Stars
The process that occurs within the cores of stars to produce energy.
What is nuclear fusion?
The longest, most stable phase of a star's life cycle.
What is the main sequence?
The Milky Way is an example of this type of galaxy.
What is a spiral galaxy?
The approximate age of the universe.
What is 13.8 billion years?
These are the only two planets in the solar system that do not have any moons.
What are Mercury and Venus?
The spectral class to which the Sun belongs.
What is G?
The Sun will become one of these in about 5 billion years, once hydrogen fuel in its core runs out.
What is a red giant star?
Most, if not all, galaxies in the observable universe contain one of these near their centers.
What is a supermassive black hole?
The observed relationship between a galaxy's distance from us and its apparent velocity.
What is Hubble's Law?
Titan is the largest moon of this planet.
What is Saturn?
Out of the seven spectral classes, this type is the hottest.
What is O?
Despite sometimes being called "stars," there is no nuclear fusion happening in their interiors. They are essentially the hot, dense, leftover cores of dead low or intermediate-mass stars.
What are white dwarfs?
This type of galaxy is characterized by having many young, blue stars and dense regions of highly-active star formation.
What is a spiral galaxy?
The very faint "glow" from when the universe became transparent for the first time, allowing photons to travel freely across space. It is one of the major "pillars" of the Big Bang theory.
What is the Cosmic Microwave Background?
This natural process, whereby certain gasses retain thermal energy from the Sun, is the reason for the extreme temperatures at the surface of Venus.
What is the greenhouse effect?
Out of the seven spectral classes, this type has the lowest temperature.
What is M?
When a large star explodes in a supernova event, the core may collapse into one of these: a hot, dense ball of subatomic particles, whence the name is derived.
What is a neutron star?
These types of galaxies tend to be populated with very old, evolved stars and have very little interstellar gas and dust.
What are elliptical galaxies?
About 4 billion years ago, the density of matter in the universe dropped below the density of this mysterious "substance," which caused the rate of cosmic expansion to accelerate.
What is Dark Energy?
Coming from the Latin word for "seas," the dark, flat plains on the surface of the Moon are called this.
What are maria?
The length of time that a star will live is almost entirely dependent on this physical quantity of the star.
What is mass?
At the event horizon of a black hole, this quantity exceeds the speed of light, meaning that nothing can ever return from beyond the horizon.
What is escape velocity?
One of the only galaxies in the universe that is actually moving toward us; it is estimated to collide with the Milky Way about 4 to 5 billion years from now.
What is the Andromeda galaxy?
The process whereby the very first atomic nuclei were formed, via nuclear fusion, within the first few minutes of the Big Bang.
What is Big Bang nucleosynthesis?
Being about 3 times the height of Mt. Everest, this Martian mountain is the tallest in the entire solar system.
What is Olympus Mons?