The Tully-Fisher Relation A relation between the rotation speed of a spiral galaxy and its luminosity The more mass a galaxy has  the brighter it is 

Slides:



Advertisements
Similar presentations
Origin & Evolution of the Universe
Advertisements

When Galaxies Collide. It is not uncommon for galaxies to gravitationally interact with each other, and even collide!
Chapter 26: Cosmology Why is the sky dark? The expanding universe Beginning of the universe: The Big Bang Cosmic microwave background The early universe.
Announcements Pick up graded tests Homework 12 due today Pick up Homework 13 Second project is due a week from Friday If you’re following our syllabus,
Chapter 28 Cosmology The Creation and Fate of the Universe.
The Fate of the Universe. The cosmological principle The simplest universes is: Homogenous – the same everywhere you go Isotropic – the same in all directions.
Dark Energy. Conclusions from Hubble’s Law The universe is expanding Space itself is expanding Galaxies are held together by gravity on “small” distance.
The Expanding Universe Except for a few nearby galaxies (like Andromeda), all the galaxies are seen to be moving away from us Generally, the recession.
Cosmology Past, present and future of the universe Is space flat or curved? Where is the center? What lies beyond our limit of vision? What is the universe.
Galaxies What is a galaxy? How many stars are there in an average galaxy? About how many galaxies are there in the universe? What is the name of our galaxy?
Cosmology Astronomy 315 Professor Lee Carkner Lecture 22 "In the beginning the Universe was created. This has made a lot of people very angry and been.
1.Homogeneity 2.Isotropy 3.Universality 4.Cosmological Principle Matter is distributed evenly throughout the universe on the largest scales (~ 300 Mpc).
Cepheids are the key link One primary justification for the Hubble Space Telescope was to resolve Cepheids in galaxies far enough away to measure the Hubble.
Types of Galaxies Elliptical: Spiral: Irregular:.
Universe Eighth Edition Universe Roger A. Freedman William J. Kaufmann III CHAPTER 26 Cosmology Cosmology.
No Structure on Largest Scales (Galaxies distributed fairly uniformly)‏ Surprising given structure on smaller scales Cosmological Principle: Universe is.
Galaxies What is a galaxy? How many stars are there in an average galaxy? About how many galaxies are there in the universe? What is the name of our galaxy?
Lecture 36: The Expanding Universe. Review the ‘zoo’ of observed galaxies and the Hubble Sequence the ‘zoo’ of observed galaxies and the Hubble Sequence.
Friday, October 24 Next planetarium show: Thurs, Nov. 6
Scales in Space and Time in the Cosmos By Dr. Harold Williams of Montgomery College Planetarium
ISkylab 4 Two rungs of cosmic distance ladder –First measure distance to Cepheids with parallax, also note their periods –Establish period-luminosity relationship.
Chapter 26: Cosmology How big is the universe? How long has it been around and how long will it last?
The Evolution of the Universe Nicola Loaring. The Big Bang According to scientists the Universe began ~15 billion years ago in a hot Big Bang. At creation.
Please press “1” to test your transmitter.
Cosmology. Observation #1: universe is homogeneous and isotropic at large scales It cannot be stationary! It should expand or contract Observation #2:
Expanding Universe 1)Hubble’s Law 2)Expanding Universe 3)Fate of the Universe November 20, 2002 Final Exam will be held in Ruby Diamond Auditorium NOTE.
Astronomy 101 Lecture 26, Apr Cosmology: the Expanding Universe – (Chapter 26.1 – 26.4 in text) Our exploration of astronomy from the small scale.
Cosmology: The Study of the Universe as a Whole Physics 360 Geol 360 Astronomy John Swez.
Standard Cosmology.
Astrophysics Cosmology - the study of the nature of the universe.
Introduction to Cosmology. Types of Universes If you were to make a universe, would you give it a finite size, or make it infinite? In a finite universe,
General Relativity and the Expanding Universe Allan Johnston 4/4/06.
Hubble’s galaxy classes Spheroid Dominates Disk Dominates.
Ch : Galaxies & the Expanding Universe How do astronomers know the universe is expanding? What is the big bang theory & what evidence supports.
© 2012 Pearson Education, Inc. Conceptual Physical Science 5 th Edition Chapter 28: THE STRUCTURE OF SPACE AND TIME © 2012 Pearson Education, Inc.
HUBBLE’S LAW Edwin Hubble Hubble’s Law “the farther away a galaxy is from its observer, the faster it appears to be moving away from the observer”
The Universe. Galaxies are believed to have formed from mergers of smaller galaxies and star clusters. Galaxy Formation and Evolution.
Hubble’s Law AST 112. Spectra If a light source is moving toward or away from an observer, its spectral lines shift We can use this to measure approaching.
Quiz #10 What would really happen to you if you were to fall all the way into the Event Horizon of a black hole? We know the gravity is unbelievably strong.
Galaxies and the Universe Ch 25 Section 3. What are the objects in the sky? GALAXIES! Groups of stars, dust, and gases held together by gravity.
DCMST May 22 nd, 2007 Dark matter and dark energy Gavin Lawes Wayne State University.
Galaxy Formation and the Hubble Law Assigned reading: Chapter 16 REMINDER: HW7 due Monday, plus Quiz.
The Expanding Universe
Charles Hakes Fort Lewis College1. Charles Hakes Fort Lewis College2.
General Relativity and Grade-9 Astronomy. 0) Gravity causes time to slow down. Everyday Einstein: The GPS and Relativity OAPT Conference May 12 – 14 McMaster.
Universe Tenth Edition Chapter 25 Cosmology: The Origin and Evolution of the Universe Roger Freedman Robert Geller William Kaufmann III.
The Shape and Fate of the Universe Assumptions in cosmology Olber’s paradox Expansion of the Universe Curvature of the Universe Fate of the Universe.
The Mass of the Galaxy Can be determined using Kepler’s 3 rd Law –Solar System: the orbital velocities of planets determined by mass of Sun –Galaxy: orbital.
The Fate of the Universe. The fate depends on the rate of expansion and the density Density greater than critical value – gravity will halt expansion.
Catalyst Pick up a note sheet. Pick up 1 piece of colored paper. Put “Unit 1 Astronomy” on the front of the colored paper. SIT SILENTLY IN YOUR SEAT.
Milky Way Galaxy. Galaxy A group of stars, dust and gases held together by gravity. 170 billion galaxies in the universe 200 billion stars in a galaxy.
Cosmology. Olbers’s Paradox The Universe may be infinite – if it is, why is the night sky dark?
Chapter 20 Cosmology. Hubble Ultra Deep Field Galaxies and Cosmology A galaxy’s age, its distance, and the age of the universe are all closely related.
© 2017 Pearson Education, Inc.
Solar system Orbital motions AQA SPACE PHYSICS PHYSICS ONLY Red shift
Ch. 14 Cosmology (or “The Whole Enchilada”)
Types of Galaxies Elliptical: Spiral: Irregular:.
Image of the day.
Introduction to Cosmology
Cosmological Assumptions
Galaxies.
Lectures on galaxies and cosmology
Galaxies What is a galaxy?
The Universe.
The Expanding Universe
Absorption lines of a galaxy shift toward the blue end of the spectrum when it moves toward Earth. The lines shift to the red end of the spectrum when.
A galaxy like the Milky Way contains about 10 billion stars.
Cosmology.
The Universe.
Solar system Orbital motions AQA SPACE PHYSICS PHYSICS ONLY Red shift
Presentation transcript:

