Cepheid variable stars in other galaxies tell us their absolute brightness. By accurately measuring the apparent brightness of these stars, astronomers can precisely determine the distance to the galaxy in which they reside. Star: A huge ball of gas held together by gravity. The central core of a star is extremely hot and produces energy. Some of this energy is released as visible light, which makes the star glow. Stars come in different sizes, colors, and temperatures. Our sun, the center of our solar system, is a yellow star of average temperature and size. Starburst Galaxy: A galaxy undergoing an extremely high rate of star formation. Starburst galaxies contain massive, deeply embedded stars that are among the youngest stars observed. Star Cluster: A group of stars born at almost the same time and place, capable of remaining together for billions of years because of their mutual gravitational attraction. Star Formation: Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. Static: Random noise in a radio receiver. It can also be heard in telephone lines and cell phones. Stellar Black Hole: A black hole formed from the death of a massive star during a supernova explosion. A stellar black hole, much like a supermassive black hole, feeds off of nearby material – in this case, the dead star. As it gains mass, its gravitational field increases. Stellar Disk/Circumstellar Disk: A torus, pancake, or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form.
Stellar Evolution (Stellar Lifecycle): The process of change that occurs during a star’s lifetime from its birth to its death. Stellar Nursery: A region in space where stars are forming from a cloud of gas and dust. Stellar Parallax: The apparent change in the position of a nearby star when observed from Earth due to our planet’s yearly orbit around the Sun. This method allows astronomers to calculate distances to stars that are less than 100 parsecs from Earth. Stellar Wind: Fast moving flows of material (protons, electrons, and atoms of heavier metals) that are ejected from stars. Strong Force: The force that binds protons and neutrons within atomic nuclei and is effective only at distances less than 10-13 centimeters Sun: The star at the center of our solar system. An average star in terms of size and mass, the Sun is a yellow dwarf of spectral type G2. It is about 5 billion years old, contains 2 * 10 30 kilograms of material, and has a diameter more than 100 times that of Earth. Sunspot: A region on the Sun’s photosphere that is cooler and darker than the surrounding material. Sunspots often appear in pairs or groups with specific magnetic polarities that indicate electromagnetic origins.
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- Hubble Space Telescope