1. Department of Physics, Math and Astronomy, California Institute of Technology, 1200 East California Boulevard, Mail Code 405-47, Pasadena, California 91125, USA
2. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, California 91101, USA
3. Department of Astronomy, Columbia University, New York, New York 10027, USA
4. Department of Physics and Astronomy, 430 Portola Plaza, UCLA, Los Angeles, California 90095-1547, USA
5. Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, California 94720, USA

Correspondence to: D. Christopher Martin¹ Correspondence and requests for materials should be addressed to D.C.M. (Email: cmartin@srl.caltech.edu).

Mira is one of the first variable stars ever discovered¹ and it is the prototype (and also the nearest example) of a class of low-to-intermediate-mass stars in the late stages of stellar evolution. These stars are relatively common and they return a large fraction of their original mass to the interstellar medium (ISM) (ref. 2) through a processed, dusty, molecular wind. Thus stars in Mira's stage of evolution have a direct impact on subsequent star and planet formation in their host galaxy. Previously, the only direct observation³ of the interaction between Mira-type stellar winds and the ISM was in the infrared. Here we report the discovery of an ultraviolet-emitting bow shock and turbulent wake extending over 2 degrees on the sky, arising from Mira's large space velocity and the interaction between its wind and the ISM. The wake is visible only in the far ultraviolet and is consistent with an unusual emission mechanism whereby molecular hydrogen is excited by turbulent mixing of cool molecular gas and shock-heated gas. This wind wake is a tracer of the past 30,000 years of Mira's mass-loss history and provides an excellent laboratory for studying turbulent stellar wind–ISM interactions.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.