ASTR 1120 ASTR 1120 General Astronomy: General Astronomy: Stars - - PowerPoint PPT Presentation

ASTR 1120 ASTR 1120 General Astronomy: General Astronomy: Stars & Galaxies Stars & Galaxies

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OUR Universe OUR Universe: : Accelerating Universe Accelerating Universe

• Dark Energy

Dark Energy is is causing the causing the expansion of expansion of the universe to the universe to speed up speed up over

• ver

time! time!

• Scientists don

Scientists don’ ’t t know what this know what this dark energy dark energy might be. might be.

REVIEW REVIEW

Chapter 23: In the Chapter 23: In the VERY VERY Beginning Beginning

BIG BANG: beginning of Time BIG BANG: beginning of Time

Early times in the Universe were really Early times in the Universe were really Hot Stuff!! Hot Stuff!!

• If the universe is cooling

If the universe is cooling and expanding now and expanding now… …

– – The Universe was The Universe was hotter hotter at at earlier times earlier times

• The temperature at the

The temperature at the earliest times was more earliest times was more than the energy we create than the energy we create in even our largest particle in even our largest particle accelerators accelerators

• Cosmology at the earliest

Cosmology at the earliest times is explored via times is explored via particle physics particle physics

Photons converted into Photons converted into particle-antiparticle particle-antiparticle pairs and vice-versa pairs and vice-versa (Matter and Energy are (Matter and Energy are the same!!) the same!!)

E = mc E = mc2

2

Early universe was full Early universe was full

• f particles and
• f particles and

radiation because of its radiation because of its high temperature high temperature

Matter, Antimatter, and Energy Matter, Antimatter, and Energy

Planck Era Planck Era 0 - 10 0 - 10-43

• 43 sec

sec Before Before Planck time Planck time =??? =???

• Things were

Things were so small and so small and so dense so dense… … modern modern physics fails physics fails

– –No theory No theory

• f quantum
• f quantum

gravity gravity

• Gravity

Gravity

• Electromagnetism

Electromagnetism

• Strong Force

Strong Force

• Weak Force

Weak Force

The Four The Four Known Known Forces in the Universe Forces in the Universe

Four known forces Four known forces in the universe: in the universe:

• Gravity

Gravity

• Electromagnetism

Electromagnetism

• Strong Force

Strong Force

• Weak Force

Weak Force

Do forces unify at Do forces unify at high temperatures? high temperatures?

Four known forces Four known forces in the universe: in the universe:

• Gravity

Gravity

• Electromagnetism

Electromagnetism

• Strong Force

Strong Force

• Weak Force

Weak Force Yes! Yes! (Electroweak) (Electroweak)

Do forces unify at Do forces unify at high temperatures? high temperatures?

Four known forces Four known forces in the universe: in the universe:

• Gravity

Gravity

• Electromagnetism

Electromagnetism

• Strong Force

Strong Force

• Weak Force

Weak Force Yes! Yes! (Electroweak) (Electroweak) Maybe Maybe (Grand Unified Theories) (Grand Unified Theories)

Do forces unify at Do forces unify at high temperatures? high temperatures?

Four known forces Four known forces in the universe: in the universe:

• Gravity

Gravity

• Electromagnetism

Electromagnetism

• Strong Force

Strong Force

• Weak Force

Weak Force Yes! Yes! (Electroweak) (Electroweak) Maybe Maybe (GUT) (GUT) Who knows? Who knows? (String Theory) (String Theory)

Do forces unify at Do forces unify at high temperatures? high temperatures?

GUT Era GUT Era ~10 ~10-43

• 43-10
• 10-38
• 38 sec

sec Lasts from Lasts from Planck time to Planck time to end of GUT end of GUT force force

Inflation of the Universe Inflation of the Universe

• As strong force

As strong force becomes distinct (end becomes distinct (end

• f GUT era),
• f GUT era), a huge

a huge amount of energy amount of energy is is released released

• Universe

Universe INFLATES: INFLATES:

– – Universe of atomic Universe of atomic nucleus size becomes nucleus size becomes solar system size in solar system size in 10 10-36

• 36 sec

sec

Electroweak Electroweak Era Era ~10 ~10-38

• 38-10
• 10-10
• 10 sec

sec

Lasts from end of Lasts from end of GUT force to end GUT force to end

• f electroweak
• f electroweak

force force

• Universe still

Universe still made up of made up of elementary elementary particles particles (quarks) (quarks)

