to generate employment, enable modern technology absorption and make the sector self-reliant.
It is expected to integrate Indian companies into global value chains.

About Foreign Direct Investment:

Foreign Direct Investment

FDI is the process whereby residents of one country (the home country) acquire ownership of assets for the purpose of controlling the production, distribution and other activities of a firm in another country (the host country).
It is different from Foreign Portfolio Investment where the foreign entity merely buys stocks and bonds of a company. FPI does not provide the investor with control over the business.
Flows of FDI comprise capital provided (either directly or through other related enterprises) by a foreign direct investor to an enterprise.
FDI has three components, viz., equity capital, reinvested earnings and intra-company loans.
Equity capital is the foreign direct investor’s purchase of shares of an enterprise in a country other than its own.
Reinvested earnings comprise the direct investors’ share (in proportion to direct equity participation) of earnings not distributed as dividends by affiliates, or earnings not remitted to the direct investor. Such retained profits by affiliates are reinvested.
Intra-company loans or intra-company debt transactions refer to short- or long-term borrowing and lending of funds between direct investors (or enterprises) and affiliate enterprises.

3. How a Chinese rocket failure boosted Elon Musk’s SpaceX in Indonesia

Subject: Science and tech

Section: Space tech

Context:

How a Chinese rocket failure boosted Elon Musk’s SpaceX in Indonesia

More on news:

Since the incident, SpaceX has successfully launched two Indonesian satellites, with a third scheduled for the coming Tuesday, while China has handled none.
The global space industry is witnessing fierce competition for dominance, with the satellite market alone valued at $281 billion in 2022.

About Nusantara Satu:

Nusantara Satu (formerly known as PSN VI or PSN-6) is an Indonesian communications satellite. It is a large high-throughput satellite (HTS) providing voice and data communications, and Internet access throughout the Indonesian archipelago and Southeast Asia.
Nusantara Satu is a communications satellite developed and designed by SSL for PT PasifikSatelit Nusantara (PSN), the first private company in the telecommunications and information services sector in Indonesia.
Nusantara-2 was the second satellite launch awarded by Indonesia to CGWIC, matching the two carried out by SpaceX at that time.

About Space Race:

China launched a record 67 rockets last year, out of 223 globally.
China is only behind the United States, which had 109 launches, 90% of which were done by SpaceX

About Kessler Syndrome:

The Kessler Syndrome Is a theoretical scenario in which Earth’s orbit is overpopulated with objects and debris, preventing the use of satellites in certain sections of Earth’s orbit.
Space debris are defunct human-made objects in space – principally in Earth orbit – which no longer serve a useful function.
These include derelict spacecraft, mission-related debris, and particularly-numerous in-Earth orbit fragmentation debris from the breakup of derelict rocket bodies and spacecraft.

4. Fali S Nariman: 9 notable cases of the late jurist

Subject: Polity

Section: Judiciary

Context:

Eminent jurist and Senior Advocate Fali S Nariman passed away in the early hours of February 21 at the age of 95.

More on news:

His career as a lawyer spanned over 75 years with the last half-century being spent as a senior advocate of the Supreme Court of India.

Most notable cases by Jurist Fali S Nariman:

The Second Judges Case: Supreme Court Advocates-on-Record Association v. Union of India
- In 1981, a five-judge constitution bench of the Supreme Court gave the central government the final say in matters regarding judicial appointments and transfers by allowing the President to refuse recommendations made by the Chief Justice of India (CJI).
- The court held that the requirement under Article 124 of the Constitution, stating that the CJI must be “consulted”, means that there must be an exchange of views, and there is no necessity for “concurrence” between the CJI and the President.
- Nariman argued that “consultation” in the context of judicial appointments means more than merely seeking advice.

