M4

M4

Messier 4
Image Credit & Copyright: Steve Crouch

Explanation: Messier 4 can be found west of bright red-giant star Antares, alpha star of the constellation Scorpius. M4 itself is only just visible from dark sky locations, even though the globular cluster of 100,000 stars or so is a mere 5,500 light-years away. Still, its proximity to prying telescopic eyes makes it a prime target for astronomical explorations. Recent studies have included Hubble observations of M4’s pulsating cepheid variable stars, cooling white dwarf stars, and ancient, pulsar orbiting exoplanet PSR B1620-26 b. This sharp image was captured with a small telescope on planet Earth. At M4’s estimated distance it spans about 50 light-years across the core of the globular star cluster.

Tomorrow’s picture: the climb

M4
影像提供与版权: Steve Crouch

说明: 在明亮红巨星心宿二（天蝎座α星）的西边，可见到梅西耶4（M4）。这个拥有约10万颗恒星的球状星团，距离地球仅有5,500光年左右，但只有在拥有黝黑夜空的地点才隐约可见。然而，由于M4相对邻近，是以成为天文学研究的重要目标。最近针对它的研究有：使用哈勃太空望远镜观测M4内的造父变星、冷却中的白矮星、及一颗绕脉冲星运行的古老系外行星PSR B1620-26 b。这张清晰的影像来自一部地面的小望远镜。以M4的估计距离来换算，这张影像涵盖了此球状星团核心约50光年宽的区域。

明日的图片: the climb