On 6 July 2026, the Ministry of Science & Technology (PIB Delhi) announced a striking result: an international team including Dr. Aru Beri of the Indian Institute of Astrophysics (IIA) — an autonomous institution under the Department of Science & Technology (DST) — used a high-resolution radio survey to reveal a hidden population of faint, weakly active supermassive black holes in nearby galaxies. Using the e-MERLIN radio array in the United Kingdom, the team observed 280 nearby galaxies from the Palomar sample and detected compact radio emission from the centres of nearly one-quarter of them — black holes quietly feeding at their cores. The radio data were cross-checked with X-ray observations from NASA's Chandra X-ray Observatory to confirm the emission comes from accreting black holes, not ordinary star formation. Published in the Monthly Notices of the Royal Astronomical Society (MNRAS), the finding suggests this low-level activity may be the dominant mode of black-hole growth in the present-day Universe. For NDA and CDS aspirants, this one item opens up almost the entire "black holes and astronomy" section of the General Knowledge and Physics syllabus.
What Exactly Is a Black Hole?
A black hole is a region where matter has collapsed to such extreme density that its gravity is so strong that nothing — not even light — can escape from within a certain boundary.
- Event horizon: the "point of no return." Anything crossing it can never come back out — a one-way surface, not a physical wall.
- Singularity: at the very centre, a singularity — a point of (theoretically) infinite density where the known laws of physics break down.
- Escape velocity greater than the speed of light: escape velocity is the minimum speed needed to break free of a body's gravity. At a black hole's event horizon it exceeds the speed of light (c ≈ 3 × 10⁸ m/s) — and since nothing travels faster than light, nothing escapes. Hence "black."
The idea flows from Einstein's General Theory of Relativity (1915), which describes gravity as the curvature of space-time by mass. In 1916, Karl Schwarzschild derived the radius (the Schwarzschild radius) at which an object becomes a black hole; in 1965, Roger Penrose proved black-hole formation is a robust prediction of general relativity — work for which he shared the 2020 Nobel Prize in Physics. The term "black hole" was popularised by John Wheeler in 1967.
Stellar-Mass vs Supermassive Black Holes
Not all black holes are the same size. Two families dominate the exam-relevant picture:
- Stellar-mass black holes form when a massive star (roughly 20+ times the Sun) exhausts its nuclear fuel and its core collapses in a supernova explosion. They typically weigh from a few to a few dozen solar masses (M☉). Between a white dwarf/neutron star and a black hole, the deciding factor is mass — beyond a critical limit, nothing can halt the collapse.
- Supermassive black holes (SMBHs) sit at the centres of galaxies and weigh millions to billions of solar masses. Our own Milky Way hosts one. The new IIA-linked study is specifically about supermassive black holes in the cores of nearby galaxies.
- Intermediate-mass black holes (hundreds to thousands of M☉) are a rarer, less-understood middle category, and primordial black holes (hypothetically formed in the early Universe) remain unconfirmed.
The key exam link is between stellar death and black holes — a natural crossover with the physics topics on gravitation, energy and stellar processes. Astronomers now believe almost every large galaxy harbours a supermassive black hole at its centre, which is precisely why the "quarter of galaxies show faint activity" headline matters: it hints that these hidden giants are far more active, on a low level, than earlier surveys could reveal.
The Detection Puzzle: How Do You See Something That Emits No Light?
A black hole emits no light from inside the event horizon, so astronomers detect one indirectly, through its effects on the surroundings:
- Accretion disks: gas and dust spiralling inward form a flattened, rapidly rotating accretion disk. Friction heats it to millions of degrees, making it glow fiercely — especially in X-rays. The light we see comes from matter just before it falls in.
- X-ray emission: superheated infalling material and X-ray binaries radiate high-energy X-rays — which is why an X-ray observatory (Chandra) was used here to confirm the radio glow came from an accreting black hole, not star formation.
- Radio jets and outflows: many feeding black holes launch enormous jets of charged particles at nearly light-speed, perpendicular to the disk. These jets shine brightly at radio wavelengths — the exact signature e-MERLIN hunted.
- Gravitational effects on stars: tracking stars whipping around an invisible central mass lets astronomers weigh the hidden object — how the Milky Way's central black hole was pinned down.
- Gravitational waves: merging black holes send ripples through space-time — gravitational waves — detected on Earth by observatories like LIGO.
The new PIB result is essentially a masterclass in this indirect method: radio (jets/compact emission) + X-ray (accretion) = confirmed black-hole activity.
Active Galactic Nuclei and the "Faint" Discovery
When a supermassive black hole feeds vigorously, the galaxy's core becomes extraordinarily luminous and is called an Active Galactic Nucleus (AGN). Blazars, quasars and Seyfert galaxies are all types of AGN — some outshine their entire host galaxy.
