HD 80606 b
Planet· orbits HD 80606
HD 80606 b — a giant of about 4 Jupiter masses on one of the most ECCENTRIC orbits known (e=0.93): it loops from ~0.85 AU in to just 0.03 AU from its star every 111 days. At closest approach it is flash-heated — models indicate its upper atmosphere can jump by ~500–700°C in hours — then cools on the long swing outward. Because it transits AND its mass is measured, its density is real. Never imaged.
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Key facts
Mass
7.90 × 10²⁷ kg
4.16 M♃ (1,324 M⊕)
Radius
73,712 km
11.6× wider than Earth
Surface gravity
97.1 m/s²
9.9× Earth's gravity
Year
111 Earth days
Distance from HD 80606
0.46 AU
Science
Physical
- Mass
- 7.90 × 10²⁷ kg · 4.16 M♃ (1,324 M⊕)
- Radius
- 73,712 km · 11.6× wider than Earth
- Density
- 4,711 kg/m³ · 4.7× water
- Computed from mass and radius
- Surface gravity
- 97.1 m/s² · 9.9× Earth's gravity
- Computed from mass and radius
- Escape velocity
- 120 km/s · 10.7× Earth's escape velocity
- Computed from mass and radius
Orbital
- Semi-major axis
- 0.46 AU
- From the NASA Exoplanet Archive (RV + transit + orbit fit)
- Eccentricity
- 0.9318
- From the NASA Exoplanet Archive (RV + transit + orbit fit)
- Inclination
- 0.00 °
- From the NASA Exoplanet Archive (RV + transit + orbit fit)
- Orbital period
- 111.4 days
- From the NASA Exoplanet Archive (RV + transit + orbit fit)
- Perihelion
- 4,696,245 km
- Computed from the orbital elements
- Aphelion
- 0.889 AU
- Computed from the orbital elements
- Mean orbital velocity
- 44.9 km/s
- Computed from the orbital elements
Composition
- Bulk composition
- A gas giant of ~4 Jupiter masses with a real measured density (transit + mass). Its defining trait is its orbit: an extreme ellipse (e=0.93) that carries it from ~0.85 AU in to just 0.03 AU from its star every 111 days. Near closest approach it is blasted with starlight and heats explosively — Spitzer watched it brighten as its atmosphere flash-heated — a natural experiment in planetary weather. Never imaged.
- Cloud appearance
- Appearance based on NASA/JPL-Caltech's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The banded clouds shown are a representation of its class, shown only in Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 4.5 S⊕ · 4.5× the sunlight Earth receives
- Computed from HD 80606's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 405 K (132 °C)
- Computed average — but it is far from constant: models indicate the upper atmosphere jumps by ~500–700°C in hours near periastron, then cools on the long swing out.
Discovery & history
- Method
- Transit detection
- Name
- Designated 'b' under the IAU convention that letters a star's planets 'b', 'c'… in the order found (the star is the unwritten 'a'); no IAU proper name is assigned.
Discovered by radial velocity in 2001; its transits (found 2009) confirmed the size, and Spitzer watched its atmosphere heat explosively during a periastron passage.
Images
Images from open archives · credit shown per image