M2

2024年12月19日

Messier 2
Image Credit: ESA/Hubble & NASA, G. Piotto et al.

Explanation: After the Crab Nebula, this giant star cluster is the second entry in 18th century astronomer Charles Messier’s famous list of things that are not comets. M2 is one of the largest globular star clusters now known to roam the halo of our Milky Way galaxy. Though Messier originally described it as a nebula without stars, this stunning Hubble image resolves stars across the cluster’s central 40 light-years. Its population of stars numbers close to 150,000, concentrated within a total diameter of around 175 light-years. About 55,000 light-years distant toward the constellation Aquarius, this ancient denizen of the Milky Way, also known as NGC 7089, is 13 billion years old. An extended stellar debris stream, a signature of past gravitational tidal disruption, was recently found to be associated with Messier 2.

Tomorrow’s picture: the last full moon

M2
影像提供: ESA/Hubble & NASA, G. Piotto et al.

说明: 这个排序在蟹状星云（M1）之后的庞大星团，是18世纪天文学家梅西耶著名“非彗星”星表登录的第二个天体。而在我们银河系银晕里漫游的球状星团里，M2是其中最庞大者之一。梅西耶当初宣称M2是一团没有恒星的云气，然而这幅令人屏息的哈勃望远镜影像，清楚的解晰出M2中心40光年范围内的恒星。M2的恒星数接近150,000，拥挤在直径约175光年的空间里。这个亦名为NGC 7089、高龄约130亿年的银河系古老成员，位于宝瓶座方向，离我们约55,000光年远。最近的研究发现，M2有一道绵延的恒星流，这种它过去曾受到重力潮汐扰动的特征结构。

明日的图片: the last full moon