Hd 189733 B

Information about Hd 189733 B

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**HD 189733 b**
Orbital elements

Semi-major axis a:	0.0313 Â± 0.0004 AU
Eccentricity e:	0.00
Orbital period P:	2.219 d
Inclination i:	85.3Â° Â± 0.1
Angular distance θ:	1.617 mas
Longitude of periastron ω:	?
Time of periastron τ:	? JD
Semi-Amplitude K:	205 Â± 6 m/s
Physical characteristics
Mass:	1.15 Â± 0.04 M_J
Radius:	1.26 Â± 0.03 R_J
Density:	762 Â± 80 kg/m
Gravity:	1.71 g
Temperature:	1117 Â± 42 K
Discovery
Discovery date:	2005
Discovery location:
Detection method(s):	Transit
Discoverer(s):	Mayor et al.
Other catalogue

Artist's impression of HD 189733 b.

HD 189733 b is a gas giant planet and is a hot Jupiter that closely orbits around the yellow dwarf star HD 189733 A. The planet was discovered in 2005 when astronomers observed the planet transiting across the face of the star. The mass of the planet is estimated to be 15% larger than Jupiter's. The planet completes an orbit every 2.2 days. It is occasionally referred to as HD 189733 Ab to distinguish it from the red dwarf star HD 189733 B.

This planet exhibits the largest photometric transit depth of any extrasolar planets so far observed, of approximately 3%, and clearly exhibits the Rossiter-McLaughlin effect. It also has a very large semi-amplitude (K) of 205 m/s, as one would expect for such a close hot Jupiter. It was one of the first two planets to be directly spectroscopically observed, along with HD 209458 b.

Observation

In 2006, a team led by Drake Deming announced a detection of strong infrared thermal emission from the transiting extrasolar planet HD 189733 b, by measuring the flux decrement during its prominent secondary eclipse.

"A 6-hour photometric sequence using Spitzer's infrared spectrograph in peak-up imaging mode at 16 micrometers] shows the secondary eclipse depth to be 0.551 Â± 0.030%, with accuracy limited by instrumental baseline uncertainties, but with 32-sigma precision (0.017%) on the detection. The 16-[micrometer] brightness temperature of this planet (1117 Â± 42 K) is very similar to the Spitzer detections of TrES-1 and HD 209458 b, but the observed planetary flux (660 [micro-janskies]) is an order of magnitude greater. This large signal will allow a detailed characterization of this planet in the infrared. The photometry has sufficient signal-to-noise (~400 per point) to motivate a search for structure in the ingress/egress portions of the eclipse curve, caused by putative thermal structure on the disk of the planet. We show that by binning our 6-second sampling down to 6-minute resolution, we detect the modulation in the intensity derivative during ingress/egress due to the overall shape of the planet, but our sensitivity is not yet sufficient to distinguish between realistic models of the temperature distribution across the planet's disk. We point out the potential for extending Spitzer secondary eclipse detections down to the regime of transiting hot Neptunes, if such systems are discovered among nearby lower dwarf stars."

In 2007 the Spitzer space telescope was used to map the planet's temperature emissions. A temperature range of 973 Â± 33 K to 1,212 Â± 11 K was discovered, indicating that the star's heat is distributed fairly evenly through the planet's atmosphere. Interestingly, the region of peak temperature was offset 30 degrees east of the substellar point. Assuming the planet is tidally locked with its star, this suggests that powerful easterly winds moving at more than 9,600 kilometers per hour are responsible for redistributing the heat.^[1]

Direct spectral observation

On February 21, 2007, NASA released news that HD 189733 b and HD 209458 b had been directly spectroscopically observed, using the Spitzer Space Telescope.^[2] The release came simultaneously with the public release of a new issue of Nature containing the first publication on the spectroscopic observation of the other star, HD 209458 b. The findings on HD 189733 b will appear in an upcoming issue of the Astrophysical Journal Letters. The spectroscopic observations of HD 189733 b were led by Carl Grillmair NASA's Spitzer Science Center.

