X-Rays Reveal Giant Bubble around Wolf-Rayet Star HD 50896

An international team of scientists using the European Photon Imaging Camera aboard ESA’s X-ray space observatory XMM-Newton has snapped a stunning new image of the giant bubble of material blown by powerful stellar winds of the massive Wolf-Rayet star HD 50896.

This image shows a giant bubble of material blown by the Wolf-Rayet star HD 50896: X-ray data are shown in blue, optical data are in red and green. The pink star near the center of the image is HD 50896 (ESA / J. Toala / M. Guerrero / IAA-CSIC / Y.-H. Chu / R. Gruendl / UIUC / S. Arthur / CRyA-UNAM / R. Smith / NOAO / CTIO / S. Snowden / NASA / GSFC / G. Ramos-Larios / IAM)

The bubble, known as S 308, is located some 5,000 light-years away in the constellation of Canis Major. It is about 60 light-years across and can be imagined to take on a wolf- or dog-like head.

Wolf-Rayet bubbles are the result of a hot, massive star expelling material through a strong stellar wind. This star’s howling wind is a million-degree plasma potion that emits X-rays.

The bubble S 308 is one of the only two Wolf-Rayet bubbles known to possess X-ray emission. Another one is NGC 6888.

The team, led by Dr Jesús Toalá of the Instituto de Astrofísica de Andalucía in Spain, observed the bubble in X-rays with ESA’s XMM-Newton space telescope, and in visible light with the Michigan Curtis Schmidt Telescope at Cerro Tololo Inter-American Observatory in Chile. The results were published in a paper in the Astrophysical Journal (arXiv.org version).

Where the fierce wind ploughs into surrounding material S 308 is lit up in red tones, the green halo is a result of a shock wave racing out from the star and colliding with the layers of stellar material already ejected into space.

The scientists predict that the Wolf-Rayet bubble S 308 will burst and disperse into the surrounding environment, while the star HD 50896 will end its life in a dramatic supernova explosion.


Bibliographic information: Toalá J.A. et al. 2012. X-Ray Emission from the Wolf-Rayet Bubble S 308. ApJ 755, 77; doi: 10.1088/0004-637X/755/1/77