First light for the PEPSI polarimeters | 10/13/2017 | Staff
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Thanks to a cleverly designed "two-in-one" instrument attached to the world's most powerful telescope, astronomers can extract more clues about the properties of distant stars or exoplanets than previously possible.

Developed at the Leibniz-Institute for Astrophysics in Potsdam, Germany, the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) saw first light on April 1, 2015, after being successfully installed at the Large Binocular Telescope Observatory (LBTO) in Arizona, USA. Once both of PEPSI's polarimeters were mounted in the focus points of each of the LBT's two 8.4-meter mirrors in late September 2017, the telescope was pointed to the star gamma Equ and polarized light was received. From these spectra astronomers can, for example, deduce the geometry and strength of magnetic fields on the surfaces of distant stars, or study the reflected light from the atmospheres of potentially habitable exoplanets.

Polarimeter - Oscillation - Planes - Spectrograph - Prism

A polarimeter separates starlight according to its oscillation planes. It is complementary to a spectrograph that, like a prism, separates light according to its oscillation frequencies (or colour). The two combined, polarimeter and spectrograph, added to a powerful telescope, enable astronomers to obtain spectra in polarized light. This in turn allows the characterization of the full wave-front of the incoming stellar light and extract details of its radiation physics that otherwise remain hidden.

A series of integrations in circularly and linearly polarized light was obtained when the telescope was pointed to the magnetic reference star Gamma Equulei, or gamma Equ, a double star located about 118 light-years from Earth. These spectra have a spectral resolution of R=120,000, that...
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