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A Supernova is the explosion of a star at the end of its life cycle. This explosion can outshine entire galaxies and radiate more energy than the Sun will in its lifetime. Supernovae are important for distributing elements throughout the cosmos.

Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation out of their magnetic poles. This radiation can be observed when a beam passes the Earth, and appears pulse-like.

Quasars are extremely luminous active galactic nuclei (AGN), with the light originating from an accretion disk around a supermassive black hole. Quasars are the most distant, and hence the oldest, observable objects in the universe.

The Cosmic Microwave Background is the thermal radiation left over from the time of recombination in Big Bang cosmology. It's considered the oldest light in the universe and provides evidence for the Big Bang theory.

General Relativity is a theory of gravitation developed by Albert Einstein. It describes gravity not as a force but as a consequence of the curvature of spacetime caused by the uneven distribution of mass.

Exoplanets, or extrasolar planets, are planets that orbit a star other than the Sun. They are discovered through various methods, including the transit method and the Doppler effect. They can vary hugely in size, composition, and temperature.

The Big Bang Theory is the cosmological model explaining the early development of the Universe. According to this theory, the Universe expanded from an extremely dense and hot initial state and continues to expand to this day.

Special Relativity is a theory of the relationship between space and time. It introduces concepts such as the constancy of the speed of light in a vacuum and the relativity of simultaneity. It has important implications for high-speed travel and time dilation.

Cosmic inflation is a theory describing the exponential expansion of space in the early universe. The inflationary epoch lasted from $10^{-36}$ seconds after the conjectured Big Bang singularity to some time between $10^{-33}$ and $10^{-32}$ seconds after the singularity.

Hubble's Law describes the observation in physical cosmology that galaxies are moving away from each other at speeds proportional to their distance. This is indicative of an expanding universe, supporting the Big Bang theory.

Dark Matter is a type of matter thought to account for approximately 85% of the matter in the universe. It does not emit, absorb, or reflect light, making it undetectable through direct observation, but its existence is inferred from gravitational effects on visible matter and cosmological structures.

Dark Energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. It's theorized to be responsible for the observed phenomenon of the universe expanding at an accelerating rate.

Neutron Stars are the collapsed core of large stars, which had a total mass between 10 and 29 solar masses. They are the smallest and densest stars known, consisting almost entirely of neutrons.

Black Holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape from it. The theory of general relativity predicts their existence, and they can significantly influence their surroundings.