Extrasolar Visions - HD 209458 b

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Cloudy Hot Jupiter

Object Type:

Cloudy Hot Jupiter

Parent Star:

HD 209458 (G0V)

Discovery Status:

Confirmed

Current Planet

Habitability Zone

Mass ( M sin i ):

0.69 ± 0.05 Jupiters

Radius:

1.32 Jupiters

Mean Distance:

0.045 AU

Orbital Period:

3.52474541 ± 0.00000025 Days

Eccentricity:

Argument of Perihelion (omega):

83 °

Radial Velocity of Star:

14.7652 m/s

System Age:

4000 - 6000 Myr

Planet Appearance:

Silicate clouds over dark sodium haze

Estimated Mean Temp:

1395 Kelvin

Temp from
Internal Heating :

94.872 Kelvins ¹

Mean Angular Star Size:

15.366°

Gravitational Influence
(Hill Sphere):

0.002 AU / 390000 km

Max Stable Prograde Moon Orbit:

0 AU / 140000 km

Max Moon Mass:

< 0.0001 Earths
2066.1949 x Phobos

Tidally locked if older than:

4 Myr

Estimated Bond Albedo:

~ 0.55 ²

Notes:
¹ from planet formation models of Burrows et al
² from Sudarsky et al. 2000

Year Discovered:

1999

Detection Method:

Doppler Spectroscopy/Transit

Discovered By:

Marcy et al,

Confirmed by Elodie and Coralie Teams

Transit first detected by Charbonneau et al, Transit identified by G. Henry et al

Click image below to enlarge

Soon after the detection of HD 209458 b via doppler spectroscopy, a 1.7 percent dimming of the star was detected, caused as the planet passed in front of the star from the vantage point of Earth. As the transit requires the inclination of the planet's orbit to be 90 degrees, its mass can be calculated to high accuracy. The timing and intensity of the dimming of the star allows the radius and density of an extrasolar planet to be measured for the first time.

Because HD209458 b passes in front of its star from the vantage point of the Earth, in 2001 astronomers using the Hubble Space Telescope were able to detect traces of sodium in the planet's atmosphere. This was the first detection of the chemical composition of an extrasolar planetary atmosphere.

Information about Hubble's discoveries at HD 209458 can be found at this link.

In 2003, Vidal Madjar et al announced the detection of a comet-like extended atmosphere around HD 209458 b. For more on this discovery, click here.

View a VRML model of the system. Please be patient while the file downloads.

For a VRML tour of our galaxy's exoplanets, check out Extrasolar VR.

Evaporating Osiris
The planet of HD 209458, unofficially named Osiris, is so close to its star that its atmosphere is literally boiling away into space. Here we see the dim blue glow of energized hydrogen gas escaping the planet's atmosphere, extending into a comet-like tail.

Osiris Transit
From the vantage point of the Earth, the planet of HD 209458 moves across the face of its star once every few days. Such transits allow astronomers to probe the planet's atmosphere. A surprising discovery was that the planet heated to such high temperatures by it star, that its atmosphere is slowly escaping into space, forming a long tail that dims the star as it trails behind the planet.

View the Night Sky from HD 209458 b...
	Cylindrical All Sky View (750 x 1500 pixels)
	Northern Hemisphere (750 x 750 pixels)
	Southern Hemisphere (750 x 750 pixels)