Particle Era Particle Era (10 (10-10

• 10-.001 sec)
• .001 sec)

Finally Finally temperatures low temperatures low enough that enough that quarks can quarks can combine to form combine to form subatomic subatomic particles particles (protons, (protons, antiprotons, antiprotons, neutrons, neutrons, antineutrons, antineutrons, etc etc… …) )

The Particle The Particle Era Era

• Universe still hot: 10

Universe still hot: 1015

15 to

to 10 1012

12 K

K

• Particles now exist:

Particles now exist: electrons, protons, anti- electrons, protons, anti- protons, anti-electrons, protons, anti-electrons, neutrinos etc. neutrinos etc.

• Particle soup!

Particle soup! Particles Particles and photons/energy and photons/energy created and annihilated created and annihilated

At the end of the particle era, temperatures are low At the end of the particle era, temperatures are low enough that photons cannot collide to create enough that photons cannot collide to create matter/anti-matter anymore. matter/anti-matter anymore. Nearly all the matter and Nearly all the matter and antimatter that is in the universe at that time collides antimatter that is in the universe at that time collides and forms photons. But a little and forms photons. But a little bit of bit of some some type of type of matter matter remains remains… … which type is it? which type is it? A.

• A. Regular matter

Regular matter B.

• B. Anti-matter

Anti-matter C.

• C. There

There’ ’s no way we s no way we can tell! can tell!

Clicker Question Clicker Question

At the end of the particle era, temperatures are low At the end of the particle era, temperatures are low enough that photons cannot collide to create enough that photons cannot collide to create matter/anti-matter anymore. matter/anti-matter anymore. Nearly all the matter and Nearly all the matter and antimatter that is in the universe at that time collides antimatter that is in the universe at that time collides and forms photons. But a little and forms photons. But a little bit of bit of some some type of type of matter matter remains remains… … which type is it? which type is it? A.

• A. Regular matter

Regular matter B.

• B. Anti-matter

Anti-matter C.

• C. There

There’ ’s no way we s no way we can tell! can tell!

Clicker Question Clicker Question

Matter and Anti-matter Matter and Anti-matter

• At end of particle era,

At end of particle era, universe contains matter! universe contains matter!

• Protons must have

Protons must have slightly outnumbered anti- slightly outnumbered anti- protons protons

• Universe ratio

Universe ratio today today: :

– – 1 billion photons (light) for 1 billion photons (light) for every 1 proton (matter) every 1 proton (matter)

• Universe ratio

Universe ratio then then: :

– – 1 billion and 1 protons for 1 billion and 1 protons for every 1 billion anti-protons every 1 billion anti-protons

Era of Era of Nucleo- Nucleo- synthesis synthesis 0.001 sec-3 min 0.001 sec-3 min

Begins when Begins when matter annihilates matter annihilates remaining remaining antimatter antimatter

Era of Nucleosynthesis Era of Nucleosynthesis (Fusion) (Fusion)

• Matter particles are

Matter particles are “ “frozen out frozen out” ”

– – no longer no longer spontaneously spontaneously generated to/from generated to/from photons photons

• Temperatures hot

Temperatures hot enough to enough to fuse fuse protons protons (hydrogen (hydrogen nuclei) into helium nuclei) into helium nuclei nuclei

Nucleosynthesis stops after Nucleosynthesis stops after about 3 minutes about 3 minutes

• Fusion ends because density drops

Fusion ends because density drops

– – remember the universe has been expanding this remember the universe has been expanding this whole time whole time – – Matter left as ~75% hydrogen, ~25% helium, with Matter left as ~75% hydrogen, ~25% helium, with trace amounts of lithium, deuterium trace amounts of lithium, deuterium

• Amounts seen throughout the universe today

Amounts seen throughout the universe today (with slight enhancements of heavy elements (with slight enhancements of heavy elements from from fusion fusion in stars) in stars)

Era of Nuclei Era of Nuclei 3 min - 3 min - 380,000 380,000 yrs yrs

• Most matter was

Most matter was in the shape of in the shape of hydrogen/helium hydrogen/helium nuclei, nuclei, electrons electrons

• Universe has

Universe has become become too cool too cool to blast helium to blast helium apart but apart but too hot too hot to to allow electrons allow electrons to combine with to combine with nuclei to make nuclei to make atoms atoms

The The era of nuclei created a lot of era of nuclei created a lot of light but it couldn light but it couldn’ ’t get t get anywhere!! anywhere!!

