|
The Quintuplet cluster is a dense cluster of massive young stars near the Galactic Center (GC). Its name comes from the fact it has five prominent infrared sources residing in it. Along with the Arches cluster it is one of two in the immediate GC region. Due to heavy extinction by dust in the vicinity, it is invisible to optical observation and must be studied in the X-ray, radio, and infrared bands. The Quintuplet is less compact than the nearby Arches cluster, with fewer of the most massive and luminous stars, but it does have the distinction of hosting two of the extremely rare luminous blue variables, the Pistol star and the less well-known FMM 362, and a third just a few parsecs away.〔 It also contains a number of red supergiants, all suggesting a slightly more evolved cluster around 4 million years old.〔 ==Discovery and naming== The Quintuplet was originally identified in 1983 as a pair of infra-red sources in a 2.5 micron survey of the galactic centre. These two sources were numbered 3 and 4, and later referred to with the acronym GCS for Galactic Centre Source. GCS-3 was later resolved into four sources, labelled I-IV, that together with GCS-4 formed a compact quintuplet of unusually bright small objects. They were assumed to be young hot luminous stars surrounded by dust shells and therefore extremely reddened. In 1990, a total of 15 sources in the Quintuplet region was studied in more detail at several wavelengths, later referred to by Q or GMM (after the authors Glass, Moneti, and Moorwood) numbers. The original five stars were identified as numbers Q1, Q2, Q3, Q4, and Q9, with additional sources Q5 and Q6 identified as part of the same cluster. They were still considered to be protostars reddened by surrounding dust. In 1994, several stars were identified as having broad helium emission lines in their spectra, and some showed narrow hydrogen emission lines. This was completely unexpected for protostars, instead suggesting the objects were much more evolved stars. Shortly afterwards two emission line stars were classified as Wolf Rayet stars, and a third as a Luminous Blue Variable that was thought to be one of the most luminous stars in the galaxy. A small number of red supergiants were also identified, narrowing the likely age of the cluster. In 1999, a study of nearly 600 stars in the cluster showed that the Quintuplet contained more Wolf Rayet stars than any known cluster, as well as a second Luminous Blue Variable. The numbers from this survey are referred to as qF, or sometimes as FMM after all three authors (but not QMM).〔 A 2008 study of the cluster used LHO numbers for the members and clarified the status of the unusual reddened Wolf Rayet stars as WC stars surrounded by dust presumed to be formed from colliding winds between the WR component and a less evolved OB scompanion. The cluster was also catalogued as a first magnitude "stellar" source at 4.2 microns in the Air Force Geophysics Lab survey and given the number 2004 (AFGL 2004). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quintuplet cluster」の詳細全文を読む スポンサード リンク
|