On 13 April 2029, asteroid 99942 Apophis will go roughly 32,000 kilometres above Earth’s floor. For a couple of hours it is going to be nearer than satellites in geostationary orbit, shiny sufficient to see with no telescope, and transferring quick sufficient for its progress in opposition to the celebrities to change into obvious.
The encounter is protected. NASA and ESA have dominated out an Apophis influence for no less than the subsequent century. A more moderen query is how a lot of humanity may stand exterior and watch it occur.
Visibility maps introduced in June 2026 put the potential viewers as excessive as 7.6 billion individuals, near 90 per cent of the world’s inhabitants. It describes individuals dwelling someplace contained in the cumulative viewing area, not these sharing one clear view on the similar second.
The estimate got here from a workshop presentation
Astrocartographer Michael Zeiler and astronomer Richard Tresch Fienberg introduced the work on the Apophis T-3 Years workshop on the College of Padua on 18 and 19 June 2026. It was a convention presentation, not a peer-reviewed paper. The assembly coated modelling, missions, observations and public communication.
The maps start with Apophis’s calculated trajectory. For every second, the geometry determines the place the asteroid is above the native horizon, whether or not the Solar is way sufficient under it and whether or not Apophis needs to be shiny sufficient for unaided imaginative and prescient. A inhabitants layer then estimates how many individuals reside in these altering areas.
Based on reporting on Zeiler and Fienberg’s presentation, about 7.6 billion individuals fall someplace throughout the cumulative footprint. The window lasts roughly seven hours, starting close to Australia and Asia round 15:00 UTC and ending over the North Atlantic close to 22:00 UTC.
Cumulative does an excessive amount of work right here. Australia, Asia, Africa, Europe and elements of japanese South America enter the helpful viewing geometry at totally different occasions. The calculation doesn’t put 90 per cent of humanity beneath the identical evening sky concurrently, and North America is poorly positioned for an unaided view.
Geometry isn’t a assure of clear skies
The calculation says the place seeing Apophis needs to be doable. It can’t forecast native cloud, haze or how a lot metropolis lighting will wash out the celebrities. Buildings, bushes and terrain will take away extra sightlines. Many individuals will merely not be trying.
Even beneath good circumstances, Apophis won’t resemble a meteor. It won’t enter the environment or path hearth. To the bare eye it ought to seem like a modest star transferring steadily throughout the background.
Fienberg’s observing preview for Sky & Telescope places its peak close to magnitude 2.8, similar to an extraordinary seen star. At the moment, it might cross about 30 levels of sky per hour, rising above 45 levels per hour close to closest strategy. The Moon shall be new, so moonlight mustn’t intervene.
Peak brightness is predicted round 20:35 UTC. Closest strategy comes about an hour later. These moments differ as a result of the fraction of Apophis’s sunlit aspect going through Earth adjustments because it passes, so reducing distance doesn’t preserve making it brighter.
Why Apophis has a couple of quoted dimension
ESA calls Apophis roughly 375 metres across. NASA lists a imply diameter of about 340 metres and a protracted axis of no less than 450 metres. The figures should not proof that the asteroid has grown or that its dimension is unknown by 100 metres. Apophis is elongated and irregular, so a imply diameter, an approximate general dimension and its longest dimension reply barely totally different questions.
The space comparability additionally wants care. Geostationary satellites orbit about 35,786 kilometres above the equator. Apophis will come nearer to the floor than that, however many different satellites fly a whole bunch or 1000’s of kilometres up and can stay far beneath it.
Neither is the asteroid travelling across the equatorial geostationary ring. It cuts throughout near-Earth area on a distinct path. NASA’s current overview says the flyby poses no hazard to satellites, astronauts or anybody on Earth. “Nearer than some satellites” describes altitude; it doesn’t describe a collision course by way of a belt of spacecraft.
The identical radar that eliminated the hazard enabled the map
When Apophis was found in 2004, restricted observations briefly left Earth inside a part of the possible-orbit area. Additional telescope knowledge eliminated the 2029 influence route, however a small risk in 2068 endured as a result of the shut encounter will considerably alter the asteroid’s orbit.
That residual concern ended after Goldstone and Inexperienced Financial institution radar observations in March 2021. The radar images themselves are just a few shiny pixels, recorded when Apophis was 17 million kilometres away. Exact echo timing mattered greater than visible element: it tightened the orbit sufficient for NASA to rule out influence for no less than 100 years and take away Apophis from the Sentry danger desk.
SpaceDaily not too long ago instructed the longer story of that changing risk and the spacecraft preparing for 2029. The visibility work rests on the identical achievement. The orbit is now constrained nicely sufficient to map not merely a protected miss, however the motion of a naked-eye level of sunshine throughout native horizons.
What 90 per cent ought to imply by 2029
The maps will enhance as new observations refine the trajectory and native viewing predictions. Climate forecasts won’t change into helpful till a lot nearer to the date. By then, city-specific charts ought to present the place and when to look, whereas binoculars might rescue the view the place gentle air pollution makes naked-eye detection troublesome.
The eventual viewers shall be smaller than 7.6 billion. The 90 per cent determine describes entry in precept, topic to darkness, altitude, cloud, synthetic gentle and a spotlight. It isn’t a forecast of participation.
That distinction doesn’t make the occasion extraordinary. A safely passing asteroid a couple of hundred metres large will transfer by way of naked-eye vary over a few of Earth’s most populated areas. The calculation tells us how broadly nature is providing the view. Circumstances on the bottom, and whether or not individuals keep in mind to search for, will determine what number of settle for it.
