Cosmic noise, also known asgalactic radio noise, is radio-frequency electromagnetic radiation from sourcesoutside of the Earth's atmosphere. Its characteristics are comparable to those ofthermal noise. Cosmic noise occurs at frequencies above about 15 MHz when highly directional antennas are pointed toward the Sun or other regions of the sky, such as thecenter of the Milky Way Galaxy. Celestial objects likequasars, which are super dense objects far from Earth, emit electromagnetic waves in their full spectrum, including radio waves. The fall of ameteorite can also be heard through a radio receiver; the falling object burns from friction with the Earth's atmosphere, ionizing surrounding gases and producingradio waves.Cosmic microwave background radiation (CMBR) fromouter space is also a form of cosmic noise. CMBR is thought to be a relic of theBig Bang, and pervades the space almost homogeneously over the entirecelestial sphere. Thebandwidth of the CMBR is wide, though the peak is in the microwave range.
Karl Jansky, an American physicist and radio engineer, first discoveredradio waves from theMilky Way in August, 1931. AtBell Telephone Laboratories in 1932, Jansky built an antenna designed to receive radio waves at a frequency of 20.5 MHz, which is a wavelength of approximately 14.6 meters.
After recording signals with this antenna for several months, Jansky categorized them into three types: nearby thunderstorms, distant thunderstorms, and a faint steady hiss of an unknown origin. He discovered the location of maximum intensity rose and fell once a day, which led him to believe he was detecting radiation from theSun.
A few months went by following this signal thought to be from the Sun, and Jansky found that the brightest point moved away from the Sun and concluded the cycle repeated every 23 hours and 56 minutes. After this discovery, Jansky concluded the radiation was coming from theMilky Way and was strongest in the direction of the center of thegalaxy.
Jansky's work helped to distinguish between the radio sky and theoptical sky. The optical sky is what is seen by the human eye, whereas the radio sky consists of daytime meteors, solar bursts, quasars, and gravitational waves.
Later in 1963, American physicist and radio astronomerArno Allan Penzias (born April 26, 1933) discoveredcosmic microwave background radiation. Penzias's discovery of cosmic microwave background radiation helped establish theBig Bang theory of cosmology. Penzias and his partner,Robert Woodrow Wilson worked together on ultra-sensitive cryogenicmicrowave receivers, originally intended for radio astronomy observations. In 1964, upon creating their most sensitive antenna/receiver system, theHolmdel Horn Antenna, the two discovered a radio noise they could not explain. After further investigation, Penzias contactedRobert Dicke, who suggested it could be the background radiation predicted by cosmological theories, a radio remnant of theBig Bang. Penzias and Wilson won theNobel Prize in Physics in 1978.
TheAbsolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) is a device designed to observe the transition out of the "cosmic dark ages" as the first stars ignite in nuclear fusion and theuniverse begins to resemble its current form.[1]
ARCADE consists of 7 precisionradiometers carried to an altitude of over 35 km (21 miles) by ascientific research balloon. The device measures the tiny heating of the earlyuniverse by the first generation of stars and galaxies to form after theBig Bang.
Cosmic noise refers to thebackground radio frequency radiation fromgalactic sources, which have constant intensity duringgeomagnetically quiet periods.[2]
Cosmic noise can be traced fromsolar flares, which are sudden explosive releases of storedmagnetic energy in the atmosphere of the Sun, causing sudden brightening of thephotosphere. Solar flares can last from a few minutes to several hours.
During solar flare events, particles and electromagnetic emissions can affectEarth's atmosphere by fluctuating the level ofionization in the Earth'sionosphere. Increased ionization results in absorption of the cosmic radio noise as it passes through the ionosphere.
Solar wind is a flux of particles,protons andelectrons together withnuclei of heavier elements in smaller numbers, that are accelerated by the high temperatures of thesolar corona to velocities large enough to allow them to escape from the Sun's gravitational field.[3]
Solar wind causes sudden bursts of cosmic noise absorption in the Earth's ionosphere. These bursts can only be detected only if the magnitude of the geomagnetic field perturbation caused by the solar wind shock is large enough.[4]
