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    Stars emit light in all directions. When we observe a distant star we see only the few rays of light from the star that are directed straight toward us. However, if a foreground star passes very close to our line of sight of the more distant source star, the light from the distant background star will be gravitationally focused. To understand this idea, remember that we are the observer. The distant star is the source. The intervening star is the lens, and it bends light from the source toward us . The two Figures below show the light path from a distant source star without and then with an intervening "lens" star. 
     
    ::恒星从各个方向发出光亮。 当我们观察远处的恒星时, 我们只看到从恒星直朝我们照射的少数光线。 但是, 如果前方的恒星非常接近远处的源星的视线, 远处的恒星的光线将会引力集中。 要理解这个想法, 请记住我们是观察者。 远处的恒星是源。 中枢的恒星是镜头, 它会从源头向着我们弯曲光线。 下面的两个数字显示远处的源星的光线路径, 没有, 然后有干扰的“ lens” 恒星。

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    A background source star emits light in all directions. From Earth, can we see the top and bottom diverging rays of light from the source star?
    ::背景源星会从各个方向发出光。 从地球, 我们能看到源星的上下不同的光线吗 ?

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    When another star passes between our line of site to the source star, the gravity of that star bends spacetime and directs light from a gravitational ``Einstein ring'' toward the observer on Earth. Now, can we see the all of diverging rays of light from the source that pass through that ring. What affect will that have on the brightness of the source star?
    ::当另一颗恒星在我们星站线之间经过源星时,那颗恒星的引力弯曲时空,从引力“艾因斯坦环”向地球观察者指示光线。现在,我们能看到从源星的源中穿透的所有不同的光线。对源星的亮度有什么影响?

    Every object with mass has a gravitational field. We can think of objects with spherical symmetry, like stars or planets, as point sources. The strength of the gravitational field for a star is spherically symmetric. When we consider gravitational lensing, the relevant geometry is a slice through the sphere - a disk perpendicular to our line of sight.
    ::每个有质量的天体都有引力场。 我们可以将球形对称物体, 如恒星或行星, 当作点源。 恒星的引力场的强度是球形对称。 当我们考虑引力透镜时, 相关的几何是穿过球体的切片, 即与我们视线垂直的磁盘。

    Qualitatively, the gravitational field at small radii on this disk (i.e., closest to the lensing object) is strongest, and light from the source is bent so strongly that it converges closer to the lensing object and does not reach the observer. Likewise, the gravitational field is weakest at large radii on the disk, and light from the source star focuses at distances beyond the observer. However, there is a ring on the disk where the bending of light from the source is "just right." Those rays of light from the source are brought to a focus at the position of the observer. This effect is called gravitational lensing, and it was predicted in 1936 by Einstein. The ring of light that is focused at the position of the observer is given the special name of an Einstein ring. 
    ::质量上, 磁盘( 即与透镜对象最接近的) 小半径的引力场是最强的, 源的光线弯曲得非常强烈, 以至于它接近透镜对象, 无法接近观察者。 同样, 磁盘上的引力场最弱, 源星的光点集中在观察者以外的距离。 但是, 磁盘上有一个环, 使源的光弯曲为“ 正确正确 ” 。 这些源的光线被带到观察者的位置上。 这种效果被称为引力透镜, 爱因斯坦在1936年预测。 以观察者位置为焦点的光环被赋予了爱因斯坦环的特殊名称 。

    Quantitatively, the size of the Einstein ring depends on the mass of the lens, the distance between the observer and the lens, D L , and the distance from the observer to the source, D S .  Gravitational lensing occurs even if the lens star is too faint for us to see. Since most of the stars in galaxy are low mass, low luminosity M dwarf stars, this is often the case! 
    ::从数量上讲,爱因斯坦环的大小取决于镜头的质量、观察者与镜头之间的距离、观察者与镜头的距离以及观察者与源的距离,DS。 引力透镜的出现,即使镜头星太微弱,我们看不到。 由于银河系中的多数恒星质量低、光度低、M矮星,这种情况经常发生!

    Since microlensing is an effect of gravity, it might seem like the amplitude of brightening will depend on the mass of the lens.  While the mass of the lensing star determines the radius of the Einstein ring and the duration of the lensing event, the amplitude of brightening is most sensitive to something called the impact parameter.  When the lensing object precisely lines up with our view to the source star, the impact parameter is zero and the magnification in brightness is a maximum.  If the lensing object is not as tightly aligned with our view of the source - perhaps it just clips our view of the source star, then the impact parameter is larger and the brightening of the source star (the "magnification") is not as strong. This is depicted in the   below. The Einstein ring is represented by the dashed circle. The red, yellow, green, and blue lines show the path that the lensing object travels with different offsets from precise alignment with our view of the source.  The closer the alignment of the Einstein ring of the lens to our view of the source, the stronger the magnification that we observe. Gravitational lensing from objects as massive as stars typically lasts for several days.
    ::由于微升是重力的影响, 亮度的振幅似乎取决于镜头的质量。 虽然透镜恒星的质量决定着爱因斯坦环的半径和透镜事件的持续时间, 亮度的振幅对于称为撞击参数的事物最为敏感。 当透镜对象向我们的源星排行时, 撞击参数为零, 光度放大度最大。 如果透镜对象与我们对源子的视图不那么紧密配合 - 也许它只是剪切我们对源星的视图, 那么撞击参数则更大, 源星的亮度( “ 放大” ) 也不那么强烈。 这在下面被描述。 爱因斯坦环代表的是闪光圆。 红、 黄色、 绿色 和 蓝线显示透镜对象与我们源视图的精确吻合不同的路径。 透镜环与我们源的视图更加接近, 镜像更接近于我们观察的源星的视野, 放大度越强。

     

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    The impact parameter defines the alignment of the observer, lens and source. The path of the lens star is represented by a straight-line vector. Which line is closest to our view of the source star? When the lens is very closely aligned with our line of site to the source, the lens has a small impact parameter and the amplification (red line) is a maximum. When the lens is not exactly aligned with our line of site to the source, the Einstein ring will not be centered on line of site--this is equivalent to having a larger impact parameter (blue line) and the source light magnification is weaker.
    ::撞击参数定义观察者、 镜头和源的对齐。 镜头恒星的路径由直线矢量表示。 哪个线线最接近源星的视图? 当镜头与源星的站点线非常接近时, 镜头有一个小的撞击参数, 放大( 红线) 最大。 当镜头不完全与我们站点对齐时, 爱因斯坦环不会以站点线为中心- 这相当于有更大的撞击参数( 蓝线) , 源光放大能力更弱 。

    The physical radius of the Einstein ring at the distance of the lens is described by the following equation:
    ::爱因斯坦环在镜头距离外的物理半径由以下方程式描述:

                                      R E = 2.2 A U M 0.3 M s t a r D S 8 k p c x ( 1 − x ) 0.25 ,
    ::RE=2.2AUM0.3 MstarDS8kpcx(1-x)0.25,

    where x = D L /D S .
    ::x = DL/DS。

     

    Gravitational lensing generally refers to the bending of light from a background source by a foreground massive object. Gravitational microlensing is a special case where multiple lensing events occur from more than one foreground mass. If the lensing star happens to have orbiting planets that also cross our line of sight to the source star, then a second microlensing event is superimposed during the brightening event. Because the mass of the orbiting planet is smaller than the mass of a star, the duration of the second microlensing event will be shorter, but since the alignment of the lensing planet is essentially the same as the alignment of the host star, the amplitude of the magnification will be similar.

    ::引力透镜一般是指从背景源中由表面大型物体使光从表面源中弯曲。引力微通道是一个特殊的例子,当多个透镜事件发生在一个以上表面质量中时。如果透镜恒星碰巧有轨道行星,这些行星也跨越我们的视线与源星,那么在亮亮事件期间将出现第二次微拉事件。由于轨道行星的质量小于恒星的质量,第二个微拉链事件的时间将缩短,但由于透镜行星的对齐与主星的对齐基本相同,放大度将相似。

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    The photometry of the source star is shown in the top row. Two brightenings occur because the lensing mass is a star with an orbiting planet. The time series light curve is shown in detail in the larger panel with a longer duration brightening caused by the foreground star and a short duration brightening caused by the planet.
    ::源星的光度测量在顶行显示。 出现两个亮度, 因为透镜质量是一颗带有环绕行星的恒星。 时间序列光曲线在更大的面板中详细显示, 由前景恒星引起的更长时间亮度亮度, 以及由行星引起的短时间亮度亮度亮度。