Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Equuleus |
Right ascension | 21h 06m 39.8424s [1] |
Declination | +03° 48′ 11.2240″ [1] |
Apparent magnitude (V) | +6.64 |
Characteristics | |
Spectral type | K0 IV |
Astrometry | |
Proper motion (μ) | RA: 94.608 [1] mas/yr Dec.: 50.604 [1] mas/yr |
Parallax (π) | 13.7469 ± 0.0455 mas [1] |
Distance | 237.3 ± 0.8 ly (72.7 ± 0.2 pc) |
Details [2] | |
Mass | 1.45 M☉ |
Radius | 4.92 R☉ |
Surface gravity (log g) | 3.22 cgs |
Temperature | 4982 K |
Age | 3.3 Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HD 200964 is a 7th magnitude star located approximately 237 light-years away in the constellation of Equuleus. It is a K-type subgiant with 44% more mass than the Sun, but cooler. At the age of 3 billion years, it indicates that it is an evolved A-type star. At a magnitude of 6.64, this star is too faint to be seen with the naked eye for most people, but binoculars would make it easy to see this star. Only people with a very clear eyesight and very dark sky can barely see this star.
The star is known to have two giant extrasolar planets. [4]
On July 26, 2010 the California and Carnegie Planet Search team announced the discovery of two planets around HD 200964 along with two planets around 24 Sextantis. [5] The inner planet is nearly twice as massive as Jupiter and takes 614 days to orbit the star in a circular orbit at the average distance of 1.60 AU (240 Gm). The outer planet is 9/10 the mass of Jupiter and takes 825 days to orbit eccentrically around the star at the average distance of 1.95 AU (292 Gm).
Due to the close proximity of the two planets to each other the discoverers only found stable orbits near the 4:3 resonance, meaning that every time the outer planet orbits the star three times, the inner planet orbits the star four times. The two planets are separated by only 0.35 AU. Because of the small separation between the two massive planets, the gravitational tugs between the two planets is nearly 3 million times greater than the gravitational force between Earth and Mars, 700 times larger than that between Earth and the Moon, and 4 times larger than the pull of the Sun on Earth. [5] [4] After additional radial velocity measurements were taken stable solutions in the 7:5 and 3:2 mean-motion resonances were found in addition to the 4:3 mean-motion resonance. The 7:5 configuration currently provides the best match to the measurements. [2]
There is evidence of a possible third planet in the system with a period of ~7 days however the three planet model of the system is only slightly better than the two planet model. [2]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | ≥1.85+0.14 −0.08 MJ | 1.601 ± 0.002 | 613.8+1.3 −1.4 | 0.04+0.04 −0.02 | — | 0.85 RJ |
c | ≥0.90+0.12 −0.06 MJ | 1.950+0.008 −0.005 | 825.0+3.1 −5.1 | 0.181+0.024 −0.017 | — | 0.85 RJ |
HD 20367 is a star in the constellation of Aries, close to the border with the Perseus constellation. It is a yellow-white hued star that is a challenge to view with the naked eye, having an apparent visual magnitude of 6.40. Based upon parallax measurements, it is located 85 light years from the Sun. It is drifting further away with a radial velocity of +6.5 km/s. Based upon its movement through space, it is a candidate member of the Ursa Major Moving Group of co-moving stars that probably share a common origin.
HD 188015 is a yellow-hued star with an exoplanetary companion in the northern constellation of Vulpecula. It has an apparent visual magnitude of 8.24, making it an 8th magnitude star, and thus is too faint to be readily visible to the naked eye. The distance to this star can be estimated through parallax measurements, which yield a separation of 165.5 light years from the Sun.
HD 217107 is a yellow subgiant star approximately 65 light-years away from Earth in the constellation of Pisces. Its mass is very similar to the Sun's, although it is considerably older. Two planets have been discovered orbiting the star: one is extremely close and completes an orbit every seven days, while the other is much more distant, taking fourteen years to complete an orbit.
HD 177830 is a 7th magnitude binary star system located approximately 205 light-years away in the constellation of Lyra. The primary star is slightly more massive than the Sun, but cooler being a type K star. Therefore, it is a subgiant clearly more evolved than the Sun. In visual light it is four times brighter than the Sun, but because of its distance, about 204 light years, it is not visible to the unaided eye. With binoculars it should be easily visible.
HD 108874 is a yellow dwarf star in the constellation of Coma Berenices. It is 195 light years from Earth and has two extrasolar planets that are possibly in a 9:2 orbital resonance.
