 | |
| Discovery | |
|---|---|
| Date | December 14, 2009 |
| Discoverers | Vogt et al. |
| Detection method | Radial velocity |
| Site | Keck Observatory, Anglo-Australian Observatory |
| Name & designations | |
| Pronunciation | /'de•va•na/ |
| Adjective | Devanian |
| Planet numbers | P378, 61 Virginis P1, Virgo P16, Noctua P39, 2009 P72, 2009 Vir-6, 2009 Noc-11 |
| Star designations | 61 Virginis b, 134 Noctae b, BF 4505 b, PH 309 b, P12 Virginis b, P29 Noctae b, HD 115617 b, HIP 64924 b, HR 5019 b, Gliese 506 b, SAO 157844 b |
| Location | |
| System | 61 Virginis |
| Constellation | Virgo |
| Caelregio | Noctua |
| Right ascension | 13h 18m 24.31s (199.601 31°) |
| Declination | −18° 18' 40.3" (−18.311 20°) |
| Distance | 8.555 pc (27.903 ly) |
| Orbital characteristics | |
| Semimajor axis | 0.050 267 AU (7.519 9 Gm) |
| Periastron | 0.044 297 AU (6.626 7 Gm) |
| Apastron | 0.056 238 AU (8.413 0 Gm) |
| Eccentricity | 0.118 771 4 |
| Orbital circumference | 0.315 02 AU (47.127 Gm) |
| Orbital area | 0.007 882 0 AU² (176.40 Gm²) |
| Orbital period | 4.214 994 d (0.011 540 02 yr) |
| Avg. velocity | 129.846 km/s (27.298 AU/yr) |
| Max. velocity | 137.340 km/s (28.874 AU/yr) |
| Min. velocity | 121.891 km/s (25.626 AU/yr) |
| Direction of orbit relative to star's rotation |
Prograde |
| Inclination | 74.733° to ecliptic −0.998° to star's equator −2.493° to invariable plane |
| Argument of periastron | 105.481° |
| Longitude of ascending node | 255.863° |
| Longitude of periastron | 1.344° |
| Angular separation | 5.876 mas |
| Observing the parent star | |
| Mean angular star size | 10.064 77° (603.886') |
| Max. angular star size | 11.421 29° (685.277') |
| Min. angular star size | 8.996 27° (539.776') |
| Mean star magnitude | −32.991 |
| Max. star magnitude | −33.265 |
| Min. star magnitude | −32.747 |
| Classification | |
| Bulk characteristics | |
| Mean radius | 2.117 9 R⊕ (13.493 Mm) |
| Equatorial radius | 2.117 7 E⊕ (13.507 Mm) |
| Polar radius | 2.118 2 P⊕ (13.465 Mm) |
| Mean circumference | 84.779 Mm |
| Equatorial circumference | 84.867 Mm |
| Polar circumference | 84.603 Mm |
| Surface area | 4.485 4 S⊕ (2 287.8 Mm²) |
| Volume | 9.499 4 V⊕ (10 290 Mm³) |
| Flattening | 0.003 11 (1:321.6) |
| Angular diameter | 21.085 μas |
| Mass | 5.264 1 M⊕ |
| Reciprocal mass relative to star |
59 060 |
| Density | 3.056 g/cm³ |
| Gravitational influence | |
| Surface gravity | 1.174 g (11.51m/s²) |
| Weight on Devana (150 lb on Earth) |
176 lb |
| Standard gravitational parameter | 2.098 × 106 km³/s² |
| Escape velocity | 17.64 km/s |
| Hill radius | 0.317 LD (0.121 8 Gm) |
| Roche limit (3 g/cm3 satellite) |
0.044 50 LD (17.106 Mm) |
| Stationary orbit | 0.464 20 LD (178.437 Mm) |
| Stationary velocity | 3.312 km/s (0.744 LD/d) |
| Rotation characteristics | |
| Rotation period | 101.159 9 h (4.214 994 d) |
| Rotation velocity | 839 kph (3.56°/h) |
| Direction of rotation relative to orbit |
Prograde |
| Axial tilt | 12.629° |
| Longitude of vernal equinox | 177.570° |
| North pole right ascension | 17h 08m 53s (257.222°) |
| North pole declination | +23° 18' 00" (+23.300°) |
| North polar constellation | Hercules |
| North polar caelregio | Tarandus |
| South pole right ascension | 05h 08m 53s (77.222°) |
| South pole declination | −23° 18' 00" (−23.300°) |
| South polar constellation | Lepus |
| South polar caelregio | Araneus |
| Thermal characteristics | |
| Surface temperature | 1129 K (856°C, 1572°F, 2032°R) |
| Mean irradiance | 405 693 W/m² (296.646 I⊕) |
| Irradiance at periastron | 522 420 W/m² (381.998 I⊕) |
| Irradiance at apastron | 324 126 W/m² (237.004 I⊕) |
| Albedo | 0.253 (bond), 0.219 (geom.) |
| Atmosphere | |
| Scale height | 47.83 km |
| Volume | 26.74 ae (111.98 Mm³) |
| Total mass | 1.416 atmu (7.28 Eg) |
| Surface pressure | 0.003 75 atm (0.380 kPa, 0.055 1 psi) |
| Surface density | 0.065 g/m³ |
| Molar mass | 43.53 g/mol |
| Composition | 96.796% carbon dioxide (CO2) 2.857% nitrogen (N2) 0.279% carbon monoxide (CO) 233 ppm xenon (Xe) 199 ppm krypton (Kr) 76.6 ppm oxygen (O2) 32.7 ppm water (H2O) 8.63 ppm argon (Ar) |
| Magnetosphere | |
| Dipole strength | 3.01 nT (30.1 mG) |
| Magnetic moment | 1.36 × 1015 T•m³ |
| Dipole tilt | 1.01° |
| Satellite system | |
| Number of moons | 0 |
| Number of rings | 0 |
Devana (61 Virginis b, P378) is a planet which orbits the yellow G-type main sequence star 61 Virginis, which is similar to our Sun. It is approximately 28 light-years or 9 parsecs from Earth towards the constellation Virgo in the caelregio Noctua.
