Transcript The Sun - St. Bonaventure University

The Sun
• Basic Solar Properties
• Diameter (photosphere) 1,391,980 km
• Mass1.99 x 1033 g
• Rotation Period 25 days (equator) Surface
• Temperature 5,800 K (effective)
• Spectral Class G2 V
• Apparent Visual Magnitude - 26.7
• Absolute Visual Magnitude + 4.8
• Mean Distance (Earth) 149,597,892 km
• Solar Elemental Abundances
•
•
•
•
•
•
•
•
•
•
•
Element
Hydrogen
Helium
Carbon
Nitrogen
Oxygen
Neon
Magnesium
Silicon
Sulfur
Iron
Number %
92.0
7.8
0.02
0.008
0.06
0.01
0.003
0.004
0.002
0.003
Mass %
73.4
25.0
0.20
0.09
0.8
0.16
0.06
0.09
0.05
0.14
1.
2.
3.
The core is the hot, dense central region in which the
nuclear reactions that power the Sun take place. It
comprises about 25% of the interior radius.
The radiative zone is comprised of the interior from
about 25% to 85% of the solar radius. It is called the
radiative zone because here (and in the core) the
primary transport of energy is by photons
(electromagnetic radiation).
The convective zone starts at about 85% of the solar
radius and extends to just below the surface. It is a
region in which the change in temperature with
increasing radius is so rapid that the Sun becomes
unstable to convection (rapid up and down motion of
large packets of gas), much as the Earth's
atmosphere becomes convectively unstable on a hot
Summer day and produces thunderstorms.
• Core
T~ 15,000,000 - 8,000,000
• Radiative T~ 8,000,000 - 500,000
• Convective T~ 500,000 - 10,000
Atmospheres
• Photosphere T=5800K
• Chromosphere T=10,000K
• Corona
T=2,000,000K
The Sun at X-Ray
wavelengths
The Sun at UV wavelengths
Granulation near sunspot
group
• The photosphere under
close observation
exhibits a mottled
appearance that is called
granulation. This is a
consequence of heat
convection below the
photosphere.
Granulations
The Chromosphere
of the Sun
• The chromosphere
contains spikes of gas
called spicules that rise
through it. This image is
a superposition of 11
limb images taken at
different wavelengths.
Spicules are short-lived
phenomena,
corresponding to rising
jets of gas that move
upward at about
30km/sec and last only
about 10 minutes.
The solar corona
• The extended outer
atmosphere of the
Sun is called the
corona. It has a
temperature of
millions of degrees,
but it is 10 billion
times less dense than
the atmosphere of
the Earth at sea level.
sunspots
• 4800 k temperature
• Travel in pairs
• Light and dark parts
The 11-Year Sunspot Cycle
The 22 Year Magnetic Cycle
Black denotes a
negative polarity
(magnetic field
pointing into the
Sun) while white
denotes a positive
polarity (magnetic
field pointing out of
the Sun).
Properties of sunspots
Sunspots
• 11 year number cycle
• 22 yr polarity cycle
• Limitation to 40 degrees N?S latitude
Prominence on the solar
limb
Solar
Flares
The Zeeman Effect
magnetohydrodynamics
• Rapidly rotating ball of charge
• Induced magnetic fields
• Field strength very large
Main branch of the protonproton chain
The main branch of the PP
chain consists of the following
reactions:
1. Two mass-1 isotopes of hydrogen undergo a
simultaneous fusion and beta decay to produce a
positron, a neutrino, and a mass-2 isotope of hydrogen
(deuterium).
2. The deuterium reacts with another mass-1 isotope of
hydrogen to produce Helium-3 and a gamma-ray.
3. Two helium-3 isotopes produced in separate
implementations of steps (1) and (2) fuse to form a
Helium-4 nucleus plus two protons.
• The net effect is to convert hydrogen to helium, with
the energy released going into the particles and
gamma-rays produced at each step of the sequence.