An Etymological Dictionary of Astronomy and Astrophysics

An extremely → metal-poor and high-velocity F3-type → subgiant with → apparent visual magnitude 7.205 ± 0.02. It has other designations, among which BD-10 4149, GJ 1195, HIP 76976, and SAO 159459. HD 140283 is situated in the solar neighborhood at some 200 → light-years from the Earth (→ trigonometric parallax 17.15 ± 0.14 mas) in the constellation → Libra. Its color E(B - V) = 0.000 yields a visual → absolute magnitude  M_V = +3.377. Its → surface temperature is T_eff = 5777 K. Its iron and oxygen surface → chemical abundancees relative to hydrogen are [Fe/H] = -2.40 and [O/H] = -1.67, making it the most metal-poor star so far known (2021). Using precise observational data, an age of 14.46 ± 0.8 Gyr has been derived for this star. Within the errors, the age of HD 140283 does not conflict with the age of the → Universe, 13.77 ± 0.06 Gyr, obtained from the → cosmic microwave background radiation and the → Hubble constant. HD 140283 must have formed soon after the → Big Bang and is the oldest known star. This is why it is sometimes nicknamed the → Methuselah star (H. E. Bond et al., 2013, arxiv.1302.3180).

See also: The star’s name in the → Henry Draper system

An extremely → metal-poor and high-velocity F3-type → subgiant with → apparent visual magnitude 7.205 ± 0.02. It has other designations, among which BD-10 4149, GJ 1195, HIP 76976, and SAO 159459. HD 140283 is situated in the solar neighborhood at some 200 → light-years from the Earth (→ trigonometric parallax 17.15 ± 0.14 mas) in the constellation → Libra. Its color E(B - V) = 0.000 yields a visual → absolute magnitude  M_V = +3.377. Its → surface temperature is T_eff = 5777 K. Its iron and oxygen surface → chemical abundancees relative to hydrogen are [Fe/H] = -2.40 and [O/H] = -1.67, making it the most metal-poor star so far known (2021). Using precise observational data, an age of 14.46 ± 0.8 Gyr has been derived for this star. Within the errors, the age of HD 140283 does not conflict with the age of the → Universe, 13.77 ± 0.06 Gyr, obtained from the → cosmic microwave background radiation and the → Hubble constant. HD 140283 must have formed soon after the → Big Bang and is the oldest known star. This is why it is sometimes nicknamed the → Methuselah star (H. E. Bond et al., 2013, arxiv.1302.3180).

See also: The star’s name in the → Henry Draper system

A → hot star of → apparent visual magnitude 6.61 lying in the constellation → Orion. HD 43317 has a B3.5V → spectral type and has no detected binary companion. Its chemical surface abundances agree with the solar abundances, but with some co-rotating He abundance spots at the stellar surface.

The CoRoT satellite revealed that HD 43317 is a → hybrid pulsator of → Slowly Pulsating B star (SPB)/ → Beta Cephei type. Its → rotation period is 0.897673(4) days. Zeeman signatures in the Stokes V profiles of HD 43317 are clearly detected and rotationally modulated, which proves that this star exhibits an oblique magnetic field. The strength of the dipolar magnetic field is of the order of 1 kG to 1.5 kG (Buysschaert et al., 2017, A&A 605, A104).

See also: → HD number.

A → hot star of → apparent visual magnitude 6.61 lying in the constellation → Orion. HD 43317 has a B3.5V → spectral type and has no detected binary companion. Its chemical surface abundances agree with the solar abundances, but with some co-rotating He abundance spots at the stellar surface.

The CoRoT satellite revealed that HD 43317 is a → hybrid pulsator of → Slowly Pulsating B star (SPB)/ → Beta Cephei type. Its → rotation period is 0.897673(4) days. Zeeman signatures in the Stokes V profiles of HD 43317 are clearly detected and rotationally modulated, which proves that this star exhibits an oblique magnetic field. The strength of the dipolar magnetic field is of the order of 1 kG to 1.5 kG (Buysschaert et al., 2017, A&A 605, A104).

See also: → HD number.

