Final Exam Flashcards
(52 cards)
Spiral galaxy
Disc shaped like the Milky Way
Old stars in bludgeon, new stars in disc
Low mass ones have fluffy, loose arms and a small bulge
High mass ones have tight arms and a huge bulge
Elliptical
Fuzzy ball of stars
Mainly old stars (NOT forming new stars)
Range in masses from tiny to large
Irregular
Oddly shaped- can be dwarf irregular or merging
Dwarf irregular: small and low mass, lots of new stars, still forming stars
Merging irregular: stars don’t hit each other, gas clouds hit and make new stars. Settle down into elliptical galaxy
Gravity can…
Bend light, focus it like a lens, and magnify more distant objects
Which observation helped us learn that most of the Milky ways mass is dark matter?
Stars and gas orbit the galaxy too fast to be bound by the mass of the visible matter
What is the best analogy for how stars orbit the disk of the Milky Way?
The disk is like a ring of Saturn, since each particle orbits Saturn independently depending on keplers laws
Which observation helped us learn that the sun isn’t at the center of the Milky Way?
We see more globular clusters on the sky in one direction, rather than being evenly spaced
List the parts of the galaxy in the order that they form
Nucleus and halo at the same times disk, spiral arms
Dark matter is difficult to observe because
It doesn’t absorb or emit any light at all
Most of the mass of a cluster of galaxies is
Dark matter
What is a quasar
A galaxy with a very active and very bright supermassive black hole
Distance ladder
The distance to stars near the sun in the Milky Way are measured with parallax (let us get luminosities)
Won’t work at great distances, rest of Milky Way and other galaxies are measured with standard candles
Hubbles law
More distant galaxies are moving away faster, light is redshifted
More distant galaxies have higher redshift
We see a galaxy as younger than it actually is right now
Cosmic web
Clusters of galaxies arranged on a large scale in filaments and empty voids
Most of the mass is dark matter
We can’t see it, we infer it
When we’re galaxies making the most stars
When the universe was 1-5 billion years old
What does bubbles law relate?
Distance and speed at which it is moving away from us
In the first 5 minutes of the universe when fusion was everywhere, what was fusing?
Hydrogen into helium (and a little bit of other stuff)
Photons in the CMB came from
Plasma glowing because it is hot, when the atoms formed
The atoms in your body heavier than iron were probably made
In supernovae when massive stars died
How much of the milky ways total mass is dark matter?
90%
Astronomers were able to measure the mass of the Milky Way by watching stars and applying what law?
Keplers law
Watch the orbit speed and orbit size to measure the mass that makes it orbit
How did we learn where the sun is in the Milky Way?
By mapping the location of globular clusters in the sky
Over time the slight amounts of heavier elements in the galaxy’s gas increase due to
Stars forging heavy elements in their cores and spreading that material into their deaths
Most stars form in the spiral arms of the disk because
Gas in the disk enters the arms, slows down, and gets compressed
