The hottest planet
The hottest planet
复制标题
最热的星球
作者：
Joseph Harrington;Joseph Harrington;S. Luszcz;S. Luszcz;S. Seager;D. Deming;L. J. Richardson
在200多颗已知的太阳系外行星中，只有14颗从地球上看到它们的母星前后经过。这种偶然的几何形状允许直接确定许多行星性质。先前的行星热辐射报告给出的通量与基于行星接收辐射的热平衡的预测大致一致，假设邦德的辐射量为0.3。在这里，我们报告了对已知最小的凌日行星HD 149026 b的热辐射的直接探测，它表明在8 µm处的亮度温度（通量的表达）为2，300 ± 200 K。这颗行星的预测温度均匀，球形，黑体发射和零辐射（行星前所未有的）是1，741 K。由于具有非零散射度的模型更冷，这基本上消除了均匀黑体模型，并且可能还需要比任何行星测量的散射度更低的散射度，非常强的8 µm发射，强的时间变化性，或恒星辐射以外的热源。另一方面，一个瞬时再发射黑体模型，其中每个表面区域的补丁立即重新发射所有接收到的光，匹配的数据。已知这颗行星富含重元素，这可能会产生新的大气特性尚待研究。
Of the over 200 known extrasolar planets, just 14 pass in front of and behind their parent stars as seen from Earth. This fortuitous geometry allows direct determination of many planetary properties. Previous reports of planetary thermal emission give fluxes that are roughly consistent with predictions based on thermal equilibrium with the planets’ received radiation, assuming a Bond albedo of ∼0.3. Here we report direct detection of thermal emission from the smallest known transiting planet, HD 149026b, that indicates a brightness temperature (an expression of flux) of 2,300 ± 200 K at 8 µm. The planet’s predicted temperature for uniform, spherical, blackbody emission and zero albedo (unprecedented for planets) is 1,741 K. As models with non-zero albedo are cooler, this essentially eliminates uniform blackbody models, and may also require an albedo lower than any measured for a planet, very strong 8 µm emission, strong temporal variability, or a heat source other than stellar radiation. On the other hand, an instantaneous re-emission blackbody model, in which each patch of surface area instantly re-emits all received light, matches the data. This planet is known to be enriched in heavy elements, which may give rise to novel atmospheric properties yet to be investigated.