Hi!

Interesting! This is the closest asteroid-pair
(known) to have flown by the Earth: 5 million km,
I'm informed waas the periapsis.

I did some calculations!
The smaller of the pair, orbiting the larger asteroid
at a mean distance of about 1600 meters over a peroid of about 16 hours. The larger, roughly spherical asteroid is
about 1200 meters in diameter, so the smaller asteroid's
orbital radius (r) is roughy 2200 meters (1600 + 600)m.

Vo^2 = orbital-velocity squared = GM/r = 0.27m^2/s^2.

M = 0.27 x (2200)/6.67 x 10^-11 = 125/6.67 x 10^-11.
M = 1.9 x 10^12kg.
d = (ro) density = 1.9 x 10^12kg/[{4/3}pi(600m)^2]
d = [about] 2000kg/m^3.
Am I reasonably correct, Dr. Blackwell? gbaikie?
Gary? Ilya? Mr. Grondine?

That asteroid's density would apparently make it a
"rubble pile" that flew perilously close to Earth.
What? Me worry?

Jake