盖亚卫星构建的M15
影像来源与版权:Robert Vanderbei (Princeton University), ESA, Gaia, DPAC

说明:M15是我们银河系形成初期、具有130亿年历史的古老遗迹,它是仍在银河系光晕中漫游的大约170个球状星团之一。它的直径约200光年,位于飞马座方向、距离我们约35,000光年远。然而,这幅古老球状星团的真实感视图并不是一张照片。相反,它是一张gif动态影像,由对恒星位置、亮度和颜色进行非常精确的单独测量值所构成。这个富含天文意义的数据集是由进行巡天任务的盖亚卫星制作而成,该卫星还测定了13亿银河系恒星的视差距离。在这幅gif动态影像中,闪烁的恒星是M15内、已识别出的天琴座RR型星。这类恒星在M15内非常多,是一种演化过的脉动变星,它的亮度与其通常不到一天的脉动周期有关系。
翻译:北京天文馆

The Gaia Stars of M15
Image Credit & Copyright: Robert Vanderbei (Princeton University), ESA, Gaia, DPAC

Explanation: Messier 15 is a 13 billion year old relic of the early formative years of our galaxy, one of about 170 globular star clusters that still roam the halo of the Milky Way. About 200 light-years in diameter, it lies about 35,000 light years away toward the constellation Pegasus. But this realistic looking view of the ancient globular star cluster is not a photograph. Instead it’s an animated gif image constructed from remarkably precise individual measurements of star positions, brightness, and color. The astronomically rich data set used was made by the sky-scanning Gaia satellite which also determined parallax distances for 1.3 billion Milky Way stars. In the animated gif, twinkling stars are M15’s identified RR Lyrae stars. Plentiful in M15, RR Lyrae stars are evolved pulsating variable stars whose brightness and pulsation period, typically less than a day, are related.
Astronomy Picture of the Day 03/28/2019