Three generations of stars may exist based on metallicity.
以金属度划分，恒星有三个世代。
One clue comes from the metallicity of the disc's constituent stars.
一条线索来自于主盘内恒星的金属丰度。
Different theories predict how this metallicity gradient changes over billions of years.
已有几种不同的理论对金属丰度梯度在亿万年间如何变化作了推测。
Metallicity is a measure of the relative abundance in a star of elements other than hydrogen and helium.
金属丰度是对恒星内除氢和氦之外元素的相对丰度的度量(天文学中比氦重的元素都叫金属。——译者注)。
The metallicity of a star measures the amount of "metals" it has —that is, any element heavier than helium.
恒星的金属度用于表征它含有的“金属”的量——其实是所有比氦重的元素的量。
The metallicity of a star measures the amount of " metals" it has — that is, any element heavier than helium.
恒星的金属度用于表征它含有的“金属”的量——其实是所有比氦重的元素的量。
Thus, the disc begins its existence with a steep metallicity gradient, like the one in the distant galaxy in Leo.
因此，主盘在形成伊始有一个很大的丰度梯度，就像遥远的狮子座里的那个星系那样。
In this thesis, we study the relation between the critical accretion rate and the metallicity via AGB stars approach.
在本文中我们通过agb星研究了此临界吸积率和金属丰度之间的关系。
Because we see the galaxy when it was young, this result suggests spiral discs start off with steep metallicity gradients.
因为我们看到的它还处于早期，这个结果表明螺旋星系主盘开始时有着很大的金属丰度梯度。
Because stars congregate at a galaxy's centre, the metallicity in most nearby spirals is greatest there and drops toward the edge.
因为恒星聚集在星系的中心，其附近的金属丰度最高并沿边缘方向逐渐降低。
In this model, a mass of gas collapses and creates lots of stars at the disc's centre, where the stars quickly boost the metallicity.
在这个模型下，一大团气体坍缩并在主盘中心形成大量恒星，它们在那里迅速增加着金属丰度。
Yuan and colleagues used the giant Keck ii telescope atop Mauna Kea in Hawaii to measure the galaxy's metallicity at several different points.
Yuan和她的同事利用夏威夷莫纳·克亚山上的凯克ii号望远镜对那个星系几个不同地点的金属丰度进行了测量。
The absolute magnitudes in I and K bands of 58 red clump giants are computed and the relation between them and the metallicity are also showed.
计算了共58颗红团簇巨星在I、K波段的绝对星等，讨论了它们与恒星铁丰度之间的关系。
Benson says that the steep metallicity gradient agrees with the long-standing but unconfirmed idea that spiral galaxies form their discs of stars from the inside out.
Benson说，这个高梯度的结果与一个久已有之但一直未被证实的想法相符，这个想法就是螺旋星系的恒星主盘是由内而外形成的。
In addition, last year other astronomers reported a steep metallicity gradient in an even farther galaxy, but that galaxy is not a spiral, so its relevance to the Milky Way is less clear.
另外，去年有其他天文学家报告称在一个更远的星系中发现了较大的金属丰度梯度，但那个星系不是螺旋星系，所以它与银河系的关系就没有那么明确了。
A historic progress on recent studies of whether there is a possible age-metallicity relation of stars in the Galactic disk, especially in the Galactic thick disk, is reviewed in some details.
对太阳邻域内银河系盘星、特别是厚盘恒星年龄-金属度关系的研究进展作了较为详细的回顾和评述；说明目前对盘星是否确实存在年龄-金属度关系还存在争议，而厚盘恒星可能存在这种关系。
If astronomers could observe metallicity gradients in spiral galaxies billions of light-years away, we could see how steep the gradients were billions of years ago and thus how they change over time.
如果天文学家能够观测到十亿光年外的螺旋星云的金属丰度梯度，我们就可以知道亿万年之前的梯度有多大，因此也就可以知道它是如何随时间变化的。
If astronomers could observe metallicity gradients in spiral galaxies billions of light-years away, we could see how steep the gradients were billions of years ago and thus how they change over time.
如果天文学家能够观测到十亿光年外的螺旋星云的金属丰度梯度，我们就可以知道亿万年之前的梯度有多大，因此也就可以知道它是如何随时间变化的。
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