Arcus is a proposed

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

space observatory A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched ...

proposed to NASA's Explorer program, Medium Explorer (MIDEX) class. The Arcus mission would study

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

and galaxy clusters using high-resolution X-ray spectroscopy to characterize the interactions between these objects and the diffuse hot gas that permeates them. The Principal investigator is Randall Smith at the

Smithsonian Astrophysical Observatory The Smithsonian Astrophysical Observatory (SAO) is a research institute of the Smithsonian Institution, concentrating on astrophysical studies including galactic and extragalactic astronomy, cosmology, solar, earth and planetary sciences, the ...

in Cambridge, Massachusetts; the project has significant contributions from the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

, cosine Measurement Systems (Warmond NL),

Penn State #Redirect Pennsylvania State University The Pennsylvania State University (Penn State or PSU) is a Public university, public Commonwealth System of Higher Education, state-related Land-grant university, land-grant research university with campu ...

, and the

Max Planck Institute for Extraterrestrial Physics The Max Planck Institute for Extraterrestrial Physics is a Max Planck Institute, located in Garching, near Munich, Germany. In 1991 the Max Planck Institute for Physics and Astrophysics split up into the Max Planck Institute for Extraterrestrial Ph ...

Overview

Arcus's spectrograph was originally intended to fly on the cancelled International X-ray Observatory (IXO). If selected, it would have been funded $250 million for development. Arcus is an X-ray grating spectrometer space observatory that combines X-ray optics and gratings to disperse the X-rays, much like how a prism separates sunlight into the colors of the rainbow. It would observe astrophysical phenomena in X-ray band over a broad target size range. Its mission includes investigations on the composition of

cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

grains,

stellar evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years for the least massive, which is cons ...

, identify the launching mechanisms of supermassive black hole winds, and structure formation of galaxy clusters. Using new technologies, it offers a resolution improvement of ten times better than existing X-ray observatories.High-resolution X-ray gratings enable state-of-the-art spectrometer
''Phys Org''. 9 January 2018. The space observatory would orbit Earth in a 4:1 lunar resonance, which would allow significant stability for minimal propellant consumption, which could extend the mission life to about 10 years.NASA Selects Proposals to Study Galaxies, Stars, Planets
Katherine Brown, NASA News. 9 August 2017.