A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea-猫眼课题宝

DOI：

10.1038/s41550-019-0915-8

发表时间：

2019-10

期刊：

Nature Astronomy

影响因子：

14.1

通讯作者：

中科院分区：

物理与天体物理1区

文献类型：

作者：

P. Vernazza;L. Jorda;P. Ševeček;M. Brož;M. Viikinkoski;J. Hanuš;B. Carry;A. Drouard;M. Ferrais;M. Marsset;F. Marchis;F. Marchis;M. Birlan;E. Podlewska-Gaca;E. Podlewska-Gaca;E. Jehin;P. Bartczak;G. Dudziński;J. Berthier;J. Castillo‐Rogez;F. Cipriani;F. Colas;F. DeMeo;C. Dumas;J. Ďurech;R. Fétick;T. Fusco;J. Grice;J. Grice;M. Kaasalainen;A. Kryszczyńska;P. Lamy;H. Coroller;A. Marciniak;T. Michałowski;P. Michel;N. Rambaux;T. Santana-Ros;T. Santana-Ros;P. Tanga;F. Vachier;A. Vigan;O. Witasse;B. Yang;M. Gillon;Z. Benkhaldoun;R. Szakáts;R. Hirsch;R. Duffard;A. Chapman;J. L. Maestre

(10)Hygiea是第四大主带小行星，也是已知的唯一表面成分与矮行星谷神星相似的小行星，这表明这两个天体的起源相似。Hygiea在2 Gyr多年前遭受了一次巨大的撞击，这是最大的小行星家族之一的起源。然而，Hygeia从未被观测到足够高的分辨率来分辨其表面的细节或限制其大小和形状。在这里，我们报告了使用VLT/SPHERE仪器(约20 ms，600 nm)对卫生菌进行的高角度分辨率成像观测，显示出一个无盆地的近球形形状，体积等效半径为217 ± 7 km，意味着密度为1,944 ± 250 kg m−3 to 1σ。此外，我们还确定了Hygiea的新轮作周期为~13.8 h，这是目前接受的值的一半。家族形成事件的数值模拟表明，Hygiea的球形和家族可以用与大弹丸(直径~75-150 Km)的碰撞来解释。通过将Hygiea的球形度与其他太阳系天体的球度进行比较，可以看出Hygiea的球形度几乎与谷神星一样，这为该天体被重新归类为矮行星打开了可能性。

(10) Hygiea is the fourth largest main belt asteroid and the only known asteroid whose surface composition appears similar to that of the dwarf planet (1) Ceres,, suggesting a similar origin for these two objects. Hygiea suffered a giant impact more than 2 Gyr ago that is at the origin of one of the largest asteroid families. However, Hygeia has never been observed with sufficiently high resolution to resolve the details of its surface or to constrain its size and shape. Here, we report high-angular-resolution imaging observations of Hygiea with the VLT/SPHERE instrument (~20 mas at 600 nm) that reveal a basin-free nearly spherical shape with a volume-equivalent radius of 217 ± 7 km, implying a density of 1,944 ± 250 kg m−3to 1σ. In addition, we have determined a new rotation period for Hygiea of ~13.8 h, which is half the currently accepted value. Numerical simulations of the family-forming event show that Hygiea’s spherical shape and family can be explained by a collision with a large projectile (diameter ~75–150 km). By comparing Hygiea’s sphericity with that of other Solar System objects, it appears that Hygiea is nearly as spherical as Ceres, opening up the possibility for this object to be reclassified as a dwarf planet.

A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea

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