Tuonetar

Tuonetar (61 Virginis d, P380) is a which orbits the yellow   , which is similar to our. It is approximately 28 s or 9 s from towards the   in the caelregio Noctua.

Tuonetar is the outermost of the three known planets in 61 Virginis system. Tuonetar is the only known in this system.

is named after the Queen of the Underworld in.

Discovery and chronology
Tuonetar was discovered on December 14, 2009 by a team of astronomers led by. The team used the  mounted on the  in Hawaii and the  in New South Wales, Australia and found that the star 61 Virginis has three periodic variations in the. This implies evidence for a three-planet system around 61 Virginis, including Tuonetar.

Tuonetar is the 373$J$ exoplanet discovered overall, 347$J$ since 2000, and 75$J$ in 2009. Tuonetar is the 18$J$ exoplanet discovered in the constellation Virgo (8$J$ in 2009) and 41$J$ exoplanet discovered in the caelregio Noctua (13$⊕$ in 2009). Since Tuonetar is the third planet discovered in the 61 Virginis system, the planet receives the designations 61 Virginis d (a is not used because the parent star uses this letter to reduce confusion) and 61 Virginis P3. 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
Tuonetar orbits the star at an of 0.4765  (1 AU is the average distance between the Earth and the Sun) or 71.28  (million ), which is between the orbits of  and  in our. Tuonetar has an eccentric orbit. Tuonetar has an of 0.3453, which is more eccentric than the   but less eccentric than the dwarf planet. Tuonetar's orbit varies from 0.312 AU (46.67 Gm) to 0.641 AU (95.89 Gm). The planet takes 123 days or ⅓ of an Earth year to make one complete trip around the star at an of 41.3 km/s, 25.7 mi/s, or 8.69 AU/yr. Tuonetar is in a 13:4 with the middle known planet Tamar and 29:1 resonance with the innermost planet Devana.

Parent star observation and irradiance
Viewed from Tuonetar, the parent star would have a −28.11 compared to −26.74 for the magnitude of the Sun viewed from Earth. Observed from Tuonetar, 61 Virginis would appear to be 3.5 times brighter than the Sun seen from Earth. Viewed from Tuonetar, the parent star would have an of 1.1° on average, which is 2.2 times the angular diameter of the  we sometimes see at night.

Tuonetar receives between 1.8 to 7.7 I$2$ worth of stellar energy throughout its orbit with a mean of 3.3 I$2$.

Rotation
This medium-size planet takes a long time to rotate once on its axis, which indicate that its rotation rate is low, just thrice the speed of a car on a highway. Tuonetar takes 30.752 days to rotate once on its axis, which is of its orbital period. So the year on Tuonetar lasts exactly 4 days compared to 366 Earth days in an Earth year. Tuonetar tilts 21° to the plane of its orbit, which is slightly less than the Earth's tilt of 23.4°. The planet's points to the constellation  (in Testudo), while the  points to the constellation  (in Felis).

Mass and size
Tuonetar has mass 23.5 es, classifying it as midplanet in the planetary mass classification scheme. Tuonetar is 62% more massive than and. Tuonetar is 4.25 times the diameter of Earth and the diameter of. Tuonetar has a density of 1.69 g/cm³, which is ⅓ the Earth's density, implying that this planet is an like Uranus and.

Gravitational influence
The gravitational force of Tuonetar is 30% stronger than Earth's. In, its logarithmic value is 3.11. So if you weigh 150 on Earth, you would weigh 195 pounds on Tuonetar. The average human weight on Tuonetar would weigh as much as the average weight of a professional baseball player on Earth!

Tuonetar has the radius of 52.18 planetary radii or 3 times the distance between Earth and the Moon. The satellite's orbit within the hill sphere is stable while the orbit outside of hill sphere is unstable. The of Tamar is 28.2 Mm or 1.04 planetary radii. If a 3 g/cm³ satellite orbits within the roche limit, it would tear apart by tidal forces. Denser moons would withstand greater tidal forces and orbiting closer to the planet would be required to tear apart. Tuonetar's, analogous to the Earth's , is located at a distance of 42.79 planetary radii or 3 s, which is just beyond the hill sphere. Stationary orbit is an orbit where its orbital period is synchronous with the planet's rotation period. Since the planet takes 49.203 days to rotate once on its axis, then a moon in stationary orbit would also take 49.203 days to orbit the planet, that's 1. times longer than the 's orbital period around the Earth. So a moon would always present the same face to the planet and the observer on the moon appears that the planet never rotate while observer on the planet's surface appears that the moon always hang in the sky and never move.

Interior
Tuonetar's structure is very similar to the structure of Tamar, except Tuonetar has a much deeper atmosphere. Below Tuonetar's outer envelope (atmosphere), there is the mantle of liquid water, below that is the layer of the exotic form of water called or "hot ice." Below that is the layer containing an estimated 370 million times more diamond than Earth has and 1 times more diamond than Tamar has. At the planet's center lies a core made out of rock and metal, predominantly of and.

Atmosphere
Like all s and ice giants, Tuonetar has a deep atmosphere. The "surface" temperature is 382 K (108°C, 227°F). Tuonetar is seemingly releasing very little heat from its interior because this giant planet is orbiting close to the heat of its star. Heat from its interior raises the temperature by 28 K (28 C°, 51 F°).

Like all giant planets, Tuonetar's atmosphere is mostly and. This atmosphere also contains trace amounts of (H$2$O),  (H$4$S),  (CH$3$),  (NH$5$),  (PCl$8$),  (C$18$H$2$),  (S$2$Cl$3$),  (PH$3$),  (CO),  (C$8$H$rd$), and few es.

Magnetic field
Tuonetar has an extremely weak, about two millionths of a , which is 150,000 times weaker than. A possible reason for its weakness is because the planet rotates so slowly because the tidal forces of the nearby star slowed the planet's rotation by lot.

Moons and rings
Tuonetar does have two. The innermost moon has a diameter that of our moon at 256 miles or 411 kilometers. The moon orbits 0.246 LD from the parent planet. The outermost moon has a diameter more than half that of our moon at 1203 miles or 1937 kilometers. The moon orbits 1.652 LD from Tuonetar.

Tuonetar has no.

Future studies
It is speculated that Tuonetar will not transit since I speculated that the is 55.9°. Studying Tuonetar using the would not be a reliable option since the planet orbits way too close to the glare of its star. The planet can best be studied using using,  (JWST), or  (SIM). The astrometry can constrain the inclination and thus calculate the exact mass.

Maybe can reliably be used to directly image planets down to 0.01 AU from the sun-like stars. The direct imaging can see what Tuonetar may really look like. The direct imaging can constrain the size of this planet like. The derivative parameters, including density and surface gravity, can then be calculated using the radius and true mass calculated using inclination. Using the calculated density, astronomers can model the interior of this planet.

Astronomers may eventually use to study the interior, including the extent, features and compositions by layers. Using the mounted on the ATLAST, the atmosphere can be studied.

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

 * Devana (61 Virginis b, P378)
 * Tamar (61 Virginis c, P379)