Neutral Hydrogen

National Radio Astronomy Observatory

For more information contact

Sue Ann Heatherly

Atomic hydrogen emits radio waves at a unique frequency: 1420.41 MHz. But, if the hydrogen gas clouds moving away from us, this frequency will be doppler shifted to lower frequencies. If the gas is moving toward us, this frequency will be shifted to higher frequencies!

Resources:
What are spectral lines? http://www.colorado.edu/physics/PhysicsInitiative/Physics2000/quantumzone/

What is Neutral Hydrogen? http://antwrp.gsfc.nasa.gov/apod/ap961218.html

What is the Doppler Shift?

• http://www.astro.ucla.edu/~wright/doppler.htm
• http://archive.ncsa.uiuc.edu/Cyberia/Bima/doppler.html
• http://www.lon-capa.org/~mmp/applist/doppler/d.htm
• Hydrogen in the Milky Way: http://adc.gsfc.nasa.gov/mw/mmw_images.html
• Hydrogen in other galaxies: http://www.gb.nrao.edu/~rmaddale/Education/Wvsta'98/index.html

Radio Frequency Interference:

• Spectrum allocation chart: http://www.ntia.doc.gov/osmhome/allochrt.html
• Spectrum use details: http://www.jneuhaus.com/fccindex/spectrum.html
• FCC wireless services description: http://wireless.fcc.gov/services/index.htm?job=wtb_services_home
• FCC Database search:
  • http://svartifoss2.fcc.gov/reports/lat_long_freq.cfm?accessible=YES
  • http://wireless2.fcc.gov/UlsApp/UlsSearch/results.jsp
• RFI page at the NRAO: http://www.gb.nrao.edu/IPG/

Why is hydrogen important? NRAO Press Releases http://www.nrao.edu/pr/

Experiment:
Design an experiment using the Quiet Skies Detector that will inform your team about RFI around 1420.41 MHz  and below in your area.