Bell Ringer

1. If the sun were about the size of a golf ball, and it were placed on

the goal line of a football field, where would the Earth be?

Neptune?

2. About how many Earths could I put side by side from one side of

the Sun to the other?

3. Most of space is just _____________________

Science Matters

3D printing

3D Printers

“Additive Manufacturing”

Fancy hot glue gun…

Layer by layer

Plastic / Metal

Could help with a mission to

Mars, use materials already

there.

3D bioprinting

Same principle working with cells

Burn victims

Organ transplants

Blood transfusions

5

Physics 228Galaxies

Spiral Nebulae vs. Island Universes

• The Great Debate: what is the nature of the spiral nebulae?– Shapely vs. Curtis, April 26, 1920 at the

National Academy of Science in Washington, D.C.

– Each scientist presented, then took part in a joint discussion.• Shapley believed the spiral nebulae to be

part of our own Galaxy.

• Curtis believed them to be separate, completely different galaxies, external to our own.

• Result: no clear conclusion reached.

6

Harlow Shapley Heber Curtis

Debate Solved, Hubble 1929

• Hubble found a way to measure distances of galaxies using special kinds of stars.

• By measuring these stars, he determined M31 (a galaxy) was almost 1,000,000 light years away.– WELL outside our Milky Way Galaxy

7

• Side note: Hubble was actually a bit off. Actual distance to M31 is ~ 3 million ly.

Galaxies

8

Galaxies are large collections of stars that are all bound together by gravity, usually by some sort of black hole in the center.

They come in many different shapes and sizes.

Classification used to organize galaxies to help scientists better understand them.

Classification

9

Spiral Galaxies

10

Sa (NGC 2841) Sb (NGC 3031, M81) Sc (NGC

628, M74)

• Sa: big bulge, tightly wound arms, little gas and dust

• Sb: medium bulge, moderately wound, moderate gas and dust

• Sc: small bulge, loosely wound, lots of gas and dust

Barred Spiral Galaxies

11

SBa (NGC 4314) SBb (NGC 4548, M91) SBc (NGC

613)

• Sa: big bulge, tightly wound arms, little gas and dust

• Sb: medium bulge, moderately wound, moderate gas and dust

• Sc: small bulge, loosely wound, lots of gas and dust

Grand Design vs. Flocculent Spirals

12

M81: Grand Design Spiral NGC 2841: Flocculent

Spiral

• Grand Design: prominent, well-defined spiral arms.

• Flocculent: “puffy” arm structure, not well-defined arms.

Elliptical Galaxies

• Characteristics:– Smooth, ellipsoidal, tend to be reddish (Lots of older stars)

– No dark dust, little gas, no spiral arms, no star formation

– Old stars; no unified rotation: random motions of stars.

• Classification label “En” where n is a number equal to 10 times the ellipticity, ε, (rounded to nearest whole number).

– E0 are the roundest

– E6 or E7 are the flattest seen

13

e =1-b / a

ab

Elliptical Galaxies

14

E0 (NGC 4486) E3 (NGC 4365) E6 (NGC 4564)

S0 – Lenticular Galaxies

• Characteristics:– Intermediate between ellipticals and spirals.

– Flatter than ellipticals

– Also called “Lenticular Galaxies”

– Resemble spirals, but have younger stars.

15

Irregular Galaxies

• Characteristics:– Amorphous, lacking in shape.

– Rich in gas and dust, have a lot of star formation

• Example: Small and Large Magellanic Clouds (SMC, LMC)

16

Dwarf Galaxies

• Dimmest galaxies.

• Dwarf ellipticals (dE), dwarf spheroidals (dSph), and dwarf irregulars (dIrr).

• An estimated 90% of the galaxies in our immediate neighborhood are dwarfs.

17

Leo I, dwarf spheroidal galaxy, d ~

250 kpc

Peculiar Galaxies

• Don’t fit into any of the classes.

• Often galaxy mergers.

18

NGC 7252

Cartwheel Galaxy

• https://www.youtube.com/watch?v=OVDWVJGXRIk

• What kind of galaxy is the Milky Way?

• How far across is the Milky Way?

• Write down one other fact you learned.

19

Bell Ringer

1. What kind of galaxy is the Milky Way?

2. What is a light year?

3. What is the difference between a spiral galaxy and an elliptical?

4. What is at the center of most galaxies, including our own?

20

Science Matters

Lightning

Lightning never strikes the

same place twice?

FALSE!

Empire State Building struck

about 25 times a year

One park ranger was struck seven times by lightning,

and still lived

Lightning strikes taller

objects, especially ones

that conduct electricity,

more often

What to do?

1. If you are in a car, stay

inside of it! It’s actually one

of the safer places to be in

a lightning storm.

2. If you are outside, find low

ground.

3. DO NOT lay down. You

want as little contact with

the ground as possible

because lightning spreads

across the ground.

4. DO crouch down on the

balls of your feet.

5. Find shelter inside if you are

close.

The Life Cycle

of a Star

What is a Star?

A star is ball of

plasma

undergoing

nuclear fusion.