The Third Judges Case: In re: Special Reference 1
- The President of India K R Narayanan exercised his power under Article 143 of the Constitution to send a “reference” to the Supreme Court for the latter’s opinion on questions of law that may have public importance.
- Nariman made submissions to assist the court in this case.
- Further, it expanded the size of the Supreme Court Collegium to five senior most judges from the existing three.

National Judicial Appointments Commission case: Supreme Court Advocates-on-Record Association v. Union of India
- Nariman would also appear in the latest chapter of the judge appointments dispute following the challenge to the National Judicial Appointment Commission Act, 2014 (NJAC).
- The NJAC amended the Constitution to insert Article 124A which created a six-person commission for judicial appointments.
- This commission would comprise the CJI, two other senior SC Judges, the Union Minister of Law and Justice, and two “eminent persons” who would be nominated by a committee comprising the CJI, Prime Minister and Leader of Opposition.

Parliament cannot curtail fundamental rights: I.C. Golak Nath v. State of Punjab
- Two brothers in Punjab challenged the Constitution (Seventeenth) Amendment Act, 1964 as it amended Article 31A of the constitution.
- Fali Nariman appeared on behalf of the intervenors in this case who supported the petitioners. They argued that Parliament’s power to amend the constitution under Article 368 did not include articles contained in Part III of the Constitution dealing with fundamental rights.
- It was pointed out that Article 13(2) states that Parliament cannot make a law which infringe fundamental rights.

Bhopal gas tragedy: Union Carbide Corporation v. Union of India (1989)
- Senior Advocate Nariman appeared, representing Union Carbide, and offered to pay a sum of 426 million dollars as compensation to the victims of the tragedy.
- In 1989, Union Carbide reached a settlement with the central government and agreed to pay 470 million dollars as compensation.

Rights of minorities to establish and administer education institutions: TMA Pai Foundation v. State of Karnataka
- Nariman argued in the landmark TMA Pai case in support of minority rights to establish and administer educational institutions under Article 30(1) of the Constitution.
- The court held that linguistic and religious minorities have to be determined on a state-by-state basis and that the government has the power to frame regulations which will apply to minority-run educational institutions.

Governor to act only upon the aid and advice of the council of ministers, chief minister: Nabam Rebia, and Bamang Felix v. Deputy Speaker
- The Supreme Court in 2016 was tasked with navigating the political crisis in Arunachal Pradesh following the rebellion of 21 Congress MLAs in 2015.
- Nariman, on behalf of the house whip Bamang Felix, argued that the governor did not have the power to advance the assembly session as this could only be done upon the aid and advice of the council of ministers and the chief minister, as per the constitution.
- The court agreed and restored the Congress government, led by chief minister Nabam Tuki.

Obtaining bail for former Tamil Nadu Chief Minister Jayalalitha: J. Jayalalithaa v. State of Tamil Nadu
- Former Chief Minister Jayalalitha had been accused of misappropriating funds during her tenure between 1991 and 1995.
- Nariman appeared on behalf of Jayalalitha in October 2014 and convinced the court to grant bail against executing the fine and suspend the sentence passed by the Sessions judge in Bangalore.

Cauvery Water Dispute: State of Karnataka v State of Tamil Nadu
- Nariman represented Karnataka for over 30 years in the water-sharing dispute with Tamil Nadu.
- In 2016, the Supreme Court ordered the Karnataka government to release 6,000 cusecs (cubic feet per second) of water from September 21 to September 27.

5. India’s smartphone exports rise from 1% to 2.5% in a decade

Subject: Economy

Section: External Sector

Context:

In recent times, India has laid much emphasis on smartphone exports. In FY 2023, Prime Minister Narendra Modi lauded phone exports as they crossed the $10 billion mark.

Smartphone export from India

India is one of the leading players when it comes to cell phone exports by country.
The country aims to accomplish the production of electronics worth US$ 300 billion by FY 2026; manufacturing mobile phones will be the key to achieving India’s ambitious goal.
India’s electronic goods exports surged by approximately 88% from US$ 6,600 million in FY 2013-14 to US$ 12,400 million in FY 2021-22.
Mobile phones, consumer electronics, IT hardware, auto electronics, and industrial electronics were the key products exported from India.

