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          Institute: MPI für extraterrestrische Physik     Collection: High Energy Astrophysics at MPE     Display Documents

ID: 5905.0, MPI für extraterrestrische Physik / High Energy Astrophysics at MPE
Discovery of X-rays from Venus with Chandra
Authors:Dennerl, K.; Burwitz, V.; Englhauser, J.; Lisse, C.; Wolk, S.
Date of Publication (YYYY-MM-DD):2002-04
Title of Journal:Astronomy & Astrophysics
Journal Abbrev.:Astron. Astrophys.
Issue / Number:1
Start Page:319
End Page:330
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:On January 10 and 13, 2001, Venus was observed for the first time with an X-ray astronomy satellite. The observation, performed with the ACIS-I and LETG/ACIS-S instruments on Chandra, yielded data of high spatial, spectral, and temporal resolution. Venus is clearly detected as a half-lit crescent, with considerable brightening on the sunward limb. The morphology agrees well with that expected from fluorescent scattering of solar X-rays in the planetary atmosphere. The radiation is observed at discrete energies, mainly at the O-K- alpha energy of 0.53 keV. Fluorescent radiation is also detected from C-K-alpha at 0.28 keV and, marginally, from N-K- alpha at 0.40 keV. An additional emission line is indicated at 0.29 keV, which might be the signature of the C 1s --> pi* transition in CO2 and CO. Evidence for temporal variability of the X-ray flux was found at the 2.6sigma level, with fluctuations by factors of a few times indicated on time scales of minutes. All these findings are fully consistent with fluorescent scattering of solar X-rays. No other source of X- ray emission was detected, in particular none from charge exchange interactions between highly charged heavy solar wind ions and atmospheric neutrals, the dominant process for the X- ray emission of comets. This is in agreement with the sensitivity of the observation.
Free Keywords:atomic processes; molecular processes; scattering; Sun : X- rays; gamma rays; planets and satellites : individual : Venus; X-rays : general
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für extraterrestrische Physik
External Affiliations:Max Planck Inst Extraterr Phys, Giessenbachstr, D-85748; Garching, Germany; Max Planck Inst Extraterr Phys, D-85748 Garching, Germany; Univ Maryland, Dept Astron, College Pk, MD 20742 USA; Harvard Smithsonian Ctr Astrophys, Chandra Xray Ctr, Cambridge, MA 02138 USA
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