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1
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- Brian Kent
- Honors Symposium
- April 25, 2003
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2
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- Obtained in January 2001 from the National Radio Astronomy Observatory
at Green Bank
- 2.1 meter dish, observations at L-band
- Designed to observe the only radio transition of neutral hydrogen
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3
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- 2.1 meter primary reflector
- F/D = 0.375
- (Cassegrain Focus)
- Pre-Amp frequency:
- 1400-1440 MHz
- L.O. frequency:
- 1370-1800 MHz
- FWHM Beamwidth:
- Stepping motors control altitude and azimuth motion
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4
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- Analog
- 40 kHz Channel Spacing
- Manual Configuration of spectral bandwidth
- Digital
- 7.81 kHz Channel Spacing
- 4 Observing modes: 125, 250 500 and 1200 kHz
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5
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6
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7
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8
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9
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10
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- Hyperfine transition
- 1420.4058 MHz / 21 centimeters
- Occurs from change in orientation of the magnetic dipole
- HI is observed throughout the Milky Way galaxy and is an important tool
in studying other galaxies
- Predicted in the 1940’s by Hendrick van de Hulst
- (Van De Hulst, H. C.,
1945, Ned. Tijdschr. Natuurk,, 11, 201)
- and subsequently discovered
by observation in 1951
- (Ewen, H. I. &
Purcell, E. M., 1951, Nature, 168, 350; Muller, C. A. & Oort,
- J. H., 1951,
Nature, 168, 357)
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11
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12
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13
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14
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15
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16
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17
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18
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- Angular velocity w is given by
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19
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20
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21
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22
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- The amount of hydrogen per square centimeter (column density), NH is given by
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23
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24
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25
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- Instrumentation upgrades have been completed – new receiver and
calibration systems
- Study of neutral hydrogen and galactic rotation comparable to results
from larger telescopes
- System available for physics students interested in radio astronomy
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Notes