• Density was so

Density was so high, photons high, photons would hit an would hit an electron or nuclei electron or nuclei before getting before getting anywhere anywhere

– – Just like the Just like the random random walk walk inside the Sun! inside the Sun!

380,000 years 380,000 years to 1 billion to 1 billion years years

• Finally, the

Finally, the temperature temperature drops to about drops to about 3000 K and 3000 K and electrons all electrons all combine with combine with nuclei to form nuclei to form the first atoms the first atoms Era of Atoms Era of Atoms

Era of Atoms Era of Atoms

• Finally

Finally cool enough cool enough (3000 K) for electrons (3000 K) for electrons combine with nuclei combine with nuclei to to form atoms form atoms (380,000 yrs) (380,000 yrs)

• Photons now

Photons now “ “decoupled decoupled” ” = free = free to fly away to fly away

• Universe becomes

Universe becomes transparent to light transparent to light

Era of Galaxies Era of Galaxies 1 billion years - 1 billion years - now now

Era of Galaxies Era of Galaxies

• About 1 billion years after Big Bang,

About 1 billion years after Big Bang, first stars first stars and galaxies start to form and galaxies start to form

• We live in the Era of Galaxies now.

We live in the Era of Galaxies now.

Big Bang evidence Big Bang evidence

Penzias Penzias & Wilson in 1965 & Wilson in 1965 discovered discovered Cosmic Microwave Cosmic Microwave Background (CMB) Background (CMB) radiation radiation

• -> 2.73 K
• -> 2.73 K “

“black body black body” ” Photons created when Photons created when hot hot universe was only universe was only 380,000 yrs 380,000 yrs

• ld
• ld –

– as first atoms formed as first atoms formed Very uniform radiation Very uniform radiation from everywhere from everywhere – – 1 part in 100,000 1 part in 100,000 severely severely redshifted redshifted by by expansion of universe expansion of universe WMAP WMAP

1978 Nobel Prize

Spectrum of Cosmic Microwave Background (CMB) Spectrum of Cosmic Microwave Background (CMB)

2.73 K `black body 2.73 K `black body’ ’

Light from beginning of time Light from beginning of time

• This faint light looks light a solid glowing wall

This faint light looks light a solid glowing wall

• Thermal spectrum at 3000 K

Thermal spectrum at 3000 K, if , if redshifted redshifted by factor by factor ~1000 ~1000

• microwaves

microwaves! !

• Helps measure degree of isotropy in early

Helps measure degree of isotropy in early Universe Universe

Chemical abundances also Chemical abundances also confirm the Big Bang model confirm the Big Bang model

• Big Bang Theory

Big Bang Theory prediction: prediction: 7-1 7-1 proton-to-neutron proton-to-neutron ratio ratio

– – Should lead to Should lead to 75% H, 25% He 75% H, 25% He (by mass) (by mass)

• Matches

Matches

• bservations of
• bservations of

nearly primordial nearly primordial gas gas

Which of these abundance Which of these abundance patterns (by mass) is an patterns (by mass) is an unrealistic chemical composition unrealistic chemical composition for a star? for a star?

• A. 70% H, 28% He, 2% other
• B. 95% H, 5% He, less than 0.02% other
• C. 75% H, 25% He, less than 0.02% other
• D. 72% H, 27% He, 1% other

Clicker Question Clicker Question

Which of these abundance Which of these abundance patterns (by mass) is an patterns (by mass) is an unrealistic chemical composition unrealistic chemical composition for a star? for a star?

• A. 70% H, 28% He, 2% other
• B. 95% H, 5% He, less than 0.02% other
• C. 75% H, 25% He, less than 0.02% other
• D. 72% H, 27% He, 1% other

Clicker Question Clicker Question

Which of the following is not an Which of the following is not an evidence supporting the Big Bang evidence supporting the Big Bang theory? theory?

• A. Cosmic microwave radiation
• B. The Hubble expansion of the universe
• C. Helium is 25% of all matter
• D. Gamma ray bursts

Clicker Question Clicker Question

Which of the following is not an Which of the following is not an evidence supporting the Big Bang evidence supporting the Big Bang theory? theory?

• A. Cosmic microwave radiation
• B. The Hubble expansion of the universe
• C. Helium is 25% of all matter
• D. Gamma ray bursts

Clicker Question Clicker Question