Spitzer peeks under a cradle’s blanket

Bad Astronomy
By Phil Plait
Feb 12, 2008 8:52 PMNov 5, 2019 7:03 AM


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I think one of the most amazing things we have learned in the centuries of the scientific pursuit of astronomy is that stars are born, they live out their lives, and that they die. That concept by itself is stunning: a process which takes billions of years can be understood, simply by knowing a few laws of physics and taking a look around. And look we do. We have fantastic tools to investigate the lives of stars, and one of the best is the Spitzer Space Telescope. Don't believe me? Then take a look at this stunner:

Spitzer took this gorgeous picture of the star forming region around the nearby star Rho Ophiuchi (just called Rho Oph for short). At 400 light years away, it's one of the closest places where stars are actively being born, and so it provides us a front-row seat to the process. However, the problem is that our great view to the show is blocked by a stage curtain. Star birth, like human birth, is messy. Gas and dust litter the nursery, obscuring what's going on. Spitzer's advantage is that it sees light in the infrared, which can penetrate the muck. The stars being born emit a lot of infrared light, so it can pierce the veil, so to speak, and reach us and our telescopes. And what a sight! Infrared light emitted by the gas and dust themselves appears as tenuous wisps streaming across the view. The newborn stars shine brightly, and their fierce light (and strong solar winds) sculpt the gas, pushing it aside, carving sandbar-like shapes. Look at the windswept cloud just above the center of the image. That blob of material is probably a light year or more across, and its shape is due to the infant stars just below it and to the right in the picture. They are eroding it as surely as a river erodes away a spit of sand. Spitzer can see different wavelengths, different colors of infrared as well, and this tells us different things about the nebula. For example, in the image above at the very left just below center is a red star, and you can just see that is has a fuzziness to it. In this case, the light we are seeing is coming mostly from very long infrared wavelengths (24 microns, for those keeping track at home; for comparison, a human hair is about 50 microns wide). But Spitzer can also see shorter wavelengths where the view is a little better, and it made an image of this nebula using those colors of infrared as well. Here is a side-by-side of the two images, zoomed in and centered on that fuzzy star:

On the left is the short wavelength image (in this case, 8 microns) and on the right is the 24 micron image (actually, they are composites of several wavelengths, but the longest wavelength in each is 8 and 24 microns, respectively). In the 8 micron image on the left, the nebulosity is easier to see, and reveals itself to be hourglass-shaped, pinched in the middle and flaring at the ends. Astronomers call this kind of nebula bipolar: the star is emitting gas from its poles in opposite directions. This is a dead giveaway that we're looking at a very young star, only a few million years or so old. Rapid spin, strong magnetic fields and other forces are what focus that gas outflow, and the process itself will eventually slow the star's spin like a parachute slows a skydiver. After a few dozen million years the flow will shut down, and the star will look a lot like the Sun. So it's not just looking in infrared that lets us peek into the cradle (to completely mix all metaphors), but it's looking in different flavors of infrared that really lets us understand what's going on. Because of telescopes like Hubble, Chandra, Spitzer, and ground based behemoths like Gemini, Keck, and the VLT -- and a lot of smart people, hard work, and scientific progress -- we now understand a fair bit about how stars are born. It's an ongoing process of creation, it's incredibly beautiful, and we understand it. How cool is that?

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