First map of an extra-solar planet

HD 189733 b just before being eclipsed by HD 189733A Courtesy:NASA/JPL-Caltech/Harvard-Smithsonian CfA

In May 2007 NASA released a map of the surface temperature of HD 189733 b, performed by spectral observations through the Spitzer Space Telescope. This is the first map ever published of an extra-solar planet.^[3]

First solid evidence of water vapor

On July 11, 2007, a team lead by Giovanna Tinetti published the results of their observations using the Spitzer Space Telescope concluding there is solid evidence for significant amounts of water vapor in the planet's atmosphere. ^[4]

References

1. ^ Knutson, Heather A.; David Charbonneau, Lori E. Allen, Jonathan J. Fortney, Eric Agol, Nicolas B. Cowan, Adam P. Showman, Curtis S. Cooper & S. Thomas Megeath (10 May 2007). "A map of the day–night contrast of the extrasolar planet HD 189733b". Nature 447: 183-186. doi:10.1038/nature05782.
2. ^ [1]
3. ^ [2]
4. ^ [3]

Bouchy et al. (2005). "ELODIE metallicity-biased search for transiting Hot Jupiters II. A very hot Jupiter transiting the bright K star HD 189733". Astronomy and Astrophysics 444: L15-L19. (Preprint)

External links

semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae.

Ellipse

The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape.
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1 astronomical unit =
SI units
010⁹ m 010⁶ km
Astronomical units
010^-6 pc 010⁻⁶ ly
US customary / Imperial units
010⁹ ft 010⁶ mi

The
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orbit's eccentricity, is an important parameter of the orbit that defines its absolute shape. Eccentricity may be interpreted as a measure of how much this shape deviates from a circle.
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The orbital period is the time taken for a planet (or another object) to make one complete orbit.

When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.
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day (symbol: d) is a unit of time equivalent to 24 hours. It is not an SI unit but it is accepted for use with SI.^[1] The SI unit of time is the second. The term comes from the Old English dÃ¦g.

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The day has several definitions.
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For the science fiction novella by William Shunn, see .

Inclination in general is the angle between a reference plane and another plane or axis of direction.
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angular distance (or angular separation) between two point objects, as observed from a location different from either of these objects, is the size of the angle between the two directions originating from the observer and pointing towards these two objects.
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A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. ^[1] Since one degree is defined as one three hundred sixtieth (1/360) of a circle, 1 MOA is 1/21600 of the amount of arc in a closed circle, or
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In astrodynamics, the longitude of the periapsis (symbolized ω) of an orbiting body is the longitude (measured from the point of the vernal equinox) at which the periapsis (closest approach to the central body) would occur
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Julian day or Julian day number (JDN) is the integer number of days that have elapsed since the initial epoch defined as noon Universal Time (UT) Monday, January 1, 4713 BC in the proleptic Julian calendar ^[1]. That noon-to-noon day is counted as Julian day 0.
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amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation, that is, the magnitude of the maximum disturbance in the medium during one wave cycle.

Sometimes this distance is called the peak amplitude
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Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.
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Mass is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how much matter there is in an object". Mass is a central concept of classical mechanics and related subjects, and there are several definitions of mass within the framework of relativistic
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Jupiter

This processed color image of Jupiter was produced in 1990 by the U.S. Geological Survey from a Voyager image captured in 1979. The colors have been enhanced to bring out detail.
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In classical geometry, a radius (plural: radii) 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. The radius is half the diameter.
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In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
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kilogram or kilogramme (symbol: kg) is the SI base unit of mass. The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK), which is almost exactly equal to the mass of one liter of water.
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cubic metre (symbol mÂ³) is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. In the United States it is spelled cubic meter. An alternate name, which allowed a different usage with SI prefixes, was the stÃ¨re.
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Gravitation is a natural phenomenon by which all objects with mass attract each other. In everyday life, gravitation is most familiar as the agency that endows objects with weight.
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g-force (also g-load) is a measurement of an object's acceleration expressed in g's. It may also informally refer to the reaction force resulting from an acceleration, with the causing acceleration expressed in g's.
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trillion fold).]]

Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
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The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero — the coldest possible temperature — is zero kelvins
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581: L115 – L118.
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The term transit or astronomical transit has two meanings in astronomy:

A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage

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Michel G. E. Mayor (born 12 January, 1942) is a Swiss professor in the Department of Astronomy at the University of Geneva.

Together with Didier Queloz in 1995 he discovered 51 Pegasi B, the first extrasolar planet orbiting a sun-like star, 51 Pegasi.
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gas giant (sometimes also known as a Jovian planet after the planet Jupiter) is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in our Solar System; Jupiter, Saturn, Uranus, and Neptune.
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