A1 F2015 Cosmology - Los Angeles Mission College · Dark Matter • Dark matter is typically detected by its gravitational effects on matter we can “see” • Baryonic dark matter

Astronomy 1 — Elementary Astronomy LA Mission College

Spring F2015

Cosmology

Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015

Quotes & Cartoon of the Day

“There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.

There is another theory which states that this has already happened."

— Douglas Adams

“Our sun is one of 100 billion stars in our galaxy. Our galaxy is one of billions of galaxies populating the universe. It would be the height of presumption to think that we are the only living things in that enormous immensity.”

— Wernher von Braun


Announcements

• Midterm (maybe) graded…

• Final 12/15 at 10-12 AM!

• Comprehensive

• Will review Thursday


Last Class

• Midterm

• Before that

• Our Galaxy, the Milky Way

• Hubble’s Law (LT Expansion) Need to debrief

• Cosmology (time permitting)


This Class

• Debrief Midterm

• Debrief LT

• Cosmology & Fate of the Universe

• Exoplanets (time permitting)


Spring F2015

Debrief Midterm


Spring F2015

Debrief LT -- “Making Sense of the Universe and Expansion”

Lecture Tutorial pp 151-154


Which of the following statements about the observable universe is correct?

A. It includes all galaxies in the universe.

B. It is the same size for all possible vantage points.

C. It extends to the edge of the universe.

D. It includes the same region of space for all possible vantage points.

E. More than one of the above choices is correct.

Let’s Practice


In the “balloon analogy,” what aspect of the real universe does the inside of the balloon represent?

A. space and time

B. the center of the universe

C. nothing

D. where the universe used to exist


In the “raisin-bread analogy,” what aspect of the real universe does the surface of the loaf represent?

A. the size of the universe

B. the edge of the universe

C. nothing

IT ALL STARTED WITH…


Expanding Universe + General Relativity + The Cosmological Principle implies....


It all started with a Big Bang


Editorial Note

• The Bearnaked Ladies got a lot right except for making all the elements...

• But very smart people had the same wrong idea for a long time

• Only H and He (a little Li) are made by Big Bang nucelosynthesis.


Spring F2015

The Big Bang


What Was the Big Bang

• NOT an explosion

• NOT something that happened in a single place

• “It is better thought of as the simultaneous appearance of space everywhere in the universe. That region of space that is within our present horizon was indeed no bigger than a point in the past. Nevertheless, if all of space both inside and outside our horizon is infinite now, it was born infinite.”*

* WMAP Cosmology 101 Website


The Father of the Big Bang

• Belgian physicist & Catholic priest Georges Lemaitre

• Also predicted theoretically Hubble’s Law

• “Rather than expanding into pre-existing space, The Big Bang created space. It has been expanding ever since.”

http://exlaodicea.files.wordpress.com/2008/01/lemaitre-einstein.jpg

http://exlaodicea.files.wordpress.com/2008/01/lemaitre-einstein.jpg


Energy and Mass are Interchangeable

• Einstein realized that matter and energy are really the same thing

• E=mc2

• Mass can be converted to energy

• Energy can also be converted to mass

• In the hot, compact early universe, matter could not exist, only energy

• Energy later became matter...


From “the History of Everything” by the Barenaked Ladies

“Our whole universe was in a hot dense state...”

Accurate

Let’s Practice


Compared to now, how would you best describe the early universe?

A. hotter and less dense

B. colder and less dense

C. hotter and more dense

D. colder and more dense

EVIDENCE FOR THE BIG BANG


3 Main Observations Support the Big Bang

• The Expansion of the Universe

• The abundance of H, He & Li in the early universe

• The Cosmic Microwave Background Radiation


What is the CMB?

• The Big Bang theory predicts that the early universe was very hot

• Implies that the early universe should be filled with radiation from the heat left over from the Big Bang

• This is the CMB (Cosmic Microwave Background)

http://map.gsfc.nasa.gov/universe/bb_theory.html

http://www.amazon.com/The-Big-Bang-Theory-Complete/dp/B0053O89WY/ref=sr_1_3?ie=UTF8&qid=1351195713&sr=8-3&keywords=the+big+bang


Discovery of CMB

• Imagine you built a spiffy new piece of equipment to measure radio emission from communications satellites...

• ...and you kept getting this irritating noise with wavelength 7.35 cm from every direction!


Discovery of CMB

• What would you do?

• Check the equipment for errors?

• remove the pigeons nesting in your radio antenna?

• ????


