Potentially Dangerous Asteroids
As of April 5, 2025, the number of potentially dangerous asteroids being monitored and rated on the Torino Scale can be derived from data provided by various space agencies. The Torino Scale is used to categorize the impact hazard of near-Earth objects (NEOs), such as asteroids and comets, on a scale from 0 to 10, where 0 indicates no significant risk and higher numbers indicate increasing levels of concern.
"Potentially dangerous" asteroids are typically classified as Potentially Hazardous Asteroids (PHAs), defined as NEOs larger than 140 meters in diameter with orbits that bring them within 7.48 million kilometers (about 4.65 million miles) of Earth's orbit.
Current Status
According to the latest available data from NASA's Center for Near-Earth Object Studies (CNEOS), approximately 2,500 PHAs have been identified out of over 37,500 known NEOs. However, the Torino Scale is specifically applied to objects with a calculated impact risk within the next 100 years.
Currently, CNEOS reports that no known asteroid has a Torino Scale rating above 0 for the foreseeable future, meaning no significant immediate threats are identified. This is based on continuous monitoring via the Sentry system, which analyzes potential impact risks.
Recent Developments
The European Space Agency (ESA) also monitors NEOs through its Planetary Defence Office. As of early 2025, their Risk List highlights objects with non-zero impact probabilities, but most are small or have probabilities so low they remain at Torino Scale 0.
For example, asteroid 2024 YR4, which briefly reached Torino Scale 3 in January 2025, was downgraded to 0 by February 2025 after further observations refined its trajectory.
Thus, while thousands of PHAs are monitored, the number currently assigned a Torino Scale value greater than 0 is effectively zero, as additional observations typically reduce initial risk assessments to negligible levels. Historically, only a handful of asteroids—like 99942 Apophis (rated 4 in 2004) or 2024 YR4 (rated 3 in 2025)—have briefly climbed above 0, but none sustain such ratings long-term with current data.
The Torino Scale
The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets. It is intended as a communication tool for astronomers and the public to assess the seriousness of collision predictions, by combining probability statistics and known kinetic damage potentials into a single threat value.
0
White
No hazard (zero or negligible risk)
1
Green
Normal (routine pass, no unusual danger)
2-4
Yellow
Meriting attention by astronomers (close encounter, low to moderate risk)
5-7
Orange
Threatening (significant risk, warrants monitoring)
8-10
Red
Certain collision (local to global consequences)
Detailed Scale Explanation
| Level | Color | Description |
|---|---|---|
| 0 | White | The likelihood of a collision is zero, or well below the chance that a random object of the same size will strike Earth within the next few decades. This designation also applies to any small object that, in the event of a collision, is unlikely to reach Earth's surface intact. |
| 1 | Green | A routine discovery in which a pass near Earth is predicted, that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or concern. |
| 2-4 | Yellow | A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near Earth. While meriting attention by astronomers, there is no cause for public attention or concern as an actual collision is very unlikely. |
| 5-7 | Orange | A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localized destruction. Most likely, new telescopic observations will lead to re-assignment to Level 0. |
| 8-10 | Red | A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offshore. Such events occur on average between once per 50 years and once per several thousand years. |
Space Agencies Publishing NEO Data
NASA's Center for Near-Earth Object Studies (CNEOS)
Provides detailed tracking and risk assessment via the Sentry system. CNEOS maintains the most comprehensive database of NEOs and conducts ongoing monitoring and risk analysis.
Visit WebsiteESA Planetary Defence Office
Maintains a Risk List and provides regular updates on NEO hazards. The European Space Agency's dedicated office works in coordination with international partners to monitor potential threats.
Visit WebsiteInternational Astronomical Union (IAU)
While not a space agency, the IAU endorses the Torino Scale and collaborates with global observatories. It plays a crucial role in coordinating astronomical observations worldwide.
Visit WebsiteNEO Monitoring Systems
Detection Networks
Several ground-based telescope networks are dedicated to discovering and tracking NEOs:
- Catalina Sky Survey (CSS)
- Pan-STARRS (Panoramic Survey Telescope and Rapid Response System)
- ATLAS (Asteroid Terrestrial-impact Last Alert System)
- NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer)
- Spacewatch
Future Improvements
Upcoming systems that will enhance our NEO detection capabilities:
- NEO Surveyor (NASA infrared space telescope, launch planned for 2026)
- Vera C. Rubin Observatory (formerly LSST, expected to begin operations in 2025)
- Flyeye Telescope Network (ESA's planned system of automated telescopes)
These monitoring systems work together to provide comprehensive coverage of the sky, allowing astronomers to detect and track potentially hazardous objects with increasing accuracy. The continued development of these systems is crucial for planetary defense efforts.
Summary
In summary, while over 2,500 PHAs are monitored, none currently hold a Torino Scale rating above 0 as of April 2025, reflecting the effectiveness of ongoing observation efforts in ruling out near-term threats. The international community continues to improve detection and tracking capabilities, ensuring that any potential threats can be identified well in advance.
The field of NEO monitoring represents one of the most important collaborative scientific efforts in protecting our planet. Through continued investment in detection technologies and international cooperation, we are better prepared than ever to address potential asteroid threats.
For the latest information on specific NEOs and their risk assessments, visit the NASA CNEOS or ESA Planetary Defence Office websites linked above.