Magnetic moment and plasma environment of HD 209458b as determined from Lyα observations

Kristina G Kislyakova; Mats Holmström; Helmut Lammer; Petra Odert; Maxim L Khodachenko

doi:10.1126/science.1257829

Magnetic moment and plasma environment of HD 209458b as determined from Lyα observations

Science. 2014 Nov 21;346(6212):981-4. doi: 10.1126/science.1257829.

Authors

Kristina G Kislyakova¹, Mats Holmström², Helmut Lammer³, Petra Odert⁴, Maxim L Khodachenko⁵

Affiliations

¹ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria. [email protected].
² Swedish Institute of Space Physics, PO Box 812, SE-98128 Kiruna, Sweden.
³ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria.
⁴ Institute of Physics, University of Graz, Universitätsplatz 5, A-8010 Graz, Austria.
⁵ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Leninskie Gory, 119992 Moscow, Russia.

PMID: 25414310
DOI: 10.1126/science.1257829

Abstract

Transit observations of HD 209458b in the stellar Lyman-α(Lyα) line revealed strong absorption in both blue and red wings of the line interpreted as hydrogen atoms escaping from the planet's exosphere at high velocities. The following sources for the absorption were suggested: acceleration by the stellar radiation pressure, natural spectral line broadening, or charge exchange with the stellar wind. We reproduced the observation by means of modeling that includes all aforementioned processes. Our results support a stellar wind with a velocity of ≈400 kilometers per second at the time of the observation and a planetary magnetic moment of ≈1.6 × 10(26) amperes per square meter.

Publication types

Research Support, Non-U.S. Gov't