Discovery of CMB

• Arno Penzias and Robert Woodrow Wilson, at Bell Labs in 1964

• eventually concluded the faint signal was real & came from outside the galaxy

• At that same time a group of astrophysicists at Princeton were preparing to search for microwave radiation from the early universe.

• A friend told Penzias about their paper

• Penzias & Wilson realized what they had discovered

• and were awarded the Nobel Prize in Physics in 1978

http://en.wikipedia.org/wiki/Microwave_radiation


The CMB today

• Very cold

• ~2.725 K (2.725° above absolute zero)

• can be detected everywhere we look.

• astonishingly uniform in every direction

• tiny fluctuations are of extreme interest to cosmologists

http://www.astro.ubc.ca/people/scott/cmb_intro.htmlfluctuations only one part in 100,000

http://www.astro.ubc.ca/people/scott/cmb_intro.html


The Blackbody Spectrum that got a Standing Ovation

• John Mather presented this the January 1990 meeting of the American Astronomical Society Meeting.

• Based on the first 9 minutes of data from COBE (COsmic Background Explorer)

• John Mather and George Smoot were awarded the Nobel Prize in Physics in 2006.

Photo: P. Izzo

TIMING OF THE BIG BANG


When was the Big Bang?

• Until recently, astronomers estimated that the Big Bang occurred between 12 and 14 billion years ago.

• Solar System ~ 4.5 billion years old

• Humans ~ few million years.

• Astronomers estimate the age of the universe in two ways:

• by looking for the oldest stars

• by measuring the rate of expansion of the universe and extrapolating back to the Big Bang

http://www.amazon.com/The-Big-Bang-Theory-Complete/dp/B0053O89WY/ref=sr_1_3?ie=UTF8&qid=1351195713&sr=8-3&keywords=the+big+bang

http://map.gsfc.nasa.gov/universe/uni_expansion.html


When was the Big Bang?

• We Estimate the age of the universe in two ways:

• looking for oldest stars

• extrapolating back to the Big Bang

• Oldest globular clusters contain only stars less than 0.7 solar masses.

• 11-18 billion years old (15.5 ± 3.5 billion yrs)

• Working backward

• gives age 13.7 ± 0.13 billion years!

THE HISTORY OF THE UNIVERSE


The whole universe was in a hot, dense state...



“...Then nearly fourteen billion years ago expansion started

Wait!”

Accurate



“...The earth began to cool

The autotrophs began to drool

Neanderthals developed tools

We built a wall

We built the pyramids

Math, science, history

Unraveling the mystery

That all started with the Big Bang

Bang!”

FORMATION OF “STRUCTURE”


Formation of Structure

• The universe starts out uniform (homogenous and isotropic) and somehow it becomes “stringy” and “clumpy”.

• First stars and galaxies at about 2 million years

• Process not yet well understood



“... Since the dawn of man is really not that long

As every galaxy was formed in less time than it takes to sing this song”

Partially accurate. The seeds of structure... dark matter organizing the universe… occurred at about 100s. The actual galaxies appeared much later.

“A fraction of a second and the elements were made”

Inaccurate. H & He (a little Li) very quickly at few second. Everything else as massive stars fused elements up to iron in their core and then went supernova.



“... The bipeds stood up straight

The dinosaurs all met their fate

They tried to leap but they were late

And they all died

They froze their asses off

The oceans and Pangea

See ya, wouldn't wanna be ya

Set in motion by the same Big Bang

It all started with the big Bang!”

THE ROLE OF DARK MATTER AND DARK ENERGY


What is the Universe Made of?

• Current theory suggests that 95% of the universe is Dark

• 70% Dark Energy

• 25% Dark Matter

Credit: NASA / WMAP Science Team


Dark Matter

• Dark matter is typically detected by its gravitational effects on matter we can “see”

• Baryonic dark matter is “normal” matter we just haven’t detected (too cold/faint)

• Not likely to account for all the “missing matter”

• Nonbaryonic dark matter is the exotic stuff

• One of the primary motivations for building “supercolliders"


Dark Energy

• In 1998 we discovered that the Universe is actually speeding up its expansion

• total shock to astronomers.

• Discovered by observing Type Ia supernovae

• Surveys determined they were fainter than their redshift-distance indicated


Dark Energy

• "dark energy" refers to the fact that something must be causing space to accelerate in its expansion.

• We don’t know what it is. At all.

