美国宇航局太空网评出2003年十佳天文图片

4：哈勃望远镜的又一杰作

　　拍摄这些照片的天文学家当看到它们时也惊呆了，因为这是他们平生第一次见到这种景象。他们仍旧不明白这到底是怎么回事。这颗被命名为“V838 Monocerotis”的恒星虽然忽然变的与木星轨道一样大，但最终还是没有爆发。

　　这颗恒星的表面温度目前还不高。这类活动本应该是一颗温度比较高的恒星才具备的。虽然这张照片显示的是2002年的景象，但直到2003年早期才对外公布(望远镜观测恒星的活动经常需要数个月的时间)。有趣的是，伸展开的星云并不是星星此次活动的一部分。它被称为“光回波”。星光激起周围的尘云，这些尘云然后就反射到了地球上。

4. Hubble Light Echo

The astronomers who took this series of pictures were stunned when they first saw them. They still don't really know what was going on. The star, named V838 Monocerotis, suddenly grew as large as the orbit of Jupiter, but it did not erupt. The surface remained cool. This type of activity should come from a star that gets hotter.

Though the images show the scene as of 2002, the pictures were released early in 2003 (crunching telescopic observations often takes months).

The expanding cloud, interestingly, is not part of the mystery. It is just pretty. It's called a light echo. The star's light bounces off surrounding dust clouds and is reflected to Earth. The echo grows over time as the light races out to other layers of material cast into space long ago by one or more previous eruptions of the star.