antimatter: Molecules formed by atoms consisting of antiprotons, antineutrons, and positrons.
astronomer: A scientist who works in the field of research that deals with celestial objects, space and the physical universe.
astrophysics: An area of astronomy that deals with understanding the physical nature of stars and other objects in space. People who work in this field are known as astrophysicists.
atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
black hole: A region of space having a gravitational field so intense that no matter or radiation (including light) can escape.
cosmos: (adj. cosmic) A term that refers to the universe and everything within it.
disk: A round, flat and usually fairly thin object. (in astronomy) A rotating cloudlike collection of gases, dust or both from which planets may form. Or the structure of certain large rotating bodies in the cosmos, including spiral galaxies such as our Milky Way.
electric charge: The physical property responsible for electric force; it can be negative or positive.
electron: A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.
galaxy: A group of stars — and usually dark matter — all held together by gravity. Giant galaxies, such as the Milky Way, often have more than 100 billion stars. The dimmest galaxies may have just a few thousand. Some galaxies also have gas and dust from which they make new stars.
gamma rays: High-energy radiation often generated by processes in and around exploding stars. Gamma rays are the most energetic form of light.
hypothetical: An adjective that described some hypothesis, or proposed explanation for a phenomenon. In science, a hypothesis is an idea that must be rigorously tested before it is accepted or rejected.
interstellar: Between stars.
matter: Something that occupies space and has mass. Anything on Earth with matter will have a property described as “weight.”
Milky Way: The galaxy in which Earth’s solar system resides.
neutron star: The very dense corpse of what had once been a massive star. As the star died in a supernova explosion, its outer layers shot out into space. Its core then collapsed under its intense gravity, causing protons and electrons in its atoms to fuse into neutrons (hence the star’s name). A single teaspoonful of a neutron star, on Earth, would weigh more than a billion tons.
particle: A minute amount of something.
physical: (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
physics: The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the motions and behavior of matter. A scientist who works in such areas is known as a physicist.
positron: A subatomic particle with the mass of an electron, but a positive electrical charge. It is the antimatter counterpart to the electron. So when electrons and positrons collide, they annihilate each other, releasing energy.
scenario: A possible (or likely) sequence of events and how they might play out.
solar: Having to do with the sun or the radiation it emits. It comes from sol, Latin for sun.
solar system: The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
star: The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become hot enough, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
telescope: Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.
theoretical physics: A branch of physics that uses mathematical models to understand the nature and properties of matter and energy. A scientist who works in that field is known as a theoretical physicist .
universe: The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
wavelength: The distance between one peak and the next in a series of waves, or the distance between one trough and the next. It’s also one of the “yardsticks” used to measure radiation. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.