Scylla

Scylla (HD 11964 c, P152) is a which orbits the yellow   , meaning the star has just ran out of hydrogen fuel in its core. The star is considerably larger but cooler and lot more luminous than our. It is approximately 107 s or 33 s from towards the   in the caelregio Hippocampus.

Scylla is a so-called blue Jupiter with no global cloud cover as it lacks suitable chemicals for clouds at a temperature of 509 K (536°C or 457°F), although there are few bands of high-altitude clouds near the equator and the poles. This planet takes 38 days to orbit the star.

is named after the monster in that lived on one side of a narrow channel of water.

Discovery and chronology
Scylla was discovered on August 7, 2005 by a team of astronomers led by. The team used the mounted on the  in  and found that this star wobble caused by planets. On that same day, the second planet Deino was also announced but reported unconfirmed.

Scylla is the 145$J$ exoplanet discovered overall, 119$J$ since 2000, and 24$J$ in 2005. Scylla is also the 4$J$ exoplanet discovered in the constellation Cetus (2$J$ in 2005) and 19$J$ exoplanet discovered in the caelregio Hippocampus (4$⊕$ in 2005). Scylla is the first planet discovered in the HD 11964 system, despite its designation HD 11964 c (a is not used because the parent star uses this letter to reduce confusion). More accurately, this planet is also designated HD 11964 P1. However, at the time of its discovery, this planet was designated HD 11964 b. Note that the chronology does not include speculative s (objects with minimum masses below 13 M$⊕$ but with speculative true masses above 13 M$⊕$).

Orbit
Scylla takes 3.28 s (37.9 s) to orbit the star at an of 1.114 microparsecs (0.2297 s), which is 59% the average distance between  and the Sun. Scylla orbits with an of 0.298, which corresponds to the distances ranging from 0.782 to 1.446 μpc (0.1613 to 0.2982 AU). The planet moves at an of 65.05 km/s and it varies from 54.50 to 74.11 km/s during its orbit. Like some of the s known, Scylla orbits opposite to the rotation of the star, so-called. The retrograde orbit maybe caused by the orbit being flipped by the gravitational interactions with three other planets in this system just after the planet formed. It's speculated to  is 173° (−179.78° to star's ). The is 102°, which is the angle between periastron and. The is 250° counterclockwise from the  at  as seen from north. Adding argument of periastron and longitude of ascensing node yields 352° in.

Parent star observation and irradiance
When viewing HD 11964 from one of its moons since this planet is a with no solid surface, that sun would appear to be 47 times brighter than the Sun as seen from Earth, corresponding to its  −30.93. The of HD 11964 as seen from Scylla is 2.251°, which is 4 times the angular diameter of the full moon and sun as seen from Earth, because Scylla orbits nearly 4 times closer to the star than Earth to the Sun. However that magnitude and angular diameter of a star change during its planetary orbit because the orbit is eccentric. During half of its year when the planet moves closer to the star, the sun would appear to get brighter and larger, while at the other half when the planet moves further away from the star, it would appear to get dimmer and smaller.

Scylla receives 20 kilowatts worth of stellar energy over every square meter, which is 14.75 I$2$. However with its eccentric orbit, its varies from 12 to 41 kW/m² or from 8.76 to 29.93 I$2$.

Rotation
Scylla takes 909 hours, 52 minutes, and 35 seconds to rotate once on its axis, which is nearly 38 Earth days. The is 504 kph, or 313 mph. This planet rotates in the same direction as its revolution, but opposite to the rotation of the parent star. Scylla is ed, because its period of rotation is identical to the period of its orbit. The tilt of this planet is such that its points to the constellation  (in Noctua) while the  points to the constellation  (in Solarium).

Mass and size
Using the speculated inclination, its speculated for Scylla is 0.97  or 308. This planet had a 0.11 M$4$ or 35 M$2$. It is classified as mid-Jupiter in the planetary mass classification scheme. This planet has a radius of 71.747 megameters, which is slightly bigger than. Scylla has density 1.16 g/cm³, which is a little denser than water.

The radius mentioned does not mean it is measured from the center to anywhere on the planet's surface. There are really three types of radii, mean radius (average when measuring from the center to everywhere on its surface), equatorial radius (from the center to the surface at the equator), and polar radius (from the center to the surface at either poles). The radius mentioned is its mean radius. Its equatorial radius is 72.945 Mm whiles its polar radius is 71.746 Mm, a difference of 1.199 Mm. Using these values, circumferences can be calculated using the equation 2πr. The calculated circumferences are 455.815 Mm (mean), 458.326 Mm (equatorial), and 450.794 Mm (polar). Its is 0.98357, derived by dividing polar radius/circum. from equatorial radius/circum. Because of its, the surface gravity at the equator is lower than at the poles since the gravity is inversely proportional to the square of its radius.

