scioly astronomy foundation

What is the electromagnetic spectrum?

Range of all electromagnetic radiation ordered by wavelength/energy

Order of EM spectrum (low to high energy)

Radio → Microwave → Infrared → Visible → UV → X-ray → Gamma

What happens to wavelength as energy increases?

Wavelength decreases

What is frequency?

Number of wave cycles per second

Energy vs frequency relationship?

Higher frequency = higher energy

What is redshift?

Light shifts to longer wavelength due to object moving away

What is blueshift?

Light shifts to shorter wavelength due to object moving toward observer

What causes Doppler shift?

Relative motion between source and observer

What is a blackbody?

Object that absorbs all radiation and emits based on temperature

Wien’s Law meaning?

Hotter objects peak at shorter wavelengths

Stefan-Boltzmann Law idea?

Hotter objects emit more total energy

What is a spectrum?

Light intensity across wavelengths

Absorption spectrum definition

Dark lines where elements absorb light

Emission spectrum definition

Bright lines where elements emit light

What is spectroscopy?

Study of light spectra to identify elements and motion

What do spectral lines tell us?

Chemical composition and motion

What is a photon?

Packet of light energy

What is main sequence?

Hydrogen-fusing stable phase of star life

What determines star position on HR diagram?

Temperature and luminosity

HR diagram x-axis?

Temperature (hot left → cool right)

HR diagram y-axis?

Luminosity (brightness)

What is luminosity?

Total energy output of a star

What is apparent magnitude?

How bright a star appears from Earth

What is absolute magnitude?

True brightness at standard distance

Magnitude scale meaning?

Lower number = brighter object

Most common star type?

Main sequence stars

Hot star color?

Blue/white

Cool star color?

Red

Spectral types order

O B A F G K M

O-type stars?

Hot

M-type stars?

Cool

What is a red giant?

Large cool star late in life

What is a white dwarf?

Dense stellar remnant of low-mass star

What is a neutron star?

Collapsed core of massive star

What is a black hole?

Object with gravity so strong light cannot escape

What is a supernova?

Explosion of massive star

What determines star lifetime?

Mass (higher mass = shorter life)

High-mass star lifecycle

Nebula → main sequence → supergiant → supernova → neutron star/black hole

Low-mass star lifecycle

Nebula → main sequence → red giant → white dwarf

What is a nebula?

Cloud of gas and dust where stars form

What is Kepler’s First Law?

Planets orbit in ellipses

What is Kepler’s Second Law?

Equal areas in equal time

What is Kepler’s Third Law?

Farther planets take longer to orbit

What is an ellipse?

Oval-shaped orbit

What is perihelion?

Closest point to Sun

What is aphelion?

Farthest point from Sun

What is gravity dependent on?

Mass and distance

Gravity vs distance relationship?

Inverse square relationship

Where is orbital speed highest?

At perihelion

What is a light-year?

Distance light travels in one year

What is an AU?

Distance from Earth to Sun

What is a parsec?

Distance based on stellar parallax

What is parallax?

Apparent motion of nearby stars due to Earth’s orbit

Large parallax means?

Star is closer

Small parallax means?

Star is farther

What is proper motion?

Actual motion of star through space

What is radial velocity?

Motion toward or away from observer

What is luminosity measured in?

Watts or solar luminosities

What is flux?

Energy received per unit area

Flux decreases when?

Distance increases

What is a refracting telescope?

Uses lenses to focus light

What is a reflecting telescope?

Uses mirrors

Why are reflecting telescopes better?

No chromatic aberration

What is resolution?

Ability to distinguish fine detail

What is light-gathering power?

Ability to collect faint light

What increases light-gathering power?

Larger diameter

Magnification vs resolution?

Magnification = size

What is atmospheric seeing?

Blurring due to Earth’s atmosphere

What is adaptive optics?

Technology correcting atmospheric distortion

Types of galaxies?

Spiral

Milky Way type?

Barred spiral galaxy

Solar System location?

Orion Arm of Milky Way

What is a galaxy?

Large system of stars

What is dark matter?

Invisible mass inferred from gravity effects

What is dark energy?

Force causing universe expansion acceleration

What is universe expansion?

Galaxies moving away from each other

Evidence of expansion?

Redshift of distant galaxies

What is Hubble’s Law?

Recessional velocity proportional to distance

What is cosmic microwave background?

Leftover radiation from early universe

What is stellar parallax used for?

Measuring distance to nearby stars

What is a light curve?

Brightness over time graph

What are variable stars?

Stars that change brightness

What is a Cepheid variable?

Star used for distance measurement

What is standard candle?

Object with known luminosity

What is redshift used for?

Measuring galaxy motion and expansion

What does blueshift indicate?

Approaching object

What does redshift indicate?

Receding object

What determines star color?

Surface temperature

Does brightness equal temperature?

No

What affects apparent brightness?

Distance and luminosity

Do planets orbit in circles?

No

What is spectral classification used for?

Temperature and composition

What is ionization?

Electron removal from atoms due to energy

What causes absorption lines?

Cool gas absorbing specific wavelengths

What causes emission lines?

Hot gas emitting specific wavelengths

What is cosmic distance ladder?

Methods used to measure distances in universe