科研之友
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摘要
In 2012 August, Voyager 1 crossed the heliopause, becoming the first human-made object to exit the solar system. This milestone signifies the beginning of an important new era for local interstellar medium (LISM) exploration. We present measurements of the structure and composition of the LISM in the immediate path of the Voyager spacecraft by using high-resolution Hubble Space Telescope (HST) spectra of nearby stars that lie along the same lines of sight. We provide a comprehensive inventory of LISM absorption in the near-ultraviolet (2600-2800 angstrom) and far-ultraviolet (1200-1500 angstrom). The LISM absorption profiles are used to make comparisons between each pair of closely spaced (< 15 degrees) sight lines. With fits to several absorption lines, we make measurements of the physical properties of the LISM. We estimate electron density along the Voyager 2 sight line, and our values are consistent with recent measurements by Voyager 1. Excess absorption in the H I Ly alpha line displays the presence of both the heliosphere and an astrosphere around GJ 780. This is only the 14th detection of an astrosphere, and the large mass-loss rate (M. = 10M circle dot) is consistent with other subgiant stars. The heliospheric absorption matches the predicted strength for a sight line 58 degrees from the upwind direction. As both HST and Voyager reach the end of their lifetimes, we have the opportunity to synthesize their respective observations, combining in situ measurements with the shortest possible line-of-sight measurements to study the Galactic ISM surrounding the Sun.
- 出版日期2018-5-20
