Bad Astronomy

The Orion VISTA

Need a new desktop image? Yeah, the ESO’s got you covered.

Holy Haleakala. Click to Orionate.

That jaw-dropper is the view of Orion as seen by the European Southern Observatory’s phenomenal VISTA telescope, a 4.1 meter telescope equipped with an infrared camera that can take pictures of enormous chunks of the night sky. This 1 x 1.5 degree view – bigger than 8 full Moons on the sky! – show the entirety of Orion’s dagger*, the group of stars dangling below the Hunter’s belt.

Obviously, they’re not all stars! In the center is the famous Orion Nebula, a star-forming factory that is among the biggest in the entire Milky Way. As fortune would have it, we’re actually rather close to it, only 1500 light years away (the galaxy is 100,000 light years across, so that qualifies as close). It’s visible to the naked eye, and binoculars show it as a fuzzy blob. Telescopes reveal its true shape and color, and our view is enhanced even more when we look in the infrared, as VISTA can, because IR light can pierce the veil of the thick dust shed by newborn stars, revealing what lies beneath.

And what’s hidden there are more stars, the young’uns blowing the gas and dust themselves. You can see the reddish streamers (really they are IR in this false-color image) showing the matter as it screams out from stars at a numbing 200 kilometers per second (120 miles/sec). That’s fast enough to cross the continental United States in 30 seconds, if that gives you any idea of the enormous velocity.

This junk slams into more material outside the star, lighting it up. Just above the main nebula you can see a horizontal stretch of matter; that’s probably bipolar emission – literally, blowing out of the two poles of a star – glowing as it moves through the thin wisp of material between the stars.

One thing I very much like about this image is the semi-illusion of the nebula being hollow. This is really best where you see bright white stars; the main bulk of the nebula itself and a smaller round region just above it. I call this a semi-illusion because it’s based on reality! There are clutches of extremely massive newborn stars there. They flood the gas around them with ultraviolet radiation as well as blowing fierce winds of material, and these carve a cavity in the nebula, creating enormous bubbles light years across. In visible light pictures this activity is hard to see, but in this infrared image it’s more obvious, since we’re seeing past the dust blocking our visible view.

That’s the power of multi-wavelength observations! By looking at objects in literally a different light, we see them in, well, a different light. Even an object as familiar as the Orion Nebula can be seen with a different perspective when viewed with new instruments like VISTA.

Right now as I write this, Orion is high in the sky at sunset. Go outside and find it; it’s easy to spot. Look to his dagger, what the hunter in myth and song used to pierce the skin of his prey, and think that we mere humans can do the same to the skin of the nebula itself, and nourish our minds with what we find inside.

* I used to point that out to students when I was in grad school, and for some reason my roommate would always chuckle and say, “Yeah, his dagger.” I never did understand why.