麒麟座V838的回光

2022年6月26日

Light Echoes from V838 Mon
Image Credit: NASA, ESA, H. E. Bond (STScI)

Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon’s outer surface suddenly greatly expanded with the result that it became one of the brighter stars in the Milky Way Galaxy in early 2002. Then, just as suddenly, it shrunk and faded. A stellar flash like this had never been seen before — supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the featured image from the Hubble Space Telescope is actually an outwardly expanding light echo of the original flash. In a light echo, light from the flash is reflected by successively more distant surfaces in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.

Tomorrow’s picture: gummy mountain stars

麒麟座V838的回光
影像提供: NASA, ESA, H. E. Bond (STScI)

说明: 是什么导致麒麟座V838星（V838 Mon）发生爆发？因某些未知的原因，麒麟座V838星的外层突然急遽扩张，让它在2002年初成为银河系的亮星之一。然后，它的变暗就如变亮一样突然快速。这种恒星亮闪前所未见。超新星或新星会把物质抛入太空中，而乍看之下，麒麟座V838星的爆发也像是有物质被抛入太空。不过，如这幅由哈伯太空望远镜所拍摄的主题影像所示，实际向外传播的只是亮闪外传所造成的回光而已。所谓回光，是指亮闪从环拱恒星、距离渐增的数个星际尘埃壳层反射之现象。V838星位在南天的麒麟座内，距离我们约20,000光年远，而上面影像的回光直径约为6光年。

明日的图片: gummy mountain stars