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Astronomy: Light echo in V838 Monocerotis
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In 2002 the Hubble Telecope witnessed strange behavior by a star in the constellation Monceros the Unicorn 20.000 light years from Earth. The star, named V838 Monocerotis swelled up to nearly 1000 times larger than our Sun and temporarily it became the brightest star in the Milky Way galaxy. Then it cooled and faded away. The glow was bright enough to light up layers of dust surrounding the star, like a flashlight shining through smoke in a dark room. NASA's Hubble Telescope watched the dust shell around V838 Mon over many months after this outburst. Every time Hubble astronomers took a picture, the dust ring looked larger than before. But in the pictures taken by the Hubble Telescope, the dust really isn't growing. Instead, light from the flash is sweeping through the dust, lighting up different parts. This illusion is called a "light echo." No typical novaThe outburst of V838 Mon was somewhat similar to that of a nova, a more common stellar outburst. However the star did not expel its outer layers. Instead, it grew enormously in size, with its surface temperature dropping to temperatures not much hotter than a light bulb.This behavior of ballooning to an immense size, but not losing its outer layers, is very unusual and completely unlike an ordinary nova explosion. It could be that this star had a transitory stage in its evolution that is rarely seen. The star has some similarities to highly unstable aging stars called eruptive variables, which suddenly and unpredictably increase in brightness. Related subject>> The Hubble Telescope |
 The Hubble Telescope witnessed the light flash spreading out in the surrounding dust clouds over time. |
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