21cm Receiver

This is a page for the LMDSRO Hydrogen Line Receiver.

The hydrogen line, 21 centimeter line or HI line refers to the spectral line created by changing in the energy state of neutral hydrogen and occurs at a frequency of 1420.40575177 MHz , equivalent to a vacuum wavelength of around 21.10611405413 cm . This line falls within the radio region of the electromagnetic spectrum and is used extensively in radio astronomy, since it can penetrate dust clouds that are opaque to visible wavelengths. The radiation comprising the hydrogen line comes from the transition between the two hyperfine levels of the hydrogen.

Assuming that the hydrogen atoms are uniformly distributed throughout the galaxy, each line of sight through the galaxy will reveal a hydrogen line. The only difference between each of these lines is the doppler shift that each of these lines has. Hence, one can calculate the relative speed of each arm of our galaxy. The rotation curve of our galaxy has also been calculated using the 21-cm hydrogen line. It is then possible to use the plot of the rotation curve and the velocity to determine the distance to a certain point within the galaxy.

It is envisaged to obtain a Spectrometer to be able to do these experiments. Although as early steps, there are ways of doing this using a very basic approach.

Also while the Radio Telecope is in "idle" mode we can use the system as SETI Receiver. The 21 cm Hydrogen line is considered a favorable frequency to search for signals from another civilization, as part of the SETI program. The original paper by Giuseppe Cocconi and Philip Morrison proposed just such a search in their paper, Search for Extra-Terrestrial Intelligence. Pyotr Makovetsky proposed to use for SETI a frequency which is equal to pi times 1420.4 MHz (pi times 1420.40575177 megahertz = 4.46233627 gigahertz. Since pi is an Transcendental number, such frequency couldn't possibly be produced in a natural way as a harmonic, and would clearly signify its artificial origin. Such signal would not be jammed by HI line itself, or any of its harmonics, this was depicted in Carl Sagan Story "CONTACT", it will be possible for us to also run a specific receiver designed at 4.462GHz...TBA

Information from the HI Receiver will be displayed here.

27.12.2009. 01:11