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|Date||November 17, 2005|
|Discoverers||Goździewski et al.|
|Detection method||Radial velocity|
|Name & designations|
|Planet numbers|| P163, 14 Herculis P2,|
Hercules P3, Tarandus P13,
2005 P35, 2005 Her-2,
|Star designations|| 14 Herculis c, 11 Tarandi c,|
BF 2110 c, PH 11 c,
P1 Herculis c, P1 Tarandi c,
HD 145675 c, HIP 79248 c,
Gliese 614 c, SAO 45933 c
|Right ascension||16h 10m 24.31s (242.601 31°)|
|Declination||+43° 49' 03.5" (+43.817 64°)|
|Eccentricity||0.004 200 4|
| Direction of orbit|
relative to star's rotation
|Inclination|| 26.510° to ecliptic|
−7.738° to star's equator
10.239° to invariable plane
|Argument of periastron||41.250°|
|Longitude of ascending node||184.999°|
|Longitude of periastron||226.249°|
|Angular separation||390.232 mas|
|Observing the parent star|
|Mean angular star size||0.069 91° (4.195')|
|Max. angular star size||0.070 21° (4.212')|
|Min. angular star size||0.069 62° (4.177')|
|Mean star magnitude||−21.946|
|Max. star magnitude||−21.955|
|Min. star magnitude||−21.937|
|Flattening||0.017 47 (1:57.257)|
|Angular diameter||51.637 μas|
| Reciprocal mass|
relative to star
| Weight on Eurystheus|
(150 lb (1 wa) on Earth)
|1 967 lb (13.11 wa)|
|Standard gravitational parameter||5.930 × 108 km³/s²|
| Roche limit|
(3 g/cm3 satellite)
| Direction of rotation|
relative to orbit
|Longitude of vernal equinox||25.114°|
|North pole right ascension||20h 50m 27s (312.612°)|
|North pole declination||+37° 59' 42" (+37.995°)|
|North polar constellation||Cygnus|
|North polar caelregio||Avis|
|South pole right ascension||08h 50m 27s (132.612°)|
|South pole declination||−37° 59' 42" (−37.995°)|
|South polar constellation||Vela|
|South polar caelregio||Malus|
|Surface temperature||239 K (−34°C, −30°F, 430°R)|
|Mean irradiance||16.6 W/m² (0.012 2 I⊕)|
|Irradiance at periastron||16.8 W/m² (0.012 3 I⊕)|
|Irradiance at apastron||16.5 W/m² (0.012 1 I⊕)|
|Albedo||0.828 (bond), 0.846 (geom.)|
|Surface density||0.433 g/m³|
|Molar mass||2.70 g/mol|
|Composition|| 92.074% hydrogen (H2)|
5.813% helium (He)
2.819% water (H2O)
437 ppm methane (CH4)
379 ppm ammonia (NH3)
173 ppm benzene (C6H6)
43.5 ppm ethane (C2H6)
31.9 ppm hydrogen deuteride (HD)
1.88 ppb argon (Ar)
133 ppt neon (Ne)
|Dipole strength||783 μT (7.83 G)|
|Magnetic moment||3.45 × 1020 T•m³|
|Number of moons||148|
|Number of rings||23|
Eurystheus (14 Herculis c, P163) is an exoplanet which orbits the yellow-orange K-type main sequence star 14 Herculis, meaning the star is smaller, cooler and thus dimmer than our Sun. It is approximately 57 light-years or 18 parsecs from Earth towards the constellation Hercules in the caelregio Tarandus.
Eurystheus is a gas giant several times more massive than Jupiter and orbits further from the star than Jupiter is to the Sun.
Discovery and chronology Edit
Eurystheus was discovered on November 17, 2005 by a team of astronomers led by Krzysztof Goździewski. The team used the spectrometer mounted on the telescope in McDonald Observatory in Texas and found that this star has a long-term trend in addition to the inner planet Cerenytis discovered seven years prior. Less than a year later on November 2, 2006, Eurystheus was confirmed.
