Transcript Life Cycle of Stars

OUTER SPACE
Other Components
of the Universe
The most common type of
T
celestial
object astronomers
see in space are stars.
Most stars appear to be gravitationally
bound together into groups
The following categories describe
various types of star groupings:
2
STAR CLUSTERS
All galaxies contain star clusters
which are groups of stars that:
• Develop together from
the same NEBULA
• Are gravitationally bound
• Travel together
STAR CLUSTERS
There are two types of star clusters:
• Open star clusters are collections of
six to thousands of usually young
stars
• Globular clusters are ball-shaped
collections of thousands to millions
of very old stars
There are approximately 20 000 open
star clusters found within the main
disc of the Milky Way.
TYPES OF GALAXIES
Galaxies are collections of millions
to hundreds of billions of stars,
planets, gas, and dust, measuring
up to 100 000 light years across.
They come in different shapes and
sizes and are spread across
the Universe
ELLIPTICAL GALAXY


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•
Spherical or flattened oval shape
Older galaxy
Very little gas, dust, or young stars
More than half of all galaxies we can
see
SPIRAL GALAXY
 Spinning flattened disc with a central
bulge and 2-4 spiral arms
 Central core: made up of old stars
• Spiral arms: made up of gas, dust and
young stars
BARRED SPIRAL GALAXY
 Subclass of spiral galaxies
 Spinning flattened disc with a central bulge and
2-4 spiral arms BUT have a central bar pattern
running down the centre
 Central core: made up of old stars
• Spiral arms: made up of gas, dust and young
stars
LENTICULAR GALAXY
 Central bulge surrounded by a
flattened disc of gas and dust
 NO spiral arms
 Are spiral galaxies that have lost their
gas and dust
 Made up of older red stars
IRREGULAR GALAXY
 No definite shape
 Have MORE gas and dust than
spiral galaxies
 NO central bulge or spiral arms
• 100 million- 10 billion stars
The Milky Way
 Consists of more than 200 billion stars and is more than
100, 000 ly across
 The sun lies 30, 000 ly away from the centre of the
galaxy
 Is a barred spiral galaxy with two spiral arms. The central
bulge is a huge collection of old stars. It is surrounded by
spinning disc of newer stars and clumps of gas and dust.
 Our solar system is located on the inner edge of one of
the spiral arms.
 A massive black hole is located at the centre of the Milky
Way
Galaxy Clusters
 The Milky Way is part of a group of more than
35 galaxies.
 Our largest and closest galaxy is the
Andromeda galaxy (a spiral galaxy consisting
of at least 300 billion stars)
 Astronomers and the University of Toronto
believe that the Milky Way and Andromeda
may collide in approximately 5 billion years!
The Origin
of the
Universe
Edwin Hubble – The
Expanding Universe
Edwin Hubble devised a classification
system for galaxies and categorized than
content, distance, shape, and brightness.
He noticed that there were redshifts in the
emission of light from many dimly lit
galaxies and realized that these were
moving away from each other at a rate
constant to the distance between them. He
used this to formulate Hubble's Law (1929)
which helped astronomers determine the
age of the universe and develop the idea
that the universe was expanding.
Monsignor Georges Lemaître
– The Big Bang Theory
It was a Belgian cosmologist and priest first
proposed the idea that the universe was
created from a single point of infinite density
which later became known as the Big Bang
theory. Fr. Lemaître first trained as a civil
engineer. In the First World War, he served in
the Belgian army as an artillery officer. In
1923, he entered a seminary, and later
became an ordained as a Jesuit priest.
After his ordination, he went to
Cambridge University, in England, and
M.I.T., in Boston, (1923-1926) to study
physics. It was in Boston where he was
influenced by ideas about the expanding
universe proposed Edwin Hubble and
Harlow Shapley . He returned to Belgium
in 1927 where he was appointed to the
position of professor of astrophysics at
the University of Louvain.
In 1933 Fr. Lemaître published
“Discussion on the Evolution of the
Universe”, in which he proposed the
universe began as a “primeval atom” a
region of space about 30 times larger
than the Sun that contained all the
material in the Universe. He proposed
that it exploded releasing matter in all
directions leading to the present
Universe. This is the first time that
anyone had proposed that there was an
initial event to start the expansion.
Fr. Lemaître travelled
to a conference in
California in 1933
where Albert
Einstein publically
remarked “This is
the most beautiful
and satisfactory
explanation of
creation to which I
have ever listened.”
Fr. Lemaître published his
Hypothesis of the Primal
Atom in 1946. In the same
year, George Gamow a
Russian physicist, who had
defected to the United States
in 1934, and his colleagues
began to develop the
nuclear physics of the Big
Bang at George Washington
University. Work is still
continuing at Universities
and other research
institutions around the world
today.
ORIGIN OF THE UNIVERSE:
The Big Bang Theory
 Time zero estimated at being 10-15 billion years ago
 At that time all matter was packed into a small,
dense, hot mass under pressure (smaller than the
period at the end of a sentence!)
 The Big Bang describes the beginning of the
Universe as we know it
 Changing our theories about the universe is a
continuing process, as scientists try to explain new
discoveries