Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Vulpecula |
HD 189733 A | |
Right ascension | 20h 00m 43.71294s [1] |
Declination | +22° 42′ 39.0732″ [1] |
Apparent magnitude (V) | 7.676 [2] |
HD 189733 B | |
Right ascension | 20h 00m 42.97791s [3] |
Declination | +22° 42′ 34.1785″ [3] |
Apparent magnitude (V) | ~10 |
Characteristics | |
Spectral type | K1.5V [2] /M [4] |
Apparent magnitude (B) | 8.609 ±0.016/ [2] |
Apparent magnitude (J) | 6.07 [2] /10.116 ±0.041 [5] |
Apparent magnitude (H) | 5.59 [2] /9.545 ±0.086 [5] |
Apparent magnitude (K) | 5.54 [2] /9.323 ±0.027 [5] |
Variable type | BY Draconis [2] [6] |
Astrometry | |
HD 189733 A | |
Radial velocity (Rv) | −2.53±0.12 [1] km/s |
Proper motion (μ) | RA: −3.208(11) mas/yr [1] Dec.: −250.323(14) mas/yr [1] |
Parallax (π) | 50.5668 ± 0.0162 mas [1] |
Distance | 64.50 ± 0.02 ly (19.776 ± 0.006 pc) |
Absolute magnitude (MV) | 6.2 [7] |
HD 189733 B | |
Radial velocity (Rv) | 1.46±1.21 [3] km/s |
Proper motion (μ) | RA: −12.193(9) mas/yr [3] Dec.: −253.993(12) mas/yr [3] |
Parallax (π) | 50.6291 ± 0.0136 mas [3] |
Distance | 64.42 ± 0.02 ly (19.751 ± 0.005 pc) |
Orbit | |
Companion | HD 189733 B |
Period (P) | 3,200 yr |
Semi-major axis (a) | 11.38 [8] " (216 AU) |
Details | |
Mass | 0.846+0.068 −0.049 [9] M☉ |
Radius | 0.805±0.016 [10] R☉ |
Luminosity | 0.328±0.011 [10] L☉ |
Surface gravity (log g) | 4.56±0.03 [10] cgs |
Temperature | 4875±43 [10] K |
Metallicity [Fe/H] | −0.03±0.08 [11] dex |
Rotation | 11.953±0.009 days [12] |
Age | 4.3±2.8 [10] Gyr |
Other designations | |
Database references | |
SIMBAD | A |
B | |
Exoplanet Archive | data |
Extrasolar Planets Encyclopaedia | data |
HD 189733, also catalogued as V452 Vulpeculae, is a binary star system 64.5 light-years (19.8 parsecs ) away in the constellation of Vulpecula (the Fox). The primary star is suspected to be an orange dwarf star, [2] while the secondary star is a red dwarf star. [5] Given that this system has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula (M27).
As of 2005, it has been confirmed that an exoplanet, HD 189733 b, orbits the primary star within the system. [13]
HD 189733 A is an orange dwarf star of the spectral type K1.5V. The star has a mass of 81 percent that of the Sun, a radius of 76 percent, and a luminosity of 33 percent. The star is between 89 and 102 percent as enriched in iron as the Sun, making the star more than 600 million years old. Its absolute magnitude is 6.2. [7]
The star has starspots which affect its luminosity by 1.5 percent in visible light. [14] As a result, it is listed in the General Catalogue of Variable Stars as a BY Draconis variable with the variable star designation V452 Vul. [6]
Discovered in 2006 by the infrared 2MASS astronomical survey, 2MASS J20004297+2242342 or HD 189733 B is a dim red dwarf star of spectral type M. The companion was observed at a separation of 216 astronomical units away from the primary star. Orbiting in a clockwise orbit (which is nearly perpendicular to the orbital plane of transiting planet HD 189733 b), the orbital period is estimated to be around 3,200 years long. [4]
HD 189733 A has one known planet, designated HD 189733 b, a gaseous giant 13% larger than Jupiter close enough to complete an orbit every two days. Using spectrometry it was found in 2007 that this planet contains significant amounts of water vapour. This planet is the second extrasolar planet where definitive evidence for water has been found. [15]
The chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above 1,000 °C (1,830 °F ) is far from being habitable, this finding increases the likelihood that water, an essential component of life, would be found on a more Earth-like planet in the future. [16]
Astronomers have created a rough map of HD 189733b's cloud-top features using data from the Spitzer infrared space telescope.
