Big Bang :
It is the primordial explosion of a highly compact universe; the origin of the expansion of the universe.
Brown dwarf :
It is the failed star, that is, a star in which the forces of heat and gravity reached equilibrium before the core temperature rose sufficiently to trigger nuclear fusion.
Core hydrogen burning :
It is the principal nuclear fusion reaction process of a star.The hydrogen at the star’s core is fused into helium, and the small amount of mass lost is used to produce enormous amounts of energy.
Cosmological redshift :
It is the lengthening of the wavelengths of electromagnetic radiation caused by the expansion of the universe.Redshift is an increase in the detected wavelength of electromagnetic radiation emitted by a celestial object as the recessional velocity between it and the observer increases. The name derives from the fact that lengthening the wavelength of visible light tends to redden the light that is observed. By analogy, “redshift” is applied to the lengthening of any electromagnetic wave.
Critical density :
It is the density of matter in the universe that represents the division between a universe that expands infinitely (unbound, or open) and one that will ultimately collapse (bound, or closed). The density of the universe determines whether it will expand forever or end with a conflagration as dramatic as the Big Bang.
Dwarf planet :
They are Planets like Pluto in our solar system that orbit the host star, but unlike “normal” planets, are too small to clear the neighborhood of their orbit.
Galactic bulge :
It is also called nuclear bulge, this is a swelling at the center of spiral galaxies. Bulges consist of old stars and extend out a few thousand light-years from the galactic centers.
Interstellar matter :
It is the material found between stars. Refers to the gas and dust thinly distributed throughout space, the matter from which the stars are formed.About 5 percent of our Galaxy’s mass is contained in its gas and dust. The remaining 95 percent is in stars.
It is a zone of electrically charged particles trapped by a planet’s magnetic field. The magnetosphere lies far above the planet’s atmosphere.
Schwarzschild Radius :
It is the radius of an object with a given mass at which the escape velocity equals the speed of light. As a rule of thumb, the Schwarzschild radius of a black hole (in km) is approximately three times its mass in solar masses, so 5-solar mass black hole has a Schwarzschild radius of about 5 × 3 = 15 km.
It is the infinitely dense remnant of a massive core collapse of a star.
Solar flares :
It is explosive event that occurs in or near an active region on the Sun’s surface.
Solar wind :
It is a continuous stream of radiation and matter that escapes from the Sun.Its effects can be seen in how it blows the tails of a comet approaching the Sun.
These are irregularly shaped dark areas on the face of the Sun appear dark because they are cooler than the surrounding material. They are tied to the presence of magnetic fields at the Sun’s surface.
A celestial object is in synchronous orbit when its period of rotation is equal to its average orbital period; the Moon, in synchronous orbit, present only one face to Earth.
Tidal bulge :
It is the deformation of one celestial body caused by the gravitational force of another extended celestial body. The Moon creates an elongation of Earth’s oceans—a tidal bulge.
Time dilation :
It is the apparent slowing of time (as perceived by an outside observer) as an object approaches the event horizon of a black hole or moves at very high velocity.