Why does this bizarro asteroid have a million-kilometer-long tail?

Three years ago, something rather cataclysmic happened to this asteroid. Whatever it was — and it was probably a collision with a smaller asteroid — has now resulted in an exceptionally long debris tail that just keeps getting longer.

Asteroids aren’t supposed to have tails. That’s comet territory. But this object, called P/2010 A2 (LINEAR), is leaking a dust trail of a kind never seen before by astronomers.

Just to put this length into perspective, a million-kilometers is roughly three times the distance from the Earth to the Moon. That’s a long distance — and a lot of debris. Observations indicate that the tail consists of chunks about one centimeter across or smaller.

Why does this bizarro asteroid have a million-kilometer-long tail?

The asteroid itself is about 100 meters across, and it’s located near the asteroid belt between Mars and Jupiter.

So what caused this? Phil Plait of Bad Astronomy offers two possible explanations:

One possible explanation for this bizarre object is that the rock was hit by another smaller asteroid, an impact that would’ve had the explosive yield of a nuclear weapon, disrupting the asteroid and blasting out thousands of tons of dust. Another possible cause is a subtle process called the YORP effect, where the very gentle pressure of sunlight spun up the asteroid, increasing its rotation until it broke apart.

If Plait’s second explanation is correct, the asteroid is of a very rare class that ejects dust in a comet-like fashion.

This object was originally discovered in 2010 when astronomers detected a strange X-shaped debris pattern and long streamers of dust.

Why does this bizarro asteroid have a million-kilometer-long tail?

The Wisconsin Indiana Yale Observatory adds some more insight:

Since the earth orbits in the same plane as this debris, we observe a line, or tail-like structure. In time these particles, under the gravitational pull of the sun, will form a meteor stream surrounding the sun. Meteor streams are what we see as "shooting stars" when the earth ploughs through the stream of debris.

Why does this bizarro asteroid have a million-kilometer-long tail?

In addition, debris from events like these contribute to the dust cloud (called zodiacal dust) that is spread out over our Solar System.

Images: WIYN, Hubble.