The Twin Quasars — a Cosmic Mirror of Einstein’s Vision
Under truly dark skies and with patient accumulation of photons, an amateur observer may achieve work ordinarily reserved for professional observatories. The photograph below — realised from 1,136 sub-exposures of 20 seconds (totaling c. 6 hours 18 minutes) at a Bortle 3 site — shows the famed twin images of quasar Q0957+561: A and B. The light arrived here from a distance of c. 8.7 billion light-years, and began its voyage long ante the birth of our Solar System.
Preface
Photons are archivists of cosmic history. When we collect them patiently, summing faint glows across hours, we assemble narratives of epochs long past. The double image of Q0957+561 is not merely an aesthetic curiosity: it is one of the earliest, most striking visual confirmations of Einstein’s General Theory of Relativity, for it manifests the bending of light by gravity — gravitational lensing.
Capturing such remote celestial light requires not merely precision optics but extraordinary patience. Each individual exposure gathers only a minute fraction of the photons arriving from the quasar — remnants of an epoch when the Universe was young. Because these photons are so few and faint, astronomers must accumulate hundreds or even thousands of exposures over several hours, later combining them digitally to enhance the signal while suppressing noise. This meticulous process, known as integration or stacking, enables the invisible to become visible, transforming random specks into coherent cosmic history.
What Is a Quasar?
The term quasar derives from “quasi-stellar radio source”, first used in the 1960s when astronomers found intense radio emissions emerging from points of light resembling stars. In truth, a quasar is the incandescent core of a remote galaxy, its brilliance powered by a supermassive black hole consuming gas and dust at extraordinary rates. The infalling material forms an accretion disc that heats to millions of degrees, radiating energy across the entire electromagnetic spectrum—from radio waves to X-rays.
By contrast, a neutron star is the dense remnant of a massive star’s core, only a few kilometres wide yet containing more mass than the Sun. When such a neutron star rotates rapidly and emits regular beams of radiation, it is termed a pulsar. A black hole, on the other hand, is a gravitational abyss from which nothing—not even light—can escape. Quasars differ in that the light we see comes not from within the black hole, but from matter in the final moments before crossing its event horizon, where gravitational energy is converted into luminous fury.
In essence, a quasar is both a monument to creation and a herald of destruction—gravity’s own paradoxical masterpiece, where annihilation becomes light.
The Enigma of the Twin Quasars
"We are seeing two apparitions where there is fundamentally one source." — paraphrase of classical lensing interpretation.
At first sight (prima facie), the two luminous points separated by approximately 5.7 arcseconds might appear as distinct celestial entities — two quasars, side by side in the far reaches of the constellation Ursa Major. Yet, beneath that illusion lies one of the most elegant demonstrations of the geometry of the cosmos. Meticulous, multi-wavelength observations — optical, radio, and infrared — have revealed that these twin sparks are, in truth, reflections of a single object: the quasar Q0957+561, seen twice because the very fabric of space-time has curved its light into twin pathways. What we behold as duality is, in reality, unity distorted by gravity — a natural optical illusion written in the mathematics of Einstein’s General Theory of Relativity.
The intervening agent responsible for this celestial mirage is an otherwise unremarkable galaxy, faint and hidden along our line of sight. Its mass — composed of visible stars, dark matter, and cosmic dust — acts as a colossal gravitational lens, bending the quasar’s light like a prism of curved space. Each photon follows a unique geodesic, one path slightly shorter, the other drawn further through the gravitational potential well. The outcome: two visible images of the same ancient source, separated by a mere few arcseconds in the sky, yet by roughly one light-year in journey length.
In the foreground, the striking spiral galaxy NGC 3079 — poetically known as the Phantom Frisbee Galaxy — contributes visual drama but not the lensing itself. Its shimmering disk of gas and dust merely frames the scene, a cosmic bystander in this grand interplay of distance and destiny. The true lensing galaxy lies beyond it: a shadowy mass whose gravitational field, invisible yet immense, warps the light of a quasar nearly nine billion years old.
And therein lies the greater wonder. The photons captured in Dr. Arun K. Shankar’s image began their journey some 8.7 billion years ago — when the universe was less than half its present age, when the Solar System, the Earth, and even the Milky Way as we know it did not yet exist. These quasar-beams are, quite literally, messengers from the cosmic dawn, traversing aeons through an expanding universe. As they travelled, the relentless stretching of space — cosmic expansion — elongated their wavelengths, softening them into the reddish glow of ancient light. Their energy diminished, their pace unchanged, they continued to arrive, photon by photon, like whispers from a vanished epoch.
In observing them, we do not see the present universe, but its memory — a tapestry woven from time-delayed light. Each captured photon is a relic, older than the Sun, older than the dust beneath our feet. And as the cosmos continues to expand, these same sources will drift ever farther, their light fading toward invisibility, until one day, perhaps, the twin quasars themselves will pass beyond the reach of human eyes. What we witness now, then, is both revelation and farewell — the universe showing us its reflection, before distance swallows it whole.
This paradox was beautifully intuited in ancient Indian philosophy. The Upanishads spoke of Kāla — Time — as the unseen thread binding existence and perception, while Buddhist thinkers described reality as Kṣaṇika (momentary), ever dissolving and renewed with each instant. The concept of Māyā, too, reflects this illusion of continuity — that what we perceive as the “now” is but a tapestry woven from delayed impressions. Science and philosophy converge here: light, the divine messenger, reveals that even when we gaze upon the stars or the face beside us, we are, in essence, beholding the past through the veil of the present.

