M44: The Beehive Cluster
Image Credit & Copyright: Drew Evans
Explanation: A mere 600 light-years away, M44 is one of the closest star clusters to our solar system. Also known as the Praesepe or the Beehive cluster its stars are young though, about 600 million years old compared to our Sun’s 4.5 billion years. Based on similar ages and motion through space, M44 and the even closer Hyades star cluster in Taurus are thought to have been born together in the same large molecular cloud. An open cluster spanning some 15 light-years, M44 holds 1,000 stars or so and covers about 3 full moons (1.5 degrees) on the sky in the constellation Cancer. Visible to the unaided eye, M44 has been recognized since antiquity. Described as a faint cloud or celestial mist long before being included as the 44th entry in Charles Messier’s 18th century catalog, the cluster was not resolved into its individual stars until telescopes were available. A popular target for modern, binocular-equipped sky gazers, the cluster’s few yellowish tinted, cool, red giants are scattered through the field of its brighter hot blue main sequence stars in this telescopic group snapshot. Dramatic diffraction spikes highlighting the brighter cluster members were created with string crossed in front of the telescope’s objective lens.
Tomorrow’s picture: black hole shadow
影像提供与版权: Drew Evans
说明: 距离只有600光年远的M44，是离我们太阳系最近的星团之一。鬼宿星团 （M44、蜂巢星团）的成员星都相当年轻，年龄大约在6亿年左右，相较之下，我们太阳的年龄已有45亿年高龄。由于它的年龄及在空间的运动，都和金牛座内离我们更近的毕宿星团类似，所以它们可能是诞生于同一个大分子云里。疏散星团M44的1,000多颗成员星，分布在15光年的区域之内，大约在巨蟹座绵延了3个满月（1.5度）的天区。肉眼即可见的M44，是个自古即知的天体，早在18世纪被梅西叶编进他的星表成为第44号天体之前，对它的描述为“一团黯淡的云气或天空云雾”，而要等到使用望远镜观测后，它的成员星才被解析出来。在现代，它是使用双筒望远镜观星者的一个热门标的。在这幅望远镜影像里，星团内少数的泛黄低温红巨星，夹杂在视野里较亮的蓝主序星之间。用于突显此星团较明亮成员星的吸睛绕射芒，是用悬在望远镜物镜前方的十字交叉细绳所产生的。 （Praesepe 鬼宿星团、the Beehive cluster 蜂巢星团）
明日的图片: black hole shadow