The local interstellar medium (LISM) is a complex environment, comprised of a suite of interstellar clouds extending tens of parsecs and surrounding the nearest stars. On our journey through the Milky Way, our solar system's heliosphere may have been significantly compressed by a dense cloud of gas and dust. The properties of the LISM are critically important in understanding the interaction between the Sun and other stars with their surrounding interstellar environments. Using high-resolution UV data obtained from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope, we focus on eight sight lines along the Sun's historical trajectory. Of the eight targets, each of which is within 50 pc, we see interstellar absorption in almost every one, primarily Mg II and Fe II. We observe CII and OI absorption in one target. In each analyzed sight line, the LIC cloud is seen bearing a similar column density. We detected the Blue and Aur cloud, which the Sun encountered before entering the LIC, and in at least one sight line a third cloud is detected. In three of the targets, additional ions are observed in the shorter wavelength range including HI, DI, CII, OI, and SiII, providing more access to additional physical properties of our past environment, such as depletion, temperature, turbulent velocity, and ionization structure, which we were able to accomplish for one target. Utilizing ground-based observations of more distant ISM and in turn a more distant time scale, Wyman and Redfield (2013) found the heliosphere could have been compressed to within 21 AU. Our observations provide the best opportunity to characterize the interstellar properties just exterior to the heliosphere and estimate the heliospheric response to interstellar environments in our recent past and for our immediate future. Our analysis established a timeline of interaction with multiple clouds of LISM over the past 140,000 years, potentially resulting in a series of heliospheric expansions and contractions. In addition, we report the discovery of two new astrospheres.
"},{"label":"Degree","value":["Bachelor of Arts with Departmental Honors"]},{"label":"Author-supplied Keywords","value":["Local interstellar medium","Heliosphere","Historical solar trajectory"]},{"label":"Administrative Note","value":"Drupal Node ID: 24121