本星际云

2024年12月22日

The Local Fluff
Illustration Credit: NASA, SVS, Adler, U. Chicago, Wesleyan

Explanation: The stars are not alone. In the disk of our Milky Way Galaxy, about 10 percent of visible matter is in the form of gas called the interstellar medium (ISM). The ISM is not uniform and shows patchiness even near our Sun. It can be quite difficult to detect the local ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some very specific colors that can be detected in the light of the nearest stars. A working map of the local ISM within 20 light-years, based on ongoing observations and particle detections from the Earth-orbiting Interstellar Boundary Exporer satellite (IBEX), is shown here. These observations indicate that our Sun is moving through a Local Interstellar Cloud as this cloud flows outwards from the Scorpius-Centaurus Association star forming region. Our Sun may exit the Local Cloud, also called the Local Fluff, during the next 10,000 years. Much remains unknown about the local ISM, including details of its distribution, its origin, and how it affects the Sun and the Earth. Unexpectedly, IBEX spacecraft measurements indicate that the direction from which neutral interstellar particles flow through our Solar System is changing.

APOD Year in Review: Night Sky Network Presentation for 2024
Tomorrow’s picture: sky tree

本星际云
图示提供: NASA, SVS, Adler, U. Chicago, Wesleyan

说明: 恒星其实并不孤独。在我们的银河系的盘面上，大约有10%的可见物质是名为星际物质（ISM）的云气。然而，星际物质的分布并不均匀，就连在太阳附近也是支离破碎的。因为星际物质非常稀薄，而且几乎不发光，所以侦测邻近星际物质的工作难度颇高。星际物质之主成分是氢气，因为它会吸收特定波长的光，所以可经由侦测最邻近恒星的星光得知它的存在。上面这幅呈现我们周围20光年内星际物质的暂订分布图，是根据地球轨道上的星际边界探测卫星（IBEX），目前的观测及粒子侦测数据所建构出来的。这些观测显示，我们的太阳正在穿过本星际云（Local Cloud），而这团云气则来自天蝎-半人马星协恒星形成区的外泛流。在接下来的一万年内，我们的太阳可能会穿出本星际云。我们对附近的星际物质所知不多，包括分布、起源、及它如何影响太阳和地球等细节都有待厘清。出乎预料的，最近的星际边界探测卫星量测指出，中性星际粒子流通过太阳系的方向正在改变之中。