The C-Band All Sky Survey (C-BASS) is a

radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...

project that aims to map the entire sky in the C Band (5 GHz). It has been conducted on two

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

s, one operating in the

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ext ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

, the other at

Owens Valley Radio Observatory Owens Valley Radio Observatory (OVRO) is a radio astronomy observatory located near Big Pine, California (US) in Owens Valley. It lies east of the Sierra Nevada, approximately north of Los Angeles and southeast of Bishop. It was established in 1 ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

Project description

The survey is a collaboration between the

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

University of Manchester , mottoeng = Knowledge, Wisdom, Humanity , established = 2004 – University of Manchester Predecessor institutions: 1956 – UMIST (as university college; university 1994) 1904 – Victoria University of Manchester 1880 – Victoria Univer ...

, the

California Institute of Technology The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

, the

Hartebeesthoek Radio Astronomy Observatory The Hartebeesthoek Radio Astronomy Observatory (HartRAO) is a radio astronomy observatory, located in a natural bowl of hills at Hartebeesthoek just south of the Magaliesberg mountain range, Gauteng, South Africa, about 50 km west of Johannes ...

(HartRAO), and the

King Abdulaziz City for Science and Technology King Abdulaziz City for Science and Technology (KACST; ar, مدينة الملك عبدالعزيز للعلوم والتقنية) in Riyadh, Saudi Arabia is an organization established in 1977 as the Saudi Arabian National Center for Science & ...

. The initial observations were made with two telescopes; one based at the

(OVRO) in

, United States, and the other near Klerefontein in the Karoo desert in

.Square Kilometer Array Media Release
, South Africa. For an all sky survey two ground-based telescopes are required, one in the southern and one in the northern hemisphere. C-BASS North was a 6.1m Gregorian telescope, the dish was donated to the project by the

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

. C-BASS South is a 7.6-m Cassegrain telescope with a dish donated by

Telkom (South Africa) Telkom SA SOC Limited is a South African wireline and wireless telecommunications provider, operating in more than 38 countries across the African continent. Telkom is majority state-owned (55.3%) with the South African government owning 40 ...

. It was commissioned at

and began survey observations in 2014 when it was deployed in the Karoo. The secondary mirrors on both telescopes were supported by cones of radio-transparent foam to minimize the contamination from ground pick up and to avoid scattering the incoming polarized radiation. The C-BASS North telescope was retired in April 2015 after the initial observing phase was complete. C-BASS South continues to operate as of 2019.

Scientific goals

The survey has mapped not only the intensity but also the orientation of the incoming electromagnetic waves ( polarization) at every point on the sky with an angular resolution of 0.73 degrees. The angular resolution represents the smallest details that can be distinguished in the images. This has been the first survey to map the sky at a frequency of 5 GHz—low enough to be synchrotron radiation dominated but high enough to be relatively unaffected by

Faraday rotation The Faraday effect or Faraday rotation, sometimes referred to as the magneto-optic Faraday effect (MOFE), is a physical magneto-optical phenomenon. The Faraday effect causes a polarization rotation which is proportional to the projection of the ...

. At this frequency most of the signal comes from emissions from high-energy electrons spiraling around magnetic fields in the galaxy. This radiation is highly polarized and a major foreground distorting the

Cosmic Microwave Background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

(CMB) signal. The primary scientific goal of the project is to aid in the subtraction of foreground radiation, mainly from our own galaxy, from measurements of the CMB in order to improve the exactness of the CMB measurements. The CMB is polarized, this polarization can help shed light on

inflation theory In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from seconds after the conjectured Big Bang singularit ...

and

gravity waves In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere ...

in the

early universe The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, wit ...

. Secondary goals include studying the

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

s within the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

, the WMAP Haze and

spinning dust In astronomy, spinning dust emission is a mechanism proposed to explain anomalous microwave emission from the Milky Way. The emission could arise from the electric dipole of very rapidly spinning (10–60 GHz) extremely small (nanometer) dus ...

References

{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Radio telescopes Educational institutions in the United States with year of establishment missing Organisations associated with the University of Oxford University of Manchester California Institute of Technology Radio astronomy Karoo Collaborative projects Astronomical surveys