Galaxy Basics
What is the definition of a galaxy?
a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity
What is the name of the effect that describes how light from galaxies shifts to longer wavelengths as they move away?
Doppler red-shift
In what year was the Hubble Space Telescope launched?
1990
What are the four main types of galaxies in Hubble’s classification system?
Elliptical, Spiral, Barred Spiral, and Irregular
How many galaxies are estimated to exist in the observable universe?
Between 100 billion and 2 trillion.
On average, how many stars does a galaxy contain?
100 million stars
What is the name of the mysterious force that is causing the expansion of the universe to accelerate?
Dark energy
What are the three types of light used in Hubble’s deepest images?
Visible, near-infrared, and ultraviolet
What type of galaxy is the Milky Way?
Barred spiral galaxy
What are the two main galaxies in the Local Group?
The Milky Way and Andromeda
What is the typical size range of a galaxy in light-years?
3,000 to 300,000 light-years in diameter
How much of the known universe is made up of "normal" matter?
About 5%
What is the most famous image taken by Hubble that showed thousands of distant galaxies in a tiny patch of sky?
The Hubble Deep Field
How are elliptical galaxies classified within Hubble’s tuning fork?
By their shape, from E0 (nearly spherical) to E9 (highly elongated)
What did Edwin Hubble originally think about the "tuning fork" classification of galaxies?
He believed galaxies evolved from one type to another, but this idea was later proven incorrect.
What is the name of the galaxy cluster that the Milky Way belongs to?
The Local Group
What is the name of the large-scale structure that describes how galaxies, clusters, and superclusters are arranged in the universe?
The Cosmic Web
What did Hubble confirm about black holes?
It confirmed the existence of supermassive black holes at the centers of most galaxies.
What is the main difference between a barred spiral and a regular spiral galaxy?
A barred spiral has a distinct central bar structure that extends through its core, while a regular spiral does not.
What are the two dwarf galaxies that orbit the Milky Way and can be seen from the Southern Hemisphere?
The Large Magellanic Cloud and the Small Magellanic Cloud.
What is the largest known structure in the universe that is made up of groups and clusters of galaxies?
supercluster
What did Edwin Hubble discover about galaxies that led to the conclusion that the universe is expanding?
He discovered that galaxies are moving away from us, and the farther away they are, the faster they are moving (redshift).
What is the name of the Hubble image that revealed the most distant galaxies ever seen, dating back to 450 million years after the Big Bang?
The Hubble eXtreme Deep Field (XDF)
What type of galaxy is most likely to form after a major galaxy collision?
An elliptical galaxy.
How long will it take to count to 1 billion if counting one number per second?
32 years