Violence Inherent
in the System

13 January 2013

The Orion Nebula has been in the news recently due to a new set of pictures such as this one from Astronomy Picture of the Day. It is an image of high velocity “bullets.”

Cosmic bullets in the Orion Nebula. GeMS/GSAOI Team, Gemini Observatory, AURA
Cosmic bullets in the Orion Nebula.

It can be a bit difficult to wrap your head around what is really going on here. The small blue dots at the tip of these orange streams are the “bullets,” and each one is about 10x larger than our solar system. These bullets are not solid objects, but rather dense lumps of iron-rich gas. They’ve probably been pushed away from the central region of the nebula by intense stellar winds, and now create shock waves as they stream through the surrounding nebular gas. They are moving at about 400 km/s, ripping through the gas as they go.

We tend to think of nebula as static clouds of gas floating peacefully in space, but many nebulae are actually violent and complex interactions of gas, dust and stars. Within the Orion Nebula there is a cluster of bright central stars, there are dust masses colliding, new stars are being born with planetary systems forming around them. There’s intense stellar wind colliding with all the gas and dust, pushing lumps like these bullets outward at supersonic speeds.

The Orion Nebula is not a particularly unusual nebula, but it is only about 1300 light years away, so it gives us a front row seat to the type of nebula that gives birth to stars. Our own Sun likely formed in a similar stellar nursery billions of years ago. So in a way this is like looking at baby pictures of your cousins.