[keyfc天文部]2014.01.04_Sextans星座流星雨观测指南

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2013-01-03 09:41 |只看楼主 楼主

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象限仪座流星雨（Quadrantid）是出现在一月初的大流星雨。
虽然这个流星雨的辐射点位于牧夫座的区域内，但名称却来自一个已经废弃的星座——象限仪座，有一部分是现在的牧夫座。

六分仪座 A
Sextans A (also known as UGCA 205), is a tiny dwarf
irregular
galaxy. It spans about 5000 light-years across, and is located within the Local Group of galaxies, which includes our Milky Way galaxy. At 4.3 million light-years away from Earth, Sextans A is one of most distant members of the Local Group, and is notable for its peculiar square shape. Massive short-lived stars exploded in supernovae that caused more star formation, triggering yet more supernovae, ultimately resulting in an expanding shell. Young blue stars now highlight areas and shell edges high in current star formation, which from the perspective of observers on Earth appears roughly square.[5]

六分仪座 B或称UGC 5373,、DDO 70是一个位在六分仪座的不规则星系，距离地球有四百万光年，是位在本星系团边缘星系之一。
Sextans B (also known as UGC 5373 and DDO 70) is an irregular galaxy that may be part of the Local Group, or lie just beyond it. Sextans B is 4.44 million light-years away from Earth and thus is one of most distant members of the Local Group, if it is indeed a member. It forms a pair with its neighbouring galaxy Sextans A.[4] It is a type Ir IV-V galaxy according to the galaxy morphological classification scheme.[5] Sextans B may also be gravitationally associated with the galaxies NGC 3109 and the Antlia Dwarf.[6]
Sextans B has a uniform stellar population,[7] but the interstellar medium in it may be inhomogeneous.[8] Its mass is estimated to be about 2 × 108 times the mass of the Sun, of which 5.5 × 107 is in the form of atomic hydrogen.[7] Star formation in the galaxy seems to have proceeded in distinct periods of low intensity, separated by shorter periods of no activity.[7] The existence of Cepheid variables in the galaxy implies that Sextans B contains at least some young stars.[5] The metallicity of Sextans B is rather low, with a value of approximately Z = 0.001.[7] Sextans B is receding from the Milky Way with a speed of approximately 300 kilometres per second (190 mi/s),[8] and probably lies just outside the edge of the Local Group, so as its neighbour Sextans A.[9]
Five planetary nebulae have been identified in Sextans B. It is one of the smallest galaxies in which planetary nebulae have been observed. These appear point-like and can be identified by their spectral emission lines.[10] It also contains a massive globular cluster.[11]

六分仪座由AB两颗星组成wwwww于是有了以下图示

正东方22：00左右升出地面，以东南方向约45度向上升起，每小时仰角增大10°左右。大体只需对大地东面星空发呆即可……