Suppose that we measure the spectrum of a new star that we have discovered, and find that the peak of its continuum is at a wavelength of 150 nm. What part of the spectrum does this maximum emission wavelength fall in? What do we deduce the effective surface temperature of this star to be (in degrees Kelvin)?
What spectral classification, based up this temperature, would we assign to our star?
What sorts of absorption lines would we expect to see in its spectrum?
The effective blackbody temperature of the Sun is about 5800 K. How many times more energy per second will our star radiate from each square meter of its surface than the Sun does?
Close examination of the spectrum of our star reveals that the Balmer series absorption line of H-Alpha, which has a rest wavelength of 656.3 nm, is for this star measured at the wavelength of 656.956 nm. What do we deduce the relative velocity of this star to be (in km/s) with respect to us on the earth? Is this star moving toward us or away from us? (Note: this is the doppler effect.)
Give a name to our newly discovered and catalogued star. (Note: astronomers would give a name based on the constellation, like Alpha Lyrae, VV Herculis, or 61 Cygni, or their own name, like Lalande 21185 or Barnard's Star. Im sure you can come up with something more interesting! Be imaginative!) What does your name mean?
These are the sorts of tools we have at our disposal to measure the properties of distant stars, merely by inspecting the light that reaches us. Please read Chapter 6, which describes all these mechanisms, and also gives the relevant formulae.
Be sure to visit the DRL rooftop Student's Observatory on a clear Monday or Thursday night, or the Flower & Cook observatory during one of the bi-weekly field trips (next one scheduled Wed Feb 28).
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Steven T. Myers - Last revised 23Feb96