ASTR 005 spring 23 final study guide

uvm astr 005 (or astr 1400 and astr 1405 if you're looking at the new course numbers) spring 23 final exam study guide made by yours truly

name the pressure that stabilizes as a white dwarf against gravity, and describe how it is produced

electron degeneracy pressure - once the lowest energy level is filled, the other electrons are forced into higher and higher energy states, resulting in them traveling at progressively faster speeds. These fast moving electrons create a pressure (electron degeneracy pressure)

hat is the upper mass limit of white dwarf stars and why?

aroun 1.4 solar masses because beyond this mass, electron pressure can no longer support the star and it ends up collapsing into an even denser state (either into a neutron star or a black hole)

who discovered the first pulsar, when did they discover it, what kind of instrument were they using, and what were they trying to do?

Professor Dame Jocelyn Bell Burnell discovered the first pulsar in 1967 using a radio telescope meant to look for quasars. She noticed a strange "bit of scruff" in the data coming from her radio telescope, and she initially thought she might have detected a signal from an extraterrestrial civilization.

draw a diagram illustrating what we think a pulsar actually is and label all the important parts of the diagram

study pulsar diagram

what do astronomers look for to detect a black hole and why?

they look for
1: a binary star system with to be a source of X-rays
2: a dark companion (sark star greater than ab 5 solar masses/Ms) so it cannot be a white dwarf or neutron star
3: bright star must be a red giant so the mass pulled towards the hole creates a very hot accretion disk

name the first black hole discovered, when it was discovered, the telescope directly involved in the discovery, and what part of the spectrum that telescope discovered

-Cgynus X-1
-1971 (the 70s)
-the Uhuru X-ray satellite
-X-ray

name the first galactic (supermassive) black hole discovered and describe how it was detected

Sagittarius A was discovered in 1974 using the Green Bank Interferometer of the National Radio Astronomy Observatory

draw a graph showing the strain between the two legs of a LIGO interferometer vs time as a gravitational wave passes through, briefly explain why the wave produces that strain

-Space stretches and compresses as a gravitational wave passes through, and each interferometer can measure that tiny modulation of space. The wave loses amplitude as it travels through space, but we might detec binary black holes or neutron stars as they spiral together and have a higher amplitude.
-study strain diagram

Why are O and B stars usually found in galactic spiral arms + include a diagram

O and B-type stars live for only a few million years, not long enough to move outside of a spiral arm, which is why they are exclusively found there
-study diagram

explain how the first quasar was discovered

The first quasars were discovered in the late 1950s as radio sources in all-sky radio surveys. Using small telescopes and the Lovell Telescope as an interferometer, they were shown to have a very small angular size. Maarten Schmidt measured highly red-shifted hydrogen emission lines and it was determined that these relativistic red-shifts resulted from the general expansion of the universe

3 properties of quasars that were unusual at the time of discovery

1: quasars are very distant
2: very luminous
3: active in early galaxies that are harboring super-massive black holes at their centers

Explain why Einstein manipulated his equations to get a steady state for the Friedmann and Steady State models of the universe
+diagram

Einstein didn't like that the model started with a singularity so he added a constant to it to avoid it. This "cosmological constant" represents a repulsive force
-study diagram

Name 2 observational results that contradict the steady state theory and explain why they do

1: Cosmic Microwave Background (CMB) shows remnants of the Big Band and its radiation proves that the universe is cooling down, which proves that the universe has not always been the same (it must be constant to prove the steady state model)
2: Quasars are old black holes that no longer exist, which proves that the state of the universe is not constant. If the steady state model were correct, there would be quasars much closer to us.

Birefly describe 2 different types of observational evidence for dark matter and include diagrams where appropriate

1: The rotation of galaxies indicates more mass than we can see (include diagram)
2: Light for distant objects is lensed around galaxies more than they should, indicating there to be more mass within the galaxy. Gravitational lensing also occurs when there is no object to be lensed around, leading dark matter to be the cause of the lensing

The Horizon Problem

Distant regions of space in opposite directions of the sky are so far apart that, assuming standard Big Bang expansion, they could never have been in casual contact with each other. How could the CMB be so isotropic so quickly?

The Lumpiness Problem

Gravity pulls objects together in a sort of snowball effect, but every snowball must have a beginning or "seed" around which the material started gathering. If the CMB shows a close to uniform temperature, then there would be no initial seed for gravity to collapse into.
How did mass lump into galaxies and clusters

How did the WMAP telescope confirm the inflationary big bang model?

measured the temperature differences in the CMB radiation. The anisotropies then were used to measure the universe's geometry, content, and evolution. Used to test the Big Band model and the cosmic inflation theory

how did the Planck telescope confirm the inflationary big band model?

To analyze, with the highest accuracy ever achieved, the remnants of the radiation that filled the universe immediately after the Big Bang. We observe this today as the cosmic background

Explain the connection between string theory and holographic universe theory

The holographic principle is an axiom (assumption) in string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region - such as a light-like boundary like a gravitational horizon.