Asteroid (152637) 1997 NC1 will sweep past Earth on Saturday, 27 June, at a distance of 2.56 million kilometres—equivalent to 6.66 times the Earth–Moon separation—with no possibility of collision, the European Space Agency’s Planetary Defence Office confirmed on Wednesday. The encounter, while harmless, marks the closest approach of an object this size in several years and has triggered a coordinated radar observation campaign by NASA to refine its physical properties.

The body, discovered in 1997, is estimated to span between 750 metres and 1,650 metres, though the range reflects uncertainty in its surface reflectivity, or albedo. Some analyses suggest an albedo as high as 60 percent, which would imply a smaller diameter. At the moment of closest approach, 11:14 GMT, it will be travelling at 8.9 kilometres per second. The last time a larger object came nearer was in January 2022, when asteroid 1994 PC1 passed at 5.2 lunar distances. NASA’s Jet Propulsion Laboratory plans to use the 34-metre DSS-26 and DSS-13 antennas at Goldstone to obtain radar images, which will yield a more precise size and shape model.

For ground-based observers, the asteroid will be visible primarily from the Northern Hemisphere during its inbound phase, then from nearly all longitudes at peak proximity, and only from the Southern Hemisphere as it departs. A small telescope of at least 15-centimetre aperture or large binoculars will be needed; the object will appear as a faint, slow-moving point of light rather than a streaking meteor. Bright moonlight, however, is expected to interfere with observations at the moment of closest approach, according to Juan Luis Cano of ESA’s Planetary Defence Office. The asteroid is roughly 50 to 60 times wider than the Chelyabinsk impactor that caused widespread window damage and injuries in Russia in 2013, underscoring why objects of this scale are continuously tracked despite their extremely low impact frequency.

After Saturday’s flyby, the asteroid will recede and become observable only from southern skies. The immediate scientific milestone is the radar imaging campaign, which will deliver refined orbital and physical data in the days following the encounter. No comparably close passage by an object of this size is currently on the near-term horizon.