PIB TrackerTen years watching one flickering quasar, from 48 institutions worldwide
An ARIES-led campaign tracked the blazar OJ 287 from 2015 to 2025 and put the larger of its two black holes at a minimum 3.89 billion solar masses.
What happened
- A study coordinated by ARIES, Nainital (DST) tracked the blazar OJ 287 over ten years, 2015 to 2025.
- OJ 287 lies about four billion light years away and holds two supermassive black holes in a twelve-year orbit.
- The campaign involved 106 scientists from 18 countries and 48 institutions, using two dozen telescopes.
- It produced the most extensive and densely sampled optical time series for the object in 150 years.
- From eight optical spectra taken at Steward Observatory in late 2017, the central black hole mass was estimated at at least 3.89 billion solar masses from the [O III] line width.
For Prelims
- Blazar: an active galactic nucleus whose relativistic jet points almost directly at Earth. The alignment amplifies the apparent brightness and variability, which is why blazars are the most violently variable objects in the sky.
- Supermassive black hole: millions to billions of solar masses, found at the centre of most large galaxies. OJ 287 is unusual in holding two, which is the expected outcome of a galaxy merger.
- How the mass is measured here: from the width of the [O III] emission line. Gas orbiting a massive object moves faster the heavier the object, and that motion broadens the line - so line width is a velocity measurement, and velocity gives mass.
- Why the orbit is twelve years: the smaller black hole crosses the larger one’s accretion disc twice per orbit, each crossing producing a flare. That is the double-peaked outburst pattern the campaign was timed to catch.
- ARIES: the Aryabhatta Research Institute of Observational Sciences, Nainital, an autonomous institute of DST. It operates the 3.6 m Devasthal Optical Telescope, the largest in India.
- Multimessenger astronomy: observing the same source through different carriers - light, gravitational waves, neutrinos and cosmic rays. A binary supermassive black hole is a predicted gravitational wave source, which is why this object matters beyond optical astronomy.
- Light year: the distance light travels in a year, about 9.46 trillion km. Four billion light years means the light now arriving left before the Earth’s present-day continents formed.
- Why archival plates matter: the 1988 discovery used photographic observations back to 1880. For phenomena with decade-scale periods, old plate archives are irreplaceable data that no modern instrument can regenerate.
For UPSC: Indian-led international astronomy with a concrete published result, which is the version of science news worth keeping. Use it on big science collaboration and India’s place in it, on the institutions of Indian astronomy from ARIES to Devasthal, on multimessenger astronomy and gravitational wave sources, and as the standard example of why long-baseline observation programmes need patient funding.
What it is NOT: The release does not name the journal or give a citation, so the result cannot be looked up from it. No uncertainty is attached to the 3.89 billion solar mass figure, and it is given as a minimum rather than a measurement with error bars. No mass is given for the smaller black hole, and the release says the search for its emission was undertaken without saying what was found. Nothing on how many of the 106 scientists or the 48 institutions were Indian, or which Indian telescopes contributed - the one thing a reader would want from a release about an Indian-led campaign.
For Mains
Syllabus: GS3.13 · GS3.11 · Linkage L1
Anchor
A campaign coordinated from ARIES Nainital has published ten years of optical monitoring of OJ 287, a blazar four billion light years away whose centre holds two supermassive black holes orbiting each other every twelve years. The study drew 106 scientists from 18 countries and 48 institutions, using two dozen telescopes between 2015 and 2025.
Substantiation (data)
The result is the densest optical time series ever assembled for the object across a 150-year record. It was used to place the two black holes relative to each other at different times, to track brightness, spectrum and polarisation across timescales from years to hours, and to look for emission from the smaller companion. From eight spectra taken in low-flux states at the Steward Observatory in late 2017, the larger black hole was estimated at a minimum of 3.89 billion solar masses, derived from the [O III] emission line width.
Position
The structure of the project is the lesson. A twelve-year orbit means a single cycle of evidence takes twelve years to collect, and the periodicity itself was only established in 1988 from photographic plates reaching back to 1880. Science of this shape cannot be done by one observatory or inside one funding cycle: it needs a century of archives, two dozen telescopes spread across longitudes so the object is never out of view, and an institution willing to coordinate for a decade. That ARIES did the coordinating is the part worth noting.
Counterpoint
The release is thin where it should be precise. No journal or citation, so a reader cannot reach the paper. The mass figure carries no uncertainty and is stated as a minimum. The smaller black hole’s mass is absent, and the search for its emission is described as undertaken without a result being reported. And for a release about an Indian-led collaboration, it never says which Indian telescopes contributed or how many of the 106 scientists were from Indian institutions.
Way forward
The scientific interest now moves to the gravitational wave side. A binary of this mass and separation is exactly what pulsar timing arrays are built to detect, and OJ 287 is one of the few systems where the optical orbit is well enough characterised to predict what those arrays should see. Optical monitoring that establishes the orbit precisely is what makes the multimessenger test possible.
Conclusion
A genuine Indian-led contribution to a long-running international problem, and a useful reminder that some results are bought with time rather than with instruments. The archival plates from 1880 are doing work no new telescope could replace.
Deploys into: Big science collaboration and India’s role · Indian astronomy institutions and facilities · Multimessenger astronomy and gravitational waves · Long-baseline research and patient funding
Ministry of Science & Technology · 2026-10-06 · PRID 2319522 · PIB source ↗