NASA's census reveals a significantly smaller threat from space

Space · Published 17 October 2026 Swipe more like this →

In short: We used to fear a crowded neighborhood of mid-sized space rocks. New infrared data suggests the celestial vicinity is much emptier than we imagined, potentially lowering the risk of a major impact. By looking for heat instead of light, NASA has rewritten the planetary defense playbook.

Data from the Wide-field Infrared Survey Explorer (WISE) satellite has fundamentally shifted our understanding of near-Earth asteroids. To be precise, the asteroid-hunting branch of the WISE mission, known as NEOWISE, tallied space rocks moving within 195 million kilometres (120 million miles) of the sun. The findings reveal that there are roughly 19,500 mid-size near-Earth asteroids, a number significantly lower than the previous estimate of 35,000.

This discrepancy exists because previous surveys relied heavily on visible light. Dark asteroids reflect very little light, making them nearly invisible to traditional telescopes. However, WISE uses infrared detectors to sense an object's heat. Because heat is dependent on an object's size rather than its reflective properties, WISE can capture a more representative sample of the population, including both dark and light bodies. This allowed researchers to poll a small group of objects to draw conclusions about the entire population, much like a national census.

The results are a major milestone for planetary defense. A 1998 target set with Congress has been reached, as NASA has now located over 90 percent of the biggest near-Earth asteroids exceeding 1 kilometre in width. While scientists note that the majority of mid-size asteroids (ranging from 330 to 3,300 feet wide) remain undiscovered, the lower population count suggests that the overall hazard to Earth may be less than previously feared. Further research is still required to confirm if this lower density directly correlates to a decrease in potentially hazardous objects that come closest to our orbit.

Between January 2010 and February 2011, the survey mapped the whole celestial sphere twice using infrared light. During this timeframe, at least 585 near-Earth objects and over 100,000 asteroids in the main belt between Jupiter and Mars were spotted by NEOWISE.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• NASA's asteroid obsession is a matter of planetary survival
• Why space agencies are looking far beyond the threat of asteroid collisions
• The cosmic neighborhood between Mars and Jupiter hides a persistent threat
• Space rocks are moving targets in a high-stakes game of celestial billiards
• Why tracking our oldest cosmic neighbors is a matter of survival
• Is that alien megastructure just a galaxy hiding in plain sight?
• How NASA is sharpening its view of the high-energy universe
• When a planet falls into a star, it can trigger a cosmic explosion.
• A record-breaking pulsar discovered in a distant galaxy
• A new era of discovery begins with the James Webb Space Telescope
• The 3.9 billion-year-old cosmic record preserved on Mars
• How astronauts once tackled 111 tiny screws to revive a broken telescope

More in Astronomy · More in Space · Latest · A–Z · All topics