Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt
Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt
复制标题
太阳系外原柯伊伯带橄榄石晶体的类彗星矿物学
DOI：
10.1038/nature11469
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发表时间：
2012
期刊：
影响因子：
64.8
通讯作者：
B. Sibthorpe
中科院分区：
文献类型：
--
作者：
B. D. Vries;B. Acke;J. Blommaert;C. Waelkens;L. Waters;B. Vandenbussche;M. Min;G. Olofsson;C. Dominik;L. Decin;M. Barlow;A. Brandeker;J. Francesco;A. Glauser;J. Greaves;P. Harvey;W. Holland;R. Ivison;R. Liseau;E. Pantin;G. Pilbratt;P. Royer;B. Sibthorpe
一些行星系统中有包含小行星和彗星等微行星的碎片盘。这类天体之间的碰撞会产生小的尘埃粒子，其光谱特征揭示了它们的组成，从而揭示了它们的母体。对原行星盘HD 100546（参考文献3、4）和行星系统温暖内部的橄榄石晶体（Mg 2 − 2xFe 2xSiO 4）的成分进行了测量。后者可以与小行星中富含铁的橄榄石（x = 0.29）相媲美。在风景如画的β星系（类似于年轻的太阳系）的寒冷外围，发现了橄榄石晶体，但其成分仍然不确定，因此不知道太阳系彗星橄榄石颗粒的大部分成分与太阳系外彗星的成分如何比较。在这里，我们报告的69微米波段的橄榄石晶体的β Piccadine光谱的检测。由于该盘在光学上很薄，我们可以将这些晶体与太阳系外的原柯伊伯带联系起来，该带距离星星15-45个天文单位（一个天文单位是日地距离），确定它们富含镁的成分（x = 0.01 ± 0.001），并表明它们占尘埃总质量的3.6 ± 1.0%。这些数值与太阳系中最原始的彗星所释放出的尘埃惊人地相似，尽管如画星β质量更大，亮度更高，并且具有不同的行星系统结构。
Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2−2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x ≈ 0.29). In the cold outskirts of the β Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of β Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15–45 astronomical units from the star (one astronomical unit is the Sun–Earth distance), determine their magnesium-rich composition (x = 0.01 ± 0.001) and show that they make up 3.6 ± 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though β Pictoris is more massive and more luminous and has a different planetary system architecture.