Eurystheus is the 156th exoplanet discovered overall, 130th since 2000, and 35th in 2005. Eurystheus is the 3rd exoplanet discovered in the constellation Hercules (2nd in 2005) and 13th in the caelregio Tarandus (4th in 2005). Since Eurystheus is the second planet discovered in the 14 Herculis system, the planet receives the designations 14 Herculis c (a is not used because the parent star uses this letter to reduce confusion) and 14 Herculis P2. Note that the chronology does not include speculative brown dwarfs (objects with minimum masses below 13 MJ but with speculative true masses above 13 MJ).
Orbit and rotation Edit
Eurystheus is located near the middle of the Jovian orbit (which is a classification of orbit) as it orbits the star at an average distance of 6.86 AU (1 AU is the average distance between the Earth and the Sun). If we place this planet in our solar system, it would orbit between the orbits of Jupiter and Saturn. Eurystheus has an almost perfectly circular orbit with an eccentricity of 0.004. Despite the Eurystheus' wide orbit, the orbital distance can only vary by about 0.06 AU from the star. The planet takes 18.91 years or nearly 227 months to make one complete trip around the star at an average velocity of 2.28 AU/yr or 10.8 km/s. Eurystheus is in a 4:1 resonance with the inner known planet Cerenytis.
Parent star observation and irradiance Edit
Viewed from Eurystheus, the parent star would appear to be 83 times fainter than the Sun seen from Earth. The parent star has a magnitude −21.95 compared to −26.74 for the Sun's magnitude viewed from Earth. Viewed from Eurystheus, the parent star would have an angular diameter of 4.2' on average, which is 1⁄7 the angular diameter of the full moon we see every month.
Eurystheus receives 17 watts worth of energy per square meter from the parent star compared 1368 W/m² for Earth.
Eurystheus rotates very rapidly, even more rapid than the fastest rotator in the solar system, Jupiter. It takes just 8.2 hours to make one complete turn, similar to the period of Cerenytis. A year on Eurystheus lasts 20181 Eurystheus days, which is 55.10 times longer than a year on Earth. Even more stranger is that the planet rotates on its side like Uranus. The planet tilts 80.8° to the plane of its orbit, which is almost perpendicular to its orbit. The planet's north pole points to the constellation Cygnus (in Avis), while the south pole points to the constellation Vela (in Malus).
Structure and composition Edit
Mass and size Edit
Eurystheus is massive, 4.68 times more massive than Jupiter, the most massive planet in our solar system. It is classified as super-Jupiter in the planetary mass classification scheme. Even though this planet is much more massive than Jupiter, it is slightly smaller than Jupiter, meaning that Eurystheus must be very dense, has very strong gravity, and has very high escape velocity. Even though Eurystheus is denser than Earth (6.8 vs. 5.5 g/cm³), the densest planet in our solar system, it would still be a gas giant with no solid surface.
This planet is more spherical than any giant planet in our solar system with a flattening of 0.01747. The equatorial radius is 68,258 km while the polar radius is 67,073 km. Using these three datas, its mean radius is calculated to be 67,863 km, actually twice as close to its equatorial radius than its polar radius.
Gravitational influence Edit
The gravitational force of Eurystheus is over 13 times stronger than Earth's. So if you weigh 150 pounds (1 wame) on Earth, you would weigh 1967 pounds (13.11 wames) or almost a ton on Eurystheus. So a person standing on Eurystheus would weigh nearly as much as a small car parked on Earth! To escape this planet, it would need to go more than twice as fast as required to escape Jupiter and 12 times faster than is required to escape Earth.
Since the gravity of this planet is so strong, the roche limit lies relatively far from the planet at 1.65 planetary radii. Eurystheus has a very large hill sphere, with its boundary lying at 1850 times the radius of the planet or 327 LD. The stationary orbit lies nearly 60% further out than roche limit. The orbital velocity at stationary orbit is calculated to be 50.2 km/s or 31.2 mi/s. Since the planet takes 8.2 hours to rotate, then a moon would also take 8.2 hours to orbit the planet at stationary orbit.