Although Spitzer could not resolve the planet into a disk, by measuring changes as the planet rotated, the team created a simple longitudinal map. That is, they measured the planet's brightness in a series of pole-to-pole strips across the planet's visible cloud-tops, then assembled those strips into an overall picture.
Probably due to strong winds, the hottest point on the planet seems to be "offset by about 30 degrees longitudinally" from the substellar point ("high noon"). [17]
In late 2008, the spectral signature of carbon dioxide was found in HD 189733b's atmosphere. [18]
In 2013, albedo measurements at visible wavelengths in the range of 290–570 nm using the Hubble Space Telescope STIS (Space Telescope Imaging Spectrograph) instrument, reported in the Astrophysical Journal Letters, determine the planet to have a deep blue hue due to optically thick reflective clouds containing silicates (glass) "rain". [19] [20] The paper detailing the results reports measurement of "geometric albedos of Ag = 0.40 ± 0.12 at 290–450 nm [near ultraviolet to blue in the visible light region of the electromagnetic spectrum] and Ag < 0.12 at 450–570 nm ... with sodium absorption suppressing the scattered light signal beyond ~450 nm as predicted by models of hot Jupiter atmospheres." [20]
An atmospheric transmission spectrum taken in 2020 has shown the presence of opaque haze, and spectral signatures of sodium and potassium. [21]
Transit timing variations of HD 189733 b were discovered in 2021, suggesting other planets do exist in the system. [22]
Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
---|---|---|---|---|---|---|
b | 1.123±0.045 MJ | 0.03100±0.0006 | 2.218575200(77) | <0.0039 | 85.58±0.06 ° | 1.138±0.027 RJ |
In 2008, a team of astronomers first described how as the exoplanet orbiting HD 189733 A reaches a certain place in its orbit, it causes increased stellar flaring. In 2010, a different team found that every time they observe the exoplanet at a certain position in its orbit, they also detected X-ray flares. Theoretical research since 2000 suggested that an exoplanet very near to the star that it orbits may cause increased flaring due to the interaction of their magnetic fields, or because of tidal forces. In 2019, astronomers analyzed data from Arecibo Observatory, MOST, and the Automated Photoelectric Telescope, in addition to historical observations of the star at radio, optical, ultraviolet, and X-ray wavelengths to examine these claims. They found that the previous claims were exaggerated and the host star failed to display many of the brightness and spectral characteristics associated with stellar flaring and solar active regions, including sunspots. Their statistical analysis also found that many stellar flares are seen regardless of the position of the exoplanet, therefore debunking the earlier claims. The magnetic fields of the host star and exoplanet do not interact, and this system is no longer believed to have a "star-planet interaction." [24] Some researchers had also suggested that HD 189733 accretes, or pulls, material from its orbiting exoplanet at a rate similar to those found around young protostars in T Tauri Star systems. Later analysis demonstrated that very little, if any, gas was accreted from the "hot Jupiter" companion. [25]
79 Ceti, also known as HD 16141, is a binary star system located 123 light-years from the Sun in the southern constellation of Cetus. It has an apparent visual magnitude of +6.83, which puts it below the normal limit for visibility with the average naked eye. The star is drifting closer to the Earth with a heliocentric radial velocity of −51 km/s.
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 179949 is a 6th magnitude star in the constellation of Sagittarius. It is a yellow-white dwarf, a type of star hotter and more luminous than the Sun. The star is located about 90 light years from Earth and might be visible under exceptionally good conditions to an experienced observer without technical aid; usually binoculars are needed.