• Some astronomers identify dark energy with Einstein's Cosmological Constant.

http://imagine.gsfc.nasa.gov/docs/dict_ei.html#einstein

http://imagine.gsfc.nasa.gov/docs/dict_ad.html#cosmological_constant


Here we are

• Just when you started to think you knew what was in the Universe....

• We think 70% of it is made out of something that we have no idea what it is!

• The ultimate fate of the Universe depends on this unknown stuff

THE FATE OF THE UNIVERSE


Big Crunch, Big Freeze, Big Rip?

• Mass (or mass and energy) determine the scenario.


Fate of the Universe

• The most current relevant results, support the “Big Chill” scenario

• from WMAP (Wilkinson Microwave Anisotropy Probe)

• Other scenarios, however, are not conclusively ruled out.

• Stay Tuned



“... It's expanding ever outward, but one day

It will cause the stars to go the other way

Collapsing ever inward,

We won't be here,

It won't be heard

Our best and brightest figure that it'll make an even bigger Bang!”

Not ruled out! However, not what the best current data suggests. It all depends on dark energy & dark matter. Know how to defend it!



“... Austrelopithicus would really have been sick of us

Debating how we're here

They're catching deer

We're catching viruses

Religion or astronomy

Descartes, Deuteronomy

It all started with the Big Bang

Music and mythology

Einstein and astrology...”



“... It all started with the big bang

It all started with the big

Bang!”

Yep

Let’s Practice


What is the ultimate fate of the Universe?

A. To expand forever and grow colder and colder.

B. To remain exactly as it is today.

C. To stop expanding, turn around, and eventually become a point again in the “Big Crunch”.

D. We don’t really know.


What do observations of the structure and content of the universe suggest will be the ultimate fate of the Universe?

A. To expand forever and grow colder and colder.

B. To remain exactly as it is today.

C. To stop expanding, turn around, and eventually become a point again in the “Big Crunch”.

D. We don’t really know.


Most of the Universe is made up of which of the following?

A. Visible matter

B. Energy

C. Baryonic dark matter

D. Non-baryonic dark matter

E. Dark energy


Dark energy is _______.

A. what keeps the Cosmic Microwave Background warm

B. a name for the unknown cause of the Universe’s present increase in its rate of expansion

C. what you get when you plug dark matter into E=mc2

D. the cosmological equivalent of dragons


Spring F2015

Other Worlds

Extrasolar planets and systems


There are a lot of planets out there!

• 1879-1935 extrasolar planets around 1225 stars

• 471-484 multiple planet systems

• http://exoplanet.eu/catalog/

• Simple flat-table list

• 4696 Kepler candidates!

http://exoplanet.eu/catalog/


There are a lot of planets out there!

• 298 are very large

• Radius larger than 6x Earth

• 150 are small

• Radius less than 1.25 x Earth

DETECTION METHODS


How do we find them?

• Direct imaging

• Rare

• Radial Velocity (RV)

• Planet induces doppler shift in parent star

• Transit photometry

• Planet blocks light from parent star

• Gravitational microlensing

• Planet causes background object to brighten

• Astrometry

• Planet causes parent star to shift position periodically


Exoplanet Image

• Beta Pictoris about 63.5 light years from Earth

• Beta Pic b (planet)

• dist from Beta Pic about 9x dist Earth from Sun

• VERY large, ~ 1.6x radius of Jupiter

Beta Pictoris b (bright spot) orbiting its star (center) Credit: Bruce Macintosh et al.


RV Animation


Transit Method Animation

KEPLER


Kepler

• Capable of finding earth-sized planets in the habitable zone of nearby stars

• Transit method

• 962 confirmed planets to date

• Now in modified extended mission K2 (has lost 2 reaction wheels)


Kepler Overview


MOST EARTHLIKE PLANET “EARTH 2.0” KEPLER 452B


Transit Graph


Artist’s Concept


Kepler 452b


Kepler 186-f came first

• Kepler 186f discovered April 2014 was first Earth-size planet in Habitable zone.

• Composition not as clearly confirmed as rocky

• Orbits very close to a dim M-type Star

• about 500 ly distant



“Earth 2.0” Kepler 452b

• Discovered July 2015 (press con 7/23)

• Orbits G-type Star

• about 1400 ly distant

WRAP-UP


Topic for Next Class

• The Big Bang & the fate of the universe


Reading Assignment

• Astro: 11

• Astropedia:17


Homework

• None at this time

Documents

A1 F2015 Cosmology - Los Angeles Mission College · Dark Matter • Dark matter is typically detected by its gravitational effects on matter we can “see” • Baryonic dark matter