An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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<< < acc dis sol > >>

Number of Results: 45 Search : disk
solar disk
  گرده‌ی ِ خورشید   
gerde-ye xoršid

Fr.: disque solaire   

The apparent shape of the → Sun's → photosphere.

solar; → disk.

thick disk
  گرده‌ی ِ ستبر، دیسک ِ ~   
gerde-ye setabr, disk-e ~

Fr.: disque épais   

A disk component of a → spiral galaxy that lies above the → thin disk and mainly consists of stars. The thick disk of our → Galaxy makes up about 10-50% of the stellar mass of the → Milky Way and has a scale height of ~ 1,000-3,000 → light-years. Thick disk stars are, on average, moving faster in a vertical direction with respect to the → galactic plane than thin disk stars. In contrast to thin disk, the stars within the thick disk are almost all older than 10 billion years and typically have a smaller → metallicity than the average values for the thin disk stars. These facts suggest that the formation scenarios for the thin and thick disks were different. In particular, it is thought that the thick disk is much older than the thin disk.

thick; → disk;

thin disk
  گرده‌ی ِ نازک، دیسک ِ ~   
gerder-ye nâzok, disk-e ~

Fr.: disque mince   

A disk component of a → spiral galaxy containing → stars, → gas, and → dust which are confined to the galaxy's → plane of rotation. In contrast to → thick disks, thin disks contain the bulk of the → baryonic matter in spiral galaxies. For example, on the order of 60-90% of the baryonic matter in the → Milky Way is located in the thin disk. The scale height of the thin disk in the Milky Way is about 400 → light-years, whereas its scale length is about 10,000 light-years. Moreover, the outer regions of thin disks appear to be bent by the → warp phenomenon. The thin disks of spiral galaxies are active sites of → star formation, especially in the spiral arms. For this reason, stars in the thin disk tend to be relatively young. Thin disk stars also tend to be → metal-rich compared with thick disk and → halo stars, and typically have a → metallicity similar to that of the Sun.

thin; → disk;

transition disk
  گرده‌ی ِ گذرش، دیسک ِ ~   
gerde-ye gozaresh, disk-e ~

Fr.: disque de transition   

The → accretion disk of a → T Tauri star that displays very weak or no → infrared excess at → near infrared wavelengths, but shows strong excess at → intermediate infrared and longer wavelengths. This happens when the hot inner dust disk has dissipated whereas the cooler outer disk is still intact.

transition; → disk.

warped disk
  گرده‌ی ِ تابدار، دیسک ِ ~   
gerde-ye tâbdâr, disk-e ~

Fr.: disque gauchi   

A → galactic disk that exhibits a → warp phenomenon.

warp; → disk.

<< < acc dis sol > >>