But most nearby galaxies are not blazing quasars. Their central black holes are weakly accreting — faint, low-luminosity, and easily lost in the glare of surrounding stars. That is exactly what the international team addressed:
- They observed 280 galaxies from the Palomar sample at very high angular resolution, probing the central regions on parsec scales (1 parsec ≈ 3.26 light-years).
- They found compact radio emission in ~25% of them — signalling weakly accreting supermassive black holes normally missed by conventional surveys.
- Most sources were extremely compact; a smaller fraction showed jet-like structures extending over several parsecs.
- The team's conclusion: faint, low-level activity may be the dominant mode of black-hole growth today — the Universe's giants mostly grow through a slow trickle, not dramatic quasar-like feasts.
This nuance — "faint" and "low-luminosity" AGN as the norm — is the fresh, examinable hook of the 2026 story.
Sagittarius A*: The Black Hole at the Milky Way's Heart
Our own galaxy's centre hosts Sagittarius A* (pronounced "Sagittarius A-star"), a supermassive black hole of about 4 million solar masses, located roughly 26,000–27,000 light-years from Earth in the direction of the constellation Sagittarius.
- Astronomers Reinhard Genzel and Andrea Ghez independently tracked stars (notably the star S2) orbiting this invisible central mass since the 1990s using infrared telescopes, proving a supermassive compact object lurks there. Together with Roger Penrose, they shared the 2020 Nobel Prize in Physics — Ghez becoming only the fourth woman to win a physics Nobel.
- Sgr A is normally quiet — a good real-world example of exactly the kind of weakly accreting* black hole the new survey specialises in detecting elsewhere.
Understanding Sgr A* ties neatly into the astronomy and space portions of the general knowledge syllabus, where the Milky Way, galaxies and the Solar System recur every year.
Radio Astronomy: Seeing What Optical Telescopes Cannot
Why radio? Because the Universe broadcasts across the entire electromagnetic spectrum, not just visible light.
- Radio waves have the longest wavelengths and can pass through dust and gas clouds that block optical light. The galactic centre, thick with dust, is far easier to study in radio and infrared than in visible light.
- Radio telescopes reveal synchrotron emission from jets and magnetised plasma — the tell-tale signature of black-hole activity — that optical telescopes simply cannot see.
- The catch: a single radio dish has poor angular resolution (sharpness). The fix is interferometry — linking many antennas so they act as one giant telescope. The e-MERLIN array used in this study is exactly this: 7 radio telescopes spread across the UK, coordinated by Jodrell Bank, combining their signals to achieve resolution no single dish could.
This is the same principle behind India's own radio-astronomy pride — the Giant Metrewave Radio Telescope (GMRT / upgraded uGMRT) near Pune, operated by NCRA-TIFR, one of the world's most sensitive low-frequency radio arrays. While the GMRT was not the instrument in this particular study, it makes the perfect Indian comparison for how radio interferometry works.
The Indian Angle: IIA and India's Growing Astronomy Muscle
The Indian connection here is Dr. Aru Beri, a faculty member at the Indian Institute of Astrophysics (IIA), Bengaluru — an autonomous institute under the DST. IIA is one of India's premier astronomy bodies, tracing its lineage to the Madras Observatory (1786) and the Kodaikanal Solar Observatory, and formally established as IIA in 1971. Its major facilities include:
- Kodaikanal Solar Observatory (Tamil Nadu) — solar physics.
- Vainu Bappu Observatory, Kavalur (Tamil Nadu) — optical astronomy.
- Indian Astronomical Observatory, Hanle (Ladakh) — one of the world's highest observatories, and part of India's newly notified Dark Sky Reserve.
- Gauribidanur Radio Observatory (Karnataka).
India's astronomy ecosystem also includes ASTROSAT (India's first dedicated multi-wavelength space observatory, launched 2015 by ISRO), the GMRT/uGMRT at Pune, and the Aditya-L1 solar mission. Indian scientists are also part of LIGO-India, the gravitational-wave detector being built in Maharashtra — the broader "recent Indian astronomy facilities" thread examiners increasingly love.
Context Points Every Aspirant Should Know
Two landmark achievements give this story its wider frame:
- The Event Horizon Telescope (EHT) produced the first-ever image of a black hole in 2019 — the supermassive black hole M87* at the centre of galaxy Messier 87, about 53 million light-years away and roughly 6.5 billion solar masses. In 2022, the EHT unveiled the first image of Sagittarius A* itself. The EHT works by linking radio dishes across the globe into an Earth-sized virtual telescope — interferometry, again.
- LIGO (Laser Interferometer Gravitational-wave Observatory) made the first direct detection of gravitational waves in 2015 (announced Feb 2016) from two merging black holes — confirming a century-old Einstein prediction and earning the 2017 Nobel Prize in Physics.
Set against these dramatic, high-luminosity events, the 2026 IIA-linked survey is quietly profound: it maps the ordinary, faint, everyday black holes that make up the silent majority.
