Puppis中的三个集群
(原标题: Three Clusters in Puppis)
2022-02-18
浏览次数: 15
银河系或疏散星团都很年轻。这些恒星群是在银河系平面附近一起诞生的，但随着星团成员被星系潮汐和引力相互作用抛射出去，它们的数量逐渐减少。在这个直径超过3度的望远镜框架中，可以看到三个很好的银河星团的例子，朝向南方天空的航海星座Puppis。左下方的M46距离我们约5500光年。在中间的右边，M47距离我们只有1600光年，而NGC 2423（上）距离我们大约2500光年。大约3亿年前的年轻星系M46在一个直径约30光年的区域内包含了几百颗恒星。敏锐的眼睛可以发现行星状星云NGC 2438，在大约11点钟方向与M46星团的恒星相对。但是这个星云的中心恒星已经有数十亿年的历史了，NGC 2438很可能只是偶然出现在年轻的M46的视线中。M47更年轻，年龄约为8000万年，是一个更小、更松散的星团，跨度约为10光年。然而，星团NGC 2423的年龄大约是7.5亿年。已知NGC 2423有一颗系外行星，绕着它的一颗红巨星运行。
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Galactic or open star clusters are young. The swarms of stars are born together near the plane of the Milky Way, but their numbers steadily dwindle as cluster members are ejected by galactic tides and gravitational interactions. Caught in this telescopic frame over three degrees across are three good examples of galactic star clusters, seen toward the southern sky's nautical constellation Puppis. Below and left, M46 is some 5,500 light-years in the distance. Right of center M47 is only 1,600 light-years away and NGC 2423 (top) is about 2500 light-years distant. Around 300 million years young M46 contains a few hundred stars in a region about 30 light-years across. Sharp eyes can spot a planetary nebula, NGC 2438, at about 11 o'clock against the M46 cluster stars. But that nebula's central star is billions of years old, and NGC 2438 is likely a foreground object only by chance along the line of sight to youthful M46. Even younger, aged around 80 million years, M47 is a smaller and looser star cluster spanning about 10 light-years. Star cluster NGC 2423 is pushing about 750 million years in age though. NGC 2423 is known to harbor an extrasolar planet, detected orbiting one of its red giant stars.
© Dave Doctor