Download The Sun and Other Stars

The Sun and Other Stars
Sunny Facts
• The sun is 330,000 times the mass of the earth;
diameter is 109x the earth.
• 99.86% of the mass of the solar system (Jupiter is
0.1%)
• our sun is of “average” size; 5780 K at surface, 12
million degrees K at the core
• primarily composed of hydrogen 73.5% and
helium; 2% heavy elements
• is around 4.6 billion years old, slightly less than
half of its lifespan.
Sunspots
• The sun actually rotates faster at
the equator than at the poles
(Jupiter also does this).
• The sun has “weather,” which
consist of darker patches on the
surface called sunspots, which
can be 10,000 km across. They
can last for months.
• Sunspots are colder than the rest
of the sun: 4300-5000 K.
• Sunspots appear in cycles that
last around 11 years.
What
Color is
the Sun?
• The sun is appears to be yellow because of
scattering of light in the earth’s atmosphere. It is
actually white. It is called a “yellow” star because
most of its radiation is in the yellow-green portion
of the electromagnetic spectrum.
• The sun has an atmosphere of plasma, called the
corona, which extends millions of km into space.
Solar Emission Spectrum
Why does the Sun emit light?
• The massive gravity of the sun squeezes atoms
together, overcoming repulsive forces
between the atoms’ nuclei
• When (hydrogen) atoms fuse, they become a
heavier element, helium, and a bit of matter is
converted into energy
• E=mc2 A small bit of matter is converted into
a lot of energy!
Nuclear Fusion
The Electromagnetic Spectrum
The Sun’s neighborhood
• The sun is 25,000 l-y from the center of the
Milky Way.
• Imagining our immediate neighborhood as a
sphere with the sun at the center extending
17 light years, contains 50 star systems (many
with multiple stars).
• The Sun is the 4th largest in the neighborhood;
most consist of smaller “brown dwarf” stars.
TESS Telescope
The Inferred Structure of the Sun
The Core
• Up to about 25% of the earth’s radius, the core’s density can reach
150 g/cc, with a temperature of 13,600,000 K.
• The incredible density is caused by the massive size of the sun
• The core is rotating faster than the outer areas of the sun, just like
the earth
• Energy is produced in the core by fusion of hydrogen into helium;
0.7% of mass is converted into energy when hydrogen becomes
helium; fusion occurs only in the core, not outer areas.
• Our sun contains 8.9 x 1056 hydrogen atoms, and fuses 3.7 x 1038
every second!
• This results in 4 million metric tons of matter being converted into
energy every second!
• Larger stars have higher densities, higher fusion rates, shorter lives;
smaller stars the opposite – they will be around for tens of billions
of years.
The Radiative Zone
• From 0.25 to 0.7 solar radius
• Energy flows outward from the
core as radiation, decreasing in
intensity as you rise through the
sun
• Radiation is transferred from one
atom to another via absorption
and emission by electrons
around atoms
• The sun’s magnetic field is
believed to originate in the
radiative zone
The Convective Zone
• Above the radiation zone,
matter is not hot enough
for radiative transfer,
rather the energy
circulates by movement
of matter (convection)
• Density of top of
convective zone is only
0.2 g/ cubic meter.
Sunspot Lab
• Objective: to graph a set of data and use it to
predict future sunspot activity.
The Maunder Minimum 1645-1700
Tambora Eruption (1816)