Putting order to billions of Putting order to billions of starsstars

SizeSizeAstronomers use 4 sizes for the Astronomers use 4 sizes for the

stars. The largest stars in the stars. The largest stars in the universe are called universe are called super giantssuper giants. . The star Betelgeuse is a super giant The star Betelgeuse is a super giant star. The next step down in size are star. The next step down in size are called called mediummedium stars. The star in our stars. The star in our solar system, Sun, is a medium star. solar system, Sun, is a medium star. White dwarfWhite dwarf stars about the size of stars about the size of Earth, and Earth, and neutronneutron stars are the stars are the smallest at about 20km in diameter.smallest at about 20km in diameter.

TemperatureTemperature

Temperature of stars can be Temperature of stars can be estimated from earth using the estimated from earth using the colorcolor of the star. A star that is of the star. A star that is redred is cool in temperature, around is cool in temperature, around 3,2003,200°°CC. . WhiteWhite stars are stars are considered hot at about considered hot at about 5,5005,500°°CC. . BlueBlue colored stars are the hottest colored stars are the hottest with temperatures of with temperatures of 10,00010,000°°C or C or moremore..

BrightnessBrightnessBy definition, brightness is the amount of By definition, brightness is the amount of

lightlight given off. Brightness depends on given off. Brightness depends on the star’s the star’s distancedistance from Earth as well as from Earth as well as its actualits actual brightnessbrightness. Brightness is . Brightness is measured by two methods: measured by two methods: absolute absolute magnitudemagnitude which is difficult, and which is difficult, and apparent magnitudeapparent magnitude which is easier. which is easier. Absolute magnitude involves Absolute magnitude involves mathematically moving the stars to the mathematically moving the stars to the same distance from earth and then same distance from earth and then rating how bright they are. Apparent rating how bright they are. Apparent magnitude is comparing from earth, the magnitude is comparing from earth, the visual brightness of one star to another’s visual brightness of one star to another’s brightness.brightness.

How did stars get there?How did stars get there?

Red Giant or Supergiant

Protostar

Nebula

Supernova

Black Hole

White Dwarf

BlackDwarf

NeutronStar

BirthBirthAll stars, before they are formed, All stars, before they are formed,

begin as part of a begin as part of a nebulanebula (a large (a large collection of gas and dust in an collection of gas and dust in an area). As more and more matter area). As more and more matter collects in the area, collects in the area, gravitygravity begins begins to pull together the dust and gas to pull together the dust and gas which creates a protostar. This which creates a protostar. This protostar continues to form until protostar continues to form until nuclear fusionnuclear fusion begins. Once this begins. Once this happens, a star is born.happens, a star is born.

LifetimeLifetimeHow long a star will last depends on its How long a star will last depends on its

massmass. . BigBig stars with large mass, will stars with large mass, will burn up burn up veryvery rapidly and have a short rapidly and have a short life. life. SmallSmall stars with small mass have a stars with small mass have a longlong life because they burn up their fuel life because they burn up their fuel slowlyslowly. It is a lot like fuel efficiency of . It is a lot like fuel efficiency of vehicles, larger vehicles like suburbans vehicles, larger vehicles like suburbans and big trucks take more gas to move and big trucks take more gas to move than the smaller cars like minis and than the smaller cars like minis and civics.civics.

DeathDeath

Stars do eventually burn out Stars do eventually burn out or die when they or die when they run outrun out of of fuel. But the size of the star fuel. But the size of the star determines how the star will determines how the star will die. die.

Death continuedDeath continued

SmallSmall and and mediummedium stars have stars have less violent deaths. The outer less violent deaths. The outer layers layers expandexpand and drift away and drift away from the center. The from the center. The corecore is left is left behind, which forms a white behind, which forms a white dwarf star. The white dwarf dwarf star. The white dwarf then simply stops then simply stops glowingglowing, and , and is called a black dwarf.is called a black dwarf.

Death continuedDeath continued

Super giantSuper giant stars are stars are considerably more violent. considerably more violent. When their fuel runs out, these When their fuel runs out, these stars explode in what’s called a stars explode in what’s called a supernovasupernova. The material that is . The material that is left behind and not scattered left behind and not scattered too far can reform into a too far can reform into a neutronneutron star. star.

Death continuedDeath continuedThe most The most massivemassive stars follow a stars follow a

slightly different path. They slightly different path. They exploded into a supernova much exploded into a supernova much like the supergiant stars, but the like the supergiant stars, but the leftover gases do not reform leftover gases do not reform neutron stars. The incredible neutron stars. The incredible explosion creates such a huge force explosion creates such a huge force that these gases are pulled that these gases are pulled inwardinward. . GravityGravity becomes so strong so becomes so strong so quickly that everything begins to be quickly that everything begins to be drawn in and a drawn in and a black holeblack hole forms. forms.

Red Giant or Supergiant

Protostar

Nebula

Supernova

Black Hole

White Dwarf

BlackDwarf

NeutronStar

There’s more out there There’s more out there than our Milky Waythan our Milky Way

Side View

Top View

Sun’s Location

About 100,000 light-years

SpiralSpiralSpiral galaxies consists of twin Spiral galaxies consists of twin

spiralsspirals that slowly rotate. The arms that slowly rotate. The arms appear to rotate appear to rotate and spiral outwardand spiral outward due to its rotation. Spiral galaxies due to its rotation. Spiral galaxies contain lots of contain lots of dustdust, and , and particlesparticles. . therefore astronomers watch these therefore astronomers watch these types of galaxies for new stars to types of galaxies for new stars to form. Earth is located in a spiral form. Earth is located in a spiral galaxy called the Milky Way.galaxy called the Milky Way.

EllipticalElliptical

Elliptical galaxies are Elliptical galaxies are ovaloval or look or look like a football. These galaxies like a football. These galaxies contain contain very littlevery little gas and dust. gas and dust. Astronomers watch elliptical Astronomers watch elliptical galaxies for black dwarfs or galaxies for black dwarfs or supernovas, since most of the stars supernovas, since most of the stars here are here are oldold stars. stars.

IrregularIrregular Irregular galaxies are very diverse. Irregular galaxies are very diverse.

There are no There are no regularregular shapes or shapes or patterns to these galaxies. The Large patterns to these galaxies. The Large MagellanicMagellanic Cloud is the name of the Cloud is the name of the closestclosest galaxy to us in space. galaxy to us in space.