HD 28185 b is an extrasolar planet 128 light-years away from Earth in the constellation of Eridanus. The planet was discovered orbiting the Sun-like star HD 28185 in April 2001 as a part of the CORALIE survey for southern extrasolar planets, and its existence was independently confirmed by the Magellan Planet Search Survey in 2008. HD 28185 b orbits its sun in a circular orbit that is at the inner edge of its star's habitable zone.
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported as of April 2014 have been observed directly, with even fewer being resolved from their host star.
HD 155358 is a low metallicity yellow dwarf star approximately 43 pc away in the constellation Hercules. This star is known to be orbited by two extrasolar planets.
ρ Indi, Latinised as Rho Indi, is a yellow-hued star in the constellation Indus. With an apparent visual magnitude of +6.05 it is, barely, a naked eye star, not visible in the northern hemisphere outside the tropics. Based upon an annual parallax shift of 37.46 mas, it is located 87 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −2 km/s.
HD 11964 is a binary star system located 110 light-years away from the Sun in the equatorial constellation of Cetus. It is visible in binoculars or a telescope but is too faint to be seen with the naked eye, having an apparent visual magnitude of 7.51. The system is drifting closer to the Sun with a radial velocity of −9 km/s. Two extrasolar planets have been confirmed to orbit the primary.
54 Piscium b, occasionally catalogued as 54 Piscium Ab to differentiate from the brown dwarf in the system, is an extrasolar planet approximately 36 light-years away in the constellation of Pisces. It was discovered orbiting the orange dwarf star 54 Piscium. Its minimum mass is one-fifth that of Jupiter, and it orbits the star in a very eccentric orbit about every two months.
HD 5319 is an 8th magnitude star approximately 319 light years away in the constellation Cetus. It is a subgiant star of spectral type K3, having run out of hydrogen in its core. When it was main-sequence, the spectral type was early F or late A.
HD 41004 is a visual binary star system in the southern constellation of Pictor. It is too faint to be visible to the naked eye, having a combined apparent visual magnitude of 8.65. The two components have a magnitude difference of 3.7, and share a common proper motion with an angular separation of 0.30″, as of 2018. The distance to this system is approximately 136 light years based on parallax. It is drifting further away from the Sun with a radial velocity of +42.5 km/s, having come to within 44.5 ly some 831,000 years ago.
HD 92788 is a star in the equatorial constellation of Sextans. It has a yellow hue but is too dim to be visible to the naked eye, having an apparent visual magnitude of 7.31. The star is located at a distance of 113 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −4.5 km/s. Two planets have been found in orbit around the star.
HD 109749 is a binary star system about 206 light years away in the constellation of Centaurus. The pair have a combined apparent visual magnitude of 8.08, which is too faint to be visible to the naked eye. The primary component has a close orbiting exoplanet companion. The system is drifting closer with a heliocentric radial velocity of −13.2 km/s.
HD 204313 is a star with two and possibly three exoplanetary companions in the southern constellation of Capricornus. With an apparent magnitude of 7.99, it is an eighth magnitude star that is too faint to be readily visible to the naked eye. The star is located at a distance of 157 light years from the Sun based on parallax measurements, but it is drifting closer with a radial velocity of −10 km/s.
HD 28254 is a binary star system located 180 light-years away in the constellation Dorado. The primary component is an 8th magnitude G-type main-sequence star. This star is larger, cooler, brighter, and more massive than the Sun, and its metal content is 2.3 times as much as the Sun. In 2009, a gas giant exoplanet was found in orbit around the star.
24 Sextantis, often abbreviated as 24 Sex, is the Flamsteed designation of a 7th-magnitude star located approximately 236 light years away in the constellation of Sextans. At an apparent visual magnitude of 6.61, this star can only be viewed from rural skies under good seeing conditions.
HD 134606 is a yellow-hued star with a planetary system, positioned in the southern constellation of Apus. It is below the nominal limit for visibility with the naked eye, having an apparent visual magnitude of 6.86. Based upon an annual parallax shift of 37.3 mas, it is located 87.45 light years away. The star appears to be moving further from the Earth with a heliocentric radial velocity of +2.3 km/s.
HD 47366 is the Henry Draper Catalogue designation for a star in the southern constellation of Canis Major. It has an apparent visual magnitude of 6.12, which puts it near the lower limit of stars visible to the naked eye. According to the Bortle scale, it can be viewed from dark rural skies. Parallax measurements performed by the Gaia spacecraft provide a distance estimate of 276 light-years.