Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Hercules |
Right ascension | 16h 19m 44.43666s [1] |
Declination | 46° 18′ 48.1123″ [1] |
Apparent magnitude (V) | 3.91 [2] 3.83 to 3.86 [3] |
Characteristics | |
Evolutionary stage | Main sequence [4] |
Spectral type | B5 IV [5] |
U−B color index | −0.569 [2] |
B−V color index | −0.151±0.009 [2] |
Variable type | SPB [3] |
Astrometry | |
Radial velocity (Rv) | −15.5±0.5 [2] km/s |
Proper motion (μ) |
RA: −13.33
[1]
mas/
yr Dec.: 38.48 [1] mas/ yr |
Parallax (π) | 10.61 ± 0.11 mas [1] |
Distance | 307 ± 3
ly (94.3 ± 1.0 pc) |
Absolute magnitude (MV) | −0.96 [2] |
Details | |
Mass | 4.01 [6] M☉ |
Radius | 3.55±0.19 R☉
[7] 3.80±0.25 [8] R☉ |
Luminosity | 574 [2] L☉ |
Surface gravity (log g) | 4.02±0.05 [7] cgs |
Temperature | 15,615±301 [7] K |
Metallicity [Fe/H] | 0.15 [9] dex |
Rotational velocity (v sin i) | 32 [6] km/s |
Age | 26 [6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Tau Herculis, a name Latinized from τ Herculis, is a variable star in the northern constellation of Hercules. It has a blue-white hue and is visible to the naked eye at night with an apparent visual magnitude that fluctuates around 3.91. [2] The star is located at a distance of approximately 307 light years from the Sun based on parallax, [1] but it is drifting closer with a radial velocity of −16 km/s. [2]
The stellar classification of Tau Hercules is B5 IV, [5] and it serves as a standard spectrum in the modern Morgan–Keenan (MK) classification. [12] It is estimated to be just 26 million years old with a relatively low projected rotational velocity of 32 km/s. [6] Slowly rotating B-type stars are often chemically peculiar, so the mostly normal spectra of this star suggests we may be viewing it from near pole-on. [13] The abundance of most heavier elements in this star are about 85% of those in the Sun. [14] The star has four times the mass of the Sun [6] and around 3.8 [8] times the Sun's radius. On average, it is radiating 574 [2] times the luminosity of the Sun from its photosphere at an effective temperature of 15,615 K. [7]
During the Hipparcos mission, [4] Tau Hercules was discovered to be a variable star of the slowly pulsating B-type. These are mid-B main sequence stars that vary with a period of about a day; [4] the brightness of Tau Hercules varies by 0.03 magnitude [3] over a period of 1.24970±0.00008 days. The radial velocity of the star varies at a different rate than the photometric period, with the object showing both radial and non-radial pulsation modes. [4] [15]
Tau Herculis is located within 1° of the precessional path traced across the celestial sphere by the Earth's North pole. It could have served the northern pole star around the year 7400 BCE, a phenomenon which is expected to reoccur in the year 18,400 due to precession. [13]
Preceded by | Pole Star | Succeeded by |
---|---|---|
Iota Herculis | 18,400 AD | Alpha Draconis |
Its traditional name, Rukbalgethi Shemali, is of Arabic origin and shares certain etymological characteristics with the stars Ruchbah and Zubeneschamali, signifying Hercules' "northern knee". [16][ better source needed]
In Chinese, 七公 (Qī Gōng), meaning Seven Excellencies, refers to an asterism consisting of τ Herculis, 42 Herculis, φ Herculis, χ Herculis, ν1 Boötis, μ1 Boötis and δ Boötis. [17] Consequently, the Chinese name for τ Herculis itself is 七公二 (Qī Gōng èr, English: the Second Star of Seven Excellencies.) [18]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Hercules |
Right ascension | 16h 19m 44.43666s [1] |
Declination | 46° 18′ 48.1123″ [1] |
Apparent magnitude (V) | 3.91 [2] 3.83 to 3.86 [3] |
Characteristics | |
Evolutionary stage | Main sequence [4] |
Spectral type | B5 IV [5] |
U−B color index | −0.569 [2] |
B−V color index | −0.151±0.009 [2] |
Variable type | SPB [3] |
Astrometry | |
Radial velocity (Rv) | −15.5±0.5 [2] km/s |
Proper motion (μ) |
RA: −13.33
[1]
mas/
yr Dec.: 38.48 [1] mas/ yr |
Parallax (π) | 10.61 ± 0.11 mas [1] |
Distance | 307 ± 3
ly (94.3 ± 1.0 pc) |
Absolute magnitude (MV) | −0.96 [2] |
Details | |
Mass | 4.01 [6] M☉ |
Radius | 3.55±0.19 R☉
[7] 3.80±0.25 [8] R☉ |
Luminosity | 574 [2] L☉ |
Surface gravity (log g) | 4.02±0.05 [7] cgs |
Temperature | 15,615±301 [7] K |
Metallicity [Fe/H] | 0.15 [9] dex |
Rotational velocity (v sin i) | 32 [6] km/s |
Age | 26 [6] Myr |
Other designations | |
Database references | |
SIMBAD | data |
Tau Herculis, a name Latinized from τ Herculis, is a variable star in the northern constellation of Hercules. It has a blue-white hue and is visible to the naked eye at night with an apparent visual magnitude that fluctuates around 3.91. [2] The star is located at a distance of approximately 307 light years from the Sun based on parallax, [1] but it is drifting closer with a radial velocity of −16 km/s. [2]
The stellar classification of Tau Hercules is B5 IV, [5] and it serves as a standard spectrum in the modern Morgan–Keenan (MK) classification. [12] It is estimated to be just 26 million years old with a relatively low projected rotational velocity of 32 km/s. [6] Slowly rotating B-type stars are often chemically peculiar, so the mostly normal spectra of this star suggests we may be viewing it from near pole-on. [13] The abundance of most heavier elements in this star are about 85% of those in the Sun. [14] The star has four times the mass of the Sun [6] and around 3.8 [8] times the Sun's radius. On average, it is radiating 574 [2] times the luminosity of the Sun from its photosphere at an effective temperature of 15,615 K. [7]
During the Hipparcos mission, [4] Tau Hercules was discovered to be a variable star of the slowly pulsating B-type. These are mid-B main sequence stars that vary with a period of about a day; [4] the brightness of Tau Hercules varies by 0.03 magnitude [3] over a period of 1.24970±0.00008 days. The radial velocity of the star varies at a different rate than the photometric period, with the object showing both radial and non-radial pulsation modes. [4] [15]
Tau Herculis is located within 1° of the precessional path traced across the celestial sphere by the Earth's North pole. It could have served the northern pole star around the year 7400 BCE, a phenomenon which is expected to reoccur in the year 18,400 due to precession. [13]
Preceded by | Pole Star | Succeeded by |
---|---|---|
Iota Herculis | 18,400 AD | Alpha Draconis |
Its traditional name, Rukbalgethi Shemali, is of Arabic origin and shares certain etymological characteristics with the stars Ruchbah and Zubeneschamali, signifying Hercules' "northern knee". [16][ better source needed]
In Chinese, 七公 (Qī Gōng), meaning Seven Excellencies, refers to an asterism consisting of τ Herculis, 42 Herculis, φ Herculis, χ Herculis, ν1 Boötis, μ1 Boötis and δ Boötis. [17] Consequently, the Chinese name for τ Herculis itself is 七公二 (Qī Gōng èr, English: the Second Star of Seven Excellencies.) [18]