9 Chapter 9 – How did the Sun form?
OpenStax Astronomy Chapter 20 (ISM) & Chapter 21 (Star Formation)
Interstellar Medium
What are stars and planets made of?
I. (ISM): and dust between the stars
A. are made of ISM
B. are dense regions of ISM compared to space
1. Much smaller than densities on stuff on Earth, example:
C. to holds clouds together
1. Gravitational attraction between parts of cloud pulls everything toward
II.
A. Coldest and interstellar clouds
B. atoms can become (H2)
1. cold and dense enough to bond together
C. Some places in the cloud are than the rest
1. This is where begins
D. will make denser regions under their own weight
E. Clouds fragment into , whole cloud does collapse
F. Gravity gets and collapse speeds up as piece gets
G. But, collapse by , turbulence, pressure, and spin
H. Eventually, gravity , collapse
What causes molecular clouds to collapse?
Star Formation
III. Cores
A. Collapsed pieces of molecular clouds are now denser and , called prestellar
1. May be of cores in a single molecular cloud
a. A cluster of cores can form a star
2. May be core in a small isolated cloud that forms one star
B. Only of these cores will form
1. About of matter in big molecular clouds become stars
IV.
A. Prestellar cores even more under their own
B. of core shrinks fastest because is most
C. Dense center keeps collapsing to form a
In the stages of star formation, what is formed when pieces of molecular CLOUDS collapse?
V. The Role of
A. Protostar maintains between pressure and gravity, called
1. So it doesn’t explode or collapse
B. Material from surrounding core protostar, it gets more , so gravity is
2. Gravity tries to pull everything to center, so protostar gets
C. Interior and in the protostar as particles collide when new material falls in
1. (from falling in) turned into (heat/infrared light)
D. Heat Energy (infrared) keeps protostar together so doesn’t from internal
1. Sometimes get
2. No light yet
VI. Becoming a
A. When the in the center of the protostar is high enough, begins fusing into
B. When Hydrogen starts, it is a
1. Fusion is now , not gravitational energy
2. Emits light, as well as infrared, ultraviolet, etc.
2. Mass must be than times Jupiter’s Mass to start fusion and become a star
As causes the protostar to collapse, the temperature in the core .
What is the source of a protostar’s energy before it becomes a star?
VII.
A. star or planet
B. Form from protostellar core, but temperature in the protostar gets hot enough for
1. May fuse Deuterium (heavy Hydrogen)
C. Very (13-84 Jupiter Masses) compared to a star
D. Not brown, but cool and emit mainly light
1. Keep getting cooler and with time
