Exploring the Universe Final Exam: Light, Telescopes, the Sun, Types of Stars, Stellar Evolution

Particles of light

Photons

Wavelength of light

The distance between successive peaks of a wave.

Frequency of light

The number of waves that pass a point in one second.

Relationship between wavelength and frequency

They are inversely related; as wavelength increases, frequency decreases.

Effect of wavelength on frequency

Frequency decreases when wavelength increases.

Photon energy comparison

Higher frequency has more photon energy than higher wavelength.

1-meter wavelength light

It is in the radio region of the electromagnetic spectrum.

Electromagnetic radiations reaching Earth

Visible light and some infrared and ultraviolet radiations.

Radiations partly reaching Earth

Ultraviolet and infrared radiations.

Part with highest frequency

Gamma rays.

Part with lowest frequency

Radio waves.

Part with longest wavelength

Radio waves.

Part with shortest wavelength

Gamma rays.

Gamma ray telescope wavelength

It observes the sky in the gamma-ray wavelength.

Location of Gamma ray telescopes

Above the Earth's atmosphere.

Atomic model

It describes the structure of an atom, including the nucleus and electrons.

Quantized energy levels of electron

Electrons can only exist at specific energy levels.

Absorption of a photon by an electron

The electron gains energy and moves to a higher energy level.

Emission of a photon by an electron

The electron loses energy and moves to a lower energy level.

Excited electron

An electron that has absorbed energy and moved to a higher energy level.

Ionization

The process of removing an electron from an atom, creating an ion.

Emission spectrum

A spectrum of the electromagnetic radiation emitted by a source.

Absorption spectrum

A spectrum that shows the absorption of specific wavelengths by a substance.

Continuous spectrum

A spectrum that shows a continuous range of wavelengths without gaps.

X-axis of a spectrum

Wavelength or frequency.

Y-axis of a spectrum

Intensity or brightness.

Peak wavelength calculation

It can be used to calculate the temperature of a star.

Optical/visible spectrum wavelength range

400 nm to 700 nm.

Color relation to temperature

Color is related to temperature; hotter objects emit bluer light.

Doppler shift of light

The change in frequency or wavelength of light as the light source moves closer or moves away

Blue shifted star

A star moving towards the observer, causing its light to shift to shorter wavelengths.

Red shifted star

A star moving away from the observer, causing its light to shift to longer wavelengths.

Distance effect on brightness

Apparent brightness changes with distance, while actual brightness remains constant.

Luminosity

The total amount of energy emitted by a star per unit time.

Apparent magnitude of a star

A measure of a star's brightness as seen from Earth.

Absolute magnitude of stars

A measure of the intrinsic brightness of a star, defined at a standard distance.

Brighter star comparison

A star with apparent magnitude of -5 is brighter than one with apparent magnitude of 5.

Luminosity parameters

Luminosity depends on radius and temperature.

Resolving power of a telescope

The ability of a telescope to distinguish between two closely spaced objects.

Difference between lens and mirror telescope

Lens telescopes use lenses to focus light, while mirror telescopes use mirrors.

Difference between refracting and reflecting telescope

Refracting telescopes use lenses, while reflecting telescopes use mirrors.

Disadvantages of lens telescopes

They can suffer from chromatic aberration and are often heavier.

Interferometer

An instrument that uses the interference of light waves to make precise measurements.

Ways of making observations of stars

Imaging, spectroscopy, and timing analysis.

Imaging

The process of capturing visual representations of stars.

Spectroscopy

The study of the interaction between light and matter.

Timing analysis

An examination of the timing of events or processes.

Temperature of the surface of the Sun

Approximately 6,000 K

Temperature of the core of the Sun

Approximately 10-15 million K

Color of the Sun's surface

Yellow

Energy production of the Sun

The Sun produces energy through nuclear fusion.

Gravitational contraction

The process where gravity causes a body to shrink.

Nuclear fusion reaction

Atoms of lighter elements fuse to create atoms of heavier elements plus energy

Overall nuclear reaction in the Sun

Four hydrogen atoms fuse to create one helium atom plus energy

Structure of the Sun

Consists of the core, radiation zone, convection zone, photosphere, chromosphere, and corona.

Solar wind

A stream of charged particles released from the Sun's atmosphere.

Corona

The outermost layer of the Sun's atmosphere, with an approximate temperature of 1 million K

Chromosphere

A layer of the Sun's atmosphere that appears red and is produced by hydrogen.

Photosphere

The visible surface of the Sun.

Convection zone

The outer layer of the Sun's interior where energy is transported by convection.

Radiation zone

The layer of the Sun near the core where energy is transported by radiation.

Granulation of the Sun's surface

The Sun's surface appears granulated due to convection currents.

Hydrostatic equilibrium

A state where gravitational force is balanced by thermal pressure.

Thermal pressure increase

Thermal pressure increases by increasing the temperature.

Energy balance

A state where energy input equals energy output.

Sunspots

Dark spots on the Sun's surface caused by magnetic activity.

Sunspot cycle

An approximately 11-year cycle of solar activity.

Prominences and solar flares

Are associated with the magnetic field of the Sun.

Solar storm

Occurs when the Sun emits huge bursts of energy in the form of solar flares and coronal mass ejections. These phenomena send a stream of electrical charges and magnetic fields towards Earth.

Solar cycle

A cycle of solar activity that repeats approximately every 11 years.

OBAFGKM

A classification of stars arranged according to their temperature, ordered highest to lowest

Temperature of O type stars

Approximately 30,000 to 50,000 K

Temperature of M type stars

Approximately 2,500 to 3,500 K

Temperature of G-type stars

Approximately 5,300 to 6,000 K

Main sequence stars

Stars that are in a stable phase of hydrogen burning.

Giant stars

Stars that have expanded and cooled after exhausting hydrogen in their cores.

White dwarf vs. red giant temperature

White dwarfs have higher temperatures than red giants.

O-type stars vs. M-type stars luminosity

O-type stars are more luminous than M-type stars.

O-type stars vs. M-type stars lifetime

O-type stars have shorter lifetimes than M-type stars.

Star size order

Descending order: OBAFGKM

Mass and star lifetime

More mass results in a shorter lifetime.

Lifetime of a 1 solar mass star

Approximately 10 billion years.

Limit on lowest mass of a star

0.08 solar masses, due to insufficient pressure for nuclear fusion.

Limit on highest mass of a star

150 solar masses, due to instability and rapid fusion leading to supernova.

Brown dwarfs

Substellar objects that are not massive enough to sustain hydrogen fusion.

High mass stars in a cluster

Expect to find about 1 high mass star among 50 stars.

Commonality of high-mass vs low-mass stars

Low-mass stars are more common than high-mass stars.

Types of star clusters

Open clusters and globular clusters.

Turn off main sequence point in star clusters

Indicates the age of the cluster.

What the lifetime of a star depends on

Depends on its mass.

Interstellar material

Matter that exists in the space between stars.

Molecular cloud

A dense region of gas and dust where stars can form.

Wavelength telescopes for molecular clouds

Infrared and radio telescopes are used because visible light is absorbed.

Protostar

An early stage of star formation where the object is still gathering mass.

Protostar rotation

As the size decreases, it rotates faster.

Protostar heating

As the size decreases, it heats up.

A star fusing helium in the core

A star that is no longer main sequence and is now in the giant phase.

Time to reach main sequence

Low mass stars take longer to reach the main sequence stage from the protostar stage.

Stages of evolution of a low mass star

Includes main sequence, red giant, and planetary nebula stages, smaller stars then become white dwarfs while bigger ones become neutron stars or black holes.

Red giant

A late stage in the life of a low mass star.