Unit 3 Star Birth Nebulae

Interstellar Medium (ISM)

• The space between stars in a galaxy

  • composition: 99% gases (90% H, 10% He, other gases) 1% dust (solids)

1 - (ISM) components with star formation

molecular clouds (molecular H2)

H-II Regions (ionized Hydrogen)

2 - Types of Nebulae: H-11 (H2) Regions (star birth)

• Diffuse Nebulae (meaning they do not have well-defined boundaries)

  • reflection) (light) reflect light off of nearby galaxies

  • emmission (thick) emit their own light

2 - (Types of Nebulae) Dark Nebulae - BOK GLOBULES

(absoprtion, ly) isolated and small dark nebulae containing dense cosmic dust and gas from which a star formation may take place

2 - (Types of Nebulae) EGGs

(absorption) (evaporated gaseous globules) dense compact pockets of interstellar gas, within stars may be born

2- (Types of Nebulae) Planetary Nebulae

star death, glowing, expanding, shell of gas and dust that forms when a star dies from the castoff layers

2 - (Types of Nebulae) Supernova remnant

star death, the result of a star exploding in a supernova (creates other elements (big stars)

3 - Nebular Fragmentation

a large, gaseous cloud breaks apart into smaller, denser clumps, that eventually form stars

• gravity and presure: stars are born from collpase of a large cloud with many smaller additional collapses or fragmentations during general collapse

Star forming scenarios - 1

Spontaneous Collapse - cloud by circumstance begins gravitational collapse

Star forming scenarios - 2

Forced Collapse - another force causes it (events travelling thorugh space)

4 - Cloudlets

very large clouds (low temp)

1. the cloud begins to collapse

2. fragmentation occurs

3. continue to collapse over and over

4. until we reach dark nebula (when we make star systems)

dark nebula

also known as an absorption nebula, dense cloud of gas and dust that make them appear dark

5 - Formation of a protostar

• protostar has a high luminosity (large), no fusion cause no layers

• Herbig-Haro objects (HH Objects)

  • gets rotational direction

  • jets are on the scale of AUs (ejecting material)

  • not circular

6 - T-Tauri Phase/Star

• transitional phase, young star, extreme activity

• core continues to heat up

  • (temp increase, brightness increase (luminosity drives off outer cocoon)

  • becomes circular

  • then becomes T-Tauri Star (really close to fusion)

7 - Main Sequence Star

• pressure in core halts the gravitational collapse of the star

• hydrostatic equilibrium: balance between gravity and pressure

• core = fusion, layered

• most of a stars life

Main Sequence Dwarf Stars

• 90% of stars

• Burn H into He via fusion reactions

  • small stars: proton-proton chain fusion

  • large stars: CNO cycle fusion

  • ex: the sun

  • smaller mass (0.5-5Mo)

Main. Sequence Massive Stars

• top end of the main sequence

• blue giants - O and B type stars

• stars 5x larger than the sun

• massive stars have much shorter life than normal stars

• medium to high mass - (5-8Mo)

Main Sequence Super Massive Stars

• Walt-Rayett Stars (Hyper Giants)

• hot, luminous stars, rapidly losing mass

• shortest life spans

Maximum masses of main sequence stars

Mmax = 50-100 solar masses

• more massive clouds fragment into smaller pieces during star formation

• very massive stars lose mass in strong stellar winds

What dictates the death of a star

its mass

Basic Stellar Properties

• stars burn via fusion (nucleosynthesis)

apparent magnitude

how bright a star appears from Earth

lower magnitude = brighter star

absolute magnitude

• how bright a star would be if all the stars were placed exactly 10 parsecs from earth

• same thing as luminosity?

luminosity

• actual brightness of a star

• depends only on size and temperature

How elements H and He were formed by the universe

made in the big bang

biggest element made in a star

Fe (IRON)

biggest natural occurring element in a star

uranium

nucleosynthesis is

the process of element (nuclei) formation

Three types of nuclei formation

• big bang nucleosynthesis - red (H→He)

• stellar nucleosynthesis (H→Fe)

• Supernova nucleosynthesis (Fe→U)

  • relative abundance of elements in our universe / atomic number

Fusion: Hydrogen

Core Temp: 13mil K

Fusion: Helium

Core Temp: 100mil K

Fusion: Carbon

Core Temp: 500mil K

Fusion: Neon

Core Temp: 1.2bil K

Fusion: Oxygen

Core Temp: 1.5bil K

Fusion: Silicon

Core Temp: 3bil K

Brown Dwarf Stars

• almost a star

• mass and temperature is too small to allow fusion reactions to occur (no luminosity)

• 70-80 times larger than jupiter

• mass up to 0.08 Mo

most common stars

M Dwarf Stars

Least common stars

B stars (massive)

Luminosity Classes

• 1a Bright Supergiants

• 1b Supergiants

• II brightgiants

• III giants

• IV subgiants

• V main sequence stars

1a

bright supergiants

1b

supergiants

II

bright giants

IV

subgiants

V main sequence

G2V

G=yellow (color/temp), 2=scale of color (to next color), V=main sequence star (brightness)

