Every year on June 30, the global scientific community pauses to look upward. Established by the United Nations, International Asteroid Day marks the anniversary of the 1908 Tunguska event -- the largest recorded asteroid impact in modern history, which flattened over 2,000 square kilometers of Siberian forest.
The day is a stark annual reminder of our planet’s cosmic vulnerability. The theme for 2026, “Planetary Defence and Asteroid Impact Hazards,” highlights a truth that modern astronomy reinforces daily: Protecting Earth is not a passive waiting game, but an active, international scientific race.
Yet, when we picture planetary defence, we often imagine mega-telescopes on remote mountain peaks or high-powered governmental supercomputers. While those are vital parts of the infrastructure, there is a quieter, equally crucial frontline in the battle to map the cosmos. It exists in ordinary rooms, on personal laptops, driven by citizen scientists who hunt for moving points of light against fields of static stars. To understand why citizen science is so essential, one must look at the staggering scale of the problem.
Our solar system is teeming with the rocky remnants of its violent birth 4.6 billion years ago. While major celestial bodies are well-mapped, millions of smaller Near-Earth Objects (NEOs) remain entirely undetected.
The primary tool of a modern asteroid hunter is specialized astronomical software like Astrometrica. Citizen scientists receive data packages consisting of "image sets" -- multiple time-lapse exposures of the exact same patch of deep space taken by massive survey telescopes, such as the Pan-STARRS or the Catalina Sky Survey. When these images are layered and blinked rapidly in sequence, fixed stars and distant galaxies remain perfectly still. But an asteroid? An asteroid moves. It manifests as a tiny, persistent dot creeping across the grid.
The work requires an immense amount of patience, a sharp eye for detail and strict adherence to rigorous technical standards. Each potential moving object must be analysed for consistency in brightness (magnitude) and data alignment. A citizen scientist must rule out digital noise, camera artifacts and known satellites before submitting a detection report to the Minor Planet Center.
The journey from a blinking dot on a laptop screen to an officially recognized rock in the solar system is long, exacting and incredibly rewarding. The discovery process follows a strict hierarchy of validation:
Preliminary Discoveries: This is the first taste of success. When a citizen scientist spots a brand-new, uncatalogued moving object and submits the coordinates, the MPC logs it as a preliminary discovery. It means the observation is valid, but the object's orbit hasn't been verified yet.
Provisional Discoveries: This is where the science solidifies. For a preliminary find to graduate to a provisional discovery, other observatories around the globe must cross-observe and track the object over days or weeks. This public data calculates a reliable orbital path.
To date, my own journey in the cosmic archives has yielded 9 preliminary discoveries and 2 provisional discoveries.
While planetary defence is inherently global, the individual commitment required to sustain it often flies under the radar. Since 2019, I have been the only citizen scientist from Goa actively and consistently pursuing asteroid hunting through international citizen science campaigns. What began as an intense personal curiosity has since grown into a globally recognized endeavour, bridging the gap between my technical engineering background and the vast, unmapped data fields of deep space.
Securing validation from organizations operating under international astronomical networks has proven that breakthrough science isn't confined to institutional labs. Global recognition for tracking these rogue remnants emphasizes that every entry logged from a laptop in Mapusa directly contributes to the international database keeping watch over Earth.
Space is a shared frontier and its hazards are a shared responsibility. The stars are no longer just passive objects of myth and poetry; they form a complex, dynamic map that we must understand to ensure our longevity. You don't need access to an orbital observatory or a multi-million-dollar grant to stand guard on the frontier of planetary defence. You just need curiosity, a willingness to learn the tools of the trade and the patience to watch the background stars stand still while a new piece of the universe reveals itself to you.
(The writer is a Mechanical Engineer | NASA Citizen Scientist Mapusa, Goa)
