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| Keywords: GJ581orbits.svg validSVG element in the SVG's source code gives further information <b>Assumptions </b> It is assumed that the system is coplanar This cannot be constrained by the radial velocity observations used to detect the planets in this system but our solar system's planets are nearly coplanar and both the systems of PSR B1257+12 planets B and C and Epsilon Eridani planet b and the circumstellar disk are coplanar see http //adsabs harvard edu/abs/2003ApJ 591L 147K Konacki and Wolszczan 2003 The Astrophysical Journal 591 L147 “L150 Masses and Orbital Inclinations of Planets in the PSR B1257+12 System and http //adsabs harvard edu/abs/2006AJ 132 2206B Beust et al 2006 The Astrophysical Journal 132 2206 “2218 The Extrasolar Planet É› Eridani b Orbit and Mass respectively so this assumption is at least reasonable The direction of rotation around the star is assumed to be the same for each planet Again this cannot be constrained by the current radial velocity observations but is a reasonable assumption since this is true for the major planets in our own solar system and is predicted by current theories of planet formation Under these first two assumptions the orientation of the orbits relative to each other is correct as depicted in this diagram however their actual orientation in 3D space with respect to external reference points e g the Sun the galactic centre is unknown hence such directions are not indicated on the diagram A further assumption is that the true masses of the planets are small compared to that of the star If the masses were comparable to that of the star the actual semimajor axis corresponding to the measured orbital period would be greater This assumption is supported both by probability the chance that we are observing a system which has sufficiently low inclination for this to be relevant is very low and by dynamical stability arguments which indicate that the planets cannot have true masses much more than 1 6 times their minimum masses Mayor et al 2009 This effect can therefore safely be neglected <b>Interpreting the diagram</b> The planetary orbits are drawn in orthographic projection as viewed from directly above the plane of the system so that the orbital direction is anticlockwise The dashed lines are drawn between the star and the periastron point of each planet in order to depict the relative orientation of the orbits with respect to each other The position of each planet in its orbit is calculated using the time of periastron in the table in the Mayor et al 2009 paper and are drawn at a time chosen to be close to the start of the Udry et al 2007 radial velocity observations which are available http //cdsarc u-strasbg fr/ftp/cats/J/A+A/469/L43/gl581 dat here This time is chosen to minimise the effects of both uncertainties in the orbital parameters and potential orbital evolution of the system While the orbits are drawn to the correct scale the star and the planets themselves are not shown to scale as they would be too small to see on the scale of this diagram In addition the true radii of the planets themselves are currently unknown as no direct observation of the planets has yet been made own Icalanise 2008-10-05 <gallery> File GJ581orbits Vogt2010 svg Planetary orbits according to Vogt et al 2010 incorporating orbit of unconfirmed super-Earth GJ 581 g </gallery> Gliese 581 Gliese 581 c Exoplanet diagrams | ||||
