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E treme Stars

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

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E treme Stars

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  1. E treme Stars Caty Pilachowski Mini-University June 2012

  2. Brightest Star in the night sky SIRIUS Alpha CanisMajoris The Dog Star Sirius b – faint companion

  3. Most Distant Star (that you can see!) Deneb • Deneb= Alpha Cygni • Distance: ~ 1500 LY • Diameter: ~20 x Sun • Mass: ~20 x Sun • Luminosity: 60,000 x Sun 1 LY = 9,460,528,400,000 Km

  4. Distance: 150 million Km The Closest Star Diameter: 1.4 million Km = 100 x Earth Our Sun is a typical, middle-aged star Temperature: 6,000 C (outside) 15 million C (inside) Mass: 2 x 1030 kg = 300,000 x Earth Age: 4.6 billion years

  5. MASS DIAMETER A Range of Size and Mass 0.08 MSun ~200 MSun • Only certain combinations of size and mass are stable • Stars will shrink or expand to reach stability 0.1 MSun ~1000 MSun

  6. A Range of Temperature A star’s brightness depends on its temperature and radius The Sun is about 6000 C Hot stars are bluish in color Cool stars are reddish in color TEMPERATURE 2000 C 200,000 C

  7. Allowed Temperature & Luminosity

  8. A Range of Ages • Stars have been forming continuously since the Universe began 13.7 billion years ago • Some old stars are still around; other stars are brand new The Sun formed 4.6 billion years ago AGE ~13 Billion Years Brand New Stars

  9. Birth of the Sun BIRTH

  10. Middle Age BIRTH H The Sun Today

  11. Inside the Sun: Energy and Motion The energy comes from nuclear fusion reactions in the Sun’s core Energy flows slowly from the inside to the surface

  12. The Visible “Surface” of the Sun • Sunspots • cooler regions • magnetic fields • prominences originate from active regions

  13. The Sun in Time The Sun is gradually growing brighter over time, as it converts hydrogen into helium Eventually…

  14. As the Sun Grows Old He BIRTH H NOW

  15. Future Sun Astronomers aren’t 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 Earth The Sun today The Sun as a red giant The orbit of Venus

  16. The Sun’s Final Glory He BIRTH H NOW

  17. What’s Left? A White Dwarf • Mass: 50% Sun • Density: 1-2 tons per cc3 • Composition: C & O, the “ashes” of nuclear fusion • Cools & fades slowly 12,000 Km Sirius B

  18. Sirius b Nearest White Dwarf Star Diameter: 1/100 Sun Mass: 98% Sun Distance: 8.6 LY

  19. The • BIGGEST VY CanisMajoris • A red “hypergiant” star • Diameter: 2000 x Sun • Mass: 30-40 x Sun • Luminosity: 500,000 x Sun • 5,000 light-years away The Sun Credit: NASA/ESA/R Humphreys/U Minnesota)

  20. BRIGHTEST & MOST MASSIVE • Mass = 265 Suns (probably 320 Suns at birth!) • Luminosity = 8-9 million x Sun • Diameter: 35 x Sun • Distance: 165,000 LY • Future hypernova? • Located in the Large Magellanic Cloud R136A*

  21. NGC 2440 (central star) • Distance: 4500 LY The HOTTEST STARS are tiny, dim, new white dwarfsT=200,000 C • NGC 6302 (central star) • Distance: 3800 LY • Hidden by central dust ring • KPD 0005+5106 • Distance: 2500 LY Only 2200 years “old”

  22. The COLDEST • Brown Dwarfs! • WISE 1828+2650 • Temperature ~25 C • About 27 LY • Mass < 0.1 Suns • Too small for nuclear fusion Stars WISE

  23. The Oldest Stars! HE 1523-0901 • 13.2 billion years old • Mass: 0.8 Suns • Distance: ~7500 LY • A red giant star 13.2 billion Years ago Today

  24. The Youngest Stars Stars are forming today in the “empty” regions of interstellar space.

  25. Stages of Star Formation

  26. Stars on the Weird Side!

  27. The Famous Pleiades • Distance: 1300 LY • Brightest Star Cluster • Formed about 115 million years ago • The blue glow is dust!

  28. V838 Monocerotis – The Light Echo V838 is a “central star” of a planetary nebula Distance: 20,000 LY Mass: 5-10 Suns (originally much more massive) Outburst in 2002 - The “expanding shell” is actually an expanding light echo

  29. V838 Monocerotis – The Light Echo To Earth Arrives first Arrives later

  30. A Real Shooting Star! • Mira = Omicron Ceti • An unstable red giant • Losing mass • Distance: 400 LY • Mass: 1.2 Suns • 13 LY tail • 291,000 mph GALEX GALEX As seen by Hubble

  31. Epsilon Aurigae • Binary star (6 + 8 Suns) • 27 year period • One star is invisible! An unseen blue star hides in a disk of dust that orbits a yellow supergiant When the blue star passes in front of the yellow star, the disk blocks the light of yellow star 8 AU Dust Disk

  32. Stellar Cannibalism Binary stars that orbit close together often transfer mass between the stars Semi -Detached Binary Detached Binary Contact Binary Warning: Artist’s Conceptions

  33. R Corona Borealis – The “Fade Out” Star • Yellow supergiant star • Distance: 6000 LY • Mass: 0.8 Suns • Sometimes fades by a factor of 1000 or more in brightness! • Emits “puffs” of soot that block the light of the star • This star smokes!

  34. MoreR Corona Borealis • Extreme helium star • Very little hydrogen • Lots of carbon • Origin: merger of two white dwarfs?

  35. Extreme Spots! HD 12545 holds the record for the largest “starspot” Artist Conception Warning: Artist’s Conception The 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.

  36. Extreme Rotation! Regulus • Regulus = Alpha Leo • Distance: 78 LY • Mass: 3.8 Suns • Radius: 3-5 Suns Altair Vega Rotates every 16 hrs! Other stars, too!

  37. MORE EXTREME ROTATION Crab Pulsar • Distance: 6500 LY • Mass: ~ 1.4-2.0 Suns • Remnant of 1054 Supernova Density: 100,000,000 tons per thimbleful Spins 30 times per second

  38. SGR 1900+14 Magnetars!Extreme Neutron Stars • Most intense magnetic fields in the Universe • Hundreds of millions times stronger than the strongest human-made magnets • Only 5 known • Sources of intense gamma ray bursts • SGR 1900+14 • Distance: 20,000 LY • Mass: ~ 2 Suns • Diameter: ~20 Km 7 LY Warning: Artist’s Conception

  39. Supernova 1987a

  40. Supernova 1987a • Detected in 1987 • Exploded 170,000 years ago • Originally about 18 solar masses • Where is the neutron star?

  41. Black Holes Best candidate: • V404 Cyg • Distance: 7,800 LY • Star mass: ~0.7 Suns • BH mass: ~12 Suns • BH Diameter: ~75 km • Orbital period: 6.5 days • Closest candidate: • V616 Mon • Distance: 3000 LY • Star mass: ~0.5Suns • BH mass: ~6 Suns • BH Diameter: ~40 km • Orbit period: 7.75 hrs

  42. The Universe is Full of Surprises! And that’s what makes astronomy so much fun!

  43. Kirkwood Observatory Open Tonight, 10:30-11:30PM Weather permitting! Kirkwood Observatory is located at the west end of Dunn’s Woods, behind Bryan Hall

  44. Happy Summer Solstice! On the handout: • URL for this presentation on the Web • Related websites • Kirkwood Observatory open tonight

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