Astronomy Exam 4 Condensed

pdf

School

New Jersey Institute Of Technology *

*We aren’t endorsed by this school

Course

202-A

Subject

Chemistry

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by MagistrateComputerWallaby18

Exam 4: Ch 24 to Ch 29 Chapter 24 Quizlet: - The main sequence O-type star is most likely to become a black hole - According to the general theory of relativity, the presence of mass causes a curvature (or warping) of spacetime - In the first detection of gravitational waves by LIGO in 2015, the waves came from the merger of 2 black holes - Black holes is more likely in the center of the crowded Milky Way - Mass is a key property to predict whether a star will become a black hole - You will be weightless if you are in a freely falling elevator near the top of a tall building Neutron Star - 10 km radius, 20 km diameter - Mainly packed with neutrons - Formed from collapse of a high mass star’s iron core in a massive star supernova Escape velocity of Earth = 11km/sec - This is the minimum speed required to escape Earth’s gravity - Slower if Earth is Bigger (gravity weak) - Faster if Earth is smaller (gravity strong) White Dwarf Limit: Chandrashekar (1.4 Msun) - Electron degeneracy cannot resist gravity above this - Thus stars collapse → Supernova explosion → forms neutron star Mass of Neutron stars has limit 2 to 3 Msun - Above this mass, neutron degeneracy cannot hold off the crush of gravity Neutron Stars in Binary Systems - X-ray binaries occasionally erupts into novae (white dwarf star that explodes on its surface) - Close binaries emits 100,000 times as much energy in X-rays as our Sun - Accreting neutron stars can sometimes erupt with a spike in luminosity Black Hole - Region in space where gravity is so strong that nothing can escape from it - Surrounded by a hot x-ray emitting accretion disk - Formed from collapse of stellar core → escape velocity of surface exceeded the speed of light - Idea originated in 18th century - Mass = times mass of bulge 1 200 Event Horizon forms between - New black hole and universe outside of it - Point of no return for objects entering black hole, nothing can escape - Escape velocity = speed of light Cygnus-1 - An example of x-ray binary - Luminous - Contains extremely luminous star with estimated 18 Solar mass - Orbits companion with a mass of 10 solar mass

- Must be a black hole because it exceeded the limit of neutron star (2 to 3 Msun) Special Relativity - We should think of the 3 dimensions of space and 1 dimension of time as a seamless 4 dimension - This 4 dimension is called Spacetime Schwarzschild Radius - Radius of event horizon (aka. “Size of the black hole”) - Only depends on its mass - Ex: Black hole with mass of Sun has radius about 3 km - Ex: Black hole with mass of 10x Sun has radius about 30 km

Chapter 25 Quizlet: - One should find a variable star (cepheid or RR Lyrae) in a cluster to measure the distance to a globular cluster of stars - A cloud of gas or star that is further from the center will generally take more time to orbit - Suggests there's a black hole at the center of the Milky Way: - Sagittarius A* is a stationary radio source, while objects around it appears to be in motion - Matter in the central region continues to be falling in toward the center - The motion of stars close to the center indicates that there is a mass of 4.6 million solar masses inside their orbits - You would look in the disk for the youngest stars in the Milky Way - The Sagittarius Dwarf Galaxy was on a collision course with the Milky Way and would be swallowed by it eventually Herschel’s Diagram of the Milky Way - Cross section of the galaxy by counting stars in various directions - He only saw the small part of the Milky Way that surrounds us Harlow Shapley - Showed location of globular clusters (part of the Halo) - Used the location of globular clusters to help him determine the extent of the Milky Way and the location of its center The interstellar medium is filled with gas & dust that blocks our view of the galactic disk The sun is located between the galactic center and the end of the disk 28,000 lightyears from the center Milky Way: - Called a spiral galaxy - Bright central bulge located at the center - Halo surrounds the disk - Mostly invisible except for its 200 globular clusters of stars (part of Halo) Andromeda Galaxy - Closest spiral galaxy and the neighbor to Milky Way - Yellow (older) stars in center - Blue (younger) stars on outer regions How did the Milky Way form? - Galaxy formed from a giant protogalactic cloud contained of hydrogen and helium gas that the galaxy turned into stars - But other studies say otherwise because if the Milky Way formed from a single protogalactic cloud, it would’ve accumulated heavy elements during its inward collapse as stars formed and exploded within it. In that case, the outermost stars in the halo would be the oldest and have the smallest proportion of heavy elements The dwarf galaxy is on opposite side of the galactic center from us Diameter of disk is much larger than its thickness (1,000 light years) Orbit of Disk Stars

