3.33.3RADIO RADIO

TELESCOPESTELESCOPES

Radio AstronomyRecall, radio waves can penetrate through Earth’s

atmosphere through atmospheric windows and be observed from the ground.Signals are astonishingly weak requires highly sensitive

equipment in order to detect such signals.

Radio TelescopesThe large dish

focuses the energy of radio waves onto a small receiver (antenna).

Amplified signals are then stored in computers and converted into images, spectra, etc.

Radio Maps

Radio telescopes do no produce an image, but rather a map of the radio intensity at different points.Just like a weather map

has contours filled with color to indicate areas of precipitation …

… Radio maps are usually represented using contours to mark areas of similar radio intensity.

Radio InterferometryA radio astronomer works under three handicaps:

1) poor resolution, 2) low intensity, and 3) interference

Can combine two or more radio telescopes to form a radio interferometer capable of much higher resolution.

Radio InterferometryThe Very Large Array (VLA) consists of 27 dish

antennas spread in a Y-shape across the New Mexico desert.Combined to simulate a large dish of 36 km. in

diameter.

Others include: Very Long Baseline Array (VLBA), Hawaii Virgin

Islands* Square Kilometer Array D ~ 6000 km.

Largest Radio Telescopes

Advantages of Radio Astronomy1. A radio telescope can reveal where clouds of

cool hydrogen and other atoms/molecules are located.Places where stars are born nebulaCool hydrogen emits radio energy at wavelengths of 21

cm.

2. Dust in space does not impact radio signals.Radio waves from far across the galaxy pass unhindered.

3. Can detect objects more luminous at radio wavelengths than at visible wavelengths.Includes intensely hot gas orbiting black holes.Some of the most violet events occurring in the universe

are detectable at radio wavelengths.