Measurement of Submicron Grains in the Coma of Comet Hale-Bopp C/1995 O1 during 1997 February 15-20 UT
Measurement of Submicron Grains in the Coma of Comet Hale-Bopp C/1995 O1 during 1997 February 15-20 UT
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1997 年 2 月 15 日至 20 日（世界标准时间）海尔-波普彗星 C/1995 O1 彗发中亚微米颗粒的测量
DOI：
10.1086/310973
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
H. Butner
中科院分区：
文献类型：
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作者：
D. M. Williams;C. G. Mason;R. Gehrz;T. J. Jones;C. Woodward;D. Harker;M. S. Hanner;D. Wooden;F. Witteborn;H. Butner
我们展示了 1997 年 2 月 15 日至 20 日（世界标准时间）期间 C/1995 O1（海尔-波普）彗星的 1.20-18.5 μm 红外 (IR) 分光光度测量结果。光谱能量分布（SED）主要由异常小的亚微米级尘埃颗粒的散射和热发射决定。海尔-波普星令人惊讶的亮度可能很大程度上是由于其彗差颗粒的特性而不是其核的大小。颗粒的热发射连续体的过热度为 S=Tcolor/TBB ≈ 1.84，10 μm 硅酸盐发射特征的峰值位于碳颗粒连续体上方 1.81 mag，并且颗粒的反照率（反射率）在 θ ≈ 144° 的散射角下约为 0.41。这些是 20 年来对明亮彗星进行光学/红外测量所观察到的经验参数的最高值。观察结果表明，主宰视觉散射和彗差近红外发射的光学重要颗粒的平均半径为a≤0.4 μm。强烈的硅酸盐特征是由具有相似尺寸范围的颗粒产生的。这些尘埃半径与某些新星流出物（“星尘”）中凝结的颗粒半径相当，但仍比产生一般星际灭绝的颗粒平均半径大约 10 倍。
We present 1.20-18.5 μm infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small. Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S=Tcolor/TBB ≈ 1.84, the peak of the 10 μm silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was ≈ 0.41 at a scattering angle of θ ≈ 144°. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a≤0.4 μm. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae (“stardust”) but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction.