Class notes
Astr 115 Our Star(The Sun)Notes
- Course
- ASTR 115
- Institution
- State University Of New York - Binghamton
Our Star(The Sun)Notes for Astr 115. *Essential Study Material!!
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photospherechromosphere
corona
convection (zone)
radiation (zone)
sunspot
sunspot group
prominence
filament
spicule(s)
granules
granulation
proton-proton chain
models of the Sun
sunspot cycles
11-year cycle
22-year cycle
Maunder minimum
differential rotation of the Sun
sudden ionospheric disturbance
aurora
geomagnetic field
solar wind
solar wind and coronal holes
, 14.1 A Closer Look At the Sun
Why was the Sun’s energy source a major mystery?
Late 19th century astronomers suggested that the Sun generates energy by
slowly contracting in size a process called gravitational contraction.
Why does the Sun shine?
The Sun converts mass into energy through the process of nuclear fission.
The Stable Sun
For the Sun to shine steadily, it must have a way of keeping the core hot and
dense.
Maintains these internal conditions through a natural balance between two
competing forces: gravity pulling inward and pressure pushing outward. This
balance is called gravitational equilibrium (or hydrostatic equilibrium).
The Sun’s internal pressure precisely balances gravity at every point within it,
thereby keeping the Sun stable in size.
Pressure must increase with depth.
The energy released by fusion, in turn, heats the gas and maintains the pressure
that keeps the Sun in balance against the inward pull of gravity.
How Fusion Started
When the central temperature and density finally grew high enough to sustain
nuclear fusion, energy generation in the Sun’s interior came into balance with
the energy lost from the surface in the form of radiation.
The Sun is therefore only about halfway through its 10-billion-year lifetime.
Gravitational contraction made the Sun hot enough to sustain nuclear fusion
in its core.
Energy liberated by fusion has maintained the Sun’s gravitational equilibrium
and kept the Sun shining steadily, supplying the light and heat that sustain life
on Earth.
What is the Sun’s structure?
Sun is a ball of plasma – a gas in which many of the atoms are ionized because
of the high temperature.
Basic Properties of the Sun
Spectroscopy tells you that the Sun is made almost entirely of hydrogen and
helium.
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