So you saw my gallery yesterday of gorgeous pictures from 2011, right? And then you read my post this morning where I whine about how Chandra releases an awesomely cool picture the day after I put up my gallery? Right. So of course Hubble releases an image today that is so insanely amazing I hardly know where to start with it. So I'll start by showing it to you. Behold, Sharpless 2-106:
Are. You. Freaking. Kidding. Me? [Click to ennbulenate, and yes, you really want to.] This devastatingly beautiful image shows the birth pangs of a massive star. Called IRS 4 (for Infrared Source 4; it was first seen in IR images), it's the really bright star just below center where the two blue lobes come together. It's a bruiser, an O-type star with at least 15 times the Sun's mass -- 30 octillion tons! -- and is a staggering 10,000 times as bright. It's still in the process of forming, but it's nearly there. Located about 2000 light years away, IRS 4 is surrounded by an enormous cloud of gas and dust that may have a mass as high as 25,000 times the mass of the Sun. When the star first ignited, fusing hydrogen into helium in its core, the vast amount of energy it started pouring out lit up the cloud in the immediate vicinity around it. Most of the cloud is still dark and cannot be seen here, but everything within a few light years of the star is being illuminated, if not ionized, by the fierce ultraviolet light from the star. Generally, very young stars are still surrounded by the thick disk of material from which they formed. That's true of IRS 4; the dark line on the left of the star is actually the shadow of that disk on the gas and dust around it. At this point, things get weird.
As it happens, I've written about Sh 2-106 before, when a gorgeous ground-based picture of it from the Gemini North telescope was released (seen here, which I rotated and cropped to match the Hubble image). When I saw that Gemini image I thought it was relatively easy to interpret, but as I examined this new Hubble image, I started seeing things that were a bit confusing. It's very common to see two gigantic lobes on either side of a young star like this. The star is rapidly rotating, and that twists up its magnetic fields like two tornadoes tip-to-tip, blasting out energy and matter at incredibly high speeds in opposite directions. When I first saw these images, I figured that's what we're seeing. But then I wondered why the star itself isn't centered between the two lobes. Look at it: if you were to draw a line down the middle of the two lobes from left to right, you'd expect the star to be on that line, but instead it's well below it. As far as I can figure out, there is still dark, dense material in the outer cloud that's blocking our view a bit, throwing off the symmetry of what we see. It's not that the star is lower than those lobes, it's that the lobes do extend farther down, but they're obscured by opaque stuff between us and them. We're only clearly seeing the upper parts of those lobes. I'll be honest and say I'm guessing a bit here; it's not entirely clear this is the case but it just seems most likely. But I was curious, so I started digging, and found out more. According to a paper I found, infrared observations of SH 2-106 indicate there are actually four lobes*!
In this diagram, we are on the left, and the arrow represents the direction we are looking. There are two lobes of matter streaming away from us on the far side of the star (labeled red; in the Hubble image one is to the left and the other to the right of the star) and one lobe moving toward us (labeled blue; to the right of the star in the Hubble image). To interpret their observations, the astronomers determined the fourth lobe is, for some reason, devoid of gas. The green cylinder is hot gas, and the entire structure is embedded in a much denser dark cloud of gas and dust. As it happens, the two lobes to the right of the star in the Hubble image (in the model, the blue and red lobes on the bottom) are nearly superposed on top of each other from our perspective, so we see one big structure to the right of the star. But what happened to that lobe on the left that was aimed in our direction? It's clear that the star IRS 4 was formed very near the edge of the dark cloud -- if it were buried deeply, it wouldn't be visible. So it's possible that jet of material punched out through the edge of the cloud, and emptied itself of material. The other lobe to the right has also started erupting out of the edge, and may evacuate the gas over the next few centuries. In the meantime, the other three jets are slamming into the surrounding material, compressing it and heating it. In their wakes are huge cavities, and turbulence from the fast-moving jets has created those incredibly lovely wisps and curlicues in the gas. And to attest to the power and might of this one star, the entire bipolar nebula is something like 2 light years in length: 20 trillion kilometers! Soon -- and by that, I mean in a million years or so -- IRS 4 will settle down, more or less. It will become a big blue star, shining steadily for quite some time. But not too long: stars that massive don't have long lives. They have a tendency to end violently and messily, exploding as supernovae, bright enough to outshine entire galaxies! When this happens to IRS 4, that material will expand outward at a fraction of the speed of light, slam into the all that junk floating around it... and then the fireworks will really begin. Image credits: Hubble: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Gemini: Gemini Observatory/AURA; Diagram: Noel, C., Joblin, J. P., Maillard, and T. Paumard.