Electromagnetic Spectrum, Solar Physics, and Stellar Spectroscopy

Colors of visible spectrum (longest to shortest wavelength)

Red orange yellow green blue indigo violet

Discoverer of infrared radiation

Sir William Herschel

Hot low-density hydrogen gas near a hot star

Emits light at specific wavelengths characteristic of hydrogen

Frequency of shortest wavelength visible light

7.5 × 10^14 Hz

Lowest-energy electromagnetic radiation (among listed choices)

Infrared radiation

Greatest-energy electromagnetic radiation

Gamma rays

Temperature (gas)

Measure of the average speed of particles in a gas

Smallest frequency electromagnetic radiation

Radio waves

Long wavelength visible light

Appears red to the human eye

Spectrograph

Instrument that reveals the spectral fingerprint of elements

Color of intensely heated metal

Changes from red through orange to white and then to blue

How stellar chemical composition is determined

By spectroscopy of the light emitted by the star

Absorption spectrum is also called a bright-line spectrum

False

Cause of dark absorption lines in the solar spectrum

Cooler gas above the hot solar surface absorbs specific wavelengths

Absorption spectrum observed when

Cool gas lies between a continuous source and the observer

Continuous spectrum observed when

Viewing a hot dense source directly

Emission spectrum observed when

Viewing a hot low-density gas cloud

Wien's Law

Peak wavelength becomes shorter as temperature increases

Solar absorption lines form in the

Photosphere

Diffraction grating

Glass or plastic with thousands of closely spaced parallel grooves

Spectrum of vaporized chemical element

Bright emission lines unique to that element

Evidence that the Sun contains iron

Iron absorption lines appear in the solar spectrum

Why each element has unique absorption lines

Each element has different electron energy levels

Hydrogen spectral line pattern

Same unique pattern seen in laboratories

Photosphere

Visible surface of the Sun

Granulation on the Sun

Evidence of convection in the photosphere

Supergranule

Large area of slowly rising and falling gas containing many granules

Chromosphere

Layer above the visible surface of the Sun

Highest temperatures in the Sun

Solar interior

Solar wind

Material from the corona accelerated into space

Heliosphere

Protective region created by the solar wind surrounding the solar system

Sunspots

Cooler darker regions on the Sun's surface

Main feature of sunspots

Very powerful magnetic fields

Sunspot cycle length

About 11 years

How Galileo discovered solar rotation

Observed sunspots moving across the Sun

Sun's rotation period

About one rotation per month

Zeeman Effect

Splitting of spectral lines in a magnetic field

Evidence of magnetic fields in sunspots

Zeeman splitting of spectral lines

The Sun contains no liquid or solid matter

True

Energy source of the Sun

Thermonuclear fusion of hydrogen into helium with energy release

Thermonuclear fusion

Combining light nuclei into heavier nuclei with energy release

Size of Sun's energy-producing core

About 1/4 of the Sun's radius

Sun's stage in hydrogen-burning lifetime

About halfway through its life

Formation of Sun and solar system

Collapse of a rotating nebula of gas and dust

Most common elements in the universe

Hydrogen and helium

Mass of universe made of hydrogen and helium

About 98%

Fraction of Earth's mass that is hydrogen and helium

Less than 1%

Origin of hydrogen in the universe

Formed during the Big Bang

Heavy elements in our bodies indicate

The solar system formed from material enriched by earlier stars

Reason little hydrogen and helium remain in inner solar system

Early solar radiation drove them outward

Birthplace of Sun and planets

Collapsing rotating nebula of gas and dust

Accretion

Gradual buildup of larger objects from smaller particles

Planets in order from the Sun

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

Planet demoted in 2006

Pluto

Location of asteroid belt

Between Mars and Jupiter

Comets

Chunks of rock and ice orbiting beyond Neptune

Kuiper Belt

Region of icy objects beyond Pluto out to about 50 AU

Distance to nearest star

4.3 light-years

Evidence for planets around other stars

Periodic stellar wobble and Doppler shifts

Quantum mechanics

Rules describing behavior of atoms and subatomic particles

Sun's peak wavelength

520 nm

Cannot be determined from stellar spectrum

Tangential velocity

Star with peak wavelength of 300 nm temperature

About 10000 K

Blue light photons

Have greater energy than red light photons