Gravitational influence
Scylla has gravitational force nearly 2.4 times stronger than Earth's and 90% that of Jupiter's. The object falling to the planet accelerates at 23.4 m/s² or 76.7 ft/s². If you weigh 150 on Earth, you would weigh 356 pounds on Scylla. So a person standing on Scylla would weigh as much as a lion, tiger, and black bear on Earth!

The, where a 3 g/cm³ moon tear apart by tidal forces, is just 0.173 s (66.4 s), which is 0.915 planetary radii. The, the boundary where the gravitational influence of the planet is identical to the star, is just 4.24 lunar distances (1.63 gigameters), which is 22 times the radius of the planet. The, where the satellite's orbital period is identical to the rotation period of the planet, analogous to the Earth's , is about 3148 Mm, which is 43.16 planetary radii and eight times the distance between Earth and the Moon. The stationary velocity, the orbital velocity at stationary orbit, is 6.2 km/s or 3.8 mi/s. Since the planet takes 30¼ days to rotate, then a moon would take 30¼ days to orbit the planet at stationary orbit, which is very similar to the 's orbital period around the Earth.

Interior
Below Scylla's outer envelope (atmosphere), the weight of all the gases pressing down produce a tremendous pressure. That pressure allow and  to condense in the upper mantle despite the higher temperatures deeper down. In the lower mantle lies liquid where hydrogen can conduct electricity under even greater pressure heated beyond its. In the lower mantle, the temperature is 11,400 K (11,200°C, 20,100°F) and a pressure 190. At the center lies a core of rock and metal with a mass 22 Earth masses, roughly 7.1% the total mass of the planet. The temperature of the core is estimated to be 20,200 K (19,900°C, 35,800°F) and an estimated pressure 4.2.

Atmosphere
Scylla's atmosphere composes of 95.8% and 4.1%. Scylla's composition other than hydrogen and helium is considerably different compared to the four giant solar system planets because this planet orbits much closer to its star. Scylla contains no in the. However, this planet has gases that are not found in our, such as , , , and. Also there are no ice crystals in the atmosphere because it is too hot.

Scylla doesn't have a global cloud cover and this planet appears deep blue, although it has bands of s around 5° north and south of the equator, another bands at 65° north and south of the equator, and significant cloud cover around the poles. These clouds are made of. These cloud bands are shaped by the planet's fast rotation and s. These clouds form from a localized concentrations of PCl$5$, which are produced by the s between hydrogen chloride and phosphine using s and ionized particles from the parent star as their s.


 * 5HCl + PH$8$ → PCl$18$ + 4H$2$

This jovian planet is cloudless as the mean temperature is 553 K (280°C or 536°F). Because there are no clouds over most of the planet, it may have only a light wind and no storms.

Magnetic field
This planet has a strong, one-and-a-half times stronger than. Even though this planet has no clouds, it can still produce s when the stellar activity is high.

Moons and rings
Scylla has one and no. The moon, designated as Scylla I or HD 11964 c1 is a volcanic moon that orbits close to the planet, at a distance of 122,341 miles or 196,889 kilometers, which is two times closer to the planet than Moon's distance from Earth. This moon has mass 1.27 Lunar masses and has diameter 0.867 Lunar diameters (1,872 miles, 3,013 kilometers), corresponding to its density 6.54 g/cm³. This moon has gravity 0.280 (2.75 m/s²). If you weigh 150 lbs on Earth, you'll weigh just 42 lbs on Scylla I. So the average weight for adults on Scylla I is as light as the average weight for 5 year olds on Earth!

The volcanism on the moon is caused by the strong s exerted by the parent planet, just like Jupiter exerting a lot of tidal bulges on which causes.

Future studies
The method will use to study Scylla might be to see what this planet actually looks like. But direct imaging of this planet can be difficult to achieve because this planet orbits real close to its star, only 23% the distance between Earth and the Sun. Maybe looking for across the star would be a better idea, but it is speculated that this planet will not transit since the speculated inclination is 173°, which is almost face-on. Even with the difficulty of direct imaging and low probability of transit, the inclination of Scylla's orbit can still be constrained using from,  (JWST), or  (SIM). Constraining the inclination is important for measuring its true mass.

Perhaps in about two decades, direct imaging of this planet can be achieved using the (ATLAST). The direct imaging can then constrain the size of this planet. After constraining its size, density and surface gravity can be calculated. Using the density of the planet, astronomers can probe the interior and estimate the mass and size of the core. Astronomers will also study the mantle and its temperature of the core using. Using the spectrometer mounted on the ATLAST, it can constrain its temperature and study the chemical makeup of the atmosphere. Using the same method, the rotation rate can also be constrained using s. Using the rotation rate and circumference of the planet (calculated using 2π radius), 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.

Related links

 * Deino (HD 11964 b, P153)