HD 130322 is an 8th-magnitude star in the constellation of Virgo. It is an orange dwarf, a type of star somewhat dimmer and cooler than the Sun. Spectral type of the star is K0V. It can only be seen with binoculars or telescope. Being almost exactly on the celestial equator the star is visible everywhere in the world except for the North Pole.
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 38529 is a binary star approximately 138 light-years away in the constellation of Orion.
HD 202206 is a binary star system in the southern constellation of Capricornus. With an apparent visual magnitude of +8.1, it is too faint to be visible to the naked eye. It is located at a distance of 150 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +14.7 km/s.
HD 102195 is an orange-hued star in the zodiac constellation of Virgo with a confirmed exoplanet companion. With an apparent visual magnitude of 8.07, the star is too faint to be seen with the naked eye. The distance to HD 102195 can be estimated from its annual parallax shift of 34.06 mas, yielding 95.8 light years. It is moving further away from the Earth with a heliocentric radial velocity of 1.85 km/s. This is a high proper motion star and a possible member of the η Cha stellar kinematic group.
HD 224693, also named Axólotl, is a star in the equatorial constellation of Cetus, and is positioned near the western constellation border with Aquarius. It can be viewed with a small telescope but is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.23. Based on parallax measurements, the object is located at a distance of approximately 306 light years from the Sun. It is drifting further away with a radial velocity of 1.5 km/s.
HD 185269 is a stellar triple system approximately 170 light-years away in the constellation Cygnus. It is easily visible to binoculars, but not the naked eye.
HD 17156, named Nushagak by the IAU, is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. A search for a binary companion star using adaptive optics at the MMT Observatory was negative.
HD 189733 b is an exoplanet in the constellation of Vulpecula approximately 64.5 light-years away from the Solar System. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 11.2% higher than that of Jupiter and a radius 11.4% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.0 kilometers per second, making it a hot Jupiter with poor prospects for extraterrestrial life.
Gliese 86 is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was orbiting the star.
HD 100777 is a single star with a planetary companion in the equatorial constellation of Leo. With an apparent visual magnitude of 8.42 it is too faint to be viewed with the naked eye, although the absolute magnitude of 4.81 indicates it could be seen if it were just 33 ly (10 pc) away. The distance to the star is approximately 162 light years based on parallax measurements.
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 117207 is a star in the southern constellation Centaurus. With an apparent visual magnitude of 7.24, it is too dim to be visible to the naked eye but can be seen with a small telescope. Based upon parallax measurements, it is located at a distance of 105.4 light-years from the Sun. The star is drifting closer with a radial velocity of −17.4 km/s. It has an absolute magnitude of 4.67.
HD 212301 is a binary star system in the south circumpolar constellation of Octans. This star is also called HIP 110852. With an apparent visual magnitude of 7.76, it is too faint to be visible to the naked eye. The system is located at a distance of 177 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +4.7 km/s. It has an absolute magnitude of 4.06.
HAT-P-4 is a wide binary star consisting of a pair of G-type main-sequence stars in the constellation of Boötes. It is also designated BD+36°2593.
HD 16760 is a binary star system approximately 227 light-years away in the constellation Perseus. The primary star HD 16760 is a G-type main sequence star similar to the Sun. The secondary, HIP 12635 is 1.521 magnitudes fainter and located at a separation of 14.6 arcseconds from the primary, corresponding to a physical separation of at least 660 AU. Announced in July 2009, HD 16760 has been confirmed to have a red dwarf orbiting it, formerly thought to be a brown dwarf or exoplanet.
HD 15082 is a star located roughly 399 light years away in the northern constellation of Andromeda. The star is a Delta Scuti variable and a planetary transit variable. A hot Jupiter type extrasolar planet, named WASP-33b or HD 15082b, orbits this star with an orbital period of 1.22 days. It is the first Delta Scuti variable known to host a planet.