Devana is the innermost of the three known planets in 61 Virginis system. Devana is super-Earth. The planet takes just four days to orbit the star and it is tidally locked.
Devana is named after the Slavic equivalent of Roman goddess Diana. Diana was the goddess of hunt and moon.
Discovery and chronology[]
Devana was discovered on December 14, 2009 by a team of astronomers led by Steven Vogt. The team used the HIRES spectrometer mounted on the Keck Telescope in Hawaii and the Anglo-Austrialian Telescope in New South Wales, Australia and found that the star 61 Virginis has three periodic variations in the spectrum. This implies evidence for a three-planet system around 61 Virginis, including Devana.
Devana is the 371st exoplanet discovered overall, 345th since 2000, and 73rd in 2009. Devana is the 16th exoplanet discovered in the constellation Virgo (6th in 2009) and 39th exoplanet discovered in the caelregio Noctua (11th in 2009). Since Devana is the first planet discovered in the 61 Virginis system, the planet receives the designations 61 Virginis b (a is not used because the parent star uses this letter to reduce confusion) and 61 Virginis P1. 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[]
Orbit[]
Devana orbits the star at an average distance of 0.0503 AU (1 AU is the average distance between the Earth and the Sun) or 7.52 Gm (million km), which is eight times closer to the star than Mercury is to the Sun. Devana has a semi-circular orbit with an eccentricity of 0.1188. Devana's orbit varies from 0.0443 AU (6.63 Gm) to 0.0562 AU (8.41 Gm). The planet takes just 4.215 days, 101.2 hours or 364.2 kiloseconds to make one complete trip around the star at an average velocity of 129.8 km/s, 80.7 mi/s, or 27.3 AU/yr. Devana is in a 1:9 resonance with the middle known planet Tamar and 1:29 resonance with the outermost known planet Tuonetar.
Parent star observation and irradiance[]
Viewed from Devana, the parent star would have a magnitude −32.99 compared to −26.74 for the magnitude of the Sun seen from Earth. Observed from Devana, 61 Virginis would appear to be 316 times brighter than the Sun seen from Earth. Viewed from Devana, the parent star would have an angular diameter of 10.1° on average, which is 20 times the angular diameter of the full moon we sometimes see at night.
Every square meter of the surface, Devana receives 405.7 kilowatts of stellar energy compared to just 1.4 kilowatts of solar energy for Earth. This means that Devana receives nearly 300 times more energy per square meter from 61 Virginis than Earth receives from the Sun. That's because the planet is orbiting 1⁄20 of the Earth-Sun distance from that energy source, and irradiance is inversely proportional to the square of the planet's distance from the star. If we square that reciprocal, we get 400, but the planet receives only 300 said times, meaning that the parent star would have to be 3⁄4 as luminous as our Sun to account for that value. In reality, the parent star is almost exactly 3⁄4 solar luminosity!
Rotation[]
Devana is tidally locked, meaning the planet rotates at a same rate as its revolution around the star. Since the planet takes 4.215 days to orbit the star, then it would also take 4.215 days to rotate once on its axis. So the year on Devana lasts exactly one day compared to 366 Earth days in an Earth year. The planet tilts 12.6° to the plane of its orbit, which is half the Earth's tilt of 23.4°. The planet's north pole points to the constellation Hercules (in Tarandus), while the south pole points to the constellation Lepus (in Araneus).
Structure and composition[]
Mass and size[]
Devana is a low-mass planet, massing 5.26 Earth masses, classifying it as super-Earth in the planetary mass classification scheme. This planet is more than twice as large as Earth at 2.12 Earth radii. Devana has a density of 3.06 g/cm³, meaning that it is less dense than Earth, meaning it has greater ratio of light-weight materials relative to heavy-weight materials than Earth.
