Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Hercules |
Right ascension | 17h 17m 40.49053s [1] |
Declination | +29° 13.6′ 38.0243″ [1] |
Apparent magnitude (V) | +8.424 [2] |
Characteristics | |
Spectral type | K3 V [2] |
U−B color index | 0.27 |
B−V color index | 1.015 [2] |
Astrometry | |
Radial velocity (Rv) | -9.427 km/s |
Proper motion (μ) | RA: -72.481±0.016 mas/yr [3] Dec.: +216.849±0.019 mas/yr [3] |
Parallax (π) | 41.1103 ± 0.0169 mas [3] |
Distance | 79.34 ± 0.03 ly (24.325 ± 0.010 pc) |
Absolute magnitude (MV) | 6.480 [2] |
Details | |
Mass | 0.772 ± 0.020 [2] M☉ |
Radius | 0.720 ± 0.013 [2] R☉ |
Luminosity | 0.230 ± 0.018 [2] L☉ |
Surface gravity (log g) | 4.60 ± 0.12 [2] cgs |
Temperature | 4850 ± 88 [2] K |
Metallicity [Fe/H] | +0.05 ± 0.06 [2] dex |
Rotation | 51.5 days [2] |
Rotational velocity (v sin i) | 0.50 ± 1.0 [2] km/s |
Age | 8.6 ± 4.8 [2] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HD 156668 is a star in the northern constellation of Hercules constellation. With an apparent visual magnitude of 8.4 [2] it is too faint to be viewed with the naked eye, but it can be seen with even a small telescope. [5] The distance to this object has been determined directly using the parallax technique, yielding a value of about 80 light-years (25 parsecs ). [1]
This star has the stellar classification of a K2 dwarf, with approximately 77% of the mass of the Sun and about 72% of the Sun's diameter. While they are on the main sequence, lower mass stars like this generate energy much more slowly than the Sun. As a result, this star is radiating only 23% of the Sun's bolometric luminosity. HD 156668 is emitting this energy from its outer atmosphere at an effective temperature of around 4850 K, [2] giving it the cool orange glow of a K-type star. [6] It is slightly more enriched in iron compared to the Sun and is rotating at a leisurely rate of once every 51.5 days. Although much older than the Sun, this star is only middle-aged at about 8.6 billion years. [2]
The HD 156668 exhibits a stellar activity cycle with a period about 10 years. [7]
From 1911 to 1915, Photographic Stellar Spectrum surveys [8] have been carried out by Annie Jump Cannon and Edward Charles Pickering. Anna Mary Palmer who was Henry Draper's wife financed the study, it was also her husband who was responsible for the star's designation in the Henry Draper Catalogue with subsequent extension (HD) although it was first designated as BD+29 2979 [9] in the original catalogue that was published in 1863 by Friedrich Wilhelm Argelander due to its position and brightness of 324,198 stars between +90° and −2° declination in the span of an 11-year observation. A number of proper motion surveys was published in 1957 where 9,867 stars in the Southern hemisphere where high proper motion was detected. [10] The name BD was taken from a catalogue of the Bonner Durchmusterung (Bonn Survey) [11] where observations are abbreviated as BD. Latter study expansions were carried out by the Cape Photographic Durchmusterung observatory in Córdoba, Argentina and further extensions by Henry Lee Giclas who designated the star as G 181-34 in the Giclas catalogues. From 1990 to 1993, HD 156668 was observed at least twice and was featured at the 6th annual catalog of the Tokyo Photoelectric Meridian Circle (PMC) where it is one of 6649 stars observed. [12]
Andrew Howard announced the discovery of a Super-Earth in orbit around HD 156668. This planet is designated HD 156668 b. The announcement was made at the 215th American Astronomical Society meeting on January 4 to 7, 2010 in Washington D.C. The planet orbits its star in only 4.6 days with a distance approximately 0.05 AU away from the parent star. The researchers used the wobble method where the resulting spectrum showed color shifts which was used to approximate the mass of the astronomical object. The observation revealed data that the exoplanet was at least 4.15 Earth masses. [13] Later observations revealed that the minimum mass is now 3.1 Earth masses. [14]
Another planet, HD 156668 c, was discovered in 2021, and presence of additional long-period object is suspected. [7]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥3.1 ± 0.4 M🜨 | 0.0211 ± 0.0002 | 1.26984 ± 0.00007 | 0.000 | — | — |
c | ≥0.0991+0.0079 −0.0077 MJ | 1.570±0.017 | 811.3+5.2 −5.3 | 0.089+0.04 −0.061 | — | — |
HD 2638 is a ternary star system system in the equatorial constellation of Cetus. The pair have an angular separation of 0.53″ along a position angle of 166.7°, as of 2015. This is system too faint to be visible to the naked eye, having a combined apparent visual magnitude of 9.44; a small telescope is required. The distance to this system is 179.5 light years based on parallax, and it is drifting further away with a radial velocity of +9.6 km/s. The magnitude 7.76 star HD 2567 forms a common proper motion companion to this pair at projected separation 839″.
HD 192263 is a star with an orbiting exoplanet in the equatorial constellation of Aquila. The system is located at a distance of 64 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of −10.7 km/s. It has an absolute magnitude of 6.36, but at that distance the apparent visual magnitude is 7.79. It is too faint to be viewed with the naked eye, but with good binoculars or small telescope it should be easy to spot.
HD 219134 is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers. This star has a magnitude 9.4 optical companion at an angular separation of 106.6 arcseconds.
HD 4308 is a single star with an orbiting exoplanet in the southern constellation of Tucana. It has a yellow hue and is a challenge to view with the naked eye even under good seeing conditions, having an apparent visual magnitude of 6.54. This object is located at a distance of 72 light years, as determined from parallax measurements. It is a population II star and is considered to be a member of the thick disk. The star is receding from the Sun with a radial velocity of +95 km/s.
