XO-5 b
XO-5 b is a hot Jupiter orbiting XO-5 in the constellation Lynx. It lies about 901 light-years from Earth and was discovered in 2008 using the transit method.
How Big Is XO-5 b?
XO-5 b has a radius of 12.78 times that of Earth, or 1.14 times the radius of Jupiter. Its mass is 378 times that of Earth, giving it a density of 1.06 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is XO-5 b in the Habitable Zone?
XO-5 b orbits inside the inner edge of the habitable zone of XO-5. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of XO-5: 0.764–1.819 AU (conservative: 0.968–1.725 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on XO-5 b
The equilibrium temperature of XO-5 b is about 1,230 K (957 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on XO-5 b — one full orbit around XO-5 — lasts 4.19 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.052 AU — closer to its star than Mercury is to the Sun.
How Was XO-5 b Discovered?
XO-5 b was discovered in 2008 using the transit method, with observations from XO.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is XO-5 b?
XO-5 b is 900.9 light-years (276.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1126. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 15,855,840 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. XO-5 b scores 0.07, ranking #4,858 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: XO-5
XO-5
- Surface temperature
- 5,430 K (Sun: 5,772 K)
- Mass
- 1.04 M☉
- Radius
- 1.13 R☉
Planetary System
XO-5 b is the only planet known to orbit XO-5 so far.
XO-5 b — Complete Data
| Radius | 12.780 Earth radii (1.140 Jupiter radii) |
|---|---|
| Mass | 378.20 Earth masses (1.190 Jupiter masses) |
| Density | 1.06 g/cm³ (Earth: 5.51) |
| Orbital period | 4.19 days |
| Orbital distance | 0.052 AU |
| Equilibrium temperature | 1,230 K (957 °C) |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 900.9 light-years (276.2 parsecs) |
| Constellation | Lynx |
| Discovery method | Transit |
| Discovery facility | XO |
| Discovery year | 2008 |
Data: NASA Exoplanet Archive, last updated 2015-02-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About XO-5 b
Is XO-5 b habitable?
No — XO-5 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is XO-5 b?
XO-5 b is about 901 light-years from Earth in the constellation Lynx. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 15,855,840 years to get there.
How big is XO-5 b compared to Earth?
XO-5 b has 12.78 times the radius of Earth and about 378 times its mass.
How long is a year on XO-5 b?
One orbit around XO-5 takes 4.2 Earth days — short enough that 87 of its years would fit into one Earth year.
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