124 Chapter 2 From the Solar System to the Milky Way
What Can a Radio Telescope Observe?
A radio telescope is another type of astronomical observation tool. But what in the world
can radio waves tell us?
Radio waves are electromagnetic waves, just like light rays or infrared rays. However,
since the wavelength of radio waves is so long, obstacles in their paths don’t cause much
obstruction. This is why you can use your cell phone indoors, whereas light from outside is
obstructed by walls.
Space contains various kinds of interstellar matter, and if some of this matter consists
of heavenly bodies that absorb light such as dark nebulas, it is impossible to use an optical
telescope to observe what is there. Therefore, radio waves are used instead.
Radio telescopes, which were developed in the middle of the 20th century, led to
major advances in astronomy. For example, one of the results that will go down in history
is the discovery of what is believed to be evidence of the Big Bang (this will be explained
in Chapter 3).
A famous radio observatory in the United States is the Very Large Array (VLA), located
near the town of Soccoro in southern New Mexico. Completed in 1980, it consists of 27
radio telescopes, each of which has a diameter of 25 meters (82 feet). The telescopes are
affixed to train tracks, and they can be repositioned and rearranged to act as a single antenna
with a maximum diameter of 36 km (22.3 miles). Astronomers use the VLA to study objects
like radio-emitting stars, black holes, and supernova remnants. Observations from the VLA
have been used to discover water on Mercury and microquasars in the Milky Way galaxy.
The Very Large Array in New Mexico (Credit: NASA)

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