Gravitational influence[]
The gravitational force of Devana is 17% stronger than Earth's. So if you weigh 150 pounds on Earth, you would weigh 176 pounds on Devana.
Since Devana orbits so close to the star, the hill sphere would be very small, at a radius of just over nine planetary radii. Like the hill sphere, the roche limit of this planet doesn't extend far, at a distance of just 1.27 planetary radii. The stationary orbit, where the satellite takes the same time to orbit the planet as the rotation of the planet, analogous to the Earth's geostationary orbit, is beyond the hill sphere at 13.21 planetary radii. If a satellite orbits at that distance, the orbit would be unstable which causes satellite to orbit in a parabolic trajectory. After some time, a satellite would eventually escape the planet's orbit into the orbit around the star. So Devana has no stable stationary orbit. If the orbit is stable, the orbital velocity at stationary orbit would be 3.31 km/s or 2.06 mi/s.
Interior[]
Like many terrestrial planets, Devana has the crust, mantle, and core. The crust is made out of carbon-rich rocks while mantle is made of molten rocks or magma. Its relatively low density for a rocky planet suggests that its core is small and made of carbon in the form of diamond under the pressure of 3.28 GPa heated to the temperature of 8500 K (8200°C, 14800°F). The size of the core is just 1⁄7 the size of the planet. Because the planet is carbon-rich, Devana is speculatively a carbon planet.
Surface[]
Since Devana is a terrestrial planet, it has a solid surface like Solar System planets Mercury, Venus, Earth, and Mars. On its surface, there are terrains like hills, mountains, canyons, ridges, and plateaus. However, much of the surface are covered in molten lava because the planet is volcanically active due to influences of its nearby star, thus the intense heat would keep the surface molten for a long time. Because of this, craters are rare on Devana.
Volcanism[]
Since Devana is almost six times more massive than Earth and orbiting very close to the star, the tidal forces of the star would cause planet to stretch and squeeze constantly, causing friction, producing heat that would go on to melt rocks into magma. The magma melted by tidal forces causes intense volcanism on Devana with many volcanoes erupting all the time all over the surface. The tidal forces of the star exerted on Devana causing intense volcanism is analogous to the tidal forces of Jupiter exerted on its moon Io, which causes Io to be the most volcanically-active world in our solar system. So Devana would be the massive version of Io, known as "Super-Io." Perhaps, Devana would be even more volcanically-active world than Io since the tidal forces of the star is lot stronger than Jupiter. With the surface temperature of 1129 K (856°C, 1572°F), which is hotter than Venus, it is hot enough for lava to cover much of the surface for long periods of time.
The only known example of a Super-Io is Icarus (COROT-7b, P311), discovered in early 2009 by transit, which spectroscopically revealed it to be a volcanically-active world.
Atmosphere[]
Since this is a low-mass planet orbiting very close to the star, Devana has very little atmosphere because the atmosphere is constantly stripping away by the radiation from the star. Devana has the atmospheric pressure of only 380 pascals, which is 266.6 times thinner than Earth's and 1.6 times thinner than Mars'.
Like Venus and Mars, Devana's atmosphere is made mostly of carbon dioxide (CO2), making up merely 96.8% of the atmosphere. All of the CO2 are given off by active volcanoes. Most of the remaining atmosphere is made of nitrogen (N2), making up 89% of the remaining atmosphere. This atmosphere does contain small amounts of life-giving oxygen (O2) at 77 ppm and water vapor (H2O) at 33 ppm.
Even though volcanoes are constantly releasing sulfur dioxide (SO2) into the atmosphere, this gas would not concentrate since SO2 would immediately decomposed by intense radiation from the nearby star, producing sulfur that fall to the surface and oxygen where it remains in the atmosphere.
Magnetic field[]
Devana has an extremely weak magnetic field, about 30 millionths of a gauss, which is 10,000 times weaker than Earth's.
Moons and rings[]
Because Devana orbits so close to its star and the small hill sphere, Devana has no moons nor rings. But if moons actually exist, they have to orbit within 0.3 LD from the planet or they will flung off into space.
Future studies[]
It is speculated that Devana will not transit since I speculated that the inclination is 58.7°. Studying Devana using the direct imaging 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 astrometry using Gaia, James Webb Space Telescope (JWST), or Space Interoferometry Mission (SIM). The astrometry can constrain the inclination and thus calculate the exact mass.
Maybe ATLAST can reliably be used to directly image planets down to 0.01 AU from the sun-like stars. The direct imaging can see what Devana may really look like. The direct imaging can constrain the planet's size like the transit method. The derivative parameters, including density and surface gravity, can then be calculated using the constrained radius and true mass calculated using 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 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.