Steps taken by India to promote smartphone exports:

Production-Linked Incentive (PLI) Scheme: The government has launched the PLI scheme to provide financial incentives to smartphone manufacturers to boost local production and exports.
Phased Manufacturing Program (PMP): The PMP program promotes domestic value addition in mobile phones and their sub-assemblies/parts manufacturing.
Foreign Direct Investment (FDI): The government has permitted 100% FDI under the automatic route for manufacturing electronic devices (excluding countries sharing land borders with India). This has helped attract foreign investment in the electronics manufacturing sector.
Incentivized Areas for Export-Oriented Units: Special Economic Zones (SEZs) have been set up across the country to facilitate export-oriented manufacturing and trading. Units for manufacturing and related services set up under the Electronic Hardware Technology Park (EHTP) scheme are major contributors to India’s electronics exports
Design Linked Incentive (DLI) Scheme: The DLI scheme offers financial incentives and design infrastructure support across various stages of development and deployment of chipsets, systems & IP cores, and semiconductor-linked design. The scheme provides both a “Product Design Linked Incentive” and a “Deployment Linked Incentive”.

Challenges to India’s Smartphone Export Ambitions:

Disparity in Export Percentages: The lower taxes in China and Vietnam helped boost their exports. Exports accounted for only 25% of India’s smartphone production in 2023, compared with 63% of China’s $270 billion worth of production and 95% of Vietnam’s $40 billion worth.
Limited Tax Reductions on Components: The finance ministry lowered taxes on some components, including battery covers, to 10% from 15%, but did not agree to many other tariff cut requests.
High Tariffs on Specific Components: India still imposes a 20% tax on parts including chargers, some circuit boards, and fully assembled phones.
Tariff Discrepancies: The lawmakers and lobby groups for Apple and other firms argue India’s high tariffs are a deterrent for companies de-risking their supply chains beyond China, and nations such as Vietnam, Thailand, and Mexico have raced ahead in phone exports by offering lower tariffs on components.
Elevated Production Costs: India has high production costs as we have one of the highest tariffs among the key manufacturing destinations.
Supply chain limitations: Made in India phones use many parts made locally, but companies import many high-end parts from China and elsewhere due to supply chain limitations.

6. Illegal lending apps on FSDC radar

Subject: Economy

Section: Monetary Policy

What is FSDC (Financial Stability and Development Council)?

Establishment:

It is a non-statutory apex council under the Ministry of Finance constituted by the Executive Order in 2010
The Raghuram Rajan committee (2008) on financial sector reforms first proposed the creation of FSDC.

Composition:

It is chaired by the Finance Minister and its members include the heads of all Financial Sector Regulators (RBI, SEBI, PFRDA & IRDA), Finance Secretary, Secretary of Department of Economic Affairs (DEA), Secretary of Department of Financial Services (DFS), and Chief Economic Adviser.
In 2018, the government reconstituted FSDC to include the Minister of State responsible for the Department of Economic Affairs (DEA), Secretary of Department of Electronics and Information Technology, Chairperson of the Insolvency and Bankruptcy Board of India (IBBI) and the Revenue Secretary.

FSDC sub-committee is headed by the Governor of RBI.

The Council can invite experts to its meeting if required.

Functions:

To strengthen and institutionalize the mechanism for maintaining financial stability, enhancing inter-regulatory coordination and promoting financial sector development.
To monitor macro-prudential supervision of the economy. It assesses the functioning of large financial conglomerates.

Recent context:

-Regulators discuss fresh measures to curb the further spread of harmful unauthorised lending through online apps during recent FSDC meet.

