如图所示，NGC 7773是一个棒旋星系的美丽例子。一个发光的棒状结构显著地穿过星系明亮的核心，延伸到NGC 7773的横扫而过的类似风车的螺旋臂的内部边界。天文学家认为，这些棒状结构出现在星系生命周期的后期，因为恒星形成物质向星系中心移动——较年轻的螺旋不像较老的螺旋那样经常具有棒状结构，这表明棒状结构是星系成熟的标志。它们也被认为是恒星的摇篮，因为它们闪耀着明亮的光芒，意味着有大量年轻的恒星。
文字来源: ESA (European Space Agency)
图像来源: ESA/Hubble & NASA, J. Walsh
This striking image was taken by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3), a powerful instrument installed on the telescope in 2009. WFC3 is responsible for many of Hubble’s most breathtaking and iconic photographs.
Shown here, NGC 7773 is a beautiful example of a barred spiral galaxy. A luminous bar-shaped structure cuts prominently through the galaxy’s bright core, extending to the inner boundary of NGC 7773’s sweeping, pinwheel-like spiral arms. Astronomers think that these bar structures emerge later in the lifetime of a galaxy, as star-forming material makes its way towards the galactic center — younger spirals do not feature barred structures as often as older spirals do, suggesting that bars are a sign of galactic maturity. They are also thought to act as stellar nurseries, as they gleam brightly with copious numbers of youthful stars.
Our galaxy, the Milky Way, is thought to be a barred spiral like NGC 7773. By studying galactic specimens such as NGC 7773 throughout the universe, researchers hope to learn more about the processes that have shaped — and continue to shape — our cosmic home.
Text credit: ESA (European Space Agency)
Image credit: ESA/Hubble & NASA, J. Walsh