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

- Stars in the disk orbits in circular paths - Individual stars bobs up and down - This motion gives the disk it’s thickness of about 1,000 light years - Takes a few tens of millions of years Halo & Bulge stars - Travels around the galactic center on a random elliptical path - They reach heights above the disk greater than those reaches by the disk stars - Rounder and puffier than disk - Halo stars are extremely fast Most luminous stars = O stars Red patches = radiation from ionized hydrogen Strongest lines = red hydrogen lines (H alpha lines) Spiral Arms - Most star formation occurs in spiral arms - Home to molecular clouds and clusters of young, blue stars surrounded by ionization nebulae - Stars and gas are densely packed - Theory says it was caused by spiral density - When large gas collides, a new star forms Sagittarius A - The best guess of where our early solar system was - Considered to be very center of galaxy - First discovered as a radio source back in 1980’s - Massive black hole at the center of Milky Way Electromagnetic Radiation is emitted when charged particles are subject to an acceleration perpendicular to their velocity If objects orbits in - Plane → disk is formed - Random → bulge is formed Dark Matter: - Invisible halo surrounding our galaxy - Stuff in space the we never seen before - 95% unknown matter & energy - 5% known matter & energy (ordinary matter) - Dominates the mass of the galaxy There are no star formations in the Halo - Doesn’t have the cold, dense molecular clouds needed for star formation - Almost no gas at all - New stars can only be born in the disk - Halo is hard to see/invisible except for the 200 globular clusters of stars

Disk Population (Population I) Spheroidal Population (Population II) - Both young and old stars - More heavy-elements - Stars in halo and bulge, both of which are roughly spherical - Consists of old stars - Low in mass

Chapter 26 Quizlet: - Elliptical galaxies contains mostly older stars - Collisions and mergers between galaxies can sometimes change a galaxy’s shape - Scientists use Cepheid variables and measure their periods to calculate the distance of very far galaxies - Scientists will find the redshift and use Hubble’s law in the event a galaxy is so far away, that individual stars are impossible to make out - Type Ia supernovae - very bright - Accretion causes it to pass Chan. limit - Useful to astronomers for determining distance to other galaxies - Farther away a galaxy = faster it is moving away from us - Large and Small Magellanic Cloud is useful for astronomers because they are (for galaxies) very close to us, so they are easy to study - To obtain the mass of a spiral galaxy, one must find the speed at which stars/gas near the outer regions of the galaxy are moving It is easier to study galaxies other than the milky way - Magellanic clouds = other galaxies - Hard to measure distances The Great Debate = are nebulae outskirts or independent galaxies? Most distant objects are irregular & red (means they’re old) The milky way is a spiral galaxy that is barred, meaning a straight bar of stars are across the center Local Galaxies are mostly: Spiral Elliptical Irregular - Flat - Cool - Made of gas & dust - Can have bar or no bar - Milky Way has bar of stars - White (stars of all colors/ages) - Yellow & red stars - No recent star formation - Older - Rounder - Hot - Made of hot gas & dust - In 1 direction - Only 2,400 light years away - Not round - Distance galaxies turn out to be more irregular - More common when the universe was younger - White (stars of all colors/ages) Galaxies are sorted based on their physical appearance (by Hubble) - Spiral - No Bar: depends on size of nucleus (A, B, C) & occurrence of spiral arms © - Bar: Sb (types A, B, C) - - Elliptical - O = very round, more stretched

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Why are galaxies different shapes? - Spins fast = spiral , disk forms - Spins slow = elliptical, no disk - High density = elliptical - More energy - Cools quicker - Rapid star formation & no time to settle in disk - Low density = spiral galaxy - Stars form slowly - Settles in disk Some galaxies have more than 1 black hole Standard candles - More luminous = more pulsations (cepheids) - Hubble Space telescope was built to discover cepheid variable stars (pulsating stars)

