Echoes of a stellar outburst

Like a flashbulb illuminating fog, light from the outburst of a star has revealed its dusty surroundings. The light bouncing off the dust, which astronomers call a light echo, hasn’t been observed in our galaxy since 1936. The new echo has been captured in exquisite detail by the Hubble Space Telescope, reports Howard Bond of the Space Telescope Science Institute in Baltimore and his colleagues in the March 27 Nature.

The echo not only reveals the dusty netherworld, but also provides a record of the star’s unusual eruption, Bond notes. During the outburst, which astronomers observed in January 2002, the star inflated to a diameter at least 800 times larger than that of the sun and briefly became the most luminous star in the Milky Way.

Although the body, known as V838 Monocerotis, has since faded, the light from the outburst continues to reflect off surrounding dust. As light bouncing off dust farther and farther from the star reaches Earth, the circular reflections provide an expanding cross-section of the star’s envelope of dust. The light-echo has now expanded to twice the size of Jupiter, as seen from Earth, and may be visible until about 2010. The Hubble images reveal that the star is 20,000 light-years from Earth.

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