Unauthorised loan apps:

RBI has shared a list of 442 unique digital lending apps used by the regulated entities with Ministry of Electronics & Information Technology (MeitY) for the purpose of whitelisting and the same was shared with Google.
As per the information received from MeitY, during April 2021 – July 2022, Google had reviewed approximately 3,500 to 4,000 loan apps and suspended / removed over 2,500 loan apps from its Play Store. Similarly, during September 2022 – August 2023, over 2,200 loan apps were removed from the Play Store. However, the problem still persists.

Various discussions at FSDC meet:

Need for uniform KYC norms to ensure ‘inter-usability’ across the financial sector
Need for “constant vigil and proactive efforts” to detect emerging financial stability risks in the current domestic and global macro-financial situation.
Maintaining the resilience of the financial sector
To strengthen inter-regulatory coordination to further develop the financial sector to provide requisite financial resources for inclusive economic growth .

Prominent discussion:

To arrest the harmful effects of unauthorised lending through online apps and measures to curb their further spread
FSDC reiterated push for regulators to simplify and digitise the KYC (Know Your Customer) process and adopt uniform KYC norms so that those KYC records can provide customers ‘inter-usability’ across the financial sector.

Diverse authorities attended FSDC meet:

Along with The chiefs of various financial sector regulators and top finance ministry officials, the FSDC meeting was also attended by the Secretary to the Ministry of Electronics and Information Technology S. Krishnan. The Ministry is critical to the process of delisting lending apps that are not authorised by the RBI.

7. On financial devolution among States

Subject: Polity

Section: Federalism

Context:

Recently various Opposition-ruled States especially from South India have claimed that they have not been receiving their fair share as per the present scheme of financial devolution.

Issue in present scheme:

Less than proportionate share of receipt in tax revenue when compared to their contribution towards tax collection highlighted in below chart 1.

Statewise analysis chart:

What is divisible pool of taxes?

Article 270 of the Constitution provides for the scheme of distribution of net tax proceedscollected by the Union government-between the Centre and the States.
The taxes that are shared between the Centre and the States include corporation tax, personal income tax, Central GST, the Centre’s share of the Integrated Goods and Services Tax (IGST) etc.
This division is based on the recommendation of the Finance Commission (FC) that is constituted every five years as per the terms of Article 280.
Apart from the share of taxes, States are also provided grants-in-aid as per the recommendation of the FC.

Note: The divisible pool, however, does not include cess and surcharge that are levied by the Centre.

Comparison across states(in share of states in divisible pool of taxes) in Chart 2 :

How is the Finance Commission constituted?

The FC is a constitutional body (Art. 280 of constitution) constituted every five years, exclusively by the Union Government.
It consists of a chairman and four other members (total 5 ) who are appointed by the President.
The Finance Commission (Miscellaneous Provisions) Act, 1951, has specified the qualifications for chairman and other members of the commission. –The Union government has notified the constitution of the 16th Finance Commission under the chairmanship of Arvind Panagariya for making its recommendations for the period of 2026-31.

What is the basis for allocation?

The share of States from the divisible pool (vertical devolution) stands at 41% as per the recommendation of the 15th FC.
The distribution among the States (horizontal devolution) is based on various criteria.

Comparison of Horizontal devolution in various FC and in various parameters and parameter changes in following Table 1:

The criteria as per the 15th FC can be briefly explained as follows: a.‘Income distance’ is the distance of a State’s income from the State with highest per capita income which is Haryana.

States with lower per capita income would be given a higher share to maintain equity among States.

‘Population’ is the population as per the 2011 Census. Till the 14th FC, weightage was given for the population as per the 1971 Census but discontinued in the 15th FC. ‘Forest and ecology’ consider the share of dense forest of each State in the aggregate dense forest of all the States.

‘The demographic performance’ criterion has been introduced to reward efforts made by States in controlling their population.

States with a lower fertility ratio will be scored higher on this criterion.

‘Tax effort’ as a criterion has been used to reward States with higher tax collection efficiency.

What are the issues?

