On November 1, 1963, the Arecibo Observatory in Arecibo, Puerto Rico, officially opened to scientists from the United States and around the world. The observatory includes what was at the time the largest single-dish radio telescope in the world. (In 2016, China built an even larger radio telescope.)
 
Radio telescopes gather data from radio waves, which have the longest wavelengths on the electromagnetic spectrum. The Arecibo radio telescope uses a large, dish-shaped antenna to direct radio waves from a specific region in the sky.
 
The radio facilities at the Arecibo Observatory serve astronomers, planetary scientists, and atmospheric scientists. Data from the observatory helped astronomers prove the existence of neutron stars—the densest stars in the known universe. Recently, planetary science researchers analyzed data from Arecibo to detect the possible presence of ice on the planet Mercury. Atmospheric science researchers at the observatory study the properties of Earth’s airglow—the faint light emitted by our planet’s atmosphere.
 
Several geographic factors made Arecibo the perfect spot for the massive dish, which measures 305 meters (1,000 feet) in diameter. First, Arecibo is a rural area far from Puerto Rico’s big cities. (Radio telescopes are ideally located in isolated areas, where few radio waves compete with the signals studied by scientists.) Second, Arecibo has a karst landscape, which allowed engineers to build the dish directly into a deep natural sinkhole. This allows the telescope even less radio “interference” from the surrounding area. Third, Puerto Rico is relatively close to the Equator, where scientists could best study planets that pass overhead.
airglow
Noun

faint light emitted by the upper atmosphere of Earth or another planet.

analyze
Verb

to study in detail.

antenna
Noun

structure through which electromagnetic signals are received.

astronomer
Noun

person who studies space and the universe beyond Earth's atmosphere.

Noun

layers of gases surrounding a planet or other celestial body.

atmospheric science
Noun

study of the atmosphere's physical characteristics, motions, and processes, and the way in which these factors affect the rest of our environment.

compete
Verb

to work against someone or something else for an award or acknowledgment.

data
Plural Noun

(singular: datum) information collected during a scientific study.

dense
Adjective

having parts or molecules that are packed closely together.

detect
Verb

to notice.

diameter
Noun

width of a circle.

electromagnetic spectrum
Noun

continous band of all kinds of radiation (heat and light).

emit
Verb

to give off or send out.

engineer
Noun

person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

Noun

imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

factor
Noun

element contributing to an event or outcome.

geographic
Adjective

having to do with places and the relationships between people and their environments.

Noun

water in its solid form.

ideal
Adjective

perfect.

interfere
Verb

to meddle or prevent a process from reaching completion.

isolate
Verb

to set one thing or organism apart from others.

Noun

landscape made of limestone.

Noun

the geographic features of a region.

locate
Verb

to find or identify a place.

massive
Adjective

very large or heavy.

neutron star
Noun

very dense stellar remnant formed by the collapse of a massive star in a supernova.

observatory
Noun

place or building equipped and used for making observations of astronomical, meteorological, or other natural phenomena, usually equipped with powerful telescopes.

Noun

large, spherical celestial body that regularly rotates around a star.

planetary science
Noun

study of planets and planetary systems, particularly our own solar system.

radio wave
Noun

electromagnetic wave with a wavelength between 1 millimeter and 30,000 meters, or a frequency between 10 kilohertz and 300,000 megahertz.

Noun

any area on Earth with one or more common characteristics. Regions are the basic units of geography.

Noun

regions with low population density and large amounts of undeveloped land. Also called "the country."

signal
Verb

to communicate using signs.

Noun

hole formed in a rock or other solid material by the weight or movement of water.

specific
Adjective

exact or precise.

telescope
Noun

scientific instrument that uses mirrors to view distant objects.

universe
Noun

all known matter, energy, and space.

wavelength
Noun

the distance between the crests of two waves.

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