The shape, internal structure and gravity of the fast spinner ß Pictoris b
The shape, internal structure and gravity of the fast spinner ß Pictoris b
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快速旋转器的形状、内部结构和重力 - Pictoris b
DOI：
10.1093/mnrasl/slu129
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Kong D
中科院分区：
文献类型：
--
作者：
Kong D
一颗年轻的太阳系外气体巨行星--基于新测量的参数-行星的旋转周期，它的质量和半径-以及气体行星β Picasso B处于流体静力平衡并由具有统一多方指数的完全可压缩正压气体组成的假设，我们能够通过混合逆方法计算它的非球形形状，内部密度/压力分布和重力纬向系数高达8度。由于行星β Picasso B的质量M β是高度不确定的，本文研究了具有不同M β值的各种模型，给出了其形状参数和引力带系数的上、下界。假设M β为6 MJ，MJ为木星质量，我们证明了行星β Picasso B的形状近似为一个扁椭球体，其偏心率在单杆面上为，引力系数（J2）β= +15 375.972 × 10−6.由此可见，如果行星β Picasso B的形状可以被测量或限制，我们的结果就有可能限制或推断它的质量M β。通过假设行星β Picasso B在冷却过程中会缩小到木星的大小，因此旋转速度会快得多，我们还计算了行星β Picasso B未来的形状和内部结构。
A young extrasolar gas giant planet, β Pictoris b, recently discovered in the β Pictoris system, spins substantially faster than the giant gas planets Jupiter and Saturn. Based on the newly measured parameters – the rotation period of the planet, its mass and radius – together with an assumption that the gas planet β Pictoris b is in hydrostatic equilibrium and made of a fully compressible barotropic gas with a polytropic index of unity, we are able to compute, via a hybrid inverse method, its non-spherical shape, internal density/pressure distribution and gravitational zonal coefficients up to degree 8. Since the massMβfor the planet β Pictoris b is highly uncertain, various models with different values ofMβare studied in this Letter, providing the upper and lower bounds for its shape parameter as well as its gravitational zonal coefficients. IfMβis assumed to be 6MJwithMJbeing Jupiter's mass, we show that the shape of the planet β Pictoris b is approximately described by an oblate spheroid whose eccentricity at the one-bar surface iswith the gravitational coefficient (J2)β= +15 375.972 × 10−6. It follows that our results open the possibility of constraining or inferring the massMβof the planet β Pictoris b if its shape can be measured or constrained. By assuming that the planet β Pictoris b will shrink to the size of Jupiter in the process of cooling down and, hence, rotate much faster, we also calculate the future shape and internal structure of the planet β Pictoris b.