PubMed · 12904775
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Eddie Baron. 2003-08-07. Astronomy: an elementary puzzle.. https://doi.org/10.1038/424628a
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The star upsilon Andromedae is orbited by three known planets, the innermost of which has an orbital period of 4.617 days and a mass at least 0.69 that of Jupiter. This planet is close enough to its host star that the radiation it absorbs overwhelms its internal heat losses. Here, we present the 24-micrometer light curve of this system, obtained with the Spitzer Space Telescope. It shows a variation in phase with the orbital motion of the innermost planet, demonstrating that such planets possess distinct hot substellar (day) and cold antistellar (night) faces.
Theoretical and experimental spectroscopic studies have underlined the contribution of large PAHs towards the astrophysical mid-infrared emission bands. Quantum chemical study of eight large PAHs using density functional theory approach is reported along with their infrared spectra. Systematic variation of bands with PAH size is noted and a better agreement with the observed astrophysical bands is obtained. Compared to small and medium sized PAHs there is substantial C-H stretch intensity in the cation spectra. This is attributed to smaller change in charge on the hydrogens upon ionization. For the C-H out-of-plane mode large PAHs correlate well with observed features on the shorter wavelength side of the 11.2 microm band. Presence of two sub-components of the broad 7.7 microm band in large PAHs compares very well with the corresponding astrophysical band and point to the abundance of large PAH cations in interstellar environments. The data presented here may be used for a more detailed study on the profile variations accompanying the mid-IR bands in various interstellar environments.