Earth and Space Science Unit 1

Color of visible light with the shortest wavelength

Violet

Type of electromagnetic radiation with the longest wavelength

Radio waves

Relationship between electromagnetic wavelength and frequency

Inverse relationship (as wavelength increases, frequency decreases)

Primary energy-producing process in the core of main sequence stars

Nuclear fusion

Structural classification of the Milky Way Galaxy

Spiral

Apparent change in a star's position when viewed from different points in Earth's orbit, used to measure distance

Parallax

Shift in spectral lines toward longer wavelengths caused by a celestial object moving away from Earth

Redshift

Uniform microwave energy filling space at approximately $3\,\text{K}$, serving as key evidence for the Big Bang

Cosmic Microwave Background Radiation (CMBR)

Inferred age of the universe based on cosmological data

Approximately $13.7\,\text{billion years}$

Stage of stellar evolution in which a star spends the largest portion of its life cycle

Main sequence

Process by which lighter elements combine to form heavier elements inside stars

Nucleosynthesis

Two primary methods of energy transfer moving heat from a star's core through its interior

Radiation and convection

Electromagnetic spectrum

The full range of all electromagnetic radiation frequencies. All EM waves travel at the speed of light in a vacuum, but differ in wavelength, frequency, and energy.

Relationships between electromagnetic wavelength, frequency, and energy

Wavelength and frequency are inversely proportional (as wavelength increases, frequency decreases). Wavelength and energy are also inversely proportional (shorter wavelengths have higher energy).

Primary reason light is important to astronomers

Light is the primary source of information from distant celestial objects, allowing astronomers to determine an object's chemical composition, surface temperature, distance, and motion.

Three main types of spectra (continuous, emission, and absorption)

1. Continuous spectrum: An unbroken band of all wavelengths from a hot, dense object. 2. Emission spectrum: Bright lines emitted by hot glowing gas. 3. Absorption spectrum: Dark lines across a continuous spectrum caused by cooler gas absorbing specific wavelengths.

Spectroscopy

The study and analysis of light spectra emitted or absorbed by matter, allowing astronomers to determine chemical composition, temperature, velocity, and distance of celestial objects.

Stellar parallax

The apparent shift in a star's position relative to background stars when viewed from different points in Earth's orbit, used to calculate its distance from Earth.

Big Bang Theory

The cosmological model stating that the universe began as an extremely hot, dense point approximately $13.7\,\text{billion years}$ ago and has been expanding and cooling ever since.

Three major lines of evidence supporting the Big Bang theory

1. Cosmic Microwave Background Radiation (CMBR) uniformly filling space at ~$3\,\text{K}$. 2. Redshift of light from distant galaxies showing space expansion. 3. Relative abundance of light elements (hydrogen, helium, and lithium) in the universe.

Process of a nebula contracting into a protostar

Gravity causes a dense cloud of dust and gas (nebula) to pull together and collapse. As it contracts, internal density, pressure, and temperature increase until a hot core (protostar) forms.

Nuclear fusion

A nuclear process in which two light atomic nuclei combine to form a heavier nucleus, releasing massive amounts of energy (such as hydrogen nuclei combining to form helium in stellar cores).

Path of solar energy from the Sun's core to Earth's surface

Energy is produced by nuclear fusion in the core, travels outward via radiation through the radiative zone, moves via convection currents through the convective zone, is emitted as electromagnetic radiation from the photosphere, and travels through space to reach Earth.

Stellar and non-stellar nucleosynthesis

The creation of heavier chemical elements from lighter ones via nuclear reactions inside stars. It can also occur during the Big Bang (primordial nucleosynthesis), in supernova explosions, or through cosmic ray spallation.

Similarities and differences among stars

Stars are similar in being composed primarily of hydrogen and helium, held together by gravity, and powered by fusion. They differ in mass, luminosity, surface temperature, color, size, age, and evolutionary stage.

Stages of the Sun's life cycle

1. Stellar nebula collapses into a protostar. 2. Main sequence star (fusing hydrogen). 3. Red giant (core contracts while outer layers expand). 4. Planetary nebula (outer gas layers shed). 5. White dwarf (dense, cooling core remnant).

Cause of stellar black hole formation

Extremely massive stars (greater than about $20$ solar masses) undergo a supernova explosion, leaving a core so massive that gravity causes it to collapse completely into a singularity from which not even light can escape.

Stellar response to hydrogen depletion in the core

Core fusion pauses, gravity causes the core to contract and heat up, and the outer layers expand and cool, transforming the star into a red giant or red supergiant where helium fusion can begin.

Connection between sunspots, solar flares, coronal mass ejections (CMEs), and Earth impacts

All three are caused by localized intense solar magnetic fields. Sunspots release solar flares (radiation bursts) and CMEs (plasma eruptions) that can trigger geomagnetic storms on Earth, disrupting satellite communications, radio signals, and power grids while producing auroras.

Electromagnetic spectrum

The entire range of electromagnetic radiation arranged by wavelength and frequency, encompassing radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Standard unit used to measure frequency

Hertz ($\text{Hz}$)

Unit equal to one billionth of a meter ($10^{-9}\,\text{m}$), commonly used to measure wavelengths of visible light

Nanometer ($\text{nm}$)

Study and analysis of light spectra emitted or absorbed by matter to determine physical properties of celestial objects

Spectroscopy

Apparent shift in position of a nearby star against distant background stars when viewed from opposite sides of Earth's orbit

Stellar parallax

Doppler shift of light toward longer wavelengths caused by a celestial body moving away from Earth

Redshift

Doppler shift of light toward shorter wavelengths caused by a celestial body moving toward Earth

Blueshift

Cosmological model stating that the universe expanded rapidly from an extremely dense, hot state approximately $13.7\,\text{billion years}$ ago

Big Bang Theory

Faint, uniform microwave radiation filling the observable universe, representing remnant heat from the early Big Bang

Cosmic Microwave Background Radiation (CMBR)

Large, gravitationally bound system containing stars, stellar remnants, interstellar gas, dust, and dark matter

Galaxy

Name and structural type of the galaxy containing our Solar System

Milky Way (Spiral galaxy)

Vast interstellar cloud of gas and dust where new stars are born

Nebula

Early stage in stellar evolution where a dense mass of gas contracts under gravity before nuclear fusion begins

Protostar

Nuclear reaction in which light atomic nuclei combine to form a heavier nucleus, releasing massive energy in stellar cores

Nuclear fusion

Process by which new chemical elements are created within stars or during cosmic events

Nucleosynthesis

Three internal zones of a main sequence star like the Sun, ordered from the center outward

Core, radiative zone, and convective zone

Visible outer surface of a star from which photons escape into space

Photosphere

Smallest unit of an element, consisting of protons, neutrons, and electrons

Atom

Two primary chemical elements that make up the vast majority of matter in the universe and stars

Hydrogen and helium

Explosive destruction of a massive star at the end of its life cycle, forging heavy elements

Supernova

Dense, low-luminosity remnant of a low- to medium-mass star after fusion has ceased

White dwarf

Outward pressure produced by photons in a star's interior that balances the inward pull of gravity

Radiation pressure

Classification of stars based on surface temperature, color, and spectral absorption lines

Spectral class

Total amount of electromagnetic energy emitted by a star per unit of time

Luminosity