18 Del b
18 Del b is a cold gas giant orbiting the G6 III star 18 Del in the constellation Delphinus. It lies about 249 light-years from Earth and was discovered in 2008 using the radial velocity method.
Is 18 Del b in the Habitable Zone?
18 Del b orbits inside the inner edge of the habitable zone of 18 Del. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of 18 Del: 5.142–12.443 AU (conservative: 6.513–11.797 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 ›
Orbit and Year Length
A year on 18 Del b — one full orbit around 18 Del — lasts 982.9 Earth days, longer than an Earth year. It orbits at an average distance of 2.476 AU. Its orbit is nearly circular (eccentricity 0.024).
How Was 18 Del b Discovered?
18 Del b was discovered in 2008 using the radial velocity method, with observations from Okayama Astrophysical Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is 18 Del b?
18 Del b is 248.6 light-years (76.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1778. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,375,360 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. 18 Del b scores 0.20, ranking #3,905 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: 18 Del
18 Del b belongs to a system of 2 stars; it orbits 18 Del.
18 Del
- Spectral type
- G6 III
- Surface temperature
- 4,980 K (Sun: 5,772 K)
- Mass
- 2.10 M☉
- Radius
- 8.80 R☉
- Luminosity
- 43.0200 L☉
Planetary System
18 Del b is the only planet known to orbit 18 Del so far.
18 Del b — Complete Data
| Mass (best estimate) | 2,926.25 Earth masses |
|---|---|
| Orbital period | 982.85 days |
| Orbital distance | 2.476 AU |
| Eccentricity | 0.024 |
| Earth Similarity Index | 0.20 |
| Distance from Earth | 248.6 light-years (76.2 parsecs) |
| Constellation | Delphinus |
| Discovery method | Radial Velocity |
| Discovery facility | Okayama Astrophysical Observatory |
| Discovery year | 2008 |
Data: NASA Exoplanet Archive, last updated 2023-09-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About 18 Del b
Is 18 Del b habitable?
No — 18 Del b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is 18 Del b?
18 Del b is about 249 light-years from Earth in the constellation Delphinus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,375,360 years to get there.
How long is a year on 18 Del b?
One orbit around 18 Del takes 982.9 Earth days.
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