The Tully-Fisher Relation A relation between the rotation speed of a spiral galaxy and its luminosity The more mass a galaxy has  the brighter it is  the faster it rotates  the wider the spectral lines are Measuring rotation speed allows us to estimate luminosity; comparing to observed (apparent) brightness then tells us the distance

Beyond the Galactic Scale – Clusters of Galaxies The Local GroupThe Virgo Cluster

Superclusters

Beyond Superclusters Strings, filaments, voids Reflect structure of the universe close to the Big Bang Largest known structure: the Great Wall (70 Mpc  200 Mpc!)

Cosmology The part of astronomy (and astrophysics) that deals with the greatest structures in the universe – and the evolution of the universe itself!

Cosmologically relevant Questions –What is in the universe? –How do these things interact? –How does the universe change in time? Is there a beginning? Is there an end?

What’s in the Universe? Answers come from observations  Let’s observe:

What’s in the Universe? THE UNIVERSE clusters and superclusters voids galaxies like the Milky Way quasars Stars nebulae molecular clouds star clusters Solar System black holes pulsars Sun planets moons comets meteors asteroids dust terrestrial jovian Big ……………………………………..small

So, why is the night sky dark? (Olbers’ Paradox) Conclusion: either –Universe is not infinite or –Universe changes in time

Everything is moving away from us! Measure spectrum of galaxies and compare to laboratory measurement lines are shifted towards red This is the Doppler effect: Red-shifted objects are moving away from us

Hubble’s Law The final rung on the cosmic distance ladder Hubble’s observations (1920’s): –Light from distant galaxies is red- shifted –The more distant the galaxy, the greater the red-shift Interpretation: –Galaxies are moving away from us –More distant galaxies are moving faster The universe is expanding, carrying the galaxies with it!

Hubble, 1929 Doppler Shifts of Galaxies

Hubble’s Law H 0 = (65 ± 15) km/sec/Mpc is Hubble’s constant Compare to distance = velocity  time Appears the universe “exploded” from a single point in the past – the Big Bang Age of the universe is 1/H 0 or about 14 billion years Velocity = H 0  Distance Distance = Velocity /H 0

The Expanding Universe Except for a few nearby galaxies (like Andromeda), all the galaxies are seen to be moving away from us Generally, the recession speed of a galaxy is proportional to its distance from us; that is, a galaxy that’s twice as far away is moving twice as fast (aside from local motions within galaxy clusters)

The Expanding Universe This expansion pattern (speed proportional to distance) actually implies that galaxies are all moving away from each other Expansion Milky Way

The Expanding Universe This expansion pattern (speed proportional to distance) actually implies that galaxies are all moving away from each other Expansion Milky Way Twice as far away, so moves twice as fast

The Expanding Universe This expansion pattern (speed proportional to distance) actually implies that galaxies are all moving away from each other A while later: d Start: d 2d2d

The Expanding Universe Each galaxy sees the others moving away with the same pattern (further → faster) As though the galaxies ride on a rubber band that is being stretched! A while later: Start:

The Expanding Universe In three dimensions, imagine the galaxies are raisins in an expanding loaf of bread

Appears the universe “exploded” from a state in which matter was extremely dense and hot – the Big Bang Where did the expansion begin? Everywhere! Every galaxy sees the others receding from it – there is no special point (center) The Expanding Universe

Cosmological Red-Shift Not really a Doppler effect Space itself is being stretched between galaxies

Conclusions from our Observations The Universe has a finite age, so light from very distant galaxies has not had time to reach us, therefore the night sky is dark. The universe e x p a n d s now, so looking back in time it actually s h r i n k s until…?  Big Bang model: The universe is born out of a hot dense medium 13.7 billion years ago.

Big Bang The “start” of the universe, a primordial fireball  the early universe was very hot and dense  intimate connection between cosmology and nuclear/particle physics  “To understand the very big we have to understand the very small”

How does the expansion work? Like an explosion (hot, dense matter in the beginning), but space itself expands! Slowed down by gravitational attraction Attraction is the stronger, the more mass there is in the universe Scientifically described by Einstein’s General theory of Relativity (1915)

More General General Relativity is more general in the sense that we drop the restriction that an observer not be accelerated The claim is that you cannot decide whether you are in a gravitational field, or just an accelerated observer The Einstein field equations describe the geometric properties of spacetimeEinstein field equations

The Idea behind General Relativity –We view space and time as a whole, we call it four- dimensional space-time. It has an unusual geometry, as we have seen –Space-time is warped by the presence of masses like the sun, so “Mass tells space how to bend” –Objects (like planets) travel in “straight” lines through this curved space (we see this as orbits), so “ Space tells matter how to move ”

Effects of General Relativity Bending of starlight by the Sun's gravitational field (and other gravitational lensing effects)

Assumption: Cosmological Principle The Cosmological Principle: on very large scales (1000 Mpc and up) the universe is homogeneous and isotropic Reasonably well-supported by observation Means the universe has no edge and no center – the ultimate Copernican principle!

What General Relativity tells us The more mass there is in the universe, the more “braking” of expansion there is So the game is: Mass vs. Expansion And we can even calculate who wins!

The Fate of the Universe – determined by a single number! Critical density is the density required to just barely stop the expansion We’ll use  0 = actual density/critical density: –  0 = 1 means it’s a tie –  0 > 1 means the universe will recollapse (Big Crunch)  Mass wins! –  0 < 1 means gravity not strong enough to halt the expansion  Expansion wins! And the number is:  0 < 1 (probably…)

The “size” of the Universe – depends on time! Expansion wins! It’s a tie! Mass wins! Time

The Shape of the Universe In the basic scenario there is a simple relation between the density and the shape of space-time: Density Curvature 2-D example Universe Time & Space  0 >1 positive sphere closed, bound finite  0 =1 zero (flat) planeopen, marginal infinite  0 <1 negative saddleopen, unbound infinite