獵戶四邊形星團
獵戶四邊形星團是位於獵戶座的M42核心的一個緻密的疏散星團。它是由伽利略發現的。在1617年2月4日，他簡要繪製了其中三顆恆星（A,C,D），但沒注意到周圍的星雲狀物質。[1][2][3]. 第四個成員星（B）在1673年被幾個觀測者辨認出，之後更多的成員被發現；到了1888年總共發現了8顆成員星。後來其中幾顆恆星被確定為是雙星。在良好的觀測條件下，業餘觀測者的5英寸口徑望遠鏡可以分解出6顆恆星。[4]
| 獵戶四邊形星團 | |
|---|---|
 | |
| 觀測數據 (J2000 曆元) | |
| 分類 | ? |
| 星座 | 獵戶座 |
| 赤經 | 05h 35.4m |
| 赤緯 | −05° 27′ |
| 距離 | 1.6 kly (490 pc) |
| 視星等 (V) | 4.0 |
| 視直徑 (V) | 47 (弧秒) |
| 物理性質 | |
| 質量 | ? (? M☉) |
| 半徑 | 10 ly |
| VHB | ? |
| 估計年齡 | 3×105 年 |
| 相關條目：疏散星團、疏散星團列表 | |
參考文獻
- ^ Galileo Galilei: Siderius Nuncius, Venice, 1610. English Translation published at Bard College, Hudson NY" October 9, 2003 English Translation[1] （頁面存檔備份，存於互聯網檔案館） Original Latin version[2] （頁面存檔備份，存於互聯網檔案館）
- ^ Tom Pope and Jim Mosher: Galilean telescope homepage" March 17, 2006 存档副本. [2008-01-30]. （原始內容存檔於2008-01-30）., "Some have expressed puzzlement that in his text Galileo does not mention the nebulosity (known in modern nomenclature as M42) enveloping these stars. ... Galileo believed, as he explains in Sidereus Nuncius, that what looks nebulous to the eye is resolved into stars by his telescope; what looks nebulous through his telescope could presumably also be resolved into stars by a still larger and more powerful telescope. Hence, a diffuse glow would be, more than anything, an indication of the limitations of his telescope and not particularly worthy of special note."
- ^ Tom Pope and Jim Mosher: Page on Galileo's February 4, 1617 notebook drawing of the Trapezium region, May 2, 2006 "Perhaps significantly, Galileo makes no mention of having noticed the now well-known gas cloud, M42, surrounding the Trapezium stars."[3] 互聯網檔案館的存檔，存檔日期2011-08-11.
- ^ Lodriguss, Jerry. The Trapezium, Theta Orionis. [2009-06-02]. （原始內容存檔於2012-11-05）.