The Constitutional scheme has always favoured a strong centre in legislative, administrative and financial relations.
- However, federalism is a basic feature and States should not feel short-changed in distribution of resources.
Political differences between the Union government and Opposition-ruled States that exacerbate the problem.

Genuine issues for consideration:

Cess and surcharge collected by the Union government is estimated at around 23% of its gross tax receipts for 2024-25, which does not form part of the divisible pool and hence not shared with the States.

Justification: The total tax revenue for the year 2022-23 (actual), 2023-24 (revised estimates) and 2024-25 (Budget estimates) of the Union government is ₹30.5, ₹34.4 and ₹38.8 lakh crore respectively. The State’s share was/is ₹9.5, ₹11.0 and ₹12.2 lakh crore respectively, which constitutes around 32% of the total tax receipts of the Centre which is way less than the 41% as recommended by the 15th FC.

Also, Cess like the GST compensation cess is for the repayment of loans taken to compensate States for the shortfall in tax collection due to GST implementation for the period 2017-22. Some amounts are used for centrally sponsored schemes that benefit the States. However, the States have no control over these components.

The amount each State gets back for every rupee they contribute to Central taxes shows steep variation. Chart 1 depicts the same for the year 2021-22.

Industrially developed States received much less than a rupee for every rupee they contributed as against States like Uttar Pradesh and Bihar.

Below factors are responsible:

Many corporations are headquartered in these State capitals where they would remit their direct taxes.

Also attributed to the difference in GST collection among various States.

The percentage share in the divisible pool of taxes has been reducing for southern States over the last six FCs as can be seen in Chart 2.

Attributed to following factors:

Higher weightage being given for equity (income gap) and needs (population, area and forest) than efficiency (demographic performance and tax effort).

Grants-in-aid as per the recommendation of the FC varies among various State.

As per the 15th FC, there are revenue deficit, sector-specific and State-specific grants given to various States as well as grants to local bodies that are given based on population and area of States.

Way forward?

As some of states generate around 40% of the revenue and bear around 60% of the expenditure. The FC and its recommendations are meant to assess this imbalance and propose a fair sharing mechanism. -It is the responsibility of all States to contribute towards the more equitable development of our country.
However, there are three important reforms that may be considered for maintaining the balance between equity and federalism while sharing revenue.
Firstly, the divisible pool can be enlarged by including some portion of cess and surcharge in it.
The Centre should also gradually discontinue various cesses and surcharges it imposes by suitably rationalising the tax slabs.
Secondly, the weightage for efficiency criteria in horizontal devolution should be increased. Case study: GST being a consumption-based destination tax that is equally divided between the Union and the State means that State GST accrual (inclusive of Integrated GST settlement on inter-state sales) should be the same as the Central GST accrual from a State. Hence, relative GST contribution from States can be included as a criterion by providing suitable weightage in future FCs.
Finally, similar to the GST council, a more formal arrangement for the participation of States in the constitution and the working of the FC should be considered.

Conclusively,

These are measures that need to be implemented by the Centre after discussion with all the States.
It is also imperative that the States uphold principles of fiscal federalism by devolving adequate resources to local bodies for vibrant and accountable development.

8. Astronomers found the small and hot helium stars they were looking for

Subject: Science and tech

Section: Space tech

Research details:

Led by assistant professor Maria Drout of the University of Toronto, the research team found these stars after spending seven years of hard work.

Outcome of Research :(Looking for):

A unique class of stars (are cosmic engines) hot and relatively small orbs covered in helium.

Importance of Research:

To understanding Stars’s diverse influences on the universe, from the creation of heavy elements to the release of gravitational waves.

Why Sun doesn’t collapse onto itself?

Newton’s law of gravity says all objects with mass attract each other.
Applying this – the Sun’s outer and inner layers should be attracted to each other, the Sun should continuously fall inwards and eventually simply collapse.

Yet the Sun rises every day, as it did yesterday and will tomorrow.

