Main sequenceIn astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars spend the majority of their lives on the main sequence, during which core hydrogen burning is dominant. These main-sequence stars, or sometimes interchangeably dwarf stars, are the most numerous true stars in the universe and include the Sun.
Stellar classificationClassification of stars based on spectral properties In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element.
Effective temperatureThe effective temperature (akaET) of a body such as a star or planet is the temperature of a black body that would emit the same total energy as electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve (as a function of wavelength) is not known.
Nuclear fusionReaction that combines atomic nucleiFusion plasma in China's Experimental Advanced Superconducting Tokamak.Nuclear fusion is a reaction in which two or more atomic nuclei combine to form a larger nucleus. The difference in mass between the reactants and products is manifested as either the release or the absorption of energy. This difference in mass arises as a result of the difference in nuclear binding energy between the atomic nuclei before and after the fusion reaction.
Solar massThe solar mass (M☉) is a frequently used unit of mass in astronomy, equal to approximately 2×10 kg. It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes.
HeliumHelium (from Ancient Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements, and it does not have a melting point at standard pressures. It is the second-lightest and second-most abundant element in the observable universe, after hydrogen.
HydrogenChemical element with atomic number 1 (H)–↑H↓Li(none) ← hydrogen → helium
Chemical elementChemical substance not composed of simpler onesThe chemical elements ordered in the periodic table, as shown in the 32-column formatA chemical element is a species of atom defined by its number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its nucleus.
KelvinThe kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI).
FahrenheitThe Fahrenheit scale () is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his scale exist, but the original paper suggests the lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from a mixture of water, ice, and ammonium chloride (a salt).
CelsiusThe degree Celsius is the unit of temperature on the Celsius temperature scale (originally known as the centigrade scale in English), one of two temperature scales used in the International System of Units (SI), the other being the closely related Kelvin scale. The degree Celsius (symbol: °C) can refer to a specific point on the Celsius temperature scale or to a difference or range between two temperatures.*As an Amazon Associate I earn from qualifying purchases.