Transcript The Birth of Stars and Lives of the stars (Ch20&21)

The Birth of Stars
of the stars
By reading this chapter, you will learn
Chapter 18
18-1 How astronomers have
18-7 Where new stars form
pieced together the story of
within galaxies
stellar evolution
18-8 How the death of old stars
18-2 What interstellar nebulae are can trigger the birth of new
stars
and what they are made of
18-3 What happens as a star
begins to form
18-4 The stages of growth from
young protostars to mainsequence stars
18-5 How stars gain and lose mass
during their growth
18-6 What insights star clusters
add to our understanding of
stellar evolution
Interstellar matter:
cold near absolute zero
mostly H&He, Low density
Different types:
Reflection nebula,
emission nebula and
absorption (dark) nebula
Interstellar matter
1. Interstellar matter is the ingredients to make new
stars. These are generally found more commonly in:
a-disk, b-center, c- outskirt : of a spiral galaxy.
2. (a-Emission, b-absorption, c-reflection, d-planetary)
nebula has signature color of blue.
3. Interstellar matter is mostly made of: a- carbon, bhydrogen & helium, c-Oxygen & Nitrogen, d-iron, edifferent composition depending on the location
within a galaxy.
4. When the light from a far away star travels long
distance, often the color is shifted towards: a-blue, bgreen, c-white, d-red
Click on “enter” to review your answers:
1. a, 2. c, 3. b, 4. d
Protostars form in
cold, dark nebulae
Size of the
stars:
• If the Giant molecular cloud is too large & cloud
of gas reaches Jeans’ instability, the cloud of
gas is now too warm to collapse.
• If the protostar is too small: The interior
temperature never reaches hot enough for
hydrogen fusion. These failed stars are called
Brown dwarfs
Mass gain / loss
Low-mass stars that vigorously eject
gas are called T Tauri stars (a
protostar may eject large amounts
of gas into space before starting H
fusion)
Mass loss
Young star clusters: star formation and evolution
Star birth can begin
in giant molecular
clouds
The spiral arms of our
Galaxy are laced with
giant molecular clouds,
immense nebulae so
cold that their
constituent atoms can
form into molecules
• Star-forming regions appear
when a giant molecular cloud is
compressed
• This can be caused by the
cloud’s passage through one of
the spiral arms of our Galaxy,
by a supernova explosion, or by
other mechanisms
OB associations give
energy for emission
nebula and trigger
star formation
1.
2.
3.
4.
5.
6.
Review EM radiation
Which range of EM radiation has
highest energy?
Which range of EM radiation has low
frequency? Hint: lf=v: (wave length x
frequency = speed)
Which range of EM radiation has
lowest energy?
Which range of EM radiation is
commonly referred to as “heat”?
Which range of EM radiation has
fastest speed?
What wavelength of light can human
eyes detect?
Click on “enter” to review your answers:
1. Gamma rays, 2. radio, 3. radio, 4. infra red, 5.all travels
@ speed of light through vacuumed 6. 400nm – 700nm
Supernovae compress the
interstellar medium
and can trigger star birth
1.
2.
3.
4.
5.
Birth of the stars
Where are we likely to see the stellar formation? A- anywhere on the
disk of spiral galaxy, b-at the core of any spiral galaxy, c- in spiral
arms. D- only at 4kpc from the center.
All the stars first form as part of: a- binary system, b-globular star
cluster, c-OB associations or open star cluster, d- galactic clusster
Observing in (a-visible range, b- UV range, c-X ray range, d- IR
range) tells us a lot about stellar formation.
T-tauri stars are: a- high mass star that have just completed its
formation, b- low-mass star that have just completed its formation, c-.
high mass star that is about to start helium fusion, d-low mass stars
that is losing mass right before staring its hydrogen fusion
Super novae could start star formations. Supernova is: a-birth of high
mass star, b- change in state during main sequence of a high mass
star, c- after glow of energy after the high mass star dies. d- explosive
dyeing process of high mass star.
1. c, 2. c, 3. d, 4. d, 5.d
Click on “enter” to review your answers: