Interpreting Hubble’s Law Barbara Ryden Department of Astronomy The Ohio State University.

Slides:

Advertisements

Similar presentations

Some Conceptual Problems in Cosmology Prof. J. V. Narlikar IUCAA, Pune.

Advertisements

Origin & Evolution of the Universe

Expanding Space. In an infinite Universe… Size Age Every line of sight would end on a star. Every star would be observable. The night sky would be very.

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,

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 Age of the Universe. The universe is expanding !!  The visible universe is made up of clusters of stars, held together in galaxies by their mutual.

If the sequence above represents a range of stars that are close to us ( ) and at increasingly far distances, how do we interpret the changing positions.

Cosmology Equipped with his five senses, man explores the universe around him, and calls the adventure "science". -- Edwin Powell Hubble.

15 The Big Bang Where do we come from, where are we going?

© 2010 Pearson Education, Inc. Chapter 20 Galaxies and the Foundation of Modern Cosmology.

Class 21 : Other galaxies The distance to other galaxies Cepheid variable stars. Other methods. The velocities of galaxies Doppler shifts. Hubble’s law.

18 The Big Bang Where do we come from, where are we going?

ASTR100 (Spring 2008) Introduction to Astronomy Other Galaxies Prof. D.C. Richardson Sections

© 2010 Pearson Education, Inc. Chapter 20 Galaxies and the Foundation of Modern Cosmology.

Physics 133: Extragalactic Astronomy ad Cosmology Lecture 4; January

Galaxies and the Foundation of Modern Cosmology II.

Observables So far we have talked about the Universe’s dynamic evolution with two Observables –a –the scale factor (tracked by redshift) –t – time So a.

Expansion of the Universe Alexandra Higareda DeMaris Wilson.

Edwin Hubble ( ) Biography American astronomer Education: University of Chicago First to show other galaxy by photographing stars of Andromeda.

GALAXY FORMATION AND EVOLUTION - 1. The Expansion of Galaxies In the 1920’s, Edwin Hubble demonstrated that all the `nebulae’ observed in the sky, which.

Lecture 36: The Expanding Universe. Review the ‘zoo’ of observed galaxies and the Hubble Sequence the ‘zoo’ of observed galaxies and the Hubble Sequence.

By Jaedyn Waggoner. Block C. Mr. Horton. Science 9 THE UNIVERSE.

Do your course evaluations. I will add 5 points on your final exam if you complete the evaluation.

Various Techniques for Measuring Astronomical Distances Alex Blanton 1.

The Expanding Universe. Discovery of Expansion 1929: Edwin Hubble measured the distances to 25 galaxies: Compared distances and recession velocities Calculated.

Invisible Universe Int. Conf - 29 June – 3 July 2009 — Paris, France Dark Energy and Cosmic Dust Thomas Prevenslik Berlin, Germany Hong Kong, China 1.

What can electromagnetic waves tell us about the movement of planets, stars, and galaxies?

Visible universe is an infinitesimal fraction of the material from the big bang.

PHYS 205 Galaxies Where we live: Milkyway Galaxy Orion Arm System of Sol Third Planet.

The Expanding Universe

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.

Hubble’s Law Our goals for learning What is Hubble’s Law?

Galaxies Chapter 16. Topics Types of galaxies Dark Matter Distances to galaxies Speed of galaxies Expansion of the universe and Hubble’s law.

Radio Galaxies and Quasars Powerful natural radio transmitters associated with Giant elliptical galaxies Demo.

Expanding Space. In an infinite Newtonian Universe… Size Age Successive shells of stars – # of stars increases R 2 Intensity decreases 1/R 2 Shells are.

Midterm exam: date: March 17, 2006, 8:15 a.m. date: March 17, 2006, 8:15 a.m. location: Conrad Naber Hall location: Conrad Naber Hall bring pocket calculator.

The Big Bang Thursday, January 17.

Chapter 16 The Milky Way Galaxy 16.1 Overview n How many stars are in the Milky Way? – About 200 billion n How many galaxies are there? – billions.

EXPANDING UNIVERSE. OLBERS PARADOX Olbers’ paradox “The night sky is dark.” This statement is called Olbers’ paradox, after astronomer who discussed.

Chapter 15 A Universe of Galaxies The Hubble Deep Field 10 day exposure –field located in the Big Dipper.

Astro-2: History of the Universe Lecture 3; April

Cosmology and extragalactic astronomy Mat Page Mullard Space Science Lab, UCL 4. Redshift.

The Expanding Universe: Evidence for Acceleration 1.Review of Hubble’s Law 2.Excel Activity: Hubble’s Law with recent data 3.Modern interpretation of a.

Ohio University - Lancaster Campus slide 1 of 17 Spring 2009 PSC 100 Hubble’s Law: The Age, Size, and Expansion of Our Universe.

Hubble’s Law Astrophysics Lesson 16.

Lecture 16: Deep Space Astronomy 1143 – Spring 2014.

The Age of Things: Sticks, Stones and the Universe Distances, Redshifts and the Age of the Universe

Learning Objective To understand how Edwin Hubble provided evidence showing the relative scale of the Universe. Learning Outcome To be able to explain.

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.

DCMST May 22 nd, 2007 Dark matter and dark energy Gavin Lawes Wayne State University.

THE BIG BANG THEORY The Expanding Universe. Review Human demonstration.

Length Contraction. Relative Space  An observer at rest measures a proper time for a clock in the same frame of reference.  An object also has a proper.

Expanding Space. In an infinite Universe… Size Age Every line of sight would end on a star. Every star would be observable. The night sky would be very.

Hubble’s Law: Measuring the Age of the Universe Dr Lisa Jardine-Wright Cavendish Laboratory, University of Cambridge.

12 OUR PLACE IN THE UNIVERSE The parallax method Review knowledge and understanding of cosmology Learn how to use the parallax method to determine distances.

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.

Option D. 3. Universe was born around 13.8 billion years ago in process called Big Bang In the beginning, all matter & energy in the entire universe was.

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.

The Cosmological Redshift DEBATE TIME!!!. The spectral features of virtually all galaxies are redshifted  They’re all moving away from us.

The Age, Size, and Expansion

Assignment #8: Due December 2

Assignment #9: Due May 1 EXERCISE

i>clicker Quiz #12 Which of the following statements is FALSE?

Expanding Space.

Winner of several awards

Chapter 20 Galaxies Determining Distance

Galaxies Chapter 16.

A galaxy like the Milky Way contains about 10 billion stars.

Presentation transcript:

Interpreting Hubble’s Law Barbara Ryden Department of Astronomy The Ohio State University

All physics & astronomy majors should take a cosmology course as a “capstone” experience. thermodynamics, statistical mechanics, quantum mechanics, classical dynamics, general relativity, nuclear physics, atomic physics, particle physics…

historical For non-science majors, a historical overview of cosmology emphasizes how new observations lead to new cosmological models.

Malcolm Longair (1993) QJRAS, 34, 157:

Hubble (1929) PNAS, 15, 168

Lesson: Typos happen. Hubble (1929) PNAS, 15, 168

What are “VELOCITY” and “DISTANCE”? Hubble (1929) PNAS, 15, 168

Humason (1931) ApJ, 74, 35

“VELOCITY” = c z, where c = speed of light and z = percentage shift in wavelength of light. Observation = redshift (z) Interpretation = velocity (v) (Mt. Wilson Observatory, 1931)

Possible interpretations of the observed redshift: Doppler shift: z = v/c (Galaxies are moving away from the observer through space.) Gravitational redshift: z = v esc /c (More distant galaxies are more luminous, and have deeper potential wells.) Cosmological redshift: z = a observation /a emission - 1 (In the limit of small redshift, z = v/c, where v is the relative speed of emitter and observer due to expansion of space.) Tired light: z = E emission /E observation - 1 (Photons lose energy as they move through static space.)

Hubble (1929) PNAS, 15, 168

Andromeda Galaxy: 2 million light-years away Big Problem Big Problem for Astronomers: no sense of depth looking at the sky. minutes Comet Hale-Bopp: 10 light-minutes away

Lesson: measuring the distance to an astronomical object is damnably difficult. Hubble used the “standard candle” method.

Obvious problem with standard candles: if your assumed luminosity is crap, your computed distance is Edwin Hubble fell into this trap. (Beware of “appeal to authority”: even Homer nods.)

Hubble (1929) PNAS, 15, 168

Hubble’s law in mathematical form: v = H 0 r v = “velocity” r = “distance” H 0 = Hubble constant Hubble’s value of the Hubble constant ≈ 500 km/s/Mpc WMAP value = 71.0 ± 2.5 km/s/Mpc

Not-as-obvious problem with standard candles: our equation assumes Euclidean geometry. What if Euclid nods on large scales? Another problem with standard candles: our equation assumes photon energy is conserved. Redshifted photons lose energy.

But wait! These aren’t problems, they are opportunities! Deviations of Hubble’s law from a straight line at large distance/redshift tells us about the expansion history of the universe.

One set of observations … many possible interpretations. both Hubble acknowledged the existence of both Doppler shifts and cosmological redshifts.