Extreme Stars

SIRIUS

Brightest Star in the night sky

Alpha Canis Majoris

The Dog Star Sirius b – faint companion

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

Most Distant Star (that you can see!)

Distance: 150 million Km

The Closest Star Our Sun is a typical, middle-aged star

Diameter: 1.4 million Km = 100 x Earth

Temperature: 6,000 C (outside) 15 million C (inside)

Mass:

Age: 4.6 billion years

2 x 1030 kg = 300,000 x Earth

A Range of Size and Mass MASS

0.08 MSun

~200 MSun DIAMETER

0.1 MSun

~1000 MSun

Only certain combinations of size and mass are stable Stars will shrink or expand to reach stability

A Range of Temperature TEMPERATURE 200,000 C

2000 C Cool stars are reddish in color

The Sun is about 6000 C

Hot stars are bluish in color

A star’s brightness depends on its temperature and radius

Allowed Temperature & Luminosity

A Range of Ages AGE ~13 Billion Years

Brand New Stars

The Sun formed 4.6 billion years ago 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

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

5

The Sun in Time

Brightness

4

3

Luminosity of the Sun 2

1

0 0

2

4

6

8

10

Time since Formation (Billions of Years)

12

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

As the Sun Grows Old He

BIRTH H

NOW

Future Sun The Sun today

The Sun as a red giant The orbit of Venus

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’s Final Glory He

BIRTH H

NOW

What’s Left? A White Dwarf 12,000 Km

Mass: 50% Sun Density: 1-2 tons per cc3 Composition: C & O, the Sirius B

“ashes” of nuclear fusion Cools & fades slowly

Nearest White Dwarf Star

Sirius b

Diameter: 1/100 Sun Mass: 98% Sun Distance: 8.6 LY

The

BIGGEST Credit: NASA/ESA/R Humphreys/U Minnesota)

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

VY Canis Majoris

BRIGHTEST & MOST MASSIVE

Mass = 265 Suns (probably 320 Suns at birth!) Luminosity = 8-9 million x Sun Diameter: 35 x Sun Located in the Large Distance: 165,000 LY Magellanic Cloud Future hypernova?

R136A*

The HOTTEST STARS NGC 2440 (central star)

are tiny, dim, new

Distance: 4500 LY

white dwarfs T=200,000 C NGC 6302 (central star) Distance: 3800 LY Hidden by central dust ring

KPD 0005+5106 Only 2200 years “old”

Distance: 2500 LY

The

WISE

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

Stars

The Oldest Stars! HE 1523-0901 13.2 billion years old Mass: 0.8 Suns

13.2 billion Years ago

Distance: ~7500 LY A red giant star

Today

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

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

V838 MONOCEROTIS – THE LIGHT ECHO

To Earth

Arrives first Arrives later

A Real Shooting Star!

13 LY tail 291,000 mph GALEX

Mira = Omicron Ceti An unstable red giant Losing mass Distance: 400 LY Mass: 1.2 Suns

As seen by Hubble

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

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

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?

HD 12545 holds the record for the largest “starspot”

Artist Conception

Extreme Spots! 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.

Extreme Rotation! Regulus = Alpha Leo Distance: 78 LY Mass: 3.8 Suns Radius: 3-5 Suns

Rotates every 16 hrs! Other stars, too!

Regulus

Altair

Vega

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

Magnetars!

SGR 1900+14

Extreme Neutron Stars SGR 1900+14 Distance: 20,000 LY Mass: ~ 2 Suns Diameter: ~20 Km

7 LY

 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

Supernova 1987a

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

Closest candidate:

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

 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!

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