XO-7 b
XO-7 b is a hot Jupiter orbiting the G0 V star XO-7 in the constellation Draco. It lies about 764 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is XO-7 b?
XO-7 b has a radius of 15.39 times that of Earth, or 1.37 times the radius of Jupiter. Its mass is 225 times that of Earth, giving it a density of 0.34 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is XO-7 b in the Habitable Zone?
XO-7 b orbits inside the inner edge of the habitable zone of XO-7. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of XO-7: 1.263–2.944 AU (conservative: 1.599–2.791 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on XO-7 b
The equilibrium temperature of XO-7 b is about 1,743 K (1,470 °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. It receives 1,540 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on XO-7 b — one full orbit around XO-7 — lasts 2.86 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.044 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.038).
How Was XO-7 b Discovered?
XO-7 b was discovered in 2019 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-7 b?
XO-7 b is 763.7 light-years (234.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1263. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 13,441,120 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-7 b scores 0.06, ranking #5,148 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: XO-7
XO-7
- Spectral type
- G0 V
- Surface temperature
- 6,250 K (Sun: 5,772 K)
- Mass
- 1.41 M☉
- Radius
- 1.48 R☉
- Age
- 1.2 billion years (Sun: 4.6)
Planetary System
XO-7 b is the only planet known to orbit XO-7 so far.
XO-7 b — Complete Data
| Radius | 15.390 Earth radii (1.373 Jupiter radii) |
|---|---|
| Mass | 225.34 Earth masses (0.709 Jupiter masses) |
| Density | 0.34 g/cm³ (Earth: 5.51) |
| Orbital period | 2.86 days |
| Orbital distance | 0.044 AU |
| Eccentricity | 0.038 |
| Equilibrium temperature | 1,743 K (1,470 °C) |
| Stellar irradiation | 1,540.00× Earth |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 763.7 light-years (234.1 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | XO |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2020-01-13. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About XO-7 b
Is XO-7 b habitable?
No — XO-7 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is XO-7 b?
XO-7 b is about 764 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 13,441,120 years to get there.
How big is XO-7 b compared to Earth?
XO-7 b has 15.39 times the radius of Earth and about 225 times its mass.
How long is a year on XO-7 b?
One orbit around XO-7 takes 2.9 Earth days — short enough that 128 of its years would fit into one Earth year.
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