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Measuring the distance to far away objects in space can be tricky. We don\u2019t even know the precise distance to even our closest neighbors in the Universe \u2013 the Small and Large Magellanic Clouds. But, we\u2019re starting to get to the tools to measure it. One type of tool is a Cepheid Variable \u2013 a type of star that varies its luminosity in a well-defined pattern. However, we don\u2019t know much about their physical properties, making utilizing them as distance markers harder. Finding their physical properties would be easier if there were any Cepheid binaries that we could study, but astronomers have only found one pair so far. Until a recent paper from researchers from Europe, the US, and Chile shows measurements of 9 additional binary Cepheid systems \u2013 enough that we can start understanding the statistics of these useful distance markers.<\/p>\n
<\/p>\n Like traditional stars, binary Cepheid systems result when two stars orbit around each other. In this case, both of those stars must be Cepheids \u2013 meaning they are massive compared to our Sun and much brighter. In addition, their luminosity must vary in a repeatable pattern so that we can track it consistently.<\/p>\n All of those features can vary a lot if two stars change in luminosity but at different rates and phases around each other. It\u2019s difficult to parse out which star is waxing, which is waning, and which direction they are moving in, both compared to us and each other. Long periods of observation are required to fix some of those variables, and that is precisely what the new paper describes.<\/p>\n \n