An asteroid with its own mini orbiting moon will fly past the Earth this weekend, and astronomers are very excited.
Asteroid 1999 KW4 is known as a "binary object" because it is made up of two asteroids that are gravitationally bound together.
The larger asteroid is just under a mile in diameter, and its companion asteroid "moon" is about a third of that size.
It will make its closest approach to Earth on Saturday, May 25, giving scientists an opportunity to observe it using telescopes on the ground.
The European Space Agency (ESA) has been tracking the asteroid, and says it is steadily getting brighter as it nears our planet.
Earlier this week, ESA shared a grainy animation composed of two 90-second exposures, obtained on 9 May with the 0.6 m telescope at the Observatoire des Makes.
The asteroid itself is the faint blob at the centre of the animation, according to ESA:
Although it is classified as "potentially hazardous", 1999 KW4 will soar safely past the Earth at a distance of 3,216,271 miles – or 13.5 times the distance to the moon.
ESA said that, during the approach, it would try to collect as many observations as possible, with as many observing techniques and wavelengths as possible.
"The goal is to put observatories and telescopes to the test, to become aware of what kind of information can be collected on short notice," ESA said.
This will help it to prepare for "a future close approach of a possibly threatening asteroid".
Analysis of 1999 KW4 will also act as a test case for a similar investigation on (65803) Didymos - another binary object.
Didymos is the designated target of NASA's Double Asteroid Redirection Test (DART), scheduled to take place in October 2022.
DART will see the US space agency crash a rocket into Didymos at high speed, in an attempt to change its trajectory.
The mission aims to demonstrate NASA's capability to deflect any space rocks that are found to be on a collision course with Earth.
