Presentation on theme: "Brightest Star in the night sky Alpha Canis Majoris The Dog Star SIRIUS Sirius b – faint companion."— Presentation transcript:
Brightest Star in the night sky Alpha Canis Majoris The Dog Star SIRIUS Sirius b – faint companion
Most Distant Star (that you can see!) 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 Deneb
The Closest Star Our Sun is a typical, middle-aged star Distance Distance : 150 million Km Diameter Diameter : 1.4 million Km = 100 x Earth Age Age : 4.6 billion years Temperature Temperature : 6,000 C (outside) 15 million C (inside) Mass Mass: 2 x kg = 300,000 x Earth
0.08 M Sun ~200 M Sun MASS DIAMETER 0.1 M Sun ~1000 M Sun A Range of Size and Mass Only certain combinations of size and mass are stable Stars will shrink or expand to reach stability
TEMPERATURE 200,000 C 2000 C 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
Allowed Temperature & Luminosity
AGE ~13 Billion YearsBrand New Stars 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
Birth of the Sun BIRTH
Middle Age BIRTH H The Sun Today
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
The Visible “Surface” of the Sun Sunspots cooler regions magnetic fields prominences originate from active regions
The Sun in Time The Sun is gradually growing brighter over time, as it converts hydrogen into helium Eventually…
As the Sun Grows Old BIRTH NOW H He
Future Sun The Sun today The Sun as a red giant 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 orbit of Venus
The Sun’s Final Glory BIRTH NOW H He
What’s Left? A White Dwarf Mass: 50% Sun Density: 1-2 tons per cc 3 Composition: C & O, the “ashes” of nuclear fusion Cools & fades slowly Sirius B 12,000 Km
Sirius b Diameter: 1/100 Sun Mass: 98% Sun Distance: 8.6 LY Nearest Nearest White Dwarf Star White Dwarf Star
VY Canis Majoris A red “hypergiant” star Diameter: 2000 x Sun Mass: x Sun Luminosity: 500,000 x Sun 5,000 light-years away Credit: NASA/ESA/R Humphreys/U Minnesota) The Sun The BIGGEST
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 R 136 A *
The HOTTEST STARS are tiny, dim, new white dwarfs T=200,000 C NGC 2440 (central star) Distance: 4500 LY NGC 6302 (central star) Distance: 3800 LY Hidden by central dust ring KPD Distance: 2500 LY Only 2200 years “old”
COLDEST Brown Dwarfs! WISE Temperature ~25 C About 27 LY Mass < 0.1 Suns Too small for nuclear fusion The Sta rs WISE
The Oldest Stars! HE 13.2 billion years old Mass: 0.8 Suns Today 13.2 billion Years ago Distance: ~7500 LY A red giant star
The Youngest Stars Stars are forming today in the “empty” regions of interstellar space. Stars are forming today in the “empty” regions of interstellar space.
Stages of Star Formation
Stars on the Weird Side!
The Famous Pleiades Distance: 1300 LY Brightest Star Cluster Formed about 115 million years ago The blue glow is dust!
V838 M ONOCEROTIS – T HE L IGHT E CHO V838 is a “central star” of a planetary nebula Distance: 20,000 LY Mass: 5-10 Suns (originally much more massive) Outburst in The “expanding shell” is actually an expanding light echo
V838 M ONOCEROTIS – T HE L IGHT E CHO Arrives first Arrives later To Earth
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 As seen by Hubble GALEX
Epsilon Aurigae Binary star (6 + 8 Suns) 27 year period One star is invisible! 8 AU Dust Disk 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
Stellar Cannibalism Binary stars that orbit close together often transfer mass between the stars Warning: Artist’s Conceptions Contact Binary Detached Binary Semi -Detached Binary
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
More R Corona Borealis Extreme helium star Very little hydrogen Lots of carbon Origin: merger of two white dwarfs?
Extreme Spots! HD holds the record for the largest “starspot” Artist 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. Warning: Artist’s Conception
Extreme Rotation! Regulus = Alpha Leo Distance: 78 LY Mass: 3.8 Suns Radius: 3-5 Suns Rotates every 16 hrs! Vega Altair Other stars, too! Regulus
Crab Pulsar Distance: 6500 LY Mass: ~ Suns Remnant of 1054 Supernova Spins 30 times per second MORE EXTREME ROTATION Density: 100,000,000 tons per thimbleful
Magnetars! 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 Warning: Artist’s Conception SGR LY SGR Distance: 20,000 LY Mass: ~ 2 Suns Diameter: ~20 Km
Detected in 1987 Exploded 170,000 years ago Originally about 18 solar masses Where is the neutron star?
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: ~0.5 Suns BH mass: ~6 Suns BH Diameter: ~40 km Orbit period: 7.75 hrs
The Universe is Full of Surprises! And that’s what makes astronomy so much fun! And that’s what makes astronomy so much fun!
Weather permitting! Kirkwood Observatory is located at the west end of Dunn’s Woods, behind Bryan Hall
Happy Summer Solstice! On the handout: URL for this presentation on the Web Related websites Kirkwood Observatory open tonight