The Subaru Telescope, operated from Mauna Kea Observatory in Hawaii, has provided crucial new data confirming that the asteroid 2024 YR4 will not impact Earth in the foreseeable future.

Initial observations in late 2024 had suggested a small but concerning probability of collision, prompting an international effort to refine its trajectory. Thanks to updated measurements, astronomers have now determined that the asteroid poses no significant risk.

Discovery And Early Impact Concerns

2024 YR4 was first detected on December 27, 2024, by the Asteroid Terrestrial-impact Last Alert System (ATLAS), a global survey designed to detect potential Earth-impacting asteroids. This near-Earth asteroid (NEA) belongs to the Apollo group, a class of space rocks that cross Earth’s orbit as they move around the Sun.

The asteroid’s discovery followed a close pass by Earth on December 25, 2024, after which it began moving away. However, initial orbital calculations suggested that 2024 YR4 had a 1% chance of impact when it makes another close approach in December 2032.

This probability, while low, was significant enough for the International Asteroid Warning Network (IAWN) to issue an official impact risk notification—the first of its kind for this object.

Refined Calculations Reduce Impact Probability

Following the IAWN alert, multiple observatories conducted additional observations to refine 2024 YR4’s orbit. Throughout February 2025, new calculations adjusted the estimated impact probability several times:

• Early February: Probability increased to 2.3%, then 3.1%
• Mid-February: Revised downward to 0.28%
• Late February: Subaru Telescope’s data further reduced risk to 0.004%

The Subaru Telescope’s Hyper Suprime-Cam (HSC), a high-performance wide-field camera, played a key role in gathering the critical positional data needed to eliminate impact concerns.

The observations were requested by the Japan Aerospace Exploration Agency (JAXA) and supported by NASA’s Center for Near-Earth Object Studies (CNEOS) and the European Space Agency’s Near-Earth Objects Coordination Centre (NEOCC).

What Makes 2024 YR4 Significant?

The asteroid completes one orbit around the Sun approximately every four years, and although it spends most of its time far from Earth, it does cross Earth’s orbit periodically.

Astronomers are especially interested in tracking asteroids that could be nudged into a collision course due to gravitational influences from planets, the Moon, or other space objects.

Even minor shifts in orbit can accumulate over decades, altering an asteroid’s long-term trajectory. 2024 YR4’s case highlights how continuous monitoring is essential for planetary defense.

What Happens Next?

According to the latest data, 2024 YR4 will pass Earth at a safe distance well beyond geostationary satellites and possibly even beyond the Moon. The IAWN has also confirmed that there is no significant impact risk from this asteroid in the next century.

Observations of 2024 YR4 will continue until early April 2025, when the asteroid will become too faint to track with current Earth-based telescopes. It will remain unobservable until it approaches Earth again in 2028.

The Importance Of Planetary Defense

This episode underscores the importance of international cooperation in asteroid tracking and impact risk assessment. The Subaru Telescope’s contribution demonstrates how ground-based observatories play a crucial role in refining asteroid trajectories.