Astro Glossary

  • Archaeoastronomy

    The study of astronomical practices and sky lore of ancient civilizations and cultures.

  • Arcturus

    The brightest star of the constellation Boötes. It is an orange-star about 37 light-years from Earth.

  • Argo Navis, the Ship Argo

    An extinct constellation that represented the ship that carried Jason and the Argonauts on their mythological journeys. Its pieces survive as the southern constellations Carina (the keel), Puppis (the poop deck), and Vela (the sails).

  • Aries, the Ram

    Aries is one of the constellations of the zodiac, between Taurus and Pisces. It is a small, faint constellation, distinguished only because of its location along the ecliptic, which is the Sun’s path across the sky. The Sun passes through the constellation in late April and early May. Aries is best viewed in autumn and early winter.

  • Artemis Project

    Artemis is NASA's next project to take astronauts to the Moon. The first test flight launched on November 16, 2022. The second flight, Artemis II, will place astronauts in lunar orbit in 2024 or later, with the third flight projected as the first lunar landing mission since Apollo 17, in December 1972. The project consists of the Space Launch System, which is NASA's most capable booster rocket since the Saturn V Moon rockets; the Orion capsule, which ferry astronauts to the Moon and back; and the SpaceX Starship rocket, which will carry Orion astronauts to the lunar surface.

  • Asian Astronomy

  • Asteroid

    A small, irregularly shaped object made of metal (iron and nickel), rocky materials, or a combination of the two that orbits the Sun or another planet. Most of the asteroids orbit in a broad band between the orbits of Mars and Jupiter. The largest is Ceres, which is about 600 miles (900 km) in diameter.

  • Asteroseismology

    The study of the interior of a star through measuring waves that ripple across its surface. The waves are generated by the motions of giant bubbles of hot gas in a star's outer layer, known as the convective zone, which extends deep below the surface. The waves can travel all the way around the star, causing "jiggles" when they reach the surface. The individual waves can reveal details about the star's structure, interior temperatures, composition, and more. Astronomers measure the waves through tiny changes in the motion of a star's surface toward or away from Earth. Studying similar waves on the Sun is known as helioseismology.

  • Astrobiology and Extraterrestrial Life

    Astrobiology is the study of the conditions under which life might exist on other planets or moons. Extraterrestrial life is hypothetical life beyond Earth. No life has been discovered on any other body, although several bodies in the solar system appear to have conditions that are conducive to life.

  • Astrology and the Zodiac

    Astrology is the art of studying the relative positions of the Sun, Moon, planets, and constellations in the zodiac to explain and predict events on Earth. Not to be confused with astronomy. The zodiac is a ring of constellations that lie along the ecliptic, including Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, and Pisces in order east of the vernal equinox. The constellations in the zodiac are often used by astrologers to help explain and predict events on Earth. Because the zodiacal constellations were defined 2,000 years ago, precession of the Earth’s axis has shifted the position of the Sun relative to the zodiac signs so that they are off by one month, as quoted in daily newspapers.

Shopping Cart
Scroll to Top