Green Bank Radio Astronomy at NRAO

Credits: 2011 Billy Vazquez, GBT @ West Virginia , NRAO

Radio Astronomy refers to the study of the electromagnetic spectrum between wavelengths of 0.3 mm to 30 m.  This covers frequencies between 1 THz to 10 MHz.    The largest Single Dish Radio Telescope on the continental US is the Green Bank Telescope in West Virginia.  It is only surpassed in dish area by the Arecibo Radio Telescope in Arecibo, Puerto Rico.  Arecibo has greater sensitivity, but operates only between 50 Mhz to 10 Ghz.  It is also restricted to plus/minus 20 degrees from its current latitude of 18 degrees, as the dish is non-steerable.  Green Bank can operate at higher frequencies above 100 Ghz and it can fully track any object in the sky above 5 degrees above the horizon.

Credits: 2006  M. Blanton , D.  Hogg and the SDSS

To the right two images of the same galaxy, NGC 5668.  It is a spiral galaxy as you can see from the optical image to the right with a clear bright core.   Also to the right the radio spectral image of the same galaxy at 1.4 Ghz.   This particular frequency is very useful for astronomers as it gives us lots of information about the observed celestial object.  This line, also known as the 21 cm line, tells us the radial velocity at which this galaxy is receding away from us.   In this case roughly about 1575 km/s away from us.  The graph also tells us that there is rotation of hydrogen gas as can be shown from the double horn feature.   Some of the gas is blue-shifted towards us , while some is red-shifted towards us at about a rate of 50 km/s.

The power of radio astronomy lets us determine many properties of celestial objects and it will only get more interesting in the future as new and improved facilities like the EVLA  and ALMA start producing new science.