47 Ursae Majoris
1.5 L ☉
47 Ursae Majoris ( abbreviated as 47 UMa ) is a main-sequence star of spectral type G1, similar to the sun, which is located about 46 light-years from the Sun in the constellation Ursa Major ( Great Bear ). To Ursae Majoris 47 two exoplanets are known, the existence of another is considered very likely.
Distance and visibility
47 Ursae Majoris is located relatively close to our solar system. Because of the astrometric parallax by the Hipparcos satellite, which resulted in a parallax of about 71 milliarcseconds, the star is located at a distance of about 14.1 parsecs. Since the star has an apparent magnitude of 5.1, it is possible under good conditions to spot this star with the naked eye in the night sky.
Stellar properties
The mass of 47 UMa is about as large as that of the sun, but the star has about 10% more iron than the Sun. The spectral type of 47 UMa is G1V, which is why it is slightly warmer than the sun with just under 5855 K surface temperature. The absolute magnitude of 4.29 magnitudes. This means that its luminance is about 60 % greater than that of the sun. As the sun is 47 UMa on the main sequence in the HR diagram. It converts at its core by nuclear fusion of hydrogen to helium so to. Due to the Chromosphärenaktivität is estimated that the star is nearly 6 billion years old, although evolutionary models give an age of 8.7 billion years.
Planetary system
1996 was found by Geoffrey Marcy and R. Paul Butler that 47 UMa is orbited by a planet. This discovery was based on measurements of the radial velocity of the star, which is easily affected by the orbiting planets. These measurements were measured using the Doppler shift in the spectrum of the star. This planet, called 47 Ursae Majoris b, has a relatively low eccentricity orbit, a mass equal to about 2.63 times the mass of Jupiter and an orbital period of about 1089 days. Would this planet are in the Solar solar system, he would reside between Mars and Jupiter. 2001 yielded preliminary measurements that the orbit by about 63.1 ° inclined to the plane of the sky. If this measurement is confirmed, it follows that the mass of 47 UMa b of 2.9 times the mass of Jupiter corresponds.
A second planet, called 47 Ursae Majoris c, was discovered in 2002 by Debra Fischer, Geoffrey Marcy and R. Paul Butler. Once again, the same radial velocity method as has been used the first planet. This second planet needs about 2594 days for a round. The eccentricity is not yet precisely known, although it is believed that it is also quite low.
The two planets are in a configuration similar to Jupiter and Saturn in the solar system. The ratio of the orbital periods in both systems is approximately 5:2, and the mass ratio is also identical. The smaller size and the larger masses imply also that take place between two planets stronger mutual gravitational influences, as between Saturn and Jupiter. It follows that the real masses of planets can not be much larger, as determined by the radial velocity measurements minimum mass.
2010 was another planet, 47 Ursae Majoris d, discovered, much further away from the central star is located (about 11.6 AU). For a round this companion takes about 38 years, its minimum mass corresponds to 1.6 times the mass of Jupiter.
Simulations show that in the inner region of the habitable zone ( the zone around a star where life could exist ) could exist on a stable orbit of 47 Ursae Majoris, a terrestrial planet.
Swell
- Individual star fifth size and darker
- Big Dipper
- Star with exoplanet