Transcript STARS
STARS By Freya What are stars made out of? • A star is a massive, luminous ball of plasma. • The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. • Stars are big exploding balls of gas, that are mostly hydrogen and helium. • A star begins as a collapsing cloud of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. Once the stellar core is sufficiently dense, some of the hydrogen is steadily converted into helium through the process of nuclear fusion. The remainder of the star's interior carries energy away from the core through a combination of radiative and convective processes. The star's internal pressure prevents it from collapsing further under its own gravity. What is the Sun made out of? • The surface of the Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24-25% of mass,7% of volume). • Other elements, include iron, nickel, oxygen, silicon, sulphur, magnesium, carbon, neon, calcium, and chromium. • The Sun has a spectral class of G2V. G2 means that it has a surface temperature of approximately 5,780 K, giving it a white colour that often, because of atmospheric scattering, appears yellow when seen from the surface of the Earth. Why do stars twinkle? • For most of its life, a star shines because thermonuclear fusion in its core releases energy that traverses the star's interior and then radiates into outer space. How old are stars? • Most stars are between 1 billion and 10 billion years old. Some stars may even be close to 13.7 billion years old—the observed age of the universe. The oldest star yet discovered, HE 1523-0901, is an estimated 13.2 billion years old. • The more massive the star, the shorter its lifespan, primarily because massive stars have greater pressure on their cores, causing them to burn hydrogen more rapidly. The most massive stars last an average of about one million years, while stars of minimum mass (red dwarfs) burn their fuel very slowly and last tens to hundreds of billions of years. What are red supergiants? • Red supergiants are supergiant stars (luminosity class I) of spectral type K-M. They are the largest stars in the universe in terms of Volume, although they are not the most massive. • Stars with more than about 10 solar masses after burning their hydrogen become red supergiants during their helium-burning phase. These stars have very cool surface temperatures (3500-4500 K), and enormous radii. Characteristics of a star. • Almost everything about a star is determined by its initial mass, including essential characteristics such as luminosity and size, as well as the star's evolution, lifespan, and eventual fate. What are shooting stars? • A shooting star is the common name for the visible path of a meteorites as it enters the atmosphere. A shooting star is also broken pieces of meteors that have become broken off in space. What is a meteoroid? • A meteoroid is a small sand to boulder-sized particle of debris in the solar system. The visible path of a meteoroid that enters Earth’s (or another body's) atmosphere is a meteor, commonly called a "shooting star" or "falling star". Many meteors are part of a meteor shower. The root word meteor comes from the Greek meteōros, meaning high in the air. THE END… By Freya!!!