|Milky Way 1
|by JimboRocks on Flickr
- This image shows
the Milky Way, and as you can see it contains millions of stars.
- The nearest star
to Earth is our Sun, and it's the source of most of
the energy on Earth.
- Earth and our Sun are part of this
Milky Way Galaxy.
- Galaxies are sprawling space systems composed of
dust, gas, and countless stars.
- The number of galaxies cannot be counted—the
observable universe alone may contain 100 billion. Some of these distant
systems are similar to our own Milky Way galaxy, while others are quite
- Galaxies with less than a billion stars are
considered "small galaxies." In
our own galaxy, the sun is just one of about 100 billion stars!!
|by jimkster on Flickr
Galaxies are classified into three
Spiral galaxies, such as the Milky Way, consist of a
flat disk with a bulging center and surrounding spiral arms.
- Spiral galaxies
- Elliptical galaxies and
- Irregular galaxies.
The galaxy's disk includes stars, planets, dust, and
gas—all of which rotate around the galactic center in a regular manner.
|by rodrigo senna on Flickr
moon orbits our planet Earth, just as Earth orbits our Sun.
gravitational effects of the mass of the moon on our planet can be noticed
in the changing tides.We also feel the effects of gravity on our
- Our Sun, and
the stars, are massive, luminous balls of plasma held together
by the same force - gravity.
|SDO Spots Extra Energy in the Sun's Corona [detail]
|by NASA Goddard Photo and Video on Flickr
colourful NASA image was only taken on April 25, 2010.
- This photography
technique allows us to see the spectrum of light coming off the sun's
we can see 'jets' of coloured energy, known as 'spicules'.
Knowledge about Stars:
- In 1913, successful models were
developed to really explain the interiors of stars and the birth of stars.
The colourful light or
spectrum coming from stars
even showed the scientists what chemicals were in the stars.
- With the exception of supernovae,
individual stars have been observed in the visible part of
the Milky Way.
- Astronomers are able to find the
mass, age, chemical composition and many other properties of a star by
observing its spectrum (colours), luminosity (brightness) and how it moves through space.
Chemicals in Stars:
- Almost all naturally occurring elements heavier than helium were
created by stars!!
- Either via stellar nucleosynthesis during
their lifetimes, or by supernovae nucleosynthesis when
- The Periodic Table below shows the placement of helium compared to all the
other heavier elements.
|Starburst and Beach Grass On Turquoise free creative commons
|by Pink Sherbet Photography on Flickr
A STAR IS BORN:
star begins as a collapsing cloud of material composed primarily of
hydrogen, along with helium and trace amounts of heavier elements.
the stars core is dense enough, some of the hydrogen is converted
into helium through the process of nuclear fusion.
star's internal pressure prevents it from collapsing further under its own
the hydrogen fuel at the core is exhausted it expands to become
a red giant.
THE RED GIANT PHASE:
- After several
billion years of stable existence, a normal star will expand enormously to
become a bloated red giant.
- The sun is 4.5
billion years old and will not enter this phase for about 5 billion more
- Before a star
becomes a Red Giant, it experiences an energy crisis; it's core collapses
when the star's basic, non-renewable energy
source - hydrogen - is used up.
- A shell of hydrogen
on the edge of the collapsed core will be compressed
- The nuclear fusion of the hydrogen in the
shell will produce a new surge of power
that will cause the outer layers of the star to expand until it has a
diameter a hundred times its present value.
- It becomes a Red Giant!!
An Exhausted Red Giant:
- Over a period of a
few hundred thousand years, much of the star's mass is expelled at a
relatively slow speed of about 50,000 miles per hour. A hundred
million years after the red giant phase all of the star's available energy
resources will be used up.
- The exhausted red
giant will puff off its outer layer leaving behind a hot core. This star
has a surface temperature of about 50,000 degrees Celsius and is furiously
boiling off its outer layers in a "fast" wind traveling 6
million kilometers per hour.
- This mass loss
creates a more or less spherical cloud around the star and eventually
uncovers the star's blazing hot core.
- The radiation from
the hot star heats the slowly moving red giant atmosphere and creates a
complex and graceful filamentary shell called a Planetary Nebula.
- X-ray images reveal
clouds of multi-million degree gas that have been compressed and heated by
the fast stellar wind.
|Mz 3, BD+30-3639, Hen 3-1475, and NGC 7027: Planetary Nebulas - Fast Winds from Dying Stars
|by Smithsonian Institution on Flickr
- Planetary Nebula - so called because some of them resemble a planet when viewed through a small telescope - are produced in the late stages of a sun-like star's life.
- Dynamic elongated clouds envelop bubbles of multi-million degree gas produced by high-velocity winds from dying stars.
|CW Leonis by HST
|by LLacertae on Flickr
- This was first
discovered in 1969 by a group of astronomers with an Infrared Telescope.
- This Carbon Star is believed to be in a late
stage of its life, blowing off its own sooty atmosphere to form a White Dwarf in a distant future.
- The gaseous
envelope surrounding this star is at least 69,000 years old!
- Recent observations
are beginning to show the complex structure of the dust. Various chemical elements and molecules have been detected; among others nitrogen, oxygen and water, silicon and iron.
- The first white dwarf was observed by optical
telescopes in the middle of the 19th century. They do not emit very
- White dwarfs represent an intriguing state of matter.
- Most stars, including our Sun, will become white dwarfs
when they reach their final, burnt-out collapsed state!!
WHITE DWARF STARS:
- Eventually the central star will collapse to form a white dwarf star.
- In the white dwarf state, all the material contained in the star, minus the amount blown off in the red giant phase, will be packed into a volume one millionth the size of the original star.
- That would mean an object the size of an olive made of this material would have the same mass as a car!
- For a billion or so years after a star collapses to form a white dwarf, it is "white" hot with surface temperatures of about twenty thousand degrees Celsius.
NEW STARS ARE BORN:
- This matter will finally form a new generation of stars with a higher proportion of heavy elements.