Space & Beyond • Strange Sky Events • Near-Earth Hazards
Asteroids and near-Earth objects (NEOs) are rocky or metallic bodies orbiting the Sun, some of which pass close to Earth. Most are harmless, but a small percentage are classified as potentially hazardous asteroids because of their size and orbital proximity.
This Strange Sounds pillar explains asteroid flybys, near-Earth objects, close approaches, impact risks, Apophis, asteroid tracking systems, planetary defense, and how scientists monitor possible future collisions with Earth.
This page also explores asteroid size estimates, viral “asteroid warning” headlines, impact probabilities, and how asteroids connect directly to fireballs, meteorites, atmospheric explosions and impact craters.
TL;DR
- Asteroids are rocky remnants from Solar System formation.
- Near-Earth objects have orbits approaching Earth.
- Most asteroid flybys are harmless.
- Some objects are classified as potentially hazardous asteroids.
- NASA and ESA continuously monitor asteroid trajectories.
- Asteroid size strongly affects damage potential.
- Large impacts are rare but scientifically possible.
- Planetary defense systems now actively test asteroid deflection methods.
What is an asteroid?
An asteroid is a rocky or metallic body orbiting the Sun.
Most asteroids are found inside the:
- main asteroid belt between Mars and Jupiter
These objects are considered leftovers from the early formation of the Solar System.
| Asteroid Type | Main Characteristics |
|---|---|
| C-type | Carbon-rich and very dark. |
| S-type | Rocky silicate asteroids. |
| M-type | Metal-rich asteroids containing iron and nickel. |
Some asteroids remain safely distant, while others evolve into near-Earth objects.
What are near-Earth objects?
A near-Earth object (NEO) is an asteroid or comet whose orbit approaches Earth’s orbital path.
NEOs are divided into orbital families:
| NEO Group | Orbital Pattern |
|---|---|
| Apollo | Earth-crossing orbit outside Earth’s path. |
| Aten | Orbit mostly inside Earth’s orbit. |
| Amor | Approaches Earth but usually does not cross orbit. |
Most near-Earth objects never pose danger, but some receive intense monitoring because of close future approaches.
Potentially hazardous asteroids explained
A potentially hazardous asteroid (PHA) is an object large enough and close enough to Earth to justify long-term tracking.
Scientists evaluate asteroid risk using:
- orbital calculations
- impact probability modeling
- size estimates
- future flyby predictions
Many alarming asteroid headlines later become downgraded as orbital precision improves.
Famous asteroids and close approaches
Historic and Notable Near-Earth Objects
99942 Apophis — Close Flyby in 2029
- Type: Potentially hazardous asteroid
- Pattern: Extremely close Earth flyby
- Importance: Will pass closer than many satellites in April 2029
- Initial Concern: Early impact fears later ruled out
Asteroid Bennu — NASA OSIRIS-REx Target
- Type: Carbon-rich asteroid
- Pattern: Carefully tracked near-Earth object
- Importance: Sample-return mission provided pristine Solar System material
- Scientific Value: Helps researchers understand early planetary formation
Chelyabinsk Parent Object — Russia — 2013
- Type: Small near-Earth asteroid
- Pattern: Unexpected atmospheric entry and airburst
- Impact: Produced shockwave injuring over 1,500 people
- Importance: Demonstrated dangers of relatively small objects
How scientists track asteroids
Modern asteroid monitoring combines automated telescopes, orbital modeling and planetary-defense systems.
Major asteroid-tracking programs include:
- NASA CNEOS
- ESA Near-Earth Object Coordination Centre
- Pan-STARRS
- Catalina Sky Survey
- Vera Rubin Observatory
Scientists continuously refine:
- orbital trajectories
- future close approaches
- impact probabilities
- size estimates
Asteroid size vs damage potential
| Approximate Size | Possible Effect |
|---|---|
| 1–5 meters | Bright fireball or meteor. |
| 20 meters | City-scale shockwave similar to Chelyabinsk. |
| 140 meters | Regional destruction and major tsunami potential. |
| 1 kilometer+ | Global climate disruption and possible extinction-level consequences. |
Fortunately, large impacts are extremely rare on human timescales.
Asteroids, fireballs and meteorites
Some asteroids eventually intersect Earth’s atmosphere.
Depending on size and composition, they may produce:
- meteors
- fireballs
- bolides
- airbursts
- meteorites
- impact craters
Explore more in:
Could an asteroid cause extinction?
Yes. Large asteroid impacts are capable of producing global environmental collapse.
The most famous example is the:
- Chicxulub impact event ~66 million years ago
That collision is strongly associated with:
- dinosaur extinction
- global wildfires
- impact winter
- tsunamis
- mass atmospheric dust loading
Planetary defense and asteroid deflection
Modern planetary-defense programs actively test methods for changing asteroid trajectories.
Major concepts include:
- kinetic impactors
- gravity tractors
- orbital nudging
- early-warning systems
NASA’s DART mission successfully demonstrated that a spacecraft can alter the orbit of an asteroid.
This marked the first real-world planetary-defense experiment in history.
Frequently Asked Questions
What is a near-Earth object?
A near-Earth object is an asteroid or comet whose orbit approaches Earth’s orbital path.
What is a potentially hazardous asteroid?
A potentially hazardous asteroid is large enough and close enough to Earth to justify long-term monitoring.
Will Apophis hit Earth?
No. Current orbital calculations show Apophis will safely pass Earth in 2029.
How do scientists track asteroids?
Scientists use telescopes, sky surveys and orbital calculations to continuously refine asteroid trajectories.
Can asteroids create meteorites?
Yes. Asteroids entering Earth’s atmosphere can fragment and produce meteorites.
Could an asteroid wipe out humanity?
Large impacts are theoretically capable of global catastrophe, but extinction-scale collisions are extremely rare.
Stay Curious
Subscribe to the Strange Sounds newsletter for asteroid flybys, near-Earth object alerts, space hazards, fireballs, impact science and strange cosmic events.
