30 Vulpeculae is a binary star system in the northern constellation of Vulpecula, located mid-way between Epsilon Cygni and a diamond-shaped asterism in Delphinus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.91.[2] The system is located approximately 350 light years away from the Sun based on parallax,[1] and is drifting further away with a mean radial velocity of +30 km/s.[4] The system has a relatively high proper motion, traversing the celestial sphere at the rate of 0.186 arc seconds per annum.[11]
The variable radial velocity of this system was announced in 1922 by W. W. Campbell. It is a single-lined spectroscopic binary system with an orbital period of 6.86 years and an eccentricity of 0.38. The a sin i value is 149 ± 4 Gm (1.00 ± 0.03 AU), where a is the semimajor axis and i is the orbital inclination. This provides a lower bound on the true semimajor axis.[6]
The visible component is an aging giant star with a stellar classification of K1 III[3] and an estimated age of 4.20[7] billion years old. Having exhausted the supply of hydrogen at its core, the star has expanded to 22[1] times the Sun's radius. It has 1.55[7] times the mass of the Sun and is radiating 173[1] times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,498 K.[1]
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