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Glossary term: 巨蟹座

Description: 巨蟹座是黄道带上的一个星座,也就是说,组成这个星座的恒星位于与黄道(由地球绕太阳运行的轨迹所确定的平面)相交的那部分天空。因此,从地球上看,我们会发现太阳和行星经常落在巨蟹座中。就太阳而言,这发生在每年7月下旬到8月上旬(当然,那时我们看不到巨蟹座中的恒星)。两千年前,每年北半球夏至时,直射北回归线的太阳位于巨蟹座,这便是北回归线在英文中被称为“巨蟹座回归线”的缘由。但由于岁差的关系,如今每年北半球夏至时太阳不再位于巨蟹座。巨蟹座是国际天文学联合会定义的88个现代星座之一,但其历史可以追溯到更久远的年代——它是公元2世纪的天文学家克罗狄斯·托勒密(Claudius Ptolemy)命名的48个星座之一。

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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道路上空的银河曲线。照片左下方,两颗明亮的恒星连成一条线,指向一个风筝状的星群。

夜空中最亮的星

Caption: 2022年国际天文学联合会(IAU)OAE天文摄影比赛静态天体图案类别荣誉奖作品。 这张照片于2016年3 月在印度尼西亚爪哇岛的婆罗摩腾格塞梅鲁国家公园拍摄,展现了银河形成的拱桥和许多突出的星座,包括了夜空中最显著的亮星。 在照片左下角,我们可以看到南门二和马腹一,前者较低,后者较高,都位于的巨大的半人马座中。可由它们的指引找到南十字座,南十字座的长轴指向南天极,而南天极大致位于地平线上,这是因为爪哇岛几乎位于赤道上。南十字座几乎完全被云层遮挡,照片中只能看到四颗明亮的星星。而南船座中的恒星组成的赝十字星群,在稍远处的银河上方也明显可见,容易使人混淆。 真正的南十字座和赝十字星群之间的粉红色斑点是船底座星云,距离地球约8500光年,位于船底座,肉眼看不到。在船底座,我们还可以看到夜空中第二亮的恒星——老人星,它就在银河和地面道路之间。 更亮的是天狼星,夜空中最亮的恒星。天狼星位于大犬座,大犬座是猎户座的两只猎犬之一。猎户座在照片的右半部分,地平线附近云层的上方。猎户座的腰带上有三颗明亮的恒星,其连线左上指向天狼星,右下指向堪堪露出地平线的毕宿五。 猎户座包含了天空中最亮的几颗恒星,是色彩最丰富的星座,因为它拥有参宿七——银河下方靠右的一颗蓝色亮星,以及参宿四——参宿七右上方较高位置的一颗红色亮星。在它们之间,三颗恒星组成了著名的星群——猎户座腰带。猎户座大星云就在猎户座腰带旁边,这是一个恒星形成区,其明亮的中心即便用肉眼看也清晰可见,在这张照片中也是如此清晰。 在参宿四的上方,银河的另一侧,可以看到明亮的南河三,其英文名称Procyon的字面意思是”在狗之前“。在希腊神话中,它被看作由单颗恒星组成的星群,是与猎户座相伴的小猎犬,后来演变成了现代的小犬座。 在照片右上角,巨蟹座的蜂巢星团很容易辨认。在其下方,可以看到双子座的北河二和北河三,它们在这张照片中并不显眼。与之形成鲜明对比的是,御夫座的明亮白色恒星五车二,在照片右边缘中部的云层中闪闪发光。 在地面道路周围可以看到一些光污染。
Credit: Giorgia Hofer/IAU OAE

