Impact Risk, and When They Come Back

← Back to current tracker · Insights · Lost asteroids · What has already arrived

Two different questions get mixed together whenever an asteroid makes the news, so this page keeps them apart. Which objects have a computed chance of hitting us is the first list. Which objects come close soon is the second. An object can be on either without being on the other, and coming close is the ordinary case: a few come inside the Moon's distance every year and nothing happens.

Ranked by Palermo Scale

2208 objects currently carry a non-zero computed impact probability, showing the top 40. Show only objects above 140 m — the highest impact probability on the whole list belongs to an object seven metres across.

NASA/JPL CNEOS Sentry, fetched 2026-10-03 11:10 UTC.

Reading Those Two Columns

The Palermo scale compares one object's risk against the background risk from everything we have not found, over the same period. It is logarithmic, so each whole number is a factor of ten. Zero means equal to the background. Negative means less than the background, and the entire list is negative — the highest, 1950 DA, sits near −1, meaning roughly a tenth of the risk you already live with from undiscovered objects.

The Torino scale is the public-facing one: a whole number from 0 to 10, where 0 means no hazard. Everything here is 0. It is only defined for impacts within the next hundred years, which is why the entries furthest in the future show no value at all rather than a zero — the scale does not reach them, which is not the same as being safe or unsafe.

A high probability is not the same as a high risk. The largest impact probability on the list is about one in ten, and it belongs to an object roughly seven metres across — something that would make a bright fireball and very little else. The Palermo scale exists precisely because probability alone misleads; it folds in energy and how soon.

An old last-seen date is the thing worth noticing. Several of these were observed briefly, years or decades ago, and the risk is a consequence of a short observation arc rather than of a known trajectory. More observations almost always remove an object from this list. Some cannot be re-observed because nobody knows where to look — those are on the lost asteroids page, and a few appear on both.

When They Come Back

The next 60 of 600 approaches by potentially hazardous objects that pass inside 0.05 AU over the coming decades. That threshold is not arbitrary: it is the same distance that puts an object in the hazardous class in the first place, so this is the list of asteroids coming back inside their own definition.

NASA/JPL close-approach data, fetched 2026-10-03 11:10 UTC. One lunar distance is about 384,400 km; anything under 1.0 in that column passes closer than the Moon.

Why is one asteroid “hazardous” when closer ones are not?

Because the flag has nothing to do with how close it came on the day. NASA marks an object a Potentially Hazardous Asteroid only if both of these are true of its orbit and its size:

• Its orbit can bring it within 0.05 AU of Earth’s — about 7.5 million km. This is the Minimum Orbit Intersection Distance, the closest the two paths ever come, not the distance on any given pass.
• It is big enough to matter — absolute magnitude 22.0 or brighter, which is roughly 140 metres across and up. Anything smaller breaks up in the atmosphere.

The two terms: AU — astronomical unit, the average Earth–Sun distance, 149,597,871 km. 0.05 AU is about 7.5 million km.
MOID — minimum orbit intersection distance, the closest the two orbits ever come, whatever the timing. See the glossary for NEO, PHA and H.

So a large rock passing at 39 million km today can be flagged, because on some future orbit it could come far nearer — while a pebble skimming past at 4 million km is not, because it would never reach the ground.

Three objects that all passed Earth on 30 August 2026 make the point better than any definition:

Object	Size	Orbit’s closest to Earth’s	Missed by, that day	Flagged
2013 JR28	122–272 m	5.3 M km (0.035 AU)	39.2 M km	Yes — both tests pass
2012 LE11	629–1,406 m	23.3 M km (0.156 AU)	26.1 M km	No — orbit never gets near enough
2007 EK	3.7–8.2 m	198,000 km (0.0013 AU)	4.2 M km	No — far too small

The middle one is five times larger than the flagged one and passed closer on the day, but its path can never come within 23 million km of ours. The last one’s orbit crosses inside the Moon’s distance — nearer than any other object here — and it is still not hazardous, because at a few metres across it would burn up long before it landed.

“Potentially hazardous” is a watchlist criterion, not a prediction. None of these is on a collision course; the label means an object is worth keeping precise track of over the coming centuries.

This page reports what NASA/JPL publishes and adds nothing to it. Risk values are recomputed by JPL whenever new observations arrive, and they move — usually downwards, as a better orbit rules out the possibility that put an object on the list. Nothing here is a prediction that anything will happen.