1. Astronomy
Thomas Cooper

2. The spectroscopic technique used to assess the

concentration or amount of a given species, such
as the elements that make up a star.
 The instrument that performs such
measurements is a spectrometer or
spectrograph.
 Most large telescopes have spectrometers,
which are used either to measure the chemical
composition and physical properties of
astronomical objects or to measure their
velocities from the Doppler shift of their spectral
lines.

4. Telescope – to capture radiation

Dispersion Device – to spread the radiation

out into a spectrum
 Detector – to record the results

5. Most spectroscopic methods are differentiated as

either atomic or molecular based on whether or not
they apply to atoms or molecules. Along with that
distinction, they can be classified on the nature of
their interaction:
 Absorption spectroscopy uses the range of the
electromagnetic spectra in which a substance absorbs.
 Emission spectroscopy uses the range of electromagnetic
spectra in which a substance radiates (emits).
 Scattering spectroscopy measures the amount of light
that a substance scatters at certain wavelengths, incident
angles, and polarization angles.

6. A luminous solid, liquid or

dense gas emits at all
wavelengths and
produces a continuous
spectrum.
 A low-density, hot gas
emits light whose
spectrum consist of a
series of bright emission
lines that represent it’s
chemical composition.
(Emission Lines).
 A cool, thin gas absorbs
certain wavelengths from
a continuous spectrum,
leaving dark absorption
lines. (Absorption Lines)

8. Spectral Emissions of a Supernova

9. (1787-1826)

Physicists

Catalogued over 600

absorption lines
 Now know as
Fraunhofer lines

12. Lines that represent wavelengths of light that were removed
(absorbed) by gasses present in the outer layers of the sun.

13. Ground State – normal energy state
Exited State – contains more than the
normal amount of energy
Ionized State – electron has
exceeded the maximum energy state

14. N81, an emission nebula
An interstellar cloud made mostly of hydrogen gas
excited by absorbing radiation emitted by
extremely hot stars.

15. Change in Energy State

Change in Vibrational State

Change in Rotational State


17. Absorption of additional energy
can boost the electron into even
higher orbitals within the atom.
As it cascades down to the
ground state, it emits photons,
each with a different energy and
wavelength.