Welcome to Project Galileo: Home of an online telescope for schools across the UK

Quick snapshot of a star's spectrum using a 100 lines/mm diffraction grating filter, imaged remotely by the Project Galileo observatory on 30th March 2009

Why Spectroscopy of Stars?

The above image, when correctly processed, can tell us a lot of useful information about a star - here's a small selection of some of the things we can find out:

• The type of star we're looking at
• Whether or not it's part of a binary system
• It's likely surface temperature
• It's evolutionary stage (Main Sequence or post-main sequence)
• The likelihood of any planetary systems orbiting the star

NOTE: What the Project Galileo observatory can find out will usually be worked out in conjunction with other known properties of any given star from other sources of information.

There are many collaborative & even worldwide amateur astronomy projects combining data from individual observatories. The total data set can be used to make new discoveries about the stars being studied. In fact, pro-am collaboration will become increasingly important as the number of high quality telescopes/observatories grows globally, and the number of new discoveries being made means there is an ever-increasing need for new data!

Lastly, in case you're wondering what the numbers mean at the bottom of the image: they are just a brightness or intensity scale, which varies from 0 to 65535 (65535 being the highest value). The colour in the image is not the actual star colour, but a false colour scale added so we can more easily see the brightness variations across the spectrum.

Once we've taken into account the natural variations that occur across the image (called Flat-Fielding), and removed all the unwanted noise that you can see as speckles (a process called dark-current removal, we can then plot a graph of the star's spectrum.

Having an accurate spectrum is then the first real step in working out what the star's composition is, and then we can begin to combine this data with other observations (a technique called photometry) to work out some of the things in the list above.

This whole process is very much like the methodology used by forensic scientists when they're trying to solve crimes! In both cases, the forensic scientist & the astronomer are trying to piece together what has happened - but the outcome of their results are obviously very different!