The Origin,Expansion,

& Dark Side

of the Universe

Lecture 25“The Planets”

Not included on the final exam. Relax! Enjoy!

Announcements

• HW• Read Ch. 24: Life in the Universe• Homework Mastering Astronomy: Chapter 24 Due Friday, Dec 5, at 6pm

Final Exam:Thursday, Dec 18, 11:30-2:30

Pimentel Auditorium (Here, usual room)

• Multiple Choice• Covers all Chapters: 1-5, 9-14, 24 & All Lectures. Emphasis on chapters 12, 13, 24

• Review Session: Thu (Dec 11) at 5pm in VLSB2050 Come with questions !

The Origin,Expansion,

& Dark Side

of the Universe

Lecture 25“The Planets”

Not included on the final exam. Relax! Enjoy!

13.8 Billion Years ago, something happened . . .

Evidence for Big Bang:

Today, all the galaxies in the universeare moving away from each other!

13.8 Billion Years ago, something happened . . .

Evidence for Big Bang:

Today, all the galaxies in the universeare moving away from each other!

13.8 Billion Years ago, something happened . . .

• Time and Space Created.

13.8 Billion Years Ago.

• Explosion: Hot and Dense. Over a trillion degrees.

• Universe expanding ever since. Accelerating now.

• Science can not describe what happened

before the Big Bang.

Depiction of Big Bang

Age of universe < 0.001 sec

• Universe temperature: trillions of degrees • Universe contains:

Quarks, Electrons, and photons.

• No atoms, nor even protons or neutrons:

At billions of degrees, protons collide,

break apart into quarks.

Protons and NeutronsAre Composed of 3 Quarks

Quarks destroy each other to create photonsand vice versa, in Equilibrium

Universe: Era of Nucleosynthesis (t < 3 min)

• Protons & neutrons fuse ! 4p He• Some He nuclei torn apart by the high temperatures

• When Universe was 3 min old, it had cooled to 109 K.• At this point, the fusion stopped

• Afterwards, the matter in the Universe was:• 70% Hydrogen nuclei (i.e. individual protons)• 25% Helium nuclei• trace amounts of Deuterium (H isotope) & Lithium nuclei

Era of Galaxies ( age > 109 yr)

• The first galaxies came into existence about 1 billion years after the Big Bang.

• This is the current era of the Universe.

The Universe since the Big Bang: Gravitational Attraction of material

Billions of years ago

• The mass of the iron (Fe) core increases

- Iron can’t burn:

- No nuclear reactions: no energy production!– Gravity overwhelms the gas pressure– Star Collapses!– Electrons are squeezed into protons neutrons

• The neutron core collapses until abruptly stopped by neutrinos flying outward!– this takes only seconds– The core recoils, bounces, and

neutrinos force the gas outward in an explosion.

Core-CollapseSupernova

When massive stars die:

Supernova Explosions

Core-Collapse Supernova Explosion

Supernova Explosions

Crab Nebula in Taurussupernova exploded in 1054

The explosion brings temperature toBillions of degrees:

The elements heavier than Fe are instantly created

Four supernovae have been observed in our part of the Milky Way Galaxy: 1006, 1054, 1572, 1604 1604

Supernovae

Veil Nebula Tycho’s Supernova (X-rays)exploded in 1572

Supernova Remains

Supernova Remains

Supernova Remains

Supernova Remains

© 2005 Pearson Education Inc., publishing as Addison-Wesley

The atoms that compose your human body were made in

supernova explosions

The 92 atomic elements were all constructed in the centers of stars

(except hydrogen, helium and lithium).

The Origin of the Atomic Elements

The Dark Side of

the Universe

Lecture 25 (continued)

Most of the Universe is Dark

Our universe is 13.8 billion years old. It is composed of 5% normal atomic matter, 27% mysterious dark matter (not atoms), and 68% dark energy,the name we give to whatever is causing the universe to expand at an acelerating rate. (From Planck – 2014)

You, me, Earth,

Planets, stars

Example 1: Gravity by Central Mass (Sun)

determines orbital speed of planets.

How do we know the Universe is Mostly Dark ?

Solar System:

“Keplerian orbits”

Earth

Jupiter

Mercury

Orbital Speed = G M / Distance

Venus

Mars

Galaxies:

“Flat rotation curve”

How do we know the Universe is Mostly Dark ?

Gravity by Central Mass (galaxy)

determines orbital speed of stars.

Orbital Speed = G M / Distance

Galaxies:

“Flat rotation curve”

How do we know the Universe is Mostly Dark ?

Gravity by Central Mass (galaxy)

determines orbital speed of stars.

Orbital Speed = G M / Distance

Speed doesn’t fall !Mass, M, must be increasing outward!

Example 2: Gravitational Bending of Light by Mass

How do we know the Universe is Mostly Dark ?

Light Source

Telescope

How do we know the Universe is Mostly Dark ?

Four images of the same galaxy

How do we know the Universe is Mostly Dark ?

Four images of the same galaxy

How do we know the Universe is Mostly Dark ?

What can dark matter be?

Not enough mass: even Jupiter weighs only

0.1% of the Sun

Planets?

What can dark matter be?

Graveyards of massive stars. But massive stars are rare and made of normal atoms.

Once formed, black holes suck in normal matter.

So you can’t hide much dark matter in it.

Black Holes?

What can dark matter be?

Top candidate:

Elementary Particles:

Yet to be discovered !

Dark Energy

39

Supernova Explosionsas

Standard Candles

The distance to the galaxy that contains the supernova: Compare how bright they know the explosion should be with how bright the explosion appears. Using the inverse square law of light, they can compute the distance to the supernova and thus to the supernova's home galaxy.

Type Ia supernovae, which give off a standard amount of light.

41

Example 4: Distant supernovae

After

Before

How do we know the Universe is Dark?

Example 4: Distant supernovae are standard candles

How do we know the Universe is Dark?

43

44

45

Accelerating Expansion of the Universe:Dark Energy

46

Most of the Universe is Dark

Our universe is 13.8 billion years old. It is composed of 5% normal atomic matter, 27% mysterious dark matter (not atoms), and 68% dark energy,the name we give to whatever is causing the universe to expand at an acelerating rate. (From Planck – 2014)

You, me, Earth,

Planets, stars

CMB: very cold (-270.275 C, -454.495 F) and nearly uniform relic radiation left over from the hot big bang

Example 3: Cosmic Microwave Background

How do we know the Universe is Dark?

(1965)

If you had microwave eyes:

Example 3: Cosmic Microwave Background

How do we know the Universe is Dark?

50

A picture of our universe, taken by the Planck satellite in 2013. Patterns in the hot and cold show regions hotter and cooler in our universe when it was only 300,000 years old. .

Our universe is 13.8 billion years old. It is composed of 4.9% normal atomic matter, 26.6 % mysterious dark matter (not atoms), and 68.5% dark energy,the name we give to whatever is causing the universe to expand at an acelerating rate. (From Planck – 2014)

Most of the Universe is Dark

Our universe is 13.8 billion years old. It is composed of 5% normal atomic matter, 27% mysterious dark matter (not atoms), and 68% dark energy,the name we give to whatever is causing the universe to expand at an acelerating rate.

You, me, Earth,

Planets, stars

© 2005 Pearson Education Inc., publishing as Addison-Wesley

The atoms in your human body were made in

supernova explosions

The 92 atomic elements were all constructed in the centers of stars

(except hydrogen, helium and lithium).

The Origin of the Atomic Elements