HAWK-I peers into a stellar cocoon

Bad Astronomy
The entire universe in blog form
Aug. 24 2007 1:20 PM

HAWK-I peers into a stellar cocoon

Check this image out:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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It's an infrared view of stars embedded in a cocoon of gas and dust. To an optical telescope there wouldn't be much to see there; the dust blocks visible light. But this image was taken in the infrared (at 3 microns, more than three times the wavelength the human eye can see) using a new camera on the Very Large Telescope in Chile. The camera, called HAWK-I (High Acuity, Wide field K-band Imaging) is pretty impressive. It is very sensitive to infrared light, has incredible resolution (0.1 arcseconds per pixel, which is basically what Hubble can do) and a wide field, peering at a field 7.5 arcminutes square. That means it's looking at an area on the sky about 1/12th the size of the Moon on the sky.

For astronomers, that's a big bite o' sky.

Better yet, it's sitting on the business end of the VLT, which sports a whopping 8 meter mirror (for comparison again, Hubble's mirror is 2.4 meters across, less than 1/10th the area). That means it can spot very faint objects. This is an astronomer's goal: faint objects are almost always really interesting; they are either intrinsically faint, like dim stars, which tells us about how stars behave at the low end of the mass scale; they are embedded in dust and hard to see otherwise; or they are really, really far away.

Very distant galaxies, for example, can have their light redshifted into the infrared because they are receding from us. Optical images won't tell you much necessarily, but HAWK-I will get a good view of them, seeing both small and faint details. This is pretty important if you're trying to compare distant galaxies -- which we see when the Universe was young -- with closer, older galaxies.

The image above is pretty interesting, but the press release is vague on details (this happens frequently with ESO press releases). I am particularly interested in the ring of material that appears to be around the bright central star. Is that a hole carved out by stellar winds from a young star? Sure looks like it; the bright rim would be where the wind from the star (actually it looks like a binary) is slamming into the dusty material around it, warming it up. The fainter star directly to its left has an arc of red dots around it. What are those?

Even cooler, look at the whitish star above the bright one. There are two cone-shaped dark regions going out from it in opposite directions. I just bet that star has a thick disk of material around it, and the light from the star is blocked by that disk. The starlight illuminates the dust above and below the disk, but in the disk's plane you see the light shadowed. I'm just guessing... but I bet I'm right.

Until the James Webb Space Telescope comes along (when? 2013? later?), HAWK-I is our best IR eye on the sky. I'm looking forward to seeing lots of cool images and science from it! And hopefully, some more about the way kewl image above.

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