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All posts for the month August, 2007

A spectrum plot of infrared data shows the strong signature of water vapor deep within the core of an embryonic star system called NGC 1333-IRAS 4B

A spectrum plot of infrared data shows the strong signature of water vapor deep within the core of an embryonic star system called NGC 1333-IRAS 4B

Stars emit light (electromagnetic radiation) and heat. If you take the light from a star and send it through an instrument called a spectrograph, you can essentially break up the light into its component colors (wavelengths). You’ve seen one form of a spectrum in nature: it’s called a rainbow and it was created by light being broken up through a prism of raindrops.

The image above is a graph spectrum showing us the chemical elements that exist in a star called NGC1333-IRAS 4B. The infrared light was analyzed by an instrument aboard the Spitzer Space Telescope (which is sensitive to infrared wavelengths). The scientists compared it to a model of a water spectrum, and found water vapor in the region surrounding the star. What they think is happening is that ice particles in the surrounding environment are falling toward the star. When they hit the disk of gas and dust around the star, they heat up and melt, forming water vapor.

These details are in the spectrum, which tells us about the motion of the ice particles surrounding the star.

Spectra are a part of astrophysical research that can look pretty boring or confusing to people who don’t see them every day. Yet, if you know how to read them and what to look for, they can reveal details of an astronomical object that you just can’t see with the naked eye or in an image. Here’s another one, from a recent Gemini Observatory press release, that shows the evidence for water and ammonia ices on Pluto’s companion world, Charon. It is centered on infrared light radiating at 2.2 microns. The solid line is a model of a surface with ices called ammonia hydrates, along with water ices. Other dots are the data from the surface of Charon that represent ammonia hydrate ices. (You can read more about this one here.)

Now I don’t normally “do” spectra in my planetarium shows, mostly because they require more explanation than we often have time for. But, spectra ARE treasure troves of information, hidden right before our eyes.

and You

Star chart for finding the Aurigids

Star chart for finding the Aurigids

There’s another meteor shower coming up in a week, and if you didn’t get enough of them with the Perseids, you should check this one out. It’s called the Aurigids, and it’s supposed to be a flurry of bright and oddly colored meteors that seem to come from the direction of the constellation Auriga.

There’s quite a bit of interest in this year’s shower, which is the debris from Comet Kiess (C/1911 N1), because it’s a rare one. Comet Kiess has only visited this end of the solar system twice in the past couple of thousand years, and so Earth rarely encounters its debris tail. This year we’ll plow right through that trail on September 1. And if we’re lucky, there could (emphasis on the “could”) be a nice meteor shower, with perhaps a hundred meteors per hour or more, if the debris stream is thick. Or, if the debris stream is thin, the shower could be a bust.

The catch here is that the peak of the shower will be best seen by people living in the Rocky Mountains and further west. Earth will be smack in the middle of this stream at 11:36 UT (that’s 4:30 AM PDT). That’s the peak time; the shower (if there is one) begins well before that.(See here and here for more information.)

If you are planning to watch for Aurigids, there’s a unique project brewing that you might want to be involved with: the Aurigid Laptop Meteor Observation Project. Essentially, it’s another distributed computing project that will take observation info sent in by people in the observing range of the shower and turn it into a three-dimensional map of the debris stream from Comet Kiess. If you’ve got the time, you’re in the right place, and want to make a contribution to solar system science, here’s your chance