MEET INDIA'S ASTEROID HUNTERS

Amateur asteroid hunters in India and across the world have taken the skies by storm. Behind their efforts and passion to find near-Earth objects is an intricate combination of citizen science and bigger scientific goals

- Nitin Sreedhar

It has been an eventful week for astronomers around the world. On 17 April, five asteroids, ranging from the size of a car to that of an aeroplane, flew past Earth. The asteroid with the closest approach was 2023 HB, around 2.9m in size; it whizzed past our planet at a distance of approximately 195,000km, based on data from the US space agency Nasa JPL (Jet Propulsion Laboratory) asteroid watch dashboard.

The good thing is: You don’t have to worry about an asteroid threat. Not for the time being at least. One thing that is hard to miss, however, is the growing curiosity—and awareness—about asteroids and other near-Earth objects, or NEOs, like comets. News alerts on “a terror rock” or a “potentially hazardous” space rock hurtling towards Earth are now commonplace.

Astronomers usually follow two methods to detect asteroids. The first is all-sky surveys, which map the night sky with no particular observational target in mind. The Catalina Sky Survey (CSS), a Nasa-funded project, is a famous example of a sky survey working towards the discovery of asteroids and comets. Founded in 1998, CSS—based at the University of Arizona’s Lunar and Planetary Lab in Tucson—has discovered more NEOs than any other survey in the world.

Sometimes, though, asteroids can be too faint to spot in an all-sky survey. That is where the second method comes in: large telescopes. These strong telescopes have a smaller field of view—they will only see a small, specific part of the sky—but can observe objects in much more detail, gathering terabytes of data.