Lesson 6: Galaxies Flashcards
What type of radiation can penetrate the dust clouds of our Galaxy, allowing us to see the spiral structure? (Also known as 21 cm hydrogen radiation)
Radio
Clusters of stars that are orbiting the galactic center at an angle are called ____.
Globular clusters
Who discovered the period-luminosity relation by observing Cepheid variables?
Henrietta Leavitt
What two properties of a Cepheid variable star do we need to know in order to calculate the approximate distance from Earth?
Luminosity and apparent magnitude
Who developed a classification system for galaxies?
Edwin Hubble
What are the broad categories of galaxies?
Spirals, Barred Spirals, Ellipticals, Irregulars
The matter that we can’t see from Earth is known as ____ matter.
Dark
Observing a significant wobble in a star’s orbit would suggest what possibility (if no binary star is visible)?
It’s companion star became a black hole
If the Sun were to become a black hole, what would happen to Earth?
It would continue in the same orbit
What is the “surface” or “boundary” of a black hole called?
Event horizon
True or False: it would be impossible to orbit a black hole, because you would always be sucked in.
False
Our sun is a member of which galaxy?
Milky Way
True or False: Cepheid variables are useful for determining the distances to some galaxies.
True
Edwin Hubble’s discovery of a Cepheid variable in the Andromeda nebula led him to conclude that the nebula was what?
A distant galaxy
True or False: Earth is near the center of the Milky Way Galaxy.
False