Below Eurystheus' outer envelope (atmosphere), the weight of all the gases pressing down produce a tremendous pressure. That pressure allow hydrogen and helium to condense in the upper mantle despite the higher temperatures deeper down. In the middle mantle lies liquid metallic hydrogen where hydrogen can conduct electricity under even greater pressure heated beyond its critical point. In the lower mantle, there is narrow layer of solid metallic hydrogen. At the center lies an ultra-dense core of rock and metal with a mass 86 Earth masses, roughly 5.8% the total mass of the planet. The temperature of the core is estimated to be 113,400 K (113,100°C, 203,700°F) and an estimated pressure 489 GPa.
Like all gas giants, Eurystheus' atmosphere composes mostly of hydrogen (92%), with helium (5.8%) and water (2.8%) making up most of the rest. Eurystheus contains trace amounts of other gases, including methane and ammonia. Ethane makes up 43 parts per million of the atmosphere. Unlike most gas giants and common on terrestrial planets, the atmosphere contains argon but at a concentration of 2 parts per billion.
Eurystheus contains banded clouds of ammonia and water and this planet would appear as orange and white stripes from space. The ammonia clouds are in the cooler upper deck and water clouds in the warmer lower deck. The temperature of this planet is 239 K (−34°C, −30°F), which is far warmer than its equilibrium temperature of 85 K (−188°C, −307°F) due to its high mass and density that produces a lot of internal heating. This planet radiates four times the amount of energy than it receives from the parent star. There are thousands of jet streams and zonal jets, which can produce violent long-lasting storms and high winds, even more violent than Jupiter's.
Magnetic field Edit
That powerful magnetic field is produced by the movements of metallic hydrogen in its interior caused by the planet's rotation. This mechanism is well known as dynamo effect. The magnetic field blocks most of stellar and cosmic radiation from reaching the planet, but occasionally it can produce beautiful, vivid aurorae when the stellar radiation got caught in the magnetic field lines and move towards their poles where it interact with the planet's upper atmosphere (ionosphere). Its magnetic field is so strong that occasional auroral display are often more brilliant than aurorae on Earth.
Moons and rings Edit
Eurystheus has a big family of 148 moons, several of them larger than our Moon. The largest moon has mass 23.7 Lunar masses (0.291 Earth masses) and has diameter 2.871 DL (6,198 miles, 9,974 kilometers). There are six moons bigger than our Moon and one of these is larger than Mars. 14 moons have diameters between 1000 miles and 2000 miles, 49 have diameters between 100 and 1000 miles and 79 have diameters less than 100 miles.
Eurystheus has 23 rings. The rings are made mainly of dusts and boulders, and little ice.
Future studies Edit
The probability that Eurystheus will transit 14 Herculis can be a slim 0.29% chance, but it is speculated that Eurystheus will not transit since I speculated that the inclination is 27°. Eurystheus can be studied effectively using astrometry or direct imaging. The planet can be studied using astrometry using Gaia, James Webb Space Telescope (JWST), Space Interoferometry Mission (SIM), or even the current Hubble Space Telescope (HST) guidance sensor. The astrometry can constrain the inclination and thus calculate the exact mass. The direct imaging can see what the planet may really look like. The direct imaging can constrain the size of this planet like transit method. The derivative parameters, including density and surface gravity, can then be calculated using the radius constrained from transit and true mass calculated by inclination. Using the calculated density, astronomers can model the interior of this planet.
Astronomers may eventually use astroseismology to study the interior, including the extent, features and compositions by layers. Using the spectrometer mounted on the JWST, the atmosphere can be studied, including temperatures, chemical makeup, and features. Using the same method, the rotation rate can be constrained using Doppler shifts, which in turn rotation period can then be calculated.
In orbit around the planet, moons can be detected using the transit across the planet, detecting the wobble of the planet, or even direct imaging. Rings can also be detected using just two methods: transit or direct imaging.
Eurystheus can further be studied using the JWST's successor: ATLAST, due to launch between 2025–35.
- Cerenytis (14 Herculis b, P20)