Census of the stars

• faint red dwarfs are most common

• bright, hot, blue, main sequence are very rare

• giants and supergiants are extremely rare

Star Death - Main Seq Dwarf Star

• hydrogen fuel is used up, helium is building up in the core

• gravity pushes in

• core becomes unbalanced and begins to collapse

• temperature increase

• helium begins to fuse

• it expands, then becomes a red giant

Star Death: Lower Mass Stars to Red Giant

• cool temp drops, bigger, brighter

Star Death: Lower Mass Stars - Red Giant to Planetary Nebulae

• fusion of Helium

• core shrinks

• outer layers are thrown off

• death nebula

• white dwarf in center

Star Death: Lower Mass Stars - Planetary Nebulae to White Dwarf

• dense, small balls of carbon

• very hot

• cools very slowly

Star Death: Lower Mass Stars - White Dwarf to Black Dwarfs

• impossible to see, remains of dead white dwarf

Star Death: Large Mass Stars - Supergiants

• largest and most luminous, burned up Hydrogen and is burning helium now, then become red supergiants

Star Death: Large Mass Stars - Supergiants to Red Supergiants

• helium fusing

• temp increase

• it expands

• super red giant, it cools

• gravity contracts core, begins burning carbon

• fusing oxygen, neon, nickel

• and silicon

• expansion and contraction, core elements keep fusing until they reach iron

• Ex: polaris

Star Death: Large Mass Stars - Red Supergiants to Cepheid Variable Stars

• yellow supergiant stars

• brightness varies

• used to determine distance to nearby galaxies

Star Death: Very Massive Stars - Supernova

• very massive stars

• core collapses

• rapidly reboounds

• core explodes, major shockwave

Final stage for massive stars from supernova

(neutron star or black hole)

• stars less than 8 solar masses become dwarf stars

• stars 8 solar masses and above become neutron stars or black holes

Neutron Stars

• massive star

• extreme density

• extremely small

• spin: pulsar (emit energy pulse)

• dont do fusion, tiniest stars

Black Hole

• inversions of matter

• so dense light cannot escape it

• time is related to gravity

• die by evaporation

  1. schwartzschild BH (non rotating) perfect circles

  2. Kerr. BH: rotates fast

• ergosphere: static limit, objects move at speed of light

Open Star Cluster

• contain < 1000 stars

• loosley gravitationally bound together

• younger than globular

• more enriched in heavy elements (population 1 stars)

  • massive

  • OBA

  • 2nd generation

moving groups

gravitationally unbound stellar associations

Globular clusters

• contains millions of stars

• extremely old by billions of years

• population II: low in heavy elements

  • H He

  • 1st generation

  • the sonner a cluster turns off the HR diagram the older it is

    • less = open cluster

    • more supergiants = open cluster

    • more white dwarfs = globular cluster

Galaxies

• huge groups of single stars, star systems, star clusters, dust, and gas bound together by gravity

Elliptical Galaxies

• 20% of mapped galaxies

• look like flattened balls

• billions of stars

• little gas and dust

• E galaxies

• compact

E0

more circular

E7

more disc like

Lenticular Galaxies

• disc galaxies, very thin

• lost interstellar matter

• little ongoing star formation

• aging stars

• produce least amount of stars

stars form in

outer arms of galaxy

spiral galaxies

• twin spirals

• 77% of galaxies

• pinwheel shape

• young stars, bright stars, has and dust may be in the arms

• more budlge than disc: A

• more disc than budlge: C

Disks

• flattened systems that rotate

• circular rotating disk axis

• ongoing star formation

• gas and dust (10-50%)

• ages of stars vary

• spiral arms form sustained density waves

Buldges

spheroid systems (no/little rotation)

stars are randomly oriented

irregular galaxies

no regular shapes

missing budlge

3% of mapped stars

concentration of billion stars

no rotation

not enough material to put them together

smaller

Active Galactic Nuclei (buldge)

AGNS’s are enormously bright, distant, galaxies with giant black holes at their center

really bright

Seyfert Galaxies (AGN)

normal spiral galaxies, bright nucleus that outshines the rest of the galaxy, active galaxies

Blazars (AGN)

very bright point like a nucleus, a jet of material emanates

Quasars (AGN)

less bright, producing enormous amounts of energy

• lens end quasar: einstein cross, four of the same picture

• used as markers for the age of Uni, give off more energy than the entire galaxy

galaxies are grouped in

clusters

Age of the Universe

13.8 billion years old

know this beacuse of quasars and red shift

milky way is

10.8 billion years old, know this because of globular clusters

Cosmology

the study of the origin, structure, and evolution of the universe

Universe is made up of

73% dark energy

23% dark matter

4% ordinary matter

the cosmological principle

the universe is a machine that follows the same laws

dominant form of mass

dark matter

The Big Bang

the formation of the universe, pure energy existed by itself

reverse enginerring

• gave us 4 fundamental forces

• photons

• fundamental particles and nucleosynthesis

4 fundamental forces (1)

electromagnetic force

• wavelength, light, radiation

• exchange of photo energy

• most important force that holds everything together on a subatomic level

4 fundamental forces (2)

gravitation (mass)

(4 fundamental forces) (3) nuclear force

strong nuclear force

• holds photons and neutrons quarks together in the nucleus

weak nuclear force

• allows for fusion to create heavier elements

(4 fundamental forces) (4) Fundamental particles: Photons

particles of light energy

(4 fundamental forces) Fundamental Particles: protons and neutrons

make up the nucleus

composed of quarks

(4 fundamental forces) fundamental particles: electrons

negative particles

nucleosynthesis

• process of creating larger elemnts from smaller ones

Evidence for Big Bang

• cosmic background radiation, radiation left over from the explosion

bok globules

isolated and SMALL dark nebulae, dense cosmic dust