AAmmaatteeuurr AAssttrroonnoommiiccaall Olivier Thizy [email protected] SSppeeccttrroossccooppyy --- April 15th, 2011 -- NEAIC ; NY, USA -- the “menu”... • Starting in spectroscopy (with some history) • Equipment • Educational • Pro/Am projects Starting in spectroscopy 15/04/11 (c) 2006 - Shelyak Instruments 3 Light & colors Isaac Newton (1642-1726) ➢ a pionnieer ➢ 1670: prisme's experience ➢ Circular “slit” of 6mm: ➢ l Dl / ~10 ! Light is a wave Thomas Young (1773-1829) ➢ Wave interpretation of light (1801) ➢ Worked with grating with 20 grooves/mm ➢ Electromagnetic spectrum Solar spectrum William Wollaston (1766-1828) ➢ ~150 years after Newton ! ➢ First observation (in 1802) of dark lines ➢ Demonstrated the importance of the slit width ➢ Joseph Fraunhofer (1787-1826) ➢ Manufacturer of high quality glasses ➢ a A, B (H ), C, D (sodium doublet)... H, K (Calcium) lines ➢ Catalog of ~600 raies in 1814 ➢ Also observed planets and some stars ! ➢ Edmon Becquerel (1820-1891) ➢ First photography of the solar spectrum (June 13th, 1842) ➢ Sodium in all shape ! Salt Match Pickel ! Sirius Sun Street lamp 15/04/11 (c) 2006 - Shelyak Instruments 8 (c) C. Buil / Benoit Minster Chemical analysis & spectroscopy Léon Foucault (1819-1868) ➢ Comparison between spectra on Earth and solar spectrum ➢ (sodium lines, 1849) Gustav Kirchhoff ➢ In parallel, he made the experiment with salt and published ➢ in 1859 that sodium should exist on solar atmosphere! A key theoritical result: Kirchhoff laws ➢ Robert Bunsen (1811-1899) ➢ Heidelberg university like Kirchhoff ➢ Together, they published in 1860 a paper on « chemical ➢ analysis by spectroscopic observation », then in 1861-1863 the analysis of several chemical elements and their work on the solar spectrum ...Spectroscopy was born... ➢ Kirchhoff's laws 1 2 3 A continuous spectra is emitted by any solid of gazeous body under high presure and high temperature. Stars are, under first 1 approximation, like black body whose continuous spectra has a shape which depends on its surface temperature; Absorption line spectra: a low pressure low temperature gaz 2 crossed by a continuous light absorbs some photons. Spectra then shows dark lines in front of the continuous spectra; Emission line spectra: a low pressure high temperature gaz emits 3 a light made of few radiations, characteristics of the atoms that constitutes this gaz. Each chemical element has its own line spectra, true identity card of its composition and state.