Caldera
Pronunciation:
kal-DEHR-uh
Definition:
A large volcanic crater formed by the collapse of a volcano into itself.
Sample Sentence:
The caldera of Yellowstone National Park, formed by a massive volcanic eruption, is one of the largest in the world and serves as a reminder of the park’s volcanic past.
Celestial Equator
Pronunciation:
suh-LES-chuhl E-kwuh-tor
Definition:
An imaginary circle on the celestial sphere that is equidistant from the celestial poles and intersects the ecliptic at two points, the equinoxes. It represents the projection of the Earth’s equator into space.
Sample Sentence:
Astronomers use the celestial equator as a reference point to locate and track objects in the sky, such as stars and planets.
Credit: Image created by Joshua Cesa.
Cepheid Variable
Pronunciation:
SEHF-eed VAY-ri-uh-bul
Definition:
A type of star that regularly changes in brightness over a characteristic period. It is used as a standard candle for measuring distances in the universe.
Sample Sentence:
The discovery of Cepheid variables in distant galaxies helped astronomers establish the size and scale of the universe and calculate the rate of its expansion.
Credit: Image created by Merikanto
Chasma
Pronunciation:
KAZ-muh
Definition:
A deep, elongated, steep-walled depression on the surface of a planetary body, such as Mars or the moon.
Sample Sentence:
Valles Marineris, the largest canyon in the solar system, is an example of a chasma on Mars, thought to have been formed by tectonic activity or the erosion of water.
Credit: European Space Agency, CC BY-SA 3.0 IGO.
Cislunar
Pronunciation:
SIZ-loo-ner
Definition:
Pertaining to the region of space surrounding the moon and within its gravitational influence, including the moon’s orbit and the near-lunar environment.
Sample Sentence:
NASA plans to establish a permanent cislunar presence, including a habitat for astronauts, in order to support future missions to the moon and beyond.
