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Anorthosite
by NASAan-or-tho-site: noun (pronunced an-awr-thuh-sahyt) – from Greek words an meaning not, and orthos meaning straight
Anorthosite is a type of igneous rock which forms when lava cools slowly. Most of the rocks found on the lunar highlands are anorthosite. These rocks are lighter in color than the basalts which make up the darker regions of the Moon known as the lunar maria, causing the highlands to appear brighter than the maria. Most of the anorthosites brought back from the lunar highlands by the Apollo astronauts are around four billion years old. The picture to the left shows a 4.4 billion year old anorthosite collected from the lunar highlands by the Apollo 16 astronauts. By studying Moon rocks, like anorthosites, we can learn about what the Moon is made of, find clues about how the Moon formed, and even learn more about the origin of our Solar System.
Apogee
ap-o-gee: noun (pronunced ap-uh-jee) – from Greek word apogaios meaning far from the earth
Apogee is the point in the Moon’s orbit when it is farthest from Earth. The term apogee is also used to describe the farthest point of any satellite from Earth. The Moon does not orbit Earth in a perfect circle. Instead it travels in a slightly elliptical (oval shaped) orbit.
As a result the Moon’s distance from Earth changes depending on where it is in its orbit around Earth. At apogee the Moon is at a distance of 251,970 miles (405,500 kilometers) from Earth, and appears smaller to us than it does at any other postion in its orbit. This is about 25,000 miles farther than the Moon is at its closest point (called perigee).
Zooniverse
Apollo Program
A-pol-lo: proper noun – named after Apollo, the Greek god of the Sun.
In 1961, President John Kennedy announced the goal of placing a man on the Moon by the end of the decade. The Apollo Program was created to meet this goal. NASA’s Apollo Program ran from 1961 to 1975. For a detailed overview of the project, visit the Apollo Moon Missions page.
Asteroid
by NASAas-ter-oid: noun (pronunced as-tuh-roid) – from the Greek word asteroeides meaning starlike
Asteroids are rocky-metallic objects which orbit the Sun, but are too small to be considered planets. They range in size from about the size of a boulder to around 600 miles (~1,000 kilometers) across. Asteroids are thought to be leftover material from the formation of our Solar System. Most are found in the Asteroid Belt, a doughnut-shaped ring which lies between the orbits of Mars and Jupiter. However, astronomers have also identified asteroids which have orbits that cross close to the orbits of Earth and the Moon. Several hundred thousand asteroids are known to exist in the Solar System, and many are yet to be discovered. Most of the undiscovered asteroids are the smaller ones (less than about 60 miles or 100 kilometers across), which are more difficult to detect. It is thought that there are over a million of these smaller asteroids. The largest known impact basin on the Moon was formed when a large object, the size of an asteroid or comet, crashed onto the Moon’s surface.
Astronaut
as-tro-naut: noun – from the Greek words astron meaning star and nautes meaning sailor
An astronaut is a person who is trained to travel into space. Some astronauts are trained to pilot or command spacecraft, while others are trained for special jobs as members of the crew. Astronauts are usually military personnel, scientists, or engineers, however people from other professions such as teachers, writers, and politicians have also traveled into space. Almost 500 astronauts from 39 countries have already flown into space. The youngest astronaut to have traveled into space was 25 year old Gherman Titov, while the oldest was 77 year old John Glenn. During the Apollo missions, twenty-four astronauts orbited the Moon, and twelve of them landed and walked on the lunar surface. Today there are always astronauts in space, orbiting Earth in the International Space Station. Sometimes astronauts also travel around Earth in the Space Shuttle. Russian astronauts are called cosmonauts.
Astronomer
as-tron-o-mer: noun (pronounced uh-stron-uh-mer) – from the Greek word astron meaning star
An astronomer is a scientist who studies the Universe and the objects within it. Since there are so many interesting things to learn about within the field of astronomy, astronomers often become specialists who focus their studies on objects such as galaxies, stars, planets, star-forming regions, the Sun, the search for life, or the origin and evolution of the Universe as a whole. In addition, astronomers might become experts on studying certain types of light from the universe and become optical, infrared, or radio astronomers, for example. Many astronomers are professors at universities or colleges and spend time teaching as well as doing research. Astronomers also work at observatories, planetariums, in industry, and for space agencies such as NASA. Anyone interested in becoming an astronomer should take as many science and math courses as they can while in school.
Astronomy
as-tron-o-my: noun (pronounced uh-stron-uh-mee) – from the Greek words astron meaning star and nomos meaning law
Astronomy is a branch of science that involves the study of the Universe beyond Earth’s atmosphere. It is the study of the matter and energy in outer space. Astronomy includes the study of planets, moons, stars, comets, asteroids, nebulae, and galaxies. It also includes the study of the light from objects in space, and the study of how the universe formed and developed. The science of astronomy has existed since ancient times. In the past, the study of astronomy was limited to what could be observed by the eye only. After the invention of the telescope, astronomy progressed rapidly, as more and more objects in the universe were discovered. Today, telescopes can observe extremely distant objects and many different types of light. So much can be studied in astronomy that it is separated into several branches concentrating on a particular type of object or on a certain type of light. Branches of astronomy include solar astronomy, stellar astronomy, planetary astronomy, galactic astronomy, optical astronomy, infrared astronomy, radio astronomy, x-ray astronomy, and more.
Atmosphere
at-mos-phere: noun (pronounced at-muhs-feer) – From the Greek word atmos meaning vapor, and the Latin word sphaera meaning sphere
The atmosphere of a moon or planet is the layer of gases that surround it. The Moon does not have an atmosphere, but very small amounts of gases as well as particles of lunar dust do travel above the Moon’s surface. This gas and dust are sometimes called the lunar atmosphere, but this is not a true atmosphere. Some of the gases, such as radon, are released from within the crust and mantle of the Moon through a process called outgassing. Another source of gas comes from atoms released from the Moon’s surface by micrometeoroid bombardment, the solar wind, and exposure to sunlight. The lunar “atmosphere” is extremely thin and does not surround the Moon as a layer. It is more than one trillion times less dense than Earth’s atmosphere at sea level. It contains elements like hydrogen, helium, sodium, potassium, and argon.
The Moon has no real atmosphere because its gravity is too weak to hold one down. The gravity on the Moon is about six times less than the gravity on Earth, so any gases on the Moon (except for the very heaviest) eventually float away into space. Because the Moon has no atmosphere, astronauts who go out onto the Moon’s surface must carry their own air supply. They also must wear helmets and spacesuits to keep them at a comfortable temperature and pressure, and to protect them against the radiation from space.