IPSIPS

Astronomy: Birth and Life of a Astronomy: Birth and Life of a StarStar

I. NebulasI. Nebulas

All stars start out as a nebulaAll stars start out as a nebula A nebula is A nebula is a stellar nurserya stellar nursery A A nebulanebula is a is a large amount of large amount of

gas and dust spread out in gas and dust spread out in an immense (or big) volumean immense (or big) volume

Don’t get a star and a nebula Don’t get a star and a nebula confused. confused.

Nebula vs. StarNebula vs. Star

NebulaNebula– LargeLarge amount of gas in a amount of gas in a largelarge volume volume

StarStar– LargeLarge amount of gas in a amount of gas in a smallsmall

volumevolume Links:Links:

– Jellyfish nebulaJellyfish nebula– Eskimo Eskimo nebulanebula– Horse head nebulaHorse head nebula

II. Protostar: II. Protostar: in Greek, “proto” in Greek, “proto” means earliest. Protostar = means earliest. Protostar = earliest starearliest star

Gravity pulls gas and dust in Gravity pulls gas and dust in (contracts)(contracts)

A contracting cloud is called a A contracting cloud is called a protostarprotostar..

Pressure and temperature Pressure and temperature increase.increase.

When the contracting gas and dust When the contracting gas and dust becomes so hot that becomes so hot that nuclear fusion nuclear fusion beginsbegins, a star is born!!, a star is born!!

– Remember: nuclear fusion starts when Remember: nuclear fusion starts when hydrogen combines to form helium. During hydrogen combines to form helium. During fusion, enormous amounts of energy are fusion, enormous amounts of energy are released.released.

– Link: Link: Pillars of Creation nebulaPillars of Creation nebula

III. Main SequenceIII. Main Sequence

The star is The star is fusing (burning) H into He fusing (burning) H into He (produces a lot of energy)(produces a lot of energy)

The star is now in the “prime of its life”; it is The star is now in the “prime of its life”; it is in in equilibrium.equilibrium.

Over time; temp, luminosity, color Over time; temp, luminosity, color change.change.

Our sunOur sun is in the main sequence phase is in the main sequence phase It will live for about 10 billion yearsIt will live for about 10 billion years Our sun is now about 4.6 billion years oldOur sun is now about 4.6 billion years old

– Links:Links: Planet swallower (artist)Planet swallower (artist) SunSun Solar prominence Solar prominence

IV. Red Giant IV. Red Giant (or (or supergiant)supergiant)

Stars begin to die when they Stars begin to die when they run out of run out of fuel (hydrogen)fuel (hydrogen)

The The center of the star shrinks and the center of the star shrinks and the outer part expandsouter part expands

The star The star may fuse all the elements may fuse all the elements through Fethrough Fe

Big, and bright, but low surface tempBig, and bright, but low surface temp All stars become a red giant or a All stars become a red giant or a

supergiantsupergiant– Camera Camera OrionOrion– Betelgeuse and Betelgeuse and RigelRigel

V. Death Phases of a V. Death Phases of a StarStar

A dying star will take one of A dying star will take one of three three pathspaths extinction extinction

The mass of the star dictates The mass of the star dictates which path it will takewhich path it will take

After the fuel is used up, a star After the fuel is used up, a star will become a…will become a…– White Dwarf, orWhite Dwarf, or– Neutron Star, orNeutron Star, or– Black HoleBlack Hole

Path #1: White DwarfsPath #1: White Dwarfs

White DwarfsWhite Dwarfs, small stars , small stars (1 X our Sun)(1 X our Sun) The outer layers of the star grow bigger and The outer layers of the star grow bigger and

slowly drift out into space. This slowly drift out into space. This material rejoins material rejoins a nebula to be recycled into a new stara nebula to be recycled into a new star

The The blue-white hot core is leftblue-white hot core is left and the “dead” and the “dead” star that is left behind is a white dwarfstar that is left behind is a white dwarf

The glow coming from the core is left-over The glow coming from the core is left-over energy from the old star. energy from the old star. The core is NOT The core is NOT making any more energy.making any more energy. (Like turning off a (Like turning off a light bulb)light bulb)

Eventually, the energy glow is gone and the core Eventually, the energy glow is gone and the core is dark. is dark. It becomes a black dwarfIt becomes a black dwarf..– Links: Links: Little Ghost NebulaLittle Ghost Nebula, , Helix NebulaHelix Nebula, ,

Eight-burst NebulaEight-burst Nebula

Path #2: Neutron StarsPath #2: Neutron Stars

Neutron stars, medium stars Neutron stars, medium stars (5 X our sun)(5 X our sun) A A supernova occurssupernova occurs when a supergiant star when a supergiant star

(5 X or more our sun) suddenly explodes(5 X or more our sun) suddenly explodes SomeSome materialmaterial rejoins a nebularejoins a nebula The remaining material from the star (or The remaining material from the star (or

corecore) ) is a neutron staris a neutron star Neutron stars are even Neutron stars are even smaller and more smaller and more

dense than white dwarfsdense than white dwarfs Some neutron stars spin, these are pulsarsSome neutron stars spin, these are pulsars

– Links: Links: Cosmic Pearls supernovaCosmic Pearls supernova,, Elusive Jellyfish nebulaElusive Jellyfish nebula (neutron star), (neutron star), Tycho’sTycho’s Supernova Supernova RemnantRemnant, , A Dark Pulsar in CTA 1A Dark Pulsar in CTA 1, , Crab Crab Pulsar Wind NebulaPulsar Wind Nebula

Path #3: Black HolesPath #3: Black Holes

Black holes are the most massive stars Black holes are the most massive stars (10-40 (10-40 X our sun)X our sun)

The (red) supergiant goes The (red) supergiant goes supernovasupernova, , throwing the outer layers into space to rejoin a throwing the outer layers into space to rejoin a nebulanebula

The gravity of the remaining core is so The gravity of the remaining core is so strong that the core collapses in on itselfstrong that the core collapses in on itself, , creating an even stronger gravitational pullcreating an even stronger gravitational pull

This gravity pulls everything to itThis gravity pulls everything to it Nothing can escape its gravitational pullNothing can escape its gravitational pull, ,

not even light waves!!not even light waves!!– Links: Links: A view near a black holeA view near a black hole, , star ripped apart by star ripped apart by

BHBH, , x-ray jet black holex-ray jet black hole, , BH candidate CygnusBH candidate Cygnus

VI. Lifetimes of StarsVI. Lifetimes of Stars

How long a star lives depends on how How long a star lives depends on how much mass it hasmuch mass it has

Small mass stars live longer than Small mass stars live longer than large mass starslarge mass stars– Stars that have Stars that have moremore mass than the sun mass than the sun

live a shorter lifetime. Approx. 10 million live a shorter lifetime. Approx. 10 million yearsyears

– Stars that have Stars that have lessless mass than the sun live mass than the sun live longer. Approx. 200 billion yearslonger. Approx. 200 billion years

Example: A small car burns a gallon of gas more Example: A small car burns a gallon of gas more efficiently than a big SUV (exp 25/mpg vs 8/mpg) efficiently than a big SUV (exp 25/mpg vs 8/mpg)

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