a note on: group behavior open clusters: contain a few hundred to a few thousands of stars. lie in...

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A note on: Group Behavior A note on: Group Behavior Open Clusters: contain a few hundred to a few housands of stars. Lie in the plane of the Milky Way alaxy. A few parsecs in diameter. Generally young ype stars Globular Clusters: Lie outside the plane of our galaxy. ery far away, thousands of parsec. Contain no main equence stars with masses > 0.8 Sun’s mass. Generally lder stars. Open Clusters Central Bulge

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Page 1: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

A note on: Group BehaviorA note on: Group Behavior

• Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky WayGalaxy. A few parsecs in diameter. Generally young type stars• Globular Clusters: Lie outside the plane of our galaxy.Very far away, thousands of parsec. Contain no main Sequence stars with masses > 0.8 Sun’s mass. Generally Older stars.

Open Clusters

Central Bulge

Page 2: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Open vs. GlobularOpen vs. GlobularPage 507 Fig.19.8 A & BPage 507 Fig.19.8 A & B

Page 3: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

More on Group BehaviorMore on Group BehaviorAssociations:

T Type: Contain pre-main sequence stars.O-B Type: Contain O,B stars

Page 4: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Cluster evolution. Cluster evolution. page 532 Figure 20.17page 532 Figure 20.17

(a). Initially stars in main seq. burning steadily while stars in lower end of the sequence are still forming.

(b).O-Type stars left the main seq., some red giants visible. ©.Type B stars have evolved off the main seq. Stars in

lower end of seq. catching up. (d).Main Seq. comprised of stars up to Type A. Sub and

Red giants becoming apparent. Lower end completed. (e) Stars with < Sun’s mass remain on the sequence. White

dwarfs have now formed.

Page 5: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Blue StragglersBlue Stragglers

Observed in many clusters. Main-Sequence beasts. Don’t make a whole lot of sense why they are

what they are but believed to be the result of Mergers which are collisions between stars or the result of binary evolutions.

Explains why such young stars amongst a cluster that may be at least 10 billion old.

Page 6: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Binary StarsBinary Stars 2 stars with a distance of

1000 star radii between them have evolved independently.

Closer than that then gravity mates them.

Page 7: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

AlgolAlgol

Page 8: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Other class mediaOther class media Slides: H-R diagrams for open cluster, cluster

evolution. Video: Stellar Formation part 1. Tomorrow video: Stellar formation, part 2.

Page 9: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

The life of a StarThe life of a Star

The life cycle of a star.1. Collapsing cloud (done that)2. Proto-star (done that)3. Star (main sequence)4. Dying star (main sequence turn-off)

Lets review and look at some pretty pictures ..

Page 10: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Stages in the life of a starStages in the life of a star

1. A gas cloud in the Orion nebula

2. A collapsing cloud, proto-starRegion.

3. A genuine star

1. -> 2. -> 3.

Page 11: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Stages, continued.Stages, continued.

4. Red Giant phase, turned off of the main sequence.

5a. A planetary nebula, from a smaller mass star like our sun.

4 -> 5a

Page 12: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Stages again…Stages again…

5b. Larger mass stars will supernova….

6. Leaving behind filamentary cloudsrich in heavy elements.

4

5a 5b

6

Page 13: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

3. Main Sequence Star3. Main Sequence Star

a. Stars enter main sequence through the Hayashi Track, a proto-star evolutionary path.

b. Once on the main sequence track, a stable star spends most of its life here. What does it do there?

p-p fusion (e.g. 4 H1 => He4 + energy) Stays in Hydrostatic equilibrium Energy produced in core through p-p chain

accounts for most of energy productionc. Dying Star

Page 14: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

c. Dying Starc. Dying StarWhen H is depleted, inner core (now mostly He) contracts & heats up.

The high temperature ignites the shell of H around the core.

Increased pressure drives the envelope of the star outward.

Creating a giant or Supergiant.

Figure 20.2c, page 517

Figure 20.3, page516

Page 15: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

He fusionHe fusion

2 He -> Be + energy He + Be -> C + energy Much higher temperatures (108 K) needed for

He fusion.

The Helium Flash: •When Tcore ~ 108 K, He begins to burn.

1. He4 + He4 => Be8 , He + Be => C2. He fusion in the core and H shell burning 3. Eventually He in core is exhausted 4. Contraction of the core raises the temperature further 5. Both He and H shells now burning.

Page 16: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Giants and Super GiantsGiants and Super GiantsOur Sun and others

like it.. Temp. never high

enough to attain carbon fusion in core.

Some conversion at He shell: C + He => O + energy.

Through subsequent temperature and density fluctuations, He shell flashes occur.

Surface layers (envelope) become unstable => blow off-> planetary nebula

High mass stars > 12 solar masses..

High temperatures insure creation of heavier elements at a rapid pace.

No He flash occurs. Die explosively.

Red giant

Lets look at the big picture =>

Page 17: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

H-R diagramsH-R diagramsA. Main sequence

starB. Sub Giant

branchC. He FlashD. Horizontal

branchE. C core/planetary

nebula

DC

B

A

E

Page 18: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Some termsSome terms

White dwarf: remainder of low mass star evolution

Shines only by the light of it’s stored energy. Eventually becomes a black dwarf. A black dwarf is a cold burned out star.

Table 20.3 , page 531.

Page 19: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

Some low mass endings; planetary Some low mass endings; planetary nebulanebula

Eskimo nebula, constellation Gemini1500 pc away

NGC 3132 nebula, 2 stars, both unrelated,Material receding from small star

½ ly

Page 20: A note on: Group Behavior Open Clusters: contain a few hundred to a few thousands of stars. Lie in the plane of the Milky Way Galaxy. A few parsecs in

High mass endingsHigh mass endings