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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Number of Results: 12 Search : B star
B star
  ستاره‌یِ B   
setâre-ye B (#)

Fr.: étoile B   

A star of → spectral type B, whose spectrum is marked by absorption lines of hydrogen; also known as B-type star. B-type optical spectra are characterized by the presence of neutral He lines (mainly He I 4471 Å) at about type B9. He I strengthens up to about B2, then decreases. Ionized helium (mainly He II 4541 Å) first appears at about B0. Most metallic lines are absent or weak, except some absorption lines for the higher ionization states of → silicon, → oxygen, → carbon, and → magnesium. These are hot stars with → effective temperatures ranging from about 10,000 K at B9 to nearly 30,000 K at B0. They are between 3 and 20 → solar masses. Some famous examples include: → Rigel, → Achernar, → Hadar.

star.

BHB star
  ستاره‌ی ِ BHB   
setâre-ye BHB

Fr.: étoile BHB   

Same as → blue horizontal branch star.

blue; → horizontal; → branch; → star.

blue HB star
  ستاره‌ی ِ BHB   
setâre-ye BHB

Fr.: étoile BHB   

Same as → blue horizontal branch star.

blue; → horizontal; → branch; → star.

born-again AGB star
  ستاره‌یِ AGBیِ باز‌زاده   
setâre-ye AGB-ye bâzzâdé

Fr.: étoile AGB recyclée   

A → post-AGB star that undergoes a last → thermal pulse when it is already on the → white dwarf  → cooling track. The thermal pulse will expand the hot central star, whereby hydrogen will be ingested into the → helium burning shell. This will temporarily return the star to the → AGB phase it has previously left.

born; → again; → asymptotic giant branch; → star.

EHB star
  ستاره‌ی ِ EHB   
setâre-ye EHB

Fr.: étoile EBH   

Same as → extreme horizontal branch star.

extreme horizontal branch star.

extreme HB star
  ستاره‌ی ِ EHB   
setâre-ye EHB

Fr.: étoile EBH   

Same as → extreme horizontal branch star.

extreme horizontal branch star.

FHB star
  ستاره‌ی ِ FHB   
setâre-ye FHB

Fr.: étoile FHB   

Same as → field horizontal branch star.

field; → horizontal; → branch; → star.

OB star
  ستاره‌ی ِ OB   
setâre-ye OB

Fr.: étoile OB   

A collective designation for massive O and B stars.

O star; → B star.

red HB star
  ستاره‌ی ِ BHR   
setâre-ye RHB

Fr.: étoile RHB   

Same as → red horizontal branch star.

red; → horizontal; → branch; → star.

RHB star
  ستاره‌ی ِ RHB   
setâre-ye RHB

Fr.: étoile RHB   

Same as → red horizontal branch star.

red; → horizontal; → branch; → star.

SHB star
  ستاره‌ی ِ SHB   
setâre-ye SHB

Fr.: étoile SHB   

Same as → supra-horizontal branch star.

supra-; → horizontal; → branch; → star.

Slowly Pulsating B star (SPB)
  ستاره‌ی ِ آهسته تپنده‌ی ِ گونه‌ی ِ B   
setâre-ye âhesté tapande-ye gune-ye B

Fr.: étoile B pulsante à longue période   

A member of a class of → B stars that are situated along the → main sequence with → spectral types ranging from B2 to B9 and masses from 3 to 7 → solar masses. In the → H-R diagram the SPB group lies below → beta Cephei variables, which are more massive. SPBs show light and line-profile variations that are multi-periodic with periods of the order of days. This variability is understood in terms of non-radial → stellar pulsations, and their → oscillation modes are high-order → g modes. Theoretical models attribute the pulsational nature of SPBs to the → kappa mechanism, acting in the metal → opacity bump at 2 x 105 K. Their g-mode pulsations penetrate deep into the stellar interior, making these objects very promising for → asteroseismology. Several oscillation modes are excited simultaneously, resulting in periodicities on time scales of the order of months or even years. The prototype of this group is 53 Per. First introduced as a distinct class by Waelkens (1991, A&A 246, 453).

slow; → pulsating; → B star.