Arcus is a proposed

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

space observatory A space telescope (also known as 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 ...

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, and 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 Sys ...

and

galaxy cluster A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. Clusters consist of galax ...

s using high-resolution

X-ray spectroscopy X-ray spectroscopy is a general term for several Spectroscopy, spectroscopic techniques for characterization of materials by using x-ray radiation. Characteristic X-ray spectroscopy When an electron from the inner shell of an atom is excited b ...

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 Astrophysics, astrophysical studies including Galactic astronomy, galactic and extragalactic astronomy, cosmology, Sun, solar ...

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

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a Private university, private research university in Cambridge, Massachusetts, United States. Established in 1861, MIT has played a significant role in the development of many areas of moder ...

, cosine Measurement Systems (

Sassenheim Sassenheim () is a town and former municipality in the western Netherlands, in the province of South Holland. The former municipality covered an area of 6.62 km2 (of which 0.23 km2 water) and had a population of 14,906 in 2005. Since ...

, Netherlands),

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 ca ...

, and the

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

Overview

Arcus's spectrograph was originally intended to fly on the cancelled

International X-ray Observatory The International X-ray Observatory (IXO) is a cancelled X-ray telescope that was to be launched in 2021 as a joint effort by NASA, the European Space Agency (ESA), and the Japan Aerospace Exploration Agency (JAXA). In May 2008, ESA and NASA e ...

(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 dustalso called extraterrestrial dust, space dust, or star dustis dust that occurs in outer space or has fallen onto Earth. Most cosmic dust particles measure between a few molecules and , such as micrometeoroids (30 μm). Cosmic dust can ...

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 consi ...

, identify the launching mechanisms of

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical ...

winds, and structure formation of

s. 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.