Although the Next Generation Science Standards (NGSS) are not federally mandated national standards or performance expectations for K-12 schools in the United States, they stand poised to become a de facto national science and education policy, as state governments, publishers of curriculum materials, and assessment providers across the country consider adopting them. In order to facilitate national buy-in and adoptions, Achieve, Inc., the non-profit corporation awarded the contract for writing the NGSS, has repeatedly asserted the development of the Standards to be a state-driven and transparent process, in which the scientific content is taken "verbatim", from the 2011 NRC report, Frameworks for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas. This paper reports on an independently conducted fidelity check within the content domain of astronomy and the space sciences, conducted to determine the extent to which the NGSS science content is guided by the Frameworks, and the extent to which any changes have altered the scientific intent of that document. The side-by-side, two-document comparative analysis indicates that the science of the NGSS is significantly different from the Frameworks. Further, the alterations in the science represent a lack of fidelity, in that they have altered the parameters of the science and the instructional exposure (e.g., timing and emphasis). As a result the NGSS are now poised to interfere with widely desired science education reform and improvement. This unexpected finding affords scientists, educators, and professional societies with an opportunity, if not a professional obligation, to engage in positively impacting the quality of science education by conducting independent fidelity checks across other disciplines. This could provide a much needed formal support and guidance to schools, teachers, curriculum developers, and assessment providers.