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A theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently that it no longer emits significant heat or light.

A star that has exhausted hydrogen in its core and has begun to fuse helium into heavier elements.

A rare, hot, and bright star that is losing its mass rapidly through a strong, stellar wind.

A cloud of gas and dust in space, serving as a nursery for new stars.

Stars with higher metallicity, typically found in the spiral arms of galaxies, that contain more elements heavier than helium.

A stage in a star's life characterized by the fusion of hydrogen atoms to form helium, which occurs in the core.

A small, dense stellar remnant that has ceased nuclear burning and emits light due to stored thermal energy.

The total amount of energy emitted by a star, galaxy, or other astronomical object per unit time.

Stars with low metallicity, found in the bulges of galaxies and in globular clusters, and are among the first stars formed in the universe.

A contracting mass of gas that represents an early stage in the formation of a star before nucleosynthesis has begun.

A very brief thermal runaway nuclear fusion of helium into carbon in the core of a low mass star.

An extremely dense object composed mostly of neutrons, which remains after a supernova explosion of a massive star.

An aging massive star that has expanded and cooled substantially after exhausting its core hydrogen.

A classification system for stars based on their temperature as determined by the characteristics of their spectral lines.

The explosive death of a star resulting in the ejection of its outer layers at high velocities.

An emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giants during their asymptotic giant branch phase.

A measure of the luminosity of a celestial object, expressed as the apparent magnitude it would have if it were located at a standard distance of 10 parsecs from the observer.

A region of spacetime exhibiting such strong gravitational effects that nothing—not even light—can escape from inside it.

A two-dimensional graph, in which the absolute magnitudes of stars are plotted against their spectral types (color).