Chandra High Energy Transmission Grating Spectrometer

Press Release, August 30, 1999
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This portion of the preliminary Capella spectrum produced by the medium energy gratings of the HETG shows the observed spectrum and the predicted wavelengths of X-ray lines that would be emitted by specific elements, e.g., Silicon (Si), Magnesium (Mg), Neon (Ne), Iron (Fe), and Oxygen (O). Multi-million degree plasma in the corona of Capella gives rise to the observed lines. Ratios of line fluxes from the same ion (such as the closely spaced magnesium lines near 9 Angstroms) give a measure of the temperature. Ratios of different ions (such as Mg+10 and Mg+11) give information about the ionization state. By using lines from different elements, one can further investigate chemical composition and abundance.


The HETGS can clearly distinguish X-rays with wavelengths differing by only a fraction of one percent. In this blowup of the region around 9 Angstroms three lines are seen emitted from the Helium-like ion Mg+10. The two brightest lines differ by approximately 1.5% in wavelength. 
"What questions will high-resolution observations answer about Capella?" one answer

Click here for more about the HETGS Capella first-light observation;
see below for information on Chandra and the HETG.