Stars give off large

amounts of energy

in the form of

electromagnetic

radiation.

X-ray image of the Sun

Nebula – Birth of Star

Stars are formed in a Nebula.

A Nebula is a very large cloud

of gas and dust in space.

Protostars

Gravity makes

dense region of

gas more

compact

Soon take on a

definite shape and

are called

protostars.

A new star!!

Once the core of

a protostar

reaches

10,000,000o C,

nuclear fusion

begins and the

protostar ignites.

The protostar now

becomes a star.The bright spot is a new star igniting

Nuclear

Nuclear Fusion is

the process by

which two nuclei

combine to form a

heavier element.

New stars initially

will fuse hydrogen

nuclei together to

form helium.

Fusion

ω Centauri

Star Cluster: All the stars are the SAME DISTANCE.

Patterns among the stars?

ω Centauri

Sort the stars by color, putting the blue

stars on the left and the red stars on the

right.

Sort the stars by brightness

putting the bright stars on top,

and the faint stars on the bottom.

• Stars don’t just fall anywhere, they tend to lie along a few well-defined sequences.

• A star’s color and brightness tell us where a star lies in this diagram.

• The unmistakable order in diagrams like this led astronomers to develop theories to explain stellar evolution.

Patterns among the stars?

Graph of color (temperature or

spectral type) vs. magnitude

(luminosity)

Lum

ino

sity

Temperature

Enjar Hertzsprung Henry Norris Russell

Russell, 1914, Nature, 93, 252

The Observatory, 1913, 36, 324

Pub. Astrophys, Obs. Potsdam 1911, 22, 1

The H-R Diagram

The Hertzsprung-

Russell (H-R)

diagram identifies a

definite relationship

between

temperature and

absolute

magnitudeHR DIAGRAM

Brightness vs Temperature

On the H-R

Diagram, stars

with similar

physical

properties fall into

groups together.

Main Sequence

Giants

Super giants

White Dwarfs

H-R Diagram Activity

Star Life Cycle

Main Sequence Stars

Once the star has ignited, it

becomes a main sequence

star.

Main Sequence stars fuse hydrogen to form helium,

releasing enormous amounts

of energy.

It takes about 10 billion years

to consume all the hydrogen

in a Main Sequence star.

Balancing Act

The core of a star is where

the heat is generated. The

radiative and conductive

zones move energy out

from the center of the star.

The incredible weight of

of all the gas and gravity

try to collapse the star on

its core.

Unbalanced Forces

As long as there is a nuclear

reaction taking place, the

internal forces will balance the

external forces.

When the hydrogen in a main

sequence star is consumed, fusion

stops and the forces suddenly

become unbalanced. Mass and

gravity cause the remaining gas

to collapse on the core.

Red Giant

Collapsing outer layers cause core to heat up.

Fusion of helium into carbon begins.

Forces regain balance.

Outer shell expands from 1 to at least 40 million miles across. ( 10 to 100 times larger than the Sun)

Red Giants last for about 100 million years.

Unbalanced Forces

(again)

When the Red Giant has fused all of the helium

into carbon, the forces acting on the star are

again unbalanced.

The massive outer layers of the star again rush into

the core and rebound, generating staggering amounts of energy.

Planetary Nebulas –Final

stages A cloud of gas that forms

around a sun-like star that

is dying

White Dwarfs

The pressure exerted on the core by the outer layers does not produce enough energy to start carbon fusion.

The core is now very dense and very hot. (A tablespoon full would weigh 5 tons!)

A white dwarf is about 8,000 miles in diameter.

After 35,000 years, the core begins to cool.

Planetary nebula around a

white dwarf star.

Black Dwarfs

As the white dwarf cools, the light it gives off will fade through the visible light spectrum, blue to red to back (no light).

A black dwarf will continue to generate gravity and low energy transmissions (radio waves).

Red Supergiants

If the mass of a star is 3 times that of our sun or greater, then the Red Giant will become a Red Supergiant.

When a massive Red Giant fuses all of the helium into carbon, fusion stops and the outer layers collapse on the core.

This time, there is enough mass to get the core hot enough to start the fusion of carbon into iron.

Red Supergiants

Once fusion begins, the star will expand to be between 10 and 1000 times larger than our sun. ( Out to the orbit of Uranus )

Supernova

When a Supergiant fuses all of the Carbon into Iron, there is no more fuel left to consume.

The Core of the supergiant will then collapse in less than a second, causing a massive explosion called a supernova.

In a supernova, a massive shockwave is produced that blows away the outer layers of the star.

Supernova shine brighter then whole galaxies for a few years.

Gas ejected from a supernova explosion

Neutron Star

Sometimes the

core will survive

the supernova.

If the surviving

core has a mass of

less than 3 solar

masses, then the

core becomes a

neutron star.

6 miles in diameter

Black Holes

If the mass of the surviving core is greater than 3 solar masses, then a black hole forms.

A black hole is a core so dense and massive that it will generate so much gravity that not even light can escape it.

Since light cant escape a

black hole, it is hard to tell

what they look like or how

they work.