Reflected light from sand grains in the terrestrial zone of a protoplanetary disk
Reflected light from sand grains in the terrestrial zone of a protoplanetary disk
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原行星盘陆地带沙粒的反射光
DOI：
10.1038/nature06671
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发表时间：
2008
期刊：
影响因子：
64.8
通讯作者：
M. Ibrahimov
中科院分区：
文献类型：
--
作者：
W. Herbst;C. Hamilton;Katherine LeDuc;J. Winn;C. Johns–Krull;R. Mundt;M. Ibrahimov
在类地行星形成的标准模型中，这个过程的第一步是星际尘埃在围绕年轻星星的原行星盘内凝结，形成大颗粒，沉降到盘平面。通常大小为10.1 μm的星际颗粒预计将相当快地增长到毫米（沙子）、厘米（卵石）甚至米（巨石）大小的物体。不幸的是，这种进化的圆盘很难观察到，因为它们的组成部分的表面积与体积之比很小。我们很容易检测到被称为“经典”金牛座T星的年轻物体周围的尘埃，但在进化程度稍高的“弱线”系统中几乎没有证据表明存在尘埃。在这里，我们报告了对一颗300万年前的星星的观测结果，结果表明，在这颗星星的地球区（在303 Au内），颗粒已经生长到大约毫米大小或更大。KH 15 D双星星星系统的偶然几何形状使我们能够推断，当两颗恒星都被周围的盘遮蔽时，它看起来像是一个由中央双星组成部分之一照亮的近边缘环。这项工作补充了最近通过干涉测量法解决的年轻磁盘的陆地区域的研究。
In the standard model of terrestrial planet formation, the first step in the process is for interstellar dust to coagulate within a protoplanetary disk surrounding a young star, forming large grains that settle towards the disk plane. Interstellar grains of typical size ∼0.1 μm are expected to grow to millimetre- (sand), centimetre- (pebble) or even metre-sized (boulder) objects rather quickly. Unfortunately, such evolved disks are hard to observe because the ratio of surface area to volume of their constituents is small. We readily detect dust around young objects known as ‘classical’ T Tauri stars, but there is little or no evidence of it in the slightly more evolved ‘weak-line’ systems. Here we report observations of a 3-Myr-old star, which show that grains have grown to about millimetre size or larger in the terrestrial zone (within ∼3 au) of this star. The fortuitous geometry of the KH 15D binary star system allows us to infer that, when both stars are occulted by the surrounding disk, it appears as a nearly edge-on ring illuminated by one of the central binary components. This work complements the study of terrestrial zones of younger disks that have been recently resolved by interferometry.