Warm Debris Disks Produced by Giant Impact During Terrestrial Planet Formation
Warm Debris Disks Produced by Giant Impact During Terrestrial Planet Formation
复制标题
类地行星形成过程中巨大撞击产生的温暖碎片盘
DOI：
10.1088/0004-637x/810/2/136
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
E.
中科院分区：
文献类型：
--
作者：
Genda;H.;Kobayashi;H.;and Kokubo;E.
在我们的太阳系中，在类地行星形成的最后阶段，也就是所谓的巨型撞击阶段，火星大小的原行星频繁地相互碰撞。巨大的撞击将大量物质从相互碰撞的原行星喷出到类地行星区域，这可能会形成具有明显红外线过剩的碎片圆盘。事实上，在年轻的太阳型恒星周围观察到了数十个温暖的碎片圆盘。在这里，我们定量地估计了在大撞击阶段抛射出的物质的总质量。我们发现，在整个大撞击阶段，总共有0.4倍于地球质量的∼被抛出。抛射出的物质被碰撞的级联粉碎，直到微米大小的颗粒被辐射压力吹出。这些被抛出的物质的耗尽时间主要由其中最大天体的质量决定。我们进行了高分辨率的巨型撞击模拟，以准确地获得最大抛射体的质量。然后，我们计算了一系列大碰撞产生的碎片盘和碰撞级联耗尽的碎片盘的演化，得到了碎片盘的红外超额演化。我们发现，在整个巨型撞击阶段(∼100Myr)，红外超额几乎总是高于恒星的红外通量，有时在巨型撞击后立即∼高出10倍。因此，巨型撞击阶段可以解释大多数观测到的热碎片盘产生的红外线过剩现象。观测到的带有热碎片盘的恒星的比例表明，我们太阳系类地行星的形成概率约为10%。
In our solar system, Mars-sized protoplanets frequently collided with each other during the last stage of terrestrial planet formation, called the giant impact stage. Giant impacts eject a large amount of material from the colliding protoplanets into the terrestrial planet region, which may form debris disks with observable infrared excesses. Indeed, tens of warm debris disks around young solar-type stars have been observed. Here we quantitatively estimate the total mass of ejected materials during the giant impact stages. We found that∼ 0.4 times the Earth's mass is ejected in total throughout the giant impact stage. Ejected materials are ground down by collisional cascade until micron-sized grains are blown out by radiation pressure. The depletion timescale of these ejected materials is determined primarily by the mass of the largest body among them. We conducted high-resolution simulations of giant impacts to accurately obtain the mass of the largest ejected body. We then calculated the evolution of the debris disks produced by a series of giant impacts and depleted by collisional cascades to obtain the infrared excess evolution of the debris disks. We found that the infrared excess is almost always higher than the stellar infrared flux throughout the giant impact stage (∼ 100 Myr) and is sometimes∼ 10 times higher immediately after a giant impact. Therefore, giant impact stages would explain the infrared excess from most observed warm debris disks. The observed fraction of stars with warm debris disks indicates that the formation probability of our solar-system-like terrestrial planets is approximately 10%.