Galaxies and Big Bang Theory Flashcards
What is a galaxy?
A gravitationally bound system consisting of stars and stellar remnants.
Describe a spiral galaxy?
Spiral galaxies have a central, dense bulge of stars with curving outward arms.
Describe a barred-spiral galaxy?
Barred-spiral galaxies have elongated central bulges (bar) with curving arms at the ends
Describe an elliptical galaxy?
A spherical to flattened-spherical shape with no spiral arms.
What is the name of the galaxy type that does not fit into the Hubble Classifications?
An irregular galaxy
What is a globular cluster?
A large, symmetrical group of stars located in the halo of a galaxy?
What is the halo of a galaxy?
An area in the outer part of a galaxy consisting of the oldest stars and probably dark matter.
What is a rich cluster?
A gravitationally bound group of many galaxies.
What is a poor cluster?
A gravitationally bound group of just a few galaxies.
What is dark matter?
A theoretical source of mass that has a gravitational influence on galaxies.
What is a galactic core?
A dense group of stars located in the center of a galaxy.
Why do scientists theorize the presence of black holes in the center of many galaxies?
Their evidence is the behavior of stars in the central core and x-ray emissions.
In which galaxy is Earth’s Sun found?
The Milky Way Galaxy
In which group is the Milky Way found?
The Local Group
What type of galaxy do scientists believe the Milky Way is?
A barred-spiral galaxy
Approximately how many stars are in the Milky Way galaxy?
Scientists believe the Milky Way contains 100 to 400 billion stars.
Why is it hard for scientists to determine the size of the Milky Way?
The gas and dust scatter visible light.
How do scientists know about some of the structures in the galactic core of the Milky Way?
They use telescopes that collect radio, infrared and x-ray radiation.
Why do scientists think there is a black hole in the center of the Milky Way Galaxy?
The stars that form Sagittarius A are a massive source of radio waves.
How old do scientists believe the Milky Way is?
13.6 billion years old
What are the members of the Local Group?
The Local Group consists of about 30 galaxies including the Milky Way galaxy, the Andromeda galaxy, and the Large and Small Magellenic Clouds.
What is a singularity?
Matter and energy under extreme pressure that is infinitely dense.
Describe the Big Bang Theory
The universe started from a singularity approximately 13.7 billion years ago. The singularity rapidly expanded.
What elements formed shortly after the Big Bang expansion?
Hydrogen, some helium, and trace amounts of Lithium
