HD 189733
Encyclopedia
HD 189733, also catalogued as V452 Vulpeculae, is a binary star
system approximately 63 light-year
s away in the constellation
of Vulpecula
(the Fox
). The primary star is suspected to be an orange dwarf
star, while the secondary star is a red dwarf
star. 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 extrasolar planet
orbits the primary star within the system.
star
of the spectral type K1.5V. The star has a mass
of 82 percent that of the Sun
, a radius
75 percent, and a luminosity
of 26.4 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.
The star has starspots which affect its luminosity by 1.5 percent in visible light. 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.
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 unit
s away from the primary star. Orbit
ing in a clockwise orbit (which is nearly perpendicular to the orbital plane of transiting planet HD 189733 b
), the orbital period is estimated around 3,200 years long.
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.
The chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above 1000 °C (1,832 °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.
Astronomers have created a rough map of HD 189733b's cloud-top features using data from the Spitzer infrared space telescope.
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").
In late 2008, the spectral signature of carbon dioxide was found in HD 189733b's atmosphere.
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
system approximately 63 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Vulpecula
Vulpecula
Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle .-Stars:There are no stars brighter than 4th magnitude in...
(the Fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
). The primary star is suspected to be an orange dwarf
Orange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
star, while the secondary star is a red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
star. Given that this system has the same visual magnitude as HD 209458
HD 209458
HD 209458 is an 8th magnitude star in the constellation Pegasus. It is very similar to our Sun, and it is classified as a yellow dwarf . Because it is located at a distance of about 150 light years, it is not visible to the unaided eye...
, 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
Dumbbell Nebula
The Dumbbell Nebula is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 light years....
(M27).
As of 2005, it has been confirmed that an extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
orbits the primary star within the system.
Stellar system
HD 189733 A is an orange dwarfOrange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
of the spectral type K1.5V. The star has a mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of 82 percent that of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, a radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
75 percent, and a luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
of 26.4 percent. The star is between 89 and 102 percent as enriched in iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
as the Sun, making the star more than 600 million years old.
The star has starspots which affect its luminosity by 1.5 percent in visible light. As a result, it is listed in the General Catalogue of Variable Stars
General Catalogue of Variable Stars
The General Catalogue of Variable Stars is a list of variable stars. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR and edited by B. V. Kukarkin and P. P. Parenago. Second and third editions were published in 1958 and 1968; the fourth...
as a BY Draconis variable
BY Draconis variable
BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other...
with the variable star designation V452 Vul.
Discovered in 2006 by the infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
2MASS
2MASS
Observations for the Two Micron All-Sky Survey began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres to ensure coverage of the entire sky...
astronomical survey, 2MASS J20004297+2242342 or HD 189733 B is a dim red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
star of spectral type M. The companion was observed at a separation of 216 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s away from the primary star. Orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
ing in a clockwise orbit (which is nearly perpendicular to the orbital plane of transiting planet HD 189733 b
HD 189733 b
HD 189733 b is an extrasolar planet approximately 63 light-years away in the constellation of Vulpecula . The planet was discovered orbiting the star HD 189733 on October 5, 2005, when astronomers in France observed the planet transiting across the face of the star. The planet is classified as a...
), the orbital period is estimated around 3,200 years long.
Planetary system
HD 189733 b
HD 189733 b is an extrasolar planet approximately 63 light-years away in the constellation of Vulpecula . The planet was discovered orbiting the star HD 189733 on October 5, 2005, when astronomers in France observed the planet transiting across the face of the star. The planet is classified as a...
, 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.
The chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above 1000 °C (1,832 °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.
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").
In late 2008, the spectral signature of carbon dioxide was found in HD 189733b's atmosphere.
See also
- List of extrasolar planets
- 2MASS2MASSObservations for the Two Micron All-Sky Survey began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres to ensure coverage of the entire sky...
The Two Micron All-Sky Survey - ELODIE spectrographELODIE spectrographELODIE was an echelle type spectrograph installed at the Observatoire de Haute-Provence 1.93m reflector in south-eastern France for the . Its optical instrumentation was developed by André Baranne from the Marseille Observatory. The purpose of this instrument was extrasolar planet detection by the...