HIP 14810 is a star with three exoplanetary companions in the northern constellation of Aries. It positioned about 1.3° to the north of Delta Arietis, but is too faint to be visible to the naked eye with an apparent visual magnitude of 8.6. The system is located at a distance of 165 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s.
HD 107148 is a wide binary star system in the constellation of Virgo. A pair of exoplanets have been confirmed in orbit around the brighter star. This system is located at a distance of 161 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 25.2 K. Although having an absolute magnitude of 4.47, at that range the system is too faint to be visible with the naked eye, having an apparent visual magnitude of 8.01.
HD 2039 is a yellow dwarf or yellow subgiant star in the constellation Phoenix. The star is not visible to the naked eye, and lies 280 light years away from the Sun. HD 2039 is a relatively stable star, and an exoplanet at least three times the mass of the planet Jupiter has been discovered in its orbit; this exoplanet, known as HD 2039 b, was the 100th exoplanet to be discovered.
HD 222582 is a multiple star system in the equatorial constellation of Aquarius. It is invisible to the naked eye with an apparent visual magnitude of 7.7, but can be viewed with binoculars or a small telescope. The system is located at a distance of 137 light years from the Sun based on parallax, and it is drifting further away with a radial velocity of +12 km/s. It is located close enough to the ecliptic that it is subject to lunar occultations.
HD 190647 is a yellow-hued star with an exoplanetary companion, located in the southern constellation of Sagittarius. It has an apparent visual magnitude of 7.78, making this an 8th magnitude star that is much too faint to be readily visible to the naked eye. The star is located at a distance of 178 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −40 km/s. It is also called HIP 99115.
HD 85512 is a solitary K-type main-sequence star 36.8 light-years away in the constellation Vela. It is about 1 billion years older than the Sun. It is extremely chromospherically inactive, only slightly more active than Tau Ceti. It exhibits a long-term variability and was thought to host one low-mass planet, although this is now doubtful.
HD 40307 is an orange (K-type) main-sequence star located approximately 42 light-years away in the constellation of Pictor, taking its primary name from its Henry Draper Catalogue designation. It is calculated to be slightly less massive than the Sun. The star has six known planets, three discovered in 2008 and three more in 2012. One of them, HD 40307 g, is a potential super-Earth in the habitable zone, with an orbital period of about 200 days. This object might be capable of supporting liquid water on its surface, although much more information must be acquired before its habitability can be assessed.
HD 47186 is a star with a pair of orbiting exoplanets in the southern constellation of Canis Major. The system is located at a distance of 122 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of 4.2 km/s. Although it has an absolute magnitude of 4.64, at the distance of this system the apparent visual magnitude is 7.63; too faint to be seen with the naked eye. It has a high proper motion, traversing the celestial sphere at an angular rate of 0.272″·yr−1.
HD 131664 is an 8th magnitude star in the southern constellation of Apus with an orbiting brown dwarf or stellar companion. Parallax measurements by the Gaia space observatory provide an estimated distance of 172.5 light years from the Earth. The system is moving further away with a baseline heliocentric radial velocity of +35 km/s.
HD 143361 is a star in the southern constellation Norma. With an apparent visual magnitude of 9.20, this star is too dim to be seen with the naked eye. It is close enough to the Earth that its distance can be determined using parallax measurements, yielding a value of 224 light-years.
HD 240210 is a star in the northern constellation of Cassiopeia. It has an orange hue but is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.33. Parallax measurements provide an estimate of its distance from the Sun as approximately 1,230 light years. It is drifting further away with a radial velocity of +8.6 km/s.
HD 190007, also known as Gliese 775, is a star with a close orbiting exoplanet in the constellation of Aquila. Parallax measurements by Gaia put the star at a distance of 41.5 light-years away from the Sun. It is drifting closer with a radial velocity of −30.3 km/s, and is predicted to come within 11.8 light-years in 375,000 years. The star has an absolute magnitude of 6.91, but at its present distance the apparent visual magnitude is 7.46, which is too faint to be viewed with the naked eye.
41 Comae Berenices is a single, orange-hued star in the northern constellation of Coma Berenices. It is visible to the naked eye, having an apparent visual magnitude of 4.80. Based upon an annual parallax shift of 8.6 mas, it is located around 379 light years away. It is moving closer to the Earth with a heliocentric radial velocity of −16 km/s.
HD 220689 is a single star in the equatorial constellation of Aquarius. It is a challenge to view with the naked eye, having an apparent visual magnitude of +7.74, but is readily viewed with a pair of binoculars. The star is located at a distance of 153 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s. A survey in 2015 has ruled out the existence of any additional stellar companions at projected distances from 26 to 305 astronomical units.
HD 20003 is a star in the southern constellation Hydrus. With an apparent visual magnitude of 8.39, this yellow-hued star is much too faint to be visible to the naked eye. It is located at a distance of 136.6 light years from the Sun based on parallax. HD 20003 is drifting closer with a radial velocity of −16 km/s, and is predicted to come to within 97 light-years in around 1.4 million years from now.
PZ Telescopii, also known as HD 174429 or simply PZ Tel, is a young star in the constellation Telescopium. Based on parallax measurements, it is located at a distance of 154 light-years from the Sun. The star is drifting closer with a radial velocity of −4 km/s. It is too faint to be visible to the naked eye and is classified as a BY Draconis variable that ranges in apparent visual magnitude from 8.33 down to 8.63 over a period of 22.581 hours. It is one of the closest and hence brightest pre-main-sequence stars to Earth.
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