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47 Ursae Majoris b

2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)

   CAPTION: 47 Ursae Majoris b

     Extrasolar planet    Lists of extrasolar planets
                      Parent star
   Star                   47 Ursae Majoris
   Constellation          Ursa Major
   Right ascension    (α) 10^h 59^m 28.0^s
   Declination        (δ) +40° 25′ 49″
   Spectral type          G1V
                   Orbital elements
   Semimajor axis     (a) 2.13 ± 0.12 AU
   Eccentricity       (e) 0.061 ± 0.014
   Orbital period     (P) 1089.0 ± 2.9 d
   Inclination        (i)  ?°
   Longitude of
   periastron         (ω) 172 ± 15°
   Time of periastron (τ) 2,450,356 ± 34 JD
               Physical characteristics
   Mass               (m) >2.63 ± 0.23 M[J]
   Radius             (r)  ? R[J]
   Density            (ρ)  ? kg/ m^3
   Temperature        (T)  ? K
                 Discovery information
   Discovery date         1996
   Discoverer(s)          Marcy, Butler et al.
   Detection method       Doppler Spectroscopy
   Discovery status       Confirmed

   47 Ursae Majoris b is an extrasolar planet orbiting the Sun-like star
   47 Ursae Majoris. It is located in a long- period, near-circular orbit
   and is the innermost known planet in its planetary system. 47 Ursae
   Majoris b was discovered in 1996 and has a mass at least 2.63 times
   that of Jupiter.

Discovery

   Like the majority of known extrasolar planets, 47 Ursae Majoris b was
   discovered by detecting the changes in its star's radial velocity as
   the planet's gravity pulls the star around. This was achieved by
   observing the Doppler shift of the spectrum of 47 Ursae Majoris. After
   the discovery of the first extrasolar planet around a Sun-like star, 51
   Pegasi b, astronomers Geoffrey Marcy and R. Paul Butler searched
   through their observational data for signs of extrasolar planets and
   soon discovered two: 47 Ursae Majoris b and 70 Virginis b. The
   discovery of 47 Ursae Majoris b was announced in 1996.

Orbit and mass

   47 Ursae Majoris b orbits at a distance of 2.13 AU from its star,
   taking 1,089 days to complete a revolution. It was the first
   long-period planet around a main sequence star to be discovered. Unlike
   the majority of known long-period extrasolar planets, the eccentricity
   of the orbit of 47 Ursae Majoris b is low. The planet lies close to a
   2:5 orbital resonance with the outer planet 47 Ursae Majoris c, a
   similar configuration to Jupiter and Saturn in our solar system. In
   addition, the ratio of the masses of the two planets is similar to the
   mass ratio of Jupiter and Saturn.

   A limitation of the radial velocity method used to detect 47 Ursae
   Majoris b is that only a lower limit on the planet's mass can be
   obtained. Preliminary astrometric measurements suggest the planet's
   orbit is inclined at an angle of 63.1° to the plane of the sky. If
   confirmed, this would imply the true mass of the planet is around 2.9
   times that of Jupiter. In any case, the mass cannot be much greater
   than the lower limit or the system would be unstable.

Characteristics

   Given the planet's high mass, it is likely that 47 Ursae Majoris b is a
   gas giant with no solid surface. Since the planet has only been
   detected indirectly, properties such as its radius, composition and
   temperature are unknown. Assuming a composition similar to that of
   Jupiter and an environment close to chemical equilibrium, the upper
   atmosphere of the planet is expected to contain water clouds, as
   opposed to the ammonia clouds typical of Jupiter.

   While 47 Ursae Majoris b lies outside its star's habitable zone, its
   gravitational influence would disrupt the orbit of planets in the outer
   part of the habitable zone. In addition, it may have disrupted the
   formation of terrestrial planets and reduced the delivery of water to
   any inner planets in the system. Therefore planets located in the
   habitable zone of 47 Ursae Majoris are likely to be small and dry.

47 Ursae Majoris b in fiction

   The Coyote series by Allen Steele is mainly set on Coyote, a fictional
   habitable moon of 47 Ursae Majoris b, which is named Bear in the books.

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