The Big Picture for an Aspirant
Reduce the story to a chain of exam-ready facts. Black holes emit no light, so they are found indirectly — through accretion disks, X-rays, radio jets, orbiting stars, and gravitational waves. Feeding SMBHs create AGN; most galaxies host an SMBH, but usually a faint, weakly accreting one. The new study used the UK's e-MERLIN radio array plus NASA's Chandra X-ray data to find this faint activity in ~25% of 280 galaxies, with an IIA/DST scientist on the team. Anchor the numbers — Sgr A* ≈ 4 million M☉, ~27,000 ly; M87* ≈ 6.5 billion M☉, imaged 2019; Sgr A* imaged 2022; gravitational waves first detected 2015 by LIGO — and connect them to India's IIA, GMRT, ASTROSAT and LIGO-India. Keeping up with such stories through the NDA current-affairs hub is the surest way to convert one PIB release into 3–4 correct marks.
🎯 Practice MCQs
Q1. The boundary of a black hole beyond which nothing, not even light, can escape is called the: (a) Singularity (b) Event horizon (c) Accretion disk (d) Photon sphere → (b) — The event horizon is the one-way "point of no return"; the singularity is the central point of infinite density.
Q2. In the July 2026 radio study of nearby galaxies, which radio facility was used to observe the 280 Palomar-sample galaxies? (a) GMRT, Pune (b) e-MERLIN, United Kingdom (c) ALMA, Chile (d) Arecibo, Puerto Rico → (b) — The e-MERLIN array of 7 radio telescopes across the UK (coordinated by Jodrell Bank) was used.
Q3. The supermassive black hole at the centre of the Milky Way is named: (a) M87 (b) Cygnus X-1 (c) Sagittarius A (d) TON 618 → (c) — Sagittarius A*, about 4 million solar masses, roughly 27,000 light-years away.
Q4. The Indian scientist linked to the 2026 faint-black-hole study, Dr. Aru Beri, is affiliated with which institution? (a) ISRO (b) NCRA-TIFR (c) Indian Institute of Astrophysics (IIA) (d) IUCAA → (c) — IIA is an autonomous institute under the Department of Science & Technology (DST).
Q5. Which observatory's X-ray data were used to confirm that the radio emission came from accreting black holes rather than star formation? (a) Hubble Space Telescope (b) Chandra X-ray Observatory (c) James Webb Space Telescope (d) ASTROSAT → (b) — NASA's Chandra X-ray Observatory provided the complementary X-ray confirmation.
Q6. The first-ever image of a black hole, released in 2019 by the Event Horizon Telescope, was of the black hole in which galaxy? (a) Andromeda (b) Milky Way (c) Messier 87 (M87) (d) Whirlpool Galaxy → (c) — M87*, about 6.5 billion solar masses, ~53 million light-years away.
Q7. The 2020 Nobel Prize in Physics for black-hole research was shared by Roger Penrose, Reinhard Genzel and: (a) Andrea Ghez (b) Kip Thorne (c) Jocelyn Bell Burnell (d) Subrahmanyan Chandrasekhar → (a) — Andrea Ghez, for the discovery of a supermassive compact object at the Milky Way's centre.
Q8. Radio telescopes are combined into large arrays (interferometry) primarily to improve their: (a) Colour sensitivity (b) Angular resolution (sharpness) (c) Weight (d) Ability to detect visible light → (b) — Linking many antennas mimics one giant dish, giving resolution no single dish can achieve.
📋 How this gets asked (PYQ pattern)
Astronomy and space science are perennial favourites in the NDA/CDS General Knowledge (General Science) and Physics papers, and this topic sits at their intersection. The recurring angles are predictable: definitions (event horizon, escape velocity, singularity), the electromagnetic spectrum and why radio/infrared penetrate dust, stellar death → black hole formation, and matching famous facilities to their achievements (EHT image 2019, LIGO gravitational waves 2015, Chandra = X-ray). Static "match the observatory" and "name the mission" questions (ASTROSAT, GMRT, Hanle, IIA) show up regularly, and Nobel-Prize-in-science one-liners are near-certain in current affairs. The fresh 2026 hook is threefold — remember that faint/weakly-accreting black holes may be the dominant growth mode, that e-MERLIN + Chandra cracked the detection, and that an IIA/DST scientist was on the international team. Expect it framed as "which telescope," "which institute," or "which method (radio + X-ray)."
Preparing for NDA/CDS? Science & technology current affairs like this convert into direct marks when you track them daily. Follow structured explainers at the Cavalier NDA current-affairs hub, and if you want mentor-led classroom coaching from ex-Army officers, explore our upcoming NDA/CDS courses at Cavalier, Delhi.
✍️ Written by Col D.N. Sharma — Veteran, Indian Army; SSB & defence-studies faculty at The Cavalier. Reviewed by the Cavalier Faculty Desk. The Cavalier, founded by ex-Army officers, has trained NDA/CDS/SSB aspirants since 2001 (Facebook · YouTube).
Source: PIB release, 6 July 2026. Facts cross-verified.