The world has taken a first step against a common threat from beyond our planet. A recent meeting at the United Nations, including a contingent of astronauts and cosmonauts, addressed the prospect of a catastrophic asteroid strike on the Earth.

In coming decades, more than a million asteroids known as NEOs, or near-Earth objects, could pose a threat. The goal of a proposed U.N. effort is to unite nations behind a plan to deflect asteroids from a collision course with Earth.

Developing a unified response will require unprecedented diplomatic and technological cooperation, and much funding. The group that met with the U.N. called for a practice launch to deflect a smaller, nonthreatening asteroid. It believes the technology to deflect asteroids exists, but must be practiced.

An asteroid that exploded over Russia in February wasn’t detected until it was on top of the planet. That NEO was only the size of a truck, but it did a lot of damage and injured more than 1,000 people.

Other asteroids that dwarf it are orbiting Earth’s neighborhood. What we don’t know about them can kill us.

First Published November 20, 2013, 12:34 a.m.