1. STARS

2. Physical Properties of Stars
Stars differ in size, density, mass, composition, and color
The color of a star is determined by it surface temperature (Reference Tables)
The hotter the star, the bluer the color. The cooler the star, the redder the color.
The sun is a yellow star

4. Physical Properties of Stars
Most stars are made up of mostly hydrogen and helium (approx. 98%)
The remaining 2% may be other elements
A spectrum analysis of the star can tell us what elements a star is made of, since the radiated spectrum depends on a star’s composition and temperature

5. Apparent Magnitude How bright a star appears on to us on Earth
The farther a star is from Earth, the dimmer it will look even though it may actually be a very bright star
Because of this, apparent magnitude does not tell the true brightness of a star

6. Luminosity The actual (true) brightness of the star
Depends on the size and temperature of the star
Hotter stars are more luminous (brighter) than cooler stars
If the temperatures are the same, a larger star will be more luminous

7. Absolute Magnitude
The luminosity of the stars if they all were the same distance from Earth
aka – picture all the stars lined up the same distance from Earth, then compare their brightness
This is the most useful when comparing the brightness of the stars

9. Distances to the Stars

10. The sun is the closest star to Earth
It is approx. 150,000,000 km (93,000,000 miles) from the Earth
This distance is called an astronomical unit (AU)
The closest star to Earth, after the sun, is Alpha Centuri
It is 300,000 times farther away from Earth than the sun. Because of the great distances in space, larger units of measure must be used
The light-year is the distance that light travels in one year
Since light can travel 300,000 km/sec (186,000 miles/sec), light travels 9.5 trillion km/year!!!
Alpha Centuri is 4.3 light-years from Earth!

11. Star Formation & Origin

12. large clouds of dust and gas in space are the basic materials needed for star formation
the majority of this gas is hydrogen
some outside force causes the cloud to be pushed together
as the gas and dust get closer, friction between the particles causes the temperature to increase
the attraction of gravity between the particles causes them to continue to move together, and density also increases

13. In a nuclear reactor like Indian Point, nuclear fission takes place
friction increases and temperature increase until the center becomes so hot that nuclear fusion takes place
hydrogen atoms are forced together to form helium atoms, and energy is released
In a nuclear reactor like Indian Point, nuclear fission takes place
This is when radioactive atoms are split apart to release energy

14. But where does the gas & dust come from????

15. SUPERNOVAS One of the most energetic explosive events
occur at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy
If the star is particularly massive, then its core will collapse and in so doing will release a huge amount of energy
This will cause a blast wave that ejects the star's envelope into interstellar space

16.                          
Etna Carinae
Supernova remnant
Supernova rings

17. SUPERNOVA 1987 – right image is the star that became the left image after going supernova – shone brighter than most galaxies for a few months!

18. NEBULA Clouds of dust & gas (supernova remnants?) 2 Main Types:
Diffuse Nebula – nearby star illuminates the gas/dust cloud
Dark Nebula – Dark patch against more-distant stars (dust/gas is blocking the light from stars behind it)

19. ORION NEBULA
VEIL NEBULA
HELIX NEBULA
KEYHOLE NEBULA

20. CAT’S EYE NEBULA

21. ESKIMO NEBULA
5000 LY FROM EARTH - 10,000 YRS OLD

22. CRAB NEBULA

23. HORSEHEAD NEBULA – PART OF ORION

25. A STAR IS BORN…
I WANT MY MOMMY!!

26. THE BIRTH OF A SOLAR SYSTEM (OOH IT’S A GIRL!)
STELLAR NURSERY
GLOBULE
GLOBULE COLLAPSE
PROTOPLANETARY DISK & CORE
DUST & GAS COMPRESS DUE TO GRAVITATIONAL FORCES, FORMING A SLOWLY ROTATING GLOBULE
GRAVITY BECOMES TOO STRONG & THE GLOBULE COLLAPSES, SPINNING INCREASES
A STAR BEGINS TO FORM IN A NEBULA (CLOUD OF GAS & DUST)
SPIN, PRESSURE, & TEMPERATURE INCREASE, PLANETS ARE FORMED, AND CENTRAL CORE (SUN) FORMED

27. LIFE CYCLE OF STARS A star’s life cycle is determined by its MASS
The larger the star, the faster it burns out!
A star’s MASS is determined by the MATTER available in the nebula of formation

28. STARS FORM IN A NEBULA OF GAS & DUST
LIFE CYCLE OF STARS
SUN-LIKE STARS
(UP TO 1.5 X MASS OF OUR SUN)
RED GIANT
PLANETARY NEBULA
WHITE DWARF
BLACK DWARF
STELLAR NURSERY
MASSIVE STARS
(1.5 – 3 X OUR SUN)
RED SUPERGIANT
SUPERNOVA
NEUTRON STAR
STARS FORM IN A NEBULA OF GAS & DUST
SUPERMASSIVE STARS
> 3 X OUR SUN
RED SUPERGIANT
SUPERNOVA
BLACKHOLE

