Harvard University Astronomy Lab and Clay Telescope

Day Labs | Evening Labs | Cloudy Day Labs | MaximDL Help

Spectra of the Double Star Albireo

SPU-21 Fall 2013

printer version

The spectrum of a star can give us a lot of information about the star, including information about its composition and its temperature. In this lab, you will take the spectrum of each star in the double star Albireo and identify their spectral type. Stars are divided into groups (O, B, A, F, G, K, M) from hottest to coolest, from about 40,000K - 2,000K. A popular mnemonic to remember the spectral sequence is "Oh, be a fine girl and kiss me!". These groups are then further subdivided from (0-9) where the B0 would be the hottest stars in the subclass and B9 would be the cooler.

Procedure:

• Let's first get the spectrograph setup. Click here if you need further instructions.
• Now that we are setup, let's slew the telescope to Albireo. Click here for detailed instructions on how to align the first star on the slit and take a spectrum.
• Immediately after you take the spectrum of Albireo, you need to take calibration spectra. We have a Mercury-Argon light source that emits light at certain discrete wavelengths. We will use this calibration spectrum to convert our object spectrum from pixels to wavelengths.
• Now, let's repeat the process to take a spectrum of the second star of Albireo and a similar calibration spectrum.

Reductions/Analysis:

• Before we can analysis our spectra, we need to convert the pixels to wavelengths so we can determine what lines we observed. The following link will guide you through calculating a wavelength solution for each spectrum.
• Now that we have a wavelength solution, we can begin to dive into the analysis of what we are seeing in each of these very different spectrums.
  • It is good to note that different stars have different spectral features and this is what distinguishes them from each other. In general, hotter stars tend to have stronger H and He lines while cooler stars are full of metal rich lines. Figure 17-11 in your book is a good visual of what prominent lines you can expect to see in different stars.
  • Name as many lines as you can and give your best estimate of what spectral type of star the two stars of Albireo are based on your observations.