Chapter 27 Quizlet: - Large elliptical galaxies formed from the collision and merger of many smaller fragments - Dark matter would affect the orbits/motion of our spacecraft as they move through the solar system - Galaxies and Quasars are related because quasars are active supermassive black holes at the center of galaxies - Quasars are very powerful and compact sources of energy at the center of distant galaxies - Have the brightest and large redshift - Resembles little blue stars Active galaxies are more luminous than normal galaxies - Energy source = black hole at the center - Emits more & different type of energy than ordinary galaxy - Seyfert Galaxies = Galaxy with very bright nucleus (strange) - Radio Galaxies - Quasars - Blazars 90% of the galaxy is beyond the edge of the galaxy Blazers = compact centers of elliptical galaxies Quasars - Brightest and largest redshift - Example of active galaxy - Looks like stars - 1,000 more luminous than typical galaxy - Discovered in 1963 - Shows redshifts (very great distances) - Lies at the centers of galaxies - Can exist in spirals and elliptical galaxies - Can support or suppress star formation Bubbles lying above and below the milky way suggests the blackhole as the center of our galaxy was a quasar a few million years ago The number of quasars was at its peak when the universe just formed The star formation rate was at its peak when the universe just formed Quasars and galaxies affect each other: the galaxy supplies fuel to the black hole, and the quasar heats and disrupts the gas clouds in the galaxy.

Chapter 28 Universe age = 13.8 billion years old Blue galaxies = recent star formation - Young stars Yellow/red stars = no recent star formation - Old stars Merger = when galaxies of similar size collides - Very common when the universe was young Galactic cannibalism = when larger galaxy swallows smaller galaxy The universe is isotropic and homogeneous - Isotropic = universe looks the same in all directions - Homogeneous = every large volume of space looks the same Local group - Contains Milky Way - 50+ galaxies - New members are still being discovered Mass bends spacetime and deviated light paths Rich Clusters Virgo Cluster Coma Cluster - Nearest large galaxy cluster - 2,000+ galaxies - 50 million light years away - 1,000+ galaxies - 330 million light years away Supercluster = when galaxy clusters group together with other clusters Galaxies form through a combination of top-down and bottom-up processes Hot & Cold Dark Matter - Hot Dark matter = blocks the growth of clusters - Cold Dark Matter = promotes the growth of clusters Formation of Spiral Galaxies - Top-down formation - All gas stars formed early on - Slow evolution afterward - Bottom-up formation - Rapid collapse - Black hole forms through many collisions - Mergers occur Formation of Clusters - Small clouds formed - Mergers occur - Clusters become superclusters/filaments There are vast empty voids between filaments Galaxies & clusters contain 10x more dark matter than luminous matter

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Chapter 29 Quizlet: - The earth is not part of the M-13 globular cluster - Dark energy makes up ~70% of the density of the universe, making it the most significant constituent of the mass-energy - There is more helium in the universe because the extra helium was made during the first few minutes of the Big Bang, where the entire universe was hot enough for fusion to occur briefly - In the future, all the stars will die and the galaxies will be dark - The expansion of the universe began everywhere at once - Neutral atoms formed a few hundred thousand years after the Big Bang - The 3 degree cosmic microwave background radiation is good evidence that the universe began with a Big Bang The universe is expanding The farther away a galaxy = faster it’s moving away from us Big Bang Theory - Partially describes the origins (start & evolution) of the universe - 13.8 billion years ago - Most likely formed with hydrogen and helium present Universe was so hot during the first few seconds after the Big Bang, that photons could transform themselves into matter, and vice versa in accordance to Einstein’s E = mc^2 The rate at which the universe is expanding is accelerating - We call this dark energy, but we don’t know much about this As universe expands - Space itself expands - Becomes cooler - Light traveling through space will stretch photons - An increase in wavelength would be seen as a redshift 4 possible models of the expanding universe - Can be arranged to predict the time of the big bang (13.8 billion years ago) Particle Era - When particles began to form - Equal amounts of matter and antimatter - Ended when the age of the universe was about 1 millisecond Today, photons outnumber protons where there is 1 billion photons for 1 proton Nucleosynthesis Era - When the universe was only 1 millisecond old, the nuclei was hot and dense enough to fuse to create heavier elements - Ended when universe was 5 minutes old At its death, the universe was about 75% hydrogen and 25% Helium and trace amounts of lithium Nuclei Era - After fusion ceased, the universe consisted of a very hot plasma of hydrogen - It was too hot so nothing could condense to form galaxies

Evidence for Big Bang - Predicts that the cosmic microwave background should have an essentially perfect thermal radiation spectrum - Cosmic Microwave Background = electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation Einstein said that space gets bent The density of matter and energy determines the overall geometry of space - Spherical space - Flat space - Hyperbolic space It is suggested that the universe must have once been hot enough to fuse hydrogen into helium