Astronomy Flashcards
A stellar core remnant composed mostly of electron-degenerate matter. Very dense: its mass is comparable to that of the Sun, while its volume is comparable to that of Earth. It’s faint luminosity comes from the emission of stored thermal energy; no fusion takes place inside this wherein mass is converted to energy.
White Dwarf
Stars that have exhausted the supply of hydrogen in their cores and have begun thermonuclear fusion of hydrogen in a shell surrounding the core. They have radii tens to hundreds of times larger than that of the Sun. However, their outer envelope is lower in temperature, giving them a reddish-orange hue. Despite the lower energy density of their envelope, they are many times more luminous than the Sun because of their great size.
Red Giant
A celestial object of very small radius (typically 30 km) and very high density, composed predominantly of closely packed neutrons. They are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole.
Neutron star
How old is our sun?
4.5 billion years
Very dim, glowing objects that never gained enough mass to become fully fledged stars. In other words, the temperatures and pressures at their centres never got high enough for nuclear fusion to start.
Brown Dwarf
How many galaxies are there (that we know of) in the universe?
Lower limit of 170 billion
Rough estimate of 2 trillion
An event that occurs upon the death of certain types of stars.
It may expel much, if not all, of the material away from a star at velocities up to 10% of the speed of light. Triggered by gravitational collapse of a massive stars core, or sudden re-ignition of nuclear fusion in a degenerate stars core causing runaway nuclear fusion.
Supernova
How wide is the Milky Way?
Around 150 to 200 thousand light years
A region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form this.
Black hole
