Tamar

Tamar (61 Virginis c, P379) 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.

Tamar is in the middle of the known three-planet 61 Virginis system. Tamar is an with all the surface covered in oceans of water hundreds of miles deep. It is a midplanet with 22 times the mass of Earth.

is named after the  who controlled the weather patterns.

Discovery and chronology
Tamar 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 Tamar.

Tamar is the 372$⊕$ exoplanet discovered overall, 346$⊕$ since 2000, and 74$⊕$ in 2009. Tamar is the 17$⊕$ exoplanet discovered in the constellation Virgo (7$⊕$ in 2009) and 40$⊕$ exoplanet discovered in the caelregio Noctua (12$⊕$ in 2009). Since Tamar is the second planet discovered in the 61 Virginis system, the planet receives the designations 61 Virginis c (a is not used because the parent star uses this letter to reduce confusion) and 61 Virginis P2. 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
Tamar orbits the star at an of 0.2178  (1 AU is the average distance between the Earth and the Sun) or 32.59  (million ), nearly two times closer to the star than  is to the Sun. Tamar has a semi-circular orbit with an eccentricity of 0.1379. Tamar's orbit varies from 0.1878 AU (28.09 Gm) to 0.2479 AU (37.08 Gm). The planet takes just 38 days, 5.4 weeks or 3.3 s to make one complete trip around the star at an of 62.3 km/s, 38.7 mi/s, or 13.1 AU/yr. Tamar is in a 4:13 with the outermost known planet Tuonetar and 9:1 resonance with the innermost planet Devana.

Parent star observation and irradiance
Viewed from Tamar, the parent star would have a −29.81 compared to −26.74 for the magnitude of the Sun seen from Earth. Observed from Tamar, 61 Virginis would appear to be 17 times brighter than the Sun seen from Earth. Viewed from Tamar, the parent star would have an of 2.3° on average, which is 4.6 times the angular diameter of the  we sometimes see at night.

Tamar receives nearly 15.8 times more energy from the star than Earth receives from the Sun, 21,605 W/m² vs. 1,368 W/m².

Rotation
Tamar is in a 9:8 ratio, meaning the planet rotates nine times every time when the planet orbits the star eight times. Since the planet takes 38.021 days to orbit the star, then it would take 33.797 days to rotate once on its axis. So the year on Tamar lasts exactly 1.125 days compared to 366 Earth days in an Earth year. The planet tilts 6.2° to the plane of its orbit, which is a quarter of the Earth's tilt of 23.4°. The planet's points to the constellation  (in Testudo), while the  points to the constellation  (in Araneus).

Mass and size
Tamar is an intermediate-mass planet, massing 18.75 es, classifying it as midplanet in the planetary mass classification scheme. Tamar is 9% more massive than and 29% more massive than. The size of this planet is 3.46, corresponding to the density of 2.50 g/cm³, meaning that it is less than half the density of Earth.

Gravitational influence
The gravitational force of Tamar is 57% stronger than Earth's. So if you weigh 150 on Earth, you would weigh 235 pounds on Tamar, which is about the weight of an average professional football player on Earth!

Tamar has the radius of just 35.79 planetary radii. The satellite's orbit within the hill sphere is stable while the orbit outside of hill sphere is unstable. The of Tamar is 1.19 planetary radii. If a 3 g/cm³ satellite orbits within a 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. Tamar's, analogous to the Earth's , is located at a distance of 52.17 planetary radii. Stationary orbit is an orbit where its orbital period is synchronous with the planet's rotation period. Since the planet takes 30.417 days to rotate once on its axis, then a moon in stationary orbit would also take 30.417 days to orbit the planet, that's very similar to the orbital period of the in orbit 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
With the density of 2.51 g/cm³, Tamar has the layers of rock, diamond and exotic forms of water. With the of 487 K (214°C, 418°F), it is too hot to have normal liquid water on its surface but cool enough to have exotic form of liquid water under pressure. All of the planet's surface is covered by liquid water with an estimated depth of 873 kilometers or 543 miles. The upper mantle composes of the exotic form of water called or "hot ice" with the radius of 5398 km or 3354 mi and a pressure 0.36. The lower mantle composes of with the radius of 6204 km or 3855 mi and a pressure 0.89 GPa. At the center of this planet is a - core with a temperature of 7100 K (6800°C, 12300°F) and a pressure 1.57 GPa. The core has a radius of 9563 km or 5942 mi.

Diamond abundance
The diamond just mentioned are found in the lower mantle underneath the layer of "hot ice" in the upper mantle. Tamar has an estimated 260 million times more diamond than Earth has! There would be enough diamond to build a city planet the size of this planet with every building and appliances made of diamond!

Atmosphere
Tamar has a thin atmosphere three times thicker than and 55. times thinner than. The atmosphere is made of 61%, 18% , 14% , 4% , 2% , and 1%. Clouds are virtually nonexistent.

Magnetic field
Tamar has an extremely weak, about six millionths of a , which is 50,000 times weaker than. A possible reason for its weakness is because the planet rotates so slowly caused by the tidal forces of the nearby star.

Moons and rings
Because Tamar orbits so close to its star and the small, Tamar has no moons nor rings. But if moons actually exist, they have to orbit within 2 LD from the planet or they will flung off into space.

Future studies
It is speculated that Tamar will not transit since I speculated that the is 56.1°. Studying Tamar 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 Tamar 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, a tenuous atmosphere and the surface can be studied.

In orbit around the planet, moons and rings can be detected (if they exist) using the transit across the planet, detecting the wobble of the planet, or even direct imaging.

Related links

 * Devana (61 Virginis b, P378)
 * Tuonetar (61 Virginis d, P380)