Astronomy Exam 2
Call Kai
Learn
Practice Test
Spaced Repetition
Match
Flashcards
Knowt Play1/128
There's no tags or description
Looks like no tags are added yet.
129 Terms
Element
A type of atom defined by its number of protons.
Proton
A positively charged particle in an atomic nucleus.
Neutron
A particle in an atomic nucleus with no electric charge.
Electron
A negatively charged particle surrounding an atomic nucleus.
Isotope
A form of an element with a different number of neutrons.
Ion
An atom that has gained or lost electrons.
Photon
A packet of electromagnetic energy.
Wavelength
The distance between matching points on neighboring waves.
Frequency
The number of waves passing a point each second.
Spectrum
The range or pattern of wavelengths in light.
Electromagnetic radiation
Energy that travels through space as oscillating electric and magnetic fields.
Photon energy
Energy carried by one photon.
Photon energy and wavelength
Photon energy decreases as wavelength increases.
Photon energy and frequency
Photon energy increases as frequency increases.
Energy level
A specific allowed energy state of an electron.
Electron absorption
An electron absorbs a photon to move to a higher energy level.
Electron emission
An electron emits a photon when it moves to a lower energy level.
Spectral fingerprint
The unique pattern of spectral lines produced by an element.
Continuous spectrum
A spectrum containing a continuous range of colors or wavelengths.
Emission spectrum
Bright lines produced by a hot low-density gas.
Absorption spectrum
Dark lines produced when continuous light passes through cooler gas.
Hot dense object
An object that produces a continuous spectrum.
Hot low-density gas
A gas that produces an emission spectrum.
Cool low-density gas
A gas that produces absorption lines when light passes through it.
Solar spectrum
An absorption spectrum produced by the Sun.
Chemical composition from spectra
The elements in an object can be identified from its spectral lines.
Temperature from spectral lines
The strength and pattern of lines can provide information about gas temperature.
Color temperature
The temperature inferred from the color or peak wavelength of a continuous spectrum.
Apparent brightness
How bright an object appears from Earth.
Luminosity
The total energy a star emits per unit time.
Standard candle
An object with a known luminosity used to estimate distance.
Brightness and distance
Apparent brightness decreases as distance increases.
Brightness and luminosity
Apparent brightness depends on both luminosity and distance.
Surface area and luminosity
A larger surface area can make a star more luminous.
Wien’s law
Hotter objects peak at shorter wavelengths.
Blue star
A star that is generally hotter than a red star.
Red star
A star that is generally cooler than a blue star.
Electromagnetic spectrum order
Radio microwave infrared visible ultraviolet X-ray gamma ray.
Longest wavelength
Radio waves have the longest wavelengths among the listed electromagnetic waves.
Shortest wavelength
Gamma rays have the shortest wavelengths among the listed electromagnetic waves.
Highest photon energy
Gamma rays have the highest photon energy among the listed electromagnetic waves.
Infrared astronomy
The use of infrared light to study cool objects and regions hidden by dust.
Radio astronomy
The use of radio waves to study cold gas and molecular clouds.
Atmospheric window
A wavelength range that can pass through Earth’s atmosphere.
Space telescope
A telescope placed above Earth’s atmosphere.
Doppler effect
A change in observed wavelength caused by relative motion.
Redshift
A shift toward longer wavelengths caused by motion away from the observer.
Blueshift
A shift toward shorter wavelengths caused by motion toward the observer.
Radial velocity
Motion toward or away from the observer.
Proper motion
Motion across the sky from the observer’s viewpoint.
Binary star
Two stars that orbit each other while gravitationally bound.
Center of mass
The common point around which two orbiting objects move.
Binary star masses
The more massive star orbits closer to the center of mass.
Exoplanet
A planet orbiting a star other than the Sun.
Doppler exoplanet method
Detecting a planet through repeated shifts in its star’s spectral lines.
Transit method
Detecting a planet through the periodic dimming of its star.
Direct imaging
Detecting an exoplanet by separating its light from the star’s light.
Transit depth
The amount of starlight blocked by a transiting planet.
Transit alignment
The planet’s orbit must be aligned so it crosses the star from our viewpoint.
Transit period
The time between transits gives the planet’s orbital period.
Parallax
The apparent shift of a nearby object against distant background objects.
Parallax and distance
A larger parallax means a smaller distance.
Arcsecond
A unit used to measure very small angles in the sky.
Parsec
A distance equal to about 3.26 light-years.
Parallax formula
Distance in parsecs equals one divided by parallax in arcseconds.
One arcsecond parallax
A parallax of one arcsecond corresponds to one parsec.
Nuclear fusion
The combination of light atomic nuclei into a heavier nucleus.
Nuclear fission
The splitting of a heavy atomic nucleus into smaller nuclei.
Fusion in stars
The process that powers stars by converting hydrogen into helium.
Mass-energy equivalence
Mass can be converted into energy according to E equals mc squared.
Proton-proton chain
The main hydrogen fusion process in the Sun.
Deuterium
A hydrogen nucleus containing one proton and one neutron.
Helium-3
An isotope of helium with two protons and one neutron.
Helium-4
A helium nucleus with two protons and two neutrons.
Gamma-ray photon
A high-energy photon produced during nuclear reactions.
Neutrino
A very low-mass electrically neutral particle produced in nuclear reactions.
Neutrino interaction
Neutrinos interact very weakly with ordinary matter.
Solar neutrinos
Neutrinos that provide evidence of fusion in the Sun’s core.
Hydrostatic equilibrium
The balance between inward gravity and outward pressure in a star.
Gravity in a star
The inward force that tries to compress the star.
Radiation pressure
Outward pressure produced by energy moving through a star.
Core temperature
The temperature at the center of a star.
Interstellar matter
Gas and dust located between stars.
Interstellar gas
Material between stars made mostly of hydrogen.
Interstellar dust
Tiny solid grains between stars that can block or absorb light.
Molecular cloud
A cold dense cloud of gas and dust where stars can form.
Star formation
The creation of a star through gravitational contraction of a gas cloud.
Protostar
A collapsing object that has not yet begun sustained hydrogen fusion.
Gravitational contraction
The shrinking of a gas cloud under its own gravity.
Minimum mass for hydrogen fusion
About 0.1 solar masses.
Minimum hydrogen-fusion temperature
About 12 million kelvin.
Main-sequence star
A star that fuses hydrogen into helium in its core.
Main-sequence lifetime
The period when a star fuses hydrogen in its core.
Stellar evolution
Changes in a star’s properties as it ages.
Stellar mass
The main factor controlling a star’s temperature luminosity lifetime and fate.
Mass and core temperature
More massive stars have hotter cores.
Mass and fusion rate
More massive stars fuse fuel faster.
Mass and stellar lifetime
More massive stars usually have shorter lifetimes.
Hydrogen depletion
The reduction of hydrogen fuel in a star’s core.
Hydrogen shell burning
Hydrogen fusion occurring in a shell around a depleted core.