29. DEATH OF A SUN-LIKE STAR
RED GIANT
PLANETARY NEBULA
WHITE DWARF
BLACK DWARF
STAR COOLS ARE SHRINKS BECOMING ONLY A FEW THOUSAND MILES ACROSS!
NO NUCLEAR REACTION
LONGEST, MOST STABLE PERIOD OF A STAR’S LIFE – CONVERTS HYDROGEN TO HELIUM, RADIATING HEAT & LIGHT
STAR LOSES ALL HEAT TO SPACE AND BECOMES COLD AND DARK
NUCLEAR FUEL DEPLETES, CORE CONTRACTS, SHELL EXPANDS
OUTER LAYERS DRIFT OFF INTO SPACE IN SPHERE-LIKE PATTERN

31. THE STAR SOL: OUR SUN

32. Handy Dandy Earth Science Reference Tables Page 15

33. H-R DIAGRAM

34. Properties of the Sun average size yellow star
fairly cool compared to other stars
diameter is approx. 110 times larger than Earth’s, with a volume that hold more than 1,000,000 Earths.
Light traveling from the sun takes approx. 8 minutes 20 seconds to reach Earth!
surface temperature is approx. 5,500 C and its interior temperature is believed to be 15,000,000 C!!

36. Sunspots & Prominences
Sunspots are regions of intense magnetic fields
Sunspot temperatures are cooler than the photosphere, which makes them appear as dark spots
Prominences are regions along a magnetic field line where conditions are right for light to be emitted
Huge, arching columns of gas often appearing above sunspots

39. Solar Flares
Occasionally, kinks and stresses occur on magnetic field lines discharging amounts  of energy (known as Solar Flares)
The amount of energy released is equivalent to a 2 billion megaton bomb
Flares release large numbers of particles into the corona

41. Source of the Sun’s Energy
The process of NUCLEAR FUSION
Einstein explained this process as
E = MC² (matter can be converted into energy)
The hydrogen molecules that the sun is made of fuse together to form a helium atom. When this occurs, energy is given off!
**It is estimated that the sun has enough mass for nuclear fusion to continue for 5 billion more years!

43. GIANTS/SUPERGIANTS the brightest & largest kind of star
luminosities of 10,000 to 100,000
radii of 20 to several hundred solar radii (about the size of Jupiter's orbit)
two types are red supergiants (Betelgeuse and Antares) and blue supergiants (Rigel)

44. Betelgeuse a red supergiant, with about 20 times the mass and 800 times the radius of the Sun, so huge that it could easily contain the orbits of Mercury, Venus, Earth, and Mars. It will probably explode as a supernova at some point within the next 100,000 years. Even at its relatively remote distance, it normally ranks as the tenth brightest star in the sky.
Rigel, a blue supergiant, has a diameter of about 100 million kilometers, some seventy times that of the Sun. Within a few million years, it will probably evolve to become a red supergiant like its neighbor in Orion (though not in physical space), Betelgeuse.

45. Dwarf Stars
A term used, oddly enough, to describe any star that is of normal size for its mass
The Sun, for example, is classified as a yellow dwarf
In general, dwarf stars lie on the main sequence and are in the process of converting hydrogen to helium by nuclear fusion in their cores

46. White Dwarfs
A medium sized star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size
Typically part of a planetary nebula
Eventually cools into a BLACK dwarf (lump of carbon)
This takes BILLIONS of years!
This is the fate of OUR SUN!

48. Neutron Star
The imploded core of a massive star produced by a supernova explosion
The most dense known objects in the universe!
A sugar cube of neutron star material weighs 100 million tons! (think Mt. Everest)

50. BLACKHOLES
A supermassive star that undergoes supernova and the core of the star is “swallowed” by its own gravity
readily attracts any matter and energy that comes near it

51. Blackholes cont…
It is an area where the escape velocity is greater than the speed of light.
The more massive an object is, the faster you have to travel to escape its gravity.
This is known as the escape velocity.
Black holes are so massive that their escape velocity is faster than the speed of light.
Since nothing can travel faster than light, nothing can escape the gravity of a black hole.

53. Blackhole at the center
of our Milky Way Galaxy!

54. 3,700 LY wide dust-disk encircling a 300 million solar mass blackhole in the center of an elliptical galaxy.
The disk is a remnant of an ancient galaxy collision and could be “swallowed” up by the blackhole in a few billion years.

55. Galaxies & the Universe

58. Galaxies system containing millions to billions of stars
Ex. the Milky Way galaxy contains over 100 billion stars
Milky Way galaxy is a spiral shaped galaxy with a large central cluster of stars, and thinner “arms” radiating out from the center
The solar system is located on one of the arms of the Milky Way galaxy

60. Origin of the Milky Way Formed 10-12 billion years ago
Possibly collided with smaller galaxies
Globular star clusters formed
Stars and solar systems formed roughly 5 billions years ago

62. Milky Way

64. Andromeda Galaxy – 2.9 million LY from earth

65. Sombrero Galaxy – 50 million LY from earth – 100,000 LY across

66. Hoag’s Galaxy – 120,000 LY wide – perfect ring of blue stars surrounding older nucleus of yellow stars

67. When galaxies collide…

68. Galaxy Formation
The formation of all the galaxies is explained by the Big Bang Theory
Simply put, it states that the universe was a big ball of hydrogen gas that exploded outward
The expanding cloud had areas that condensed into galaxies that are still expanding out from the center (the universe is getting larger)
We can see this with RED SHIFT!

72. Space is BIG. Really BIG. You just won’t believe how vastly hugely mind-bogglingly big it is.