A remarkable → binary star system composed of → massive stars that
is associated with NGC 346, the largest → H II region

• OB star cluster in the → Small Magellanic Cloud. HD 5980 is a rather complex system because it consists of at least three stars: two stars form an → eclipsing binary with a period of 19.266 days, while the third component, an → O star, is detected by means of a set of absorption lines. Whether or not the third star is physically bound to the eclipsing binary remains currently unclear. HD 5980 underwent an
  → LBV-type event in August 1994. Before the LBV eruption, both components of the eclipsing binary already showed emission lines in their spectra and were thus classified as → Wolf-Rayet stars. However, as shown by the analysis of the spectra taken during and after the LBV event, at least the star that underwent the eruption was not a classical, helium-burning, Wolf-Rayet object, but rather a WNha star. This means a rather massive star with substantial amounts of hydrogen present in its outer layers. These WNha stars have → stellar wind properties that are intermediate between those of extreme → Of stars and classical → WN Wolf-Rayet stars.

See also: → Henry Draper system; → number.

A remarkable → binary star system composed of → massive stars that
is associated with NGC 346, the largest → H II region

• OB star cluster in the → Small Magellanic Cloud. HD 5980 is a rather complex system because it consists of at least three stars: two stars form an → eclipsing binary with a period of 19.266 days, while the third component, an → O star, is detected by means of a set of absorption lines. Whether or not the third star is physically bound to the eclipsing binary remains currently unclear. HD 5980 underwent an
  → LBV-type event in August 1994. Before the LBV eruption, both components of the eclipsing binary already showed emission lines in their spectra and were thus classified as → Wolf-Rayet stars. However, as shown by the analysis of the spectra taken during and after the LBV event, at least the star that underwent the eruption was not a classical, helium-burning, Wolf-Rayet object, but rather a WNha star. This means a rather massive star with substantial amounts of hydrogen present in its outer layers. These WNha stars have → stellar wind properties that are intermediate between those of extreme → Of stars and classical → WN Wolf-Rayet stars.

See also: → Henry Draper system; → number.

A multiple → O-type star in the → Trumpler 14 cluster, which consists of at least three components. The main component, HD 93129A, is of spectral type O2 If*, a very rare hot star and the closest known O2 star (Walborn et al. 2002). It is one of the most luminous stars known.
HD 93129B, lying 2.7 arcsec apart, is an O3.5 V((f+)) type. Recent → HST observations have shown that component A is itself probably a double or → binary star with a separation of 0.055 arcsec.

See also: → HD number.

A multiple → O-type star in the → Trumpler 14 cluster, which consists of at least three components. The main component, HD 93129A, is of spectral type O2 If*, a very rare hot star and the closest known O2 star (Walborn et al. 2002). It is one of the most luminous stars known.
HD 93129B, lying 2.7 arcsec apart, is an O3.5 V((f+)) type. Recent → HST observations have shown that component A is itself probably a double or → binary star with a separation of 0.055 arcsec.

See also: → HD number.

The core of the Galactic → giant H II region, → NGC 3603. It is a multiple object composed of several → massive stars with a collective → spectral type of around WN6+O5. One of the stars, → NGC 3603A-1, is a double-eclipsing binary with an orbital period of 3.77 days. The component masses are 116 Msun for the primary and 89 Msun for the secondary, respectively. The primary WN6ha component of A1 is the most massive star ever directly weighed. A second star, C, has newly been identified, which has been classified as an SB1 binary, and in which only the primary (WN6ha) component is visible. The third star, B, shows constant radial velocities over the observed time interval, and therefore is most likely not a binary. While the primary component of C might have a mass similar to or even greater than that of A1’s primary, it is possible that star B, be the most massive member in NGC 3603 and, therefore, the most massive main-sequence star known in the Galaxy (Schnurr et al., 2008, MNRAS, 389, L38).

See also: → HD number.

The core of the Galactic → giant H II region, → NGC 3603. It is a multiple object composed of several → massive stars with a collective → spectral type of around WN6+O5. One of the stars, → NGC 3603A-1, is a double-eclipsing binary with an orbital period of 3.77 days. The component masses are 116 Msun for the primary and 89 Msun for the secondary, respectively. The primary WN6ha component of A1 is the most massive star ever directly weighed. A second star, C, has newly been identified, which has been classified as an SB1 binary, and in which only the primary (WN6ha) component is visible. The third star, B, shows constant radial velocities over the observed time interval, and therefore is most likely not a binary. While the primary component of C might have a mass similar to or even greater than that of A1’s primary, it is possible that star B, be the most massive member in NGC 3603 and, therefore, the most massive main-sequence star known in the Galaxy (Schnurr et al., 2008, MNRAS, 389, L38).

See also: → HD number.

An identifying number assigned to the stars in the Henry Draper catalog. For example, the star Vega is HD 172167.

See also: → Henry Draper system; → number.

An identifying number assigned to the stars in the Henry Draper catalog. For example, the star Vega is HD 172167.

See also: → Henry Draper system; → number.