The Experiment to Detect the Global EoR Signature (EDGES) is an experiment and radio telescope located in a

radio quiet zone A radio quiet zone is an area where radio transmissions are restricted in order to protect a radio telescope or a communications station from radio frequency interference. The Radio Regulations of the International Telecommunication Union (ITU) def ...

at the

Murchison Radio-astronomy Observatory The Murchison Radio-astronomy Observatory (MRO) was established by CSIRO (Commonwealth Scientific and Industrial Research Organisation) in 2009. It lies in a designated radio quiet zone located near Boolardy Station in the Murchison Shire of ...

in Western Australia. It is a collaboration between Arizona State University and

Haystack Observatory Haystack Observatory is a multidisciplinary radio science center, ionospheric observatory, and astronomical microwave observatory owned by Massachusetts Institute of Technology (MIT). It is located in Westford, Massachusetts (US), approximately ...

, with infrastructure provided by CSIRO. EoR stands for

epoch of reionization In the fields of Big Bang theory and cosmology, reionization is the process that caused matter in the universe to reionize after the lapse of the " dark ages". Reionization is the second of two major phase transitions of gas in the universe (t ...

, a time in cosmic history when neutral atomic hydrogen gas became ionised due to ultraviolet light from the first stars.

Low-band instruments

The experiment has two low-band instruments, each of which has a dipole antenna pointed to the

zenith The zenith (, ) is an imaginary point directly "above" a particular location, on the celestial sphere. "Above" means in the vertical direction ( plumb line) opposite to the gravity direction at that location ( nadir). The zenith is the "high ...

and observing a single polarisation. The antenna is around in size, sat on a ground shield. It is coupled with a radio receiver, with a 100m cable run to a digital spectrometer. The instruments operate at , and are separated by 150m. Observations started in August 2015.

78 MHz absorption profile

In March 2018 the collaboration published a paper in ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' announcing the discovery of a broad absorption profile centered at a frequency of

78\pm1

MHz in the sky-averaged signal after subtracting Galactic

synchrotron emission Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...

. The absorption profile has a width of

19_^

MHz and an amplitude of

0.5_^

K, against a background RMS of 0.025K, giving it a signal-to-noise ratio of 37. The equivalent redshift is centered at

z\approx17

, spanning z=20–15. The signal is possibly due to ultraviolet light from the first stars in the Universe altering the emission of the

21cm line The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...

by lowering the temperature of the hydrogen relative to 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 ...

(the mechanism is Wouthuysen–Field coupling). A "more exotic scenario," encouraged by the unexpected strength of the absorption, is that the signal is due to interactions between

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...

and

baryon In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classif ...

s. In 2022 an experiment called Shaped Antenna Measurement of the Background Radio Spectrum (SARAS) led by the

Raman Research Institute The Raman Research Institute (RRI) is an institute for scientific research located in Bangalore, India. It was founded by Nobel laureate C. V. Raman in 1948. Although it began as an institute privately owned by Sir C. V. Raman, it is now fund ...

reported that their measurements didn't replicate EDGES results rejecting them at 95.3% confidence level.

High-band instruments

The high-band instrument is of similar design, and operates at .

References

External links

Signal from age of the first stars could shake up search for dark matter - www.sciencemag.org
* {{Portal bar, Western Australia, Australia, Physics, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Physical cosmology Radio telescopes Astronomical observatories in Western Australia

Low-band instruments

78 MHz absorption profile

High-band instruments

See also

References

External links