Reason: Nuclear fusion prevents the Sun from shrinking.

Nuclear Fusion: In the heart of the star, chemical reactions merge the nuclei of two light elements — such as hydrogen or helium — to form a heavier nucleus, such as of silicon. In the process releases an enormous amount of heat.

This energy endows all particles in the star with random motion, or pressure, which then fights against the pull of gravity and maintains the star in a state of equilibrium.

Conclusion:

The fusion energy pushes the star out while gravity pulls it in, and they hold the balance for billions of years. Such stars are said to be in the main sequence.

Main sequence: On plotting stars’ colours against their brightness, many stars occupied a prominent band in the middle of the graph, referred as ‘main sequence’.

Other possibilities and associated features:

Supernova:

When a star (heavy enough) no longer fuses material and gravity overtakes, then heavy enough star blows up in an explosion, called a supernova.
By making scientific studies of light from supernovae it is observed that light contain signatures of elements that it passed.
Also, some supernovae have no hydrogen. And yet it is well understood that hydrogen (lightest element ) makes up outer layer of main-sequence stars .

Explanation of this:

The outer layers of some stars are stripped away before the supernova explosion.
Reason behind this(No hydrogen/outer layer stripped off):
If the star is part of a binary system — i.e. as one of two stars that are orbiting each other. (Most stars heavier than the Sun are in such binaries.)
Then the gravitational attraction of one star can peel away the hydrogen layer off the other, leaving an exposed surface of helium. This would leave a small, hot helium star with strong surface gravity.

Stars part of Binary system:

Most stars with more than eight solar masses are expected to be part of binary systems, so we should reasonably expect numerous binary-stripped helium stars in the universe.
Present availability of Binary system:
Till date, astronomers have found exactly one binary system in the mass range of eight to 25 solar masses (prior to stripping), and have been looking for the others.
Recent findings- Main companion star and bright outliers analysis:
Drout & co. have now reported a population of these stars.
Many binary systems start out with two main sequence stars.One of them rips the hydrogen layer off the other-resulting in one helium star and one main sequence companion.
to team, the companion would outshine the stripped star in the frequencies of light (both human eyes as well as optical telescopes are sensitive to it )
Different frequencies roughly correspond to different colours of light.
The hotter an object is, the more energy it has, the higher the frequency of emitted light, and the bluer it glows.
Helium stars are expected to be so hot that they emit more of their energy as ultraviolet radiation, which lies beyond the visible range.
So, the research catalogued around half a million stars in two nearby galaxies — the Large and the Small Magellanic Clouds — using data from a telescope that could ‘see’ ultraviolet light.

Most of the stars were main sequence stars, but also some bright outliers.

Speed analysis findings:

If a star were isolated, it would be seen moving either towards or away from the earth at a constant rate.
But some of the outliers had different speeds over time – hinting at the presence of a companion that restricted their free movement.

When the researchers examined the spectra of the 25 stars- they found–

Class 1: Several with a strong presence of helium and an absence of hydrogen.

Class 2 and Class 3: Some possessed hydrogen as well.

Based on this, the team made two conclusions:

(1) Class 1 stars have no hydrogen and are rich in helium

(2) their companions are either low-mass not-as-bright main sequence stars or compact objects (neutron stars or blackholes) that don’t emit ultraviolet light strongly.

On various researches it is concluded:

The surface temperature of Class 1 stars to be roughly 20-timesthat of the Sun and the surface gravity about 1,000-times that of the earth.

Hence, Class 1 are hot, strongly gravitating, helium-rich, and hydrogen-depleted stars and part of binary systems.

Final outcome:

The team discovered the long-awaited intermediate-mass hydrogen-stripped helium stars in binaries after seven years.

And, These stars will end their lives as hydrogen-poor supernovae that leave behind ultra-dense balls called neutron stars. And these neutron stars may ultimately smash into each other in powerful kilonova explosions, releasing gravitational waves.