12 Ophiuchi system is the conjectured planetary system of 12 Ophiuchi, located 31.8 light-years away in the constellation Ophiuchus in the caelregio Tarandus. This planetary system is similar to the configuration of our solar system. This system has nine planets, with five rocky inner planets and four gaseous outer planets.
Star[]
12 Ophiuchi is an orange star of spectral type K2V, meaning it is smaller and cooler than our Sun. The star's surface temperature is 5311 K compared to 5778 K for the Sun. It is also a variable star of BY Draconis type, giving its variable designation V2133 Ophiuchi. It is much younger than our Sun, 1.9 billion years old compared to 4.6 billion for the Sun. 12 Oph has about the same amount of metals as there are on the Sun based on the abundance of iron. Unlike the Sun, 12 Oph has not one, but two starspot cycles at once, one lasting 4.0 years while other lasts 17.4 years. For our Sun, in comparison, the only sunspot cycle lasts about 11 years.
Planetary system[]
| Class | Semimajor axis (AU) | Eccentricity | Orbital period (yr) | Radius | Mass | Density (g/cm3) | Gravity (g) | Rotation period (d) | Surface temp (K) | |
|---|---|---|---|---|---|---|---|---|---|---|
| b | CtEcV | 0.1473 | 0.00214 | 0.0622 | 0.4220 R⊕ | 0.0454 M⊕ | 3.329 | 0.255 | 22.7224 | 545 |
| c | CtEcV | 0.2331 | 0.04823 | 0.1239 | 0.3988 R⊕ | 0.0313 M⊕ | 2.723 | 0.197 | 37.6977 | 433 |
| d | BCtEcH | 0.3652 | 0.00172 | 0.2429 | 0.6112 R⊕ | 0.1823 M⊕ | 4.402 | 0.488 | 64.5247 | 346 |
| e | SiOEbC | 0.6766 | 0.00812 | 0.6125 | 1.0523 R⊕ | 0.9930 M⊕ | 4.699 | 0.897 | 1.6386 | 279 |
| f | DEaG | 1.2080 | 0.02466 | 1.4613 | 1.9443 R⊕ | 4.3523 M⊕ | 3.265 | 1.151 | 2.4587 | 325 |
| g | GJbA | 4.3681 | 0.08914 | 10.0481 | 1.0228 RJ | 0.5523 MJ | 0.686 | 1.396 | 0.6582 | 138 |
| h | GJaJ | 6.9376 | 0.03328 | 20.1124 | 1.0923 RJ | 2.7739 MJ | 2.821 | 6.133 | 0.4102 | 247 |
| i | GJaJ | 9.7358 | 0.02177 | 33.4351 | 1.0337 RJ | 3.1171 MJ | 3.739 | 7.694 | 0.3273 | 277 |
| j | GJbU | 12.9707 | 0.01475 | 51.4151 | 1.0190 RJ | 1.2072 MJ | 1.513 | 3.068 | 0.4692 | 142 |
There are nine planets orbiting around 12 Ophiuchi, one more than planets orbiting around our Sun, but was the same prior to Pluto's demotion in 2006. Like our solar system, the planetary system is split into inner and outer, with all inner planets are rocky and all outer planets are gaseous. There is an asteroid belt separating between inner system and outer system at distance ranging from 2.0 AU to 3.1 AU. The largest asteroid measures 573 miles across, the same size as Ceres.
Another remarkable property of this planetary system is that every planet orbit in circular paths with eccentricity no more than 0.1, eight with e < 0.05, and three with e < 0.01. Amongst the planets, the average eccentricity of the 12 Ophiuchi system is 0.0271, compared to 0.0603 for our solar system. The orbital periods range from about three weeks to about half a century, and orbital distances range from about 1⁄7 AU to 13 AU.
This system features three planets bigger than Jupiter and two rocky planets bigger than Earth. There are no planet with density at least 5 g/cm3; for comparison, there are three such planets in our solar system, including Earth. According to the law of heat-distance relation, the hottest planet lies closest to its sun while the coldest lies farthest away, although it doesn't apply to every planet due to their planetary contributions of heat, i.e. greenhouse effects for terrestrial planets and internal heating for giant planets.
12 Ophiuchi b[]
12 Ophiuchi b is the innermost planet of the 12 Ophiuchi system. It orbits the star at a distance of 0.15 AU or about 40% the distance of Mercury from the Sun or about the same distance from the Sun where the retracted planet Vulcan was. Its year on the planet is just over three weeks with orbit near-perfect circle.
It is the low-mass sub-Earth massing about 4⁄5 of that of Mercury and is 42% the size of Earth. This planet, due to its small size, has no significant atmosphere and the surface is pockmarked with craters. The planet's density is 3.33 g/cm3, suggesting that this planet has a small core, made of iron and silicates. Its crust is thick, at about 60 km thick, made mainly of granite, quartz, and other material. The surface temperature is 522°F, hot enough to melt tin.
12 Ophiuchi c[]
12 Ophiuchi c orbits in a 2:1 resonance with b, because c's orbital period is twice that of b's. Like b, it is a low-mass sub-Earth, but smaller and less massive, making this the smallest planet in the planetary system. It is about the size of Mercury but is only over half its mass, meaning that this rocky planet is light-weight with density of just 2.73 g/cm3, just half the density of Earth., meaning this planet must be made mainly of light-weight materials. Aluminum is the most abundant metal in the crust, found in minerals like bauxite. Beneath the crust is sulfur-rich upper mantle and in the lower mantle, with abundant amounts of diamond. Its core is very small, made of iron and nickel. The surface is cratered like b.
12 Oph c has three tiny moons, all less than 30 miles across. The largest moon has a diameter of 28 miles and takes 3 days to orbit the planet.
12 Ophiuchi d[]
12 Ophiuchi d orbits in a 4:2:1 Laplacian resonance with two interior planets. 12 Oph d has the same orbital period as Mercury's and its eccentricity is almost zero. It is a slightly bigger than Mars and 70% more massive, producing the density 4.40 g/cm3. 12 Oph d is a barren planet pockmarked with craters, and it appears brownish from space. It has a thin atmosphere, but about 8 times thicker than Mars'.
12 Ophiuchi e[]
12 Ophiuchi e orbits at 2⁄3 the Earth–Sun distance and orbital period is about the same as Venus', placing this planet at the center of its habitable zone. It mass is almost identical to Earth's but is slightly bigger than Earth, meaning it is less dense at 85% Earth. There is water on the planet's surface, covering about 68% and has eight continents. There are primitive, single-celled lifeforms living in the oceans as planet is not old enough to develop into more complex lifeforms yet. The surface temperature is 42°F, which is little colder than Earth's.
The planet rotates in the opposite direction to its orbit, called its retrograde rotation. Its period is 391⁄3 hours.
12 Ophiuchi f[]
12 Ophiuchi f orbits over 20% further from the star than Earth is from the Sun. The planet takes 534 days or 1.46 Earth years to revolve around the star. 12 Oph f is twice as big and 41⁄3 times more massive than Earth, classifying this as super-Earth. The surface of this planet is mostly occupied by deserts, hence its classification as desert planet, and surface temperature of 126°F, about the same as hot Saharan day. The planet takes 59 hours to rotate once on its axis.
12 Ophiuchi g[]
12 Ophiuchi g is a gas giant orbiting at 4.37 AU from the star and takes 10 years to revolve. The orbital distance varies due to its elliptical (not circular) orbit. The planet can be as close to the star as 3.98 AU or as far as 4.76 AU, corresponding to its eccentricity of 0.089, the highest of any planet of 12 Oph system. The planet weighs 55% the mass of Jupiter and 102% the size. The planet takes 15.8 hours to rotate once on its axis tilting at 15.2° relative to its orbital plane.
Clouds made of water are dominant on 12 Oph g because temperature is within the range where water clouds are most stable. The planet would appear gray and faintly banded.
Like many gas giants, 12 Oph g has numerous moons with the largest about the size of the largest moon in our solar system.
12 Ophiuchi h[]
12 Ophiuchi h is a superjovian planet which orbits at a semimajor axis of 6.94 AU at an eccentricity of 0.033. The planet takes 9.4 hours to rotate once on its axis but it takes 20 years or 18734 planetary stellar days, placing this planet in a 2:1 resonance with 12 Oph g. The planet weighs 2.77 Jupiter masses and is the biggest planet of this planetary system, slightly bigger than Jupiter. The planet's surface gravity is more than six times greater than Earth's, meaning that if you weigh 150 pounds on Earth, you would weigh 920 pounds on 12 Oph h.
12 Oph h contains several large moons, there are nine larger than 1000 miles across, the largest is about the size of Mars. Two moons have considerable atmospheres.
12 Ophiuchi i[]
12 Ophiuchi i is the most massive planet in the 12 Oph planetary system, but is the second largest at 31⁄3% bigger than Jupiter. It masses 3.12 Jupiter masses and the gravitational strength is nearly 7.7 times stronger than Earth's and nearly tripling the Jupiter's strength. A person of average weight (150 pounds on Earth) would weigh about 1154 pounds on 12 Oph i. Because of its internal heating due to its high mass, surface temperature of this planet is warmer than giant planets closer in despite it orbits farther from the warmth of its sun. This planet emits four times more heat than it receives from the parent star. The planet takes nearly eight hours to rotate once on its axis.
12 Oph i takes nearly 331⁄2 years to revolve around 12 Ophiuchi at an average distance similar to Saturn (9.74 AU) with eccentricity similar to Earth's (0.022).
12 Ophiuchi j[]
12 Ophiuchi j is the outermost planet of the 12 Ophiuchi system, orbiting at a semimajor axis of 12.97 AU, taking 512⁄5 years to revolve once around the star. 12 Oph j is in a 3:2 resonance with i and 5:2 resonance with h. This planet has about the same size as (2% bigger than) Jupiter, but with mass not so similar, 21% greater, and 14% denser and 16% stronger gravitational pull than Jupiter. The planet takes 111⁄4 hours to rotate once on its axis, slightly longer than rotation periods of Jupiter and Saturn. 12 Oph j features a considerable ring system but a bit less broad than Saturn's. It is orbited by many moons, most are icy.
The atmosphere of 12 Oph j is composed mainly of hydrogen and helium with trace amounts of ammonia and methane. The planet appears bluish white from space.