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons

Related Diagrams


巨蟹座在天空中呈现为倒Y字形。黄道从东南偏东(ESE)方向延伸至西北偏西(WNW)方向,几乎正好穿过倒Y字形中央的交叉点。

巨蟹座星图

Caption: 黄道星座巨蟹座与周边星座示意图。从顶部开始沿顺时针方向,巨蟹座周边的星座依次为:天猫座、双子座、小犬座、长蛇座、狮子座和小狮子座。巨蟹座位于黄道上。从地球看来,太阳以一年为周期在天球上移动,所经过的路径称为黄道,在图中以蓝色实线标注。太阳在每年七月下旬到八月下旬位于巨蟹座。太阳系中的其他行星也经常出现在巨蟹座。 巨蟹座位于天赤道以北,因此在地球上,除南极地区外,一年中的某些时候都能看到巨蟹座。巨蟹座在北半球的春季和南半球的秋季夜晚最适宜观测。 在巨蟹座中,可以看到两个星团。一个是疏散星团M44,通常被称为蜂巢星团。另一个是更稠密的疏散星团M67,其恒星数量大约是M44的四倍。这些星团在图中以带有虚线边框的黄色圆圈标注。 该图的纵轴为赤纬,横轴为赤经,方向为上北下南左东右西。图中标注的恒星大小对应其视星等——衡量天体视亮度的标准,较大的圆点代表着较亮的恒星。图中的希腊字母标注着星座中最亮的恒星。这些恒星按亮度排序,最亮的一般被标记为α星,第二亮的一般为β星,等等,不过这种字母排序并不总是和实际亮度排序完全一致。图中虚线标注的是国际天文学联合会划定的星座边界,绿色实线则是一种常见的星座形象连线。需要注意的是,在实际观测时,这些边界与连线都不会出现在天空中。
Credit: 国际天文学联合会天文教育办公室(IAU OAE)根据国际天文学联合会和《天空与望远镜》的原文改编

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons


Leo resembles a lion standing on the ecliptic (which runs ESE to WNW) with its nose pointed northwest.

Leo Constellation Map

Caption: The zodiac constellation Leo and its surrounding constellations. Starting from the top of the diagram and going clockwise, these are Leo Minor, Cancer, Sextans, Hydra, Crater, Virgo and Ursa Major. The brightest star in Leo, Regulus, lies almost exactly on the ecliptic (shown here as a blue line): the path the Sun appears to take across the sky over the course of a year. The Sun spends the period from mid August to mid September in Leo. The other planets in the Solar System can often be found in Leo. Leo spans the celestial equator and is thus part of it is visible at some time in the year from all of planet Earth with some of the constellation obscured for the most arctic and antarctic regions of the world. Leo is most visible in the evenings in the northern hemisphere spring and southern hemisphere autumn. Several objects can be seen in Leo, including M65 and M66 – two galaxies in the Leo Triplet, a trio of galaxies including NGC 3628, not listed here. In addition, M96, a spiral galaxy, can be seen as a fuzzy object using a small telescope, and Messier 105, an elliptical galaxy. Each of these objects are labelled on the map as red ellipses. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labelled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons


Hydra is shaped like a snake going from the south east to the north west

Hydra Constellation Map

Caption: The constellation Hydra with its bright stars and surrounding constellations. Hydra is surrounded by (going clockwise from the top): Leo, Cancer, Canis Minor, Monoceros, Puppis, Pyxis, Antlia, Centaurus, Lupus, Libra, Virgo, Corvus, Crater and Sextans. Hydra is a large constellation that covers over a quarter of the celestial sphere in right ascension. It also spans the celestial equator and thus part of the constellation is visible from everywhere on the Earth at some point in the year. All parts of the constellation are visible at some point for all but the most antarctic parts of the southern hemisphere and to equatorial and most temperate regions of the northern hemisphere. However the wide span of the constellation means that all of it may not be visible at the same time in many of these regions. Hydra is best viewed in the northern hemisphere spring and southern hemisphere autumn. The famous spiral galaxy M83, also known as the Pinwheel Galaxy, lies in Hydra. It is marked here with a red ellipse. The planetary nebula NGC 3242 can also be found in Hydra. It is marked here with a green circle with a plus sign superimposed on it. The open cluster M48 is marked here with a yellow circle while the globular cluster M68 is marked with a yellow circle with a plus sign superimposed on it. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. The blue line on the diagram marks the ecliptic. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons


Lynx appears as an uneven line going from the south east to the north west

Lynx Constellation Map

Caption: Lynx is a northern constellation and thus the whole constellation is visible at some point in the year throughout the northern hemisphere. The whole constellation is also visible in equatorial regions of the southern hemisphere with parts of the constellation visible in southern temperate regions. Lynx is best viewed in the evenings in the northern hemisphere winter and southern hemisphere summer. The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. The blue line at the bottom right of the diagram marks the ecliptic. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons