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E treme Stars. Caty Pilachowski Mini-University June 2012. Brightest Star in the night sky. SIRIUS. Alpha Canis Majoris The Dog Star. Sirius b – faint companion. Most Distant Star (that you can see!). Deneb. Deneb = Alpha Cygni Distance: ~ 1500 LY Diameter: ~20 x Sun - PowerPoint PPT Presentation

Transcript of E treme Stars

Extreme Stars

E treme StarsCaty PilachowskiMini-UniversityJune 2012

Brightest Star in the night skyAlpha Canis Majoris The Dog Star

SIRIUSSirius b faint companionMost Distant Star (that you can see!)Deneb = Alpha CygniDistance: ~ 1500 LYDiameter: ~20 x SunMass: ~20 x SunLuminosity: 60,000 x Sun

1 LY = 9,460,528,400,000 KmDeneb

The Closest StarOur Sun is a typical, middle-aged starDistance:150 million KmDiameter:1.4 million Km= 100 x EarthAge:4.6 billion yearsTemperature:6,000 C (outside)15 million C (inside)Mass:2 x 1030 kg = 300,000 x Earth40.08 MSun~200 MSunMASS

DIAMETER0.1 MSun~1000 MSun

A Range of Size and MassOnly certain combinations of size and mass are stableStars will shrink or expand to reach stabilityTEMPERATURE200,000 C2000 C

A Range of Temperature A stars brightness depends on its temperature and radiusThe Sun is about 6000 CHot stars are bluishin colorCool stars are reddish in colorAllowed Temperature & Luminosity

AGE~13 Billion YearsBrand New Stars

A Range of AgesStars have been forming continuously since the Universe began 13.7 billion years agoSome old stars are still around; other stars are brand newThe Sun formed 4.6 billion years agoBirth of the Sun


Middle Age


The Sun Today

Inside the Sun: Energy and MotionThe energy comes from nuclear fusion reactions in the Suns core

Energy flows slowly from the inside to the surface

The Visible Surface of the Sun

Sunspots cooler regions magnetic fields prominences originate from active regionsThe Sun in Time

The Sun is gradually growing brighter over time, as it converts hydrogen into helium

EventuallyAs the Sun Grows Old


Future SunThe Sun todayThe Sun as a red giantAstronomers arent sure how big the Sun will grow when it becomes a red giant, Perhaps as large as the orbit of Venus, or even the orbit of the EarthThe orbit of VenusThe Suns Final Glory


Whats Left? A White DwarfMass: 50% SunDensity: 1-2 tons per cc3Composition: C & O, the ashes of nuclear fusionCools & fades slowlySirius B

12,000 Km

Sirius bDiameter: 1/100 SunMass: 98% SunDistance: 8.6 LY Nearest White Dwarf Star18

VY Canis MajorisA red hypergiant star Diameter: 2000 x SunMass: 30-40 x SunLuminosity: 500,000 x Sun5,000 light-years away

Credit: NASA/ESA/R Humphreys/U Minnesota) The Sun TheBIGGEST

BRIGHTEST & MOST MASSIVE Mass = 265 Suns (probably 320 Suns at birth!)Luminosity = 8-9 million x SunDiameter: 35 x SunDistance: 165,000 LYFuture hypernova?Located in the Large Magellanic Cloud

R136A*The HOTTEST STARS are tiny, dim, new white dwarfsT=200,000 C

NGC 2440 (central star)Distance: 4500 LY NGC 6302 (central star)Distance: 3800 LYHidden by central dust ring KPD 0005+5106Distance: 2500 LYOnly 2200 years old

COLDESTBrown Dwarfs!WISE 1828+2650Temperature ~25 CAbout 27 LYMass < 0.1 SunsToo small for nuclear fusion

TheStarsWISEThe Oldest Stars! HE 1523-090113.2 billion years oldMass: 0.8 Suns

Today13.2 billion Years agoDistance: ~7500 LYA red giant star

The Youngest Stars Stars are forming today in the empty regions of interstellar space.Stages of Star Formation

Stars on the Weird Side!

The Famous PleiadesDistance: 1300 LYBrightest Star ClusterFormed about 115 million years agoThe blue glow is dust!

V838 Monocerotis The Light Echo

V838 is a central star of a planetary nebulaDistance: 20,000 LYMass: 5-10 Suns (originally much more massive)

Outburst in 2002 - The expanding shell is actually an expanding light echoV838 Monocerotis The Light Echo

Arrives firstArrives laterTo Earth

A Real Shooting Star!Mira = Omicron CetiAn unstable red giantLosing massDistance: 400 LYMass: 1.2 Suns13 LY tail291,000 mph


As seen by HubbleGALEXEpsilon AurigaeBinary star (6 + 8 Suns)27 year periodOne star is invisible!

8 AUDust DiskAn unseen blue star hides in a disk of dust that orbits a yellow supergiantWhen the blue star passes in front of the yellow star, the disk blocks the light of yellow star

Stellar Cannibalism Binary stars that orbit close together often transfer mass between the starsWarning: Artists Conceptions

Contact BinaryDetached BinarySemi -Detached BinaryR Corona Borealis The Fade Out StarYellow supergiant starDistance: 6000 LYMass: 0.8 SunsSometimes fades by a factor of 1000 or more in brightness!Emits puffs of soot that block the light of the starThis star smokes!

MoreR Corona BorealisExtreme helium starVery little hydrogenLots of carbonOrigin: merger of two white dwarfs?

Extreme Spots!

HD 12545 holds the record for the largest starspotArtist ConceptionThe rotation and revolution of close binary stars are locked together, forcing the stars to rotate as fast as they orbit. Fast rotation makes big spots.Warning: Artists ConceptionExtreme Rotation!Regulus = Alpha LeoDistance: 78 LYMass: 3.8 SunsRadius: 3-5 SunsRotates every 16 hrs!

VegaAltairOther stars, too!

Regulus36Crab Pulsar

Distance: 6500 LYMass: ~ 1.4-2.0 SunsRemnant of 1054 SupernovaSpins 30 times per secondMORE EXTREME ROTATIONDensity: 100,000,000 tonsper thimblefulMagnetars!Extreme Neutron StarsMost intense magnetic fields in the UniverseHundreds of millions times stronger than the strongest human-made magnetsOnly 5 knownSources of intense gamma ray bursts

Warning: Artists Conception

SGR 1900+147 LYSGR 1900+14Distance: 20,000 LYMass: ~ 2 SunsDiameter: ~20 KmSupernova 1987a

Supernova 1987aDetected in 1987Exploded 170,000 years agoOriginally about 18 solar massesWhere is the neutron star?

Best candidate:V404 CygDistance: 7,800 LYStar mass: ~0.7 SunsBH mass: ~12 SunsBH Diameter: ~75 kmOrbital period: 6.5 daysClosest candidate:V616 MonDistance: 3000 LYStar mass: ~0.5 SunsBH mass: ~6 SunsBH Diameter: ~40 kmOrbit period: 7.75 hrsBlack HolesThe Universe is Full of Surprises! And thats what makes astronomy so much fun!Kirkwood ObservatoryOpen Tonight, 10:30-11:30PM Weather permitting!

Kirkwood Observatory is located at the west end of Dunns Woods, behind Bryan Hall

Happy Summer Solstice!

On the handout:URL for this presentation on the WebRelated websitesKirkwood Observatory open tonightChart20.750.80.850.90.9511.

Time since Formation (Billions of Years)BrightnessLuminosity of the Sun



Time since Formation (Billions of Years)BrightnessLuminosity of the Sun