Asteroid 1999 KW4 makes closest pass to Earth since 2001

A roughly mile-wide asteroid is about to give Earth a proverbial buzz-cut this weekend. The asteroid will come within .032 au of Earth.

Zero-point-three-two! Holy moly!

But don’t worry. An au, or Astronomical Unit, is a very large measurement. It is the distance from the Earth to the Sun. Or about 93 million miles. So 0.32 of 93 million is still pretty big. And the term “buzz-cut” means something completely different to astronomers.

The asteroid will still be about 3 million miles away. That is about the same distance that the moon is from the earth… multiplied by 13.5.

Sadly, it is unlikely you’ll be able to see wit without a decent telescope. It is three-million miles away and only one mile across, moving at about 50,00mph. It would be like looking at something three miles away that is 1/64th of an inch across (like a grain of sand).

1999 KW4 was discovered, you guessed it, back in 1999 and will pass by Earth for the first time since 2001.

Orbit video

Courtesy: NASA

The thing that makes this asteroid unique is that the asteroid has a moon.

Yeah, its own moon.

Stats

Orbital and Physical Characteristics
Name 1999 KW4
Number 66391
Discoverer LINEAR
Discovery date 1999 May 20
orbit type Aten

Close approach date 2019 May 25
Close approach dist. 0.0346 au
Close approach dist. 13.5 lunar distances

semimajor axis 0.642 au
eccentricity 0.688
inclination 38.9 deg
orbital period 0.515 y
perihelion distance 0.200 au (215 solar radii)
aphelion distance 1.084 au
MOID 0.0133 au
Tisserand parameter 8.500 (asteroidal)

absolute magnitude (H) 16.5
Primary diameter 1.32 km BINARY
Secondary diameter 0.45 km
optical albedo 0.26
spectral class S
Primary rotation period 2.7645 h
Secondary rotation period 17.42 h (same as the orbital period, ignoring librations)
lightcurve amplitude 0.12 mag
pole direction (lambda, beta) = (326, -62)
PHA

Last update: 2019 May 22

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