Spectroscopy A Tool of Astronomers Title slide This ppt presentation was built to satisfy one requirement for the TAPS program at Jefferson Labs in Newport News, Virginia.

Definitions Spectroscopy- the study of the light from an object. Spectrometer- an instrument which spreads out light making a spectra. Spectra- range of electromagnetic energy separated by wavelength. definitions

Astronomers use spectroscopy because it allows them to determine the makeup of stars… without having to be present to take samples. Studying an objects spectra can tell scientists the composition of an object, its temperature, its density and its motion.

Mars Exploration Mission The Mars Exploration Rovers were launched with the goal of searching for and analyzing rock and soils on Mars. They utilized several spectrometers to analyze samples. Mini-TES: miniature thermal emission spectrometer (examine rock, soil & atmosphere) MB: Mossbauer Spectrometer (examine mineralogy of rocks & soils) APXS: Alpha Particle X-ray Spectrometer (analyze elements in rocks & soils)

2 Basic Types of Spectra Continuous- energy of all wavelengths Discrete- energy at a particular wavelength Emission or bright lines Absorption or dark lines Types of spectra Continuous Discrete emission or bright line absorption or dark line

Continuous Spectrum Also called thermal or blackbody spectra Spectra of stars, planets, moons Depends on temperature Ex: sunlight passing through a prism Most of these type of spectra are emitted from hot, dense objects. Hot objects emit EM radiation at all wavelengths. Temps above absolute zero will emit this type of spectrum. Blackbody is an object that absorbs all radiation falling on it (no reflection). When the blackbody is heated it emits light in a continuous spectrum.

Continuous Spectrum continued Hotter objects Shift toward this end Longer wavelength Shorter wavelength Cooler objects Shift toward this end The way scientists use the spectrum to tell how hot an object is is determined by how much of a particular color is present. If more red is evident, then the object is a cooler object; if it shows more violet, then it is a hotter object.

Discrete Spectrum Absorption Each element has a unique signature of absorption lines. That pattern helps scientists identify the element(s). Ex: stars, planets w/ atmospheres, & galaxies An absorption spectra forms when the spectra from a hot object passes through a cooler thin gas. When that spectra passes through the spectroscope it reveals a unique colored spectrum with dark lines. The location of the dark lines within that visible spectrum is a fingerprint that tells scientists what element is. Spectra Cool, thin gas Absorption spectrum Hot object

Discreet spectrum- Emission Again, the pattern of the lines determines the identity of the element. Ex: comets, nebula & certain stars The radiation from a colder object in space that passes through a thin, hot gas emits a spectra that is the opposite of a absorption spectrum. These colored lines tell you the identity of the element according to their color & position in the EM spectrum. Thin,hot gas Emission spectrum Spectra

Motion of Objects in Space Compare the dark lines in the middle spectra to the dark lines in the other two spectra. Blue shift shows object is moving toward the observer. This shows the normal position or no motion. Motion of objects in space. Self explanatory. This shows a red shift meaning that the object is moving away from the observer.

Determining the Spectra of Certain Elements Spectroscopy Lab Determining the Spectra of Certain Elements

Test your understanding...

What type of spectra is shown here? Continuous Absorption Emission

What type of spectra is shown here? Continuous Absorption Emission

Why does this picture represent just the continuous spectrum of light? Credits:

Light is just one portion of the electromagnetic spectrum Light is just one portion of the electromagnetic spectrum. Name 5 other parts of the EM spectrum.

No way! Were you sleeping? Back to question #1

YES, we have a winner! To next question….

Pat yourself on the back! Next question

That is a definite NO! Back to 2nd question