KOI-3503 c
KOI-3503 c is a terrestrial planet orbiting KOI-3503 in the constellation Cygnus. It lies about 2,893 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is KOI-3503 c?
KOI-3503 c has a radius of 1.21 times that of Earth. Its mass is 10.4 times that of Earth, giving it a density of 10.00 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is KOI-3503 c in the Habitable Zone?
The position of KOI-3503 c relative to the habitable zone of KOI-3503 cannot be precisely determined from the available orbital data.
Habitable zone of KOI-3503: 1.002–2.348 AU (conservative: 1.270–2.226 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on KOI-3503 c
The equilibrium temperature of KOI-3503 c is about 686 K (413 °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 KOI-3503 c — one full orbit around KOI-3503 — lasts 31.8 Earth days, shorter than Mercury's 88-day year.
How Was KOI-3503 c Discovered?
KOI-3503 c was discovered in 2021 using the transit method, with observations from Kepler.
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 KOI-3503 c?
KOI-3503 c is 2,893.2 light-years (887.1 parsecs) from Earth. Light arriving here tonight left the planet about 2,893 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 50,920,320 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. KOI-3503 c scores 0.32, ranking #1,085 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: KOI-3503
KOI-3503
- Surface temperature
- 6,001 K (Sun: 5,772 K)
- Mass
- 0.86 M☉
- Radius
- 1.25 R☉
The KOI-3503 Planetary System
KOI-3503 c is one of 2 known planets in the KOI-3503 system. Its siblings:
- KOI-3503 b (Terrestrial)
KOI-3503 c — Complete Data
| Radius | 1.210 Earth radii (0.108 Jupiter radii) |
|---|---|
| Mass | 10.36 Earth masses (0.033 Jupiter masses) |
| Density | 10.00 g/cm³ (Earth: 5.51) |
| Orbital period | 31.83 days |
| Equilibrium temperature | 686 K (413 °C) |
| Earth Similarity Index | 0.32 |
| Distance from Earth | 2,893.2 light-years (887.1 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-06-11. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About KOI-3503 c
Is KOI-3503 c habitable?
KOI-3503 c is not known to orbit within the habitable zone of KOI-3503, and as a terrestrial planet it is an unlikely candidate for life as we know it.
How far away is KOI-3503 c?
KOI-3503 c is about 2,893 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 50,920,320 years to get there.
How big is KOI-3503 c compared to Earth?
KOI-3503 c has 1.21 times the radius of Earth and about 10.4 times its mass.
How long is a year on KOI-3503 c?
One orbit around KOI-3503 takes 31.8 Earth days — short enough that 11 of its years would fit into one Earth year.
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