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Barnard's Star system

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Barnard's Star system is a small, conjectured planetary system around Barnard's Star. It is located just 5.95 light-years away in the constellation Ophiuchus in the caelregio Tarandus. Barnard's Star is the second nearest star system after Alpha Centauri.

Star Edit

Barnard's Star is a red dwarf star of spectral type M4Ve. The star's magnitude seen from Earth is 9.54, which can only be visible by using at least a small telescope. The bolometric luminosity is 1300 that of the Sun and visual luminosity 12500 of the Sun. Due to its very low luminosity, the center of habitable zone would have to be around 0.06 AU from the star and such a small separation can cause planets occupying this region to be tidally locked, meaning one hemisphere always face the star while the other never faces it.

The mass is 17 of the Sun or 150 times more massive than Jupiter. It is 80% smaller than our Sun. The star is more than twice as old as our Sun at around 10 billion years old. Due to its old age, it takes 130 days to rotate once, over five times longer than 25 days for our Sun.

This red dwarf is also metal-deficient, 25% that of the Sun's. This means it is less likely to form planets, especially gas giants and rocky super-Earths.

Barnard's Star has the highest proper motion of any star, moving at 10.3"/yr. The star would take just 150 years to transverse the diameter of the full moon. The star is approaching the Sun at 90 km/s and will make its closest approach at 3.75 light-years around 9800 AD.

Planetary system Edit

Class Semimajor axis (AU) Eccentricity Orbital period (d) Radius (R) Mass (M) Density (g/cm3) Gravity (g) Rotation period (d) Surface temp (K)
b LEcB 0.0082 0.00015 0.68 0.3173 0.0919 15.862 0.913 0.6844 854
c CtEcB 0.0237 0.00616 3.35 0.4716 0.1377 7.239 0.619 3.3472 460
d DCtEcV 0.1042 0.00428 30.82 0.3759 0.0781 8.114 0.553 30.8193 192

Barnard's Star contains three small planets orbiting within just 0.105 AU. The orbital periods range from just 16 hours to a month and all three have orbital eccentricities under 0.01. Planets have masses ranging from 0.078 to 0.138 M and have sizes from one-third to half the size of Earth. By the way, all three planets are denser than Earth's, the densest planet in our solar system.

Barnard's Star b Edit

Barnard's Star b is the innermost planet of the Barnard's Star system. It orbits extremely close to the dim star at just 1.23 Gm, 120 times closer to the star than Earth is to the Sun. It takes just two-thirds of a day to orbit once around the star, which the year on this planet is very brief. Year on Earth in hours is 8766, but on this planet, just 1612. Since orbital period lasts less than an Earth day, this planet rotates once quicker than Earth's despite it is tidally-locked. The orbit of this planet is almost a perfect circle with an eccentricity of just 0.00015, only 1% that of Earth's eccentricity. Planets in smaller orbits with same eccentricities would reduce distance differences. As in the case of this planet, 370 megameters. This miniscule eccentricity is caused by tidal circulation due to nearby star's gravity. Due to gravitational pull of two planets beyond this orbit, its eccentricity oscillates at a 6000-year cycle from as low as 0.000011 to as high 0.008. The planet's eccentricity is current increasing until it reaches its maximum around 5400 AD. It reached the minima around 800 BC. The current eccentricity is only higher than the minima, but during the 35th century, eccentricity will start a much more rapid rise.

Barnard's Star b has a mass 111 that of Earth's and slightly less massive than Mars'. It is 13 the size of Earth, producing the density approaching 16 g/cm3. This super-high density would suggest that this planet was the core of a giant planet about the size of Neptune. Periods of intense stellar winds during flaring era must have blew away the gaseous envelope and evaporated all the remaining volatiles. The surface gravity is 1011 of that of Earth's, twice as strong as usual for this mass.

This planet is active despite it's age and small size, due to gravitational tug of the star as planet orbits, same way as Jupiter exerts on Io causing geological activity. The surface temperature is hot, at 1078°F, but much less hotter than this semimajor axis around solar-type stars. It is classified as a lava planet. It has a thin, metallic atmosphere made mainly of sodium and potassium vapors as well as mercury and zinc vapors.

Barnard's Star c Edit

Barnard's Star c is a planet orbiting in a 5:1 resonance with b with an orbital period of 313 days. The planet's eccentricity is similar to Venus' at 0.006. Like the inner planet, this one is tidally locked to the star, meaning that one side always faces the star. It is slightly more massive than Mars and is just under half the size of Earth. It's density is 7.24 g/cm3, less than half the density of the inner planet. It is a crater planet with the surface temperature of 368°F and has only a tenuous atmosphere.

Barnard's Star d Edit

Barnard's Star d is the outermost of the three planets orbiting around Barnard's Star. It takes 30.8 days to orbit the star at an average distance of 0.1042 AU, which is one-tenth the Earth–Sun distance. Its eccentricity is 0.004, varying from 0.1037 to 0.1046 AU. It masses 0.078 Earth masses and sizing 0.376 Earth radii, producing a density of 8.1 g/cm3 and surface gravity of 0.55 g. The density suggests that this planet contains greater portion of iron and heavy metals like gold than Earth contains. Despite the planet orbits 10 times closer to its sun than Earth is, the planet's surface is cold with the surface temperature of −115°F. Despite this temperature, there is little ice on the surface as it is mainly deserted and